Carrier and positioning assembly thereof

Abstract

This application relates to a vehicle and its positioning component. The positioning component includes a first positioning component and a second positioning component. The first positioning component is rotatably disposed on the second positioning component and is used to detachably connect to the vehicle body, which is either a first vehicle body or a second vehicle body. When the first positioning component is used to connect to the first vehicle body and rotates relative to the second positioning component to face a first direction, the first positioning component can prevent the first vehicle body from disengaging from the first positioning component. When the first positioning component is used to connect to the second vehicle body, the first positioning component is restricted from rotating relative to the second positioning component to face the first direction.

Description

Carrier and its positioning components The present application relates to the technical field of infant products, and in particular to a carrier and a positioning component thereof. Currently available positioning assemblies are typically compatible with various types of carrier bodies, such as infant carriers and child safety seats. Each type of carrier body can be rotatably mounted on the positioning assembly, allowing the user to adjust its orientation according to actual needs. However, since different types of carrier bodies can be used in different orientations, misaligning the carrier body can pose a potential safety hazard. Based on this, it is necessary to provide a carrier and a positioning assembly thereof to address the above-mentioned problem, wherein the positioning assembly can selectively allow or limit the separation of the carrier body, and at the same time, can selectively limit the rotation angle of the carrier body. The present application provides a positioning assembly, including a first positioning assembly and a second positioning assembly, wherein the first positioning assembly can be rotatably disposed on the second positioning assembly, and the first positioning assembly is used to detachably connect to a carrier body, and the carrier body is a first carrier body or a second carrier body; wherein, when the first positioning assembly is used to connect to the first carrier body and is rotated relative to the second positioning assembly to face a first direction, the first positioning assembly can limit the first carrier body from disengaging from the first positioning assembly; when the first positioning assembly is used to connect to the second carrier body, the first positioning assembly is limited from rotating relative to the second positioning assembly to face the first direction. In one embodiment, it also includes: a first connecting mechanism, which is arranged in the first positioning assembly and has a locked state and an unlocked state, when the first connecting mechanism is in the locked state, the first connecting mechanism is connected to the carrier body, and when the first connecting mechanism is in the unlocked state, the first connecting mechanism is detached from the carrier body; and a first limiting mechanism, the first limiting mechanism is arranged between the first positioning assembly and the second positioning assembly, and is used to selectively allow or limit the first connecting mechanism to switch between the locked state and the unlocked state. In one embodiment, it further includes: a locking and holding mechanism, which is movably provided on the first positioning component and is used to maintain the connection between the first connecting mechanism and the carrier body; wherein, when the first positioning component is used to connect the first carrier body and is facing the first direction, the first limiting mechanism enters the moving path of the locking and holding mechanism, limiting the movement of the locking and holding mechanism, so as to limit the first connecting mechanism from switching from the locked state to the unlocked state. In one embodiment, the first limiting mechanism includes: a first limiting groove, which is arranged on a side of the second positioning component facing the first positioning component; and a first limiting member, which is movably arranged in the first positioning component and can be inserted into or withdrawn from the first limiting groove; wherein, when the first limiting member is inserted into the first limiting groove, the first limiting member allows the first connecting mechanism to switch to the unlocked state; when the first limiting member withdraws from the first limiting groove, the first limiting member restricts the first connecting mechanism from switching to the unlocked state; and when the first positioning component is rotated relative to the second positioning component to face the first direction, the first limiting member withdraws from the first limiting groove. In one embodiment, the first positioning component has a rotation axis, and the first limiting member is set offset from the rotation axis; a straight line passing through the rotation axis and perpendicular to the first direction is defined as a reference line, and when the first positioning component is facing the first direction, the first limiting member and the first limiting groove are offset and respectively located on both sides of the reference line. In one embodiment, the first positioning component is a circular structure, the rotation axis is the center of the first positioning component, the first limiting groove is a semicircular groove, the radius of the semicircular groove is the distance between the first limiting member and the center of the first positioning component, and when the first positioning component is rotated relative to the second positioning component to face away from the first direction, the first limiting member is located at the midpoint of the first limiting groove. In one embodiment, a sliding slope is provided on one end of the first limiting member facing the second positioning assembly, and the sliding slope can push the first limiting groove to move the first limiting member out of the first limiting groove in a direction away from the second positioning assembly. In one embodiment, the first limiting mechanism further includes a first restoring member, and the first restoring member is used to provide an elastic restoring force for the first limiting member to drive the first limiting member to be inserted into the first limiting groove. In one embodiment, the first positioning assembly includes: a first shell having a first mounting cavity, the first shell also having a first limiting hole connected to the first mounting cavity, the first limiting member is movably disposed in the first mounting cavity and at least part of the first limiting member can extend out of the first mounting cavity through the first limiting hole. In one embodiment, the first connecting mechanism includes a locking hook, which is pivotally connected to the first shell and has a locking position and a releasing position; when the locking hook is located at the locking position, the locking hook is used to engage and lock with the carrier body. In one embodiment, it further includes: a locking and holding mechanism, which is movably arranged in the first installation cavity, and when the locking hook is driven to the locking position, the locking and holding mechanism is used to lock the locking hook at the locking position. In one embodiment, the locking and holding mechanism includes a first locking member, which is movably arranged in the first mounting cavity and has a first position and a second position; one of the first locking member and the snap hook is provided with a locking groove, and the other is provided with a snap portion; when the first locking member is in the first position, the locking groove is engaged with the snap portion to lock the snap hook in the locking position; when the first locking member is in the second position, the locking groove is separated from the snap portion to allow the snap hook to switch between the locking position and the unlocking position. In one embodiment, when the first limiting member retracts from the first limiting groove, the first limiting member is located in the moving path of the first locking member to limit the first locking member from switching from the first position to the second position; when the first limiting member is inserted into the first limiting groove, the first limiting member deviates from the moving path of the first locking member to allow the first locking member to switch from the first position to the second position. In one embodiment, the locking and holding mechanism further includes a third restoring member, and the third restoring member is used to provide an elastic restoring force for the first locking member to keep the first locking member in the first position. In one embodiment, the positioning assembly further comprises a first release member movably provided on the first positioning assembly, the first release member being drivingly connected to the first locking member, and the first release member being operable to drive the first locking member to move from the first position to the second position. In one embodiment, the first release member is provided with a driving inclined surface; the first locking member is further provided with a driving portion, which is suitable for abutting against the driving inclined surface and sliding along the driving inclined surface to enable the first locking member to switch between the first position and the second position. In one embodiment, a second limiting mechanism is further included. The second limiting mechanism is disposed between the first positioning assembly and the second positioning assembly and is used to selectively limit the angular range of rotation of the first positioning assembly relative to the second positioning assembly. In one embodiment, the second limiting mechanism has a first state and a second state, and when the second limiting mechanism is in the first state, it limits the first positioning component from rotating relative to the second positioning component to the first direction, and when the second limiting mechanism is in the second state, it allows the first positioning component to rotate relative to the second positioning component to the first direction; the positioning assembly also includes an elastic member; wherein, the elastic member always keeps the second limiting mechanism in the first state, and when the first positioning assembly is used to connect to the first carrier body, the second limiting mechanism overcomes the elastic force of the elastic member through the first carrier body and is in the second state; or, the elastic member always keeps the second limiting mechanism in the second state, and when the first positioning assembly is used to connect to the second carrier body, the second limiting mechanism overcomes the elastic force of the elastic member through the second carrier body and is in the first state. In one embodiment, the second limiting mechanism includes: a second limiting groove, which is provided in one of the second positioning component and the first positioning component; and a second limiting member, which is movably provided in the other of the second positioning component and the first positioning component and can be inserted into or withdrawn from the second limiting groove; wherein, when the first positioning component is used to connect the second carrier body, the second limiting member is inserted into the second limiting groove, and the first positioning component is restricted from rotating relative to the second positioning component to the first direction. In one embodiment, the first positioning component has a rotation axis, and the second limiting member is set offset from the rotation axis; a straight line passing through the rotation axis and perpendicular to the first direction is defined as a reference straight line, and when the first positioning component is facing the first direction, the second limiting member and the second limiting groove are offset and respectively located on both sides of the reference straight line. In one embodiment, the first positioning component is a circular structure, the rotation axis is the center of the first positioning component, the second limiting groove is a semicircular groove, the radius of the semicircular groove is the distance between the second limiting member and the center of the first positioning component, and when the first positioning component is rotated relative to the second positioning component to face away from the first direction, the second limiting member is located at the midpoint of the second limiting groove. In one embodiment, a linkage mechanism is further included. The linkage mechanism is provided in the first positioning assembly and is used for driving connection with the second limiting member. The linkage mechanism can drive the second limiting member to withdraw from or insert into the second limiting groove. In one embodiment, the linkage mechanism includes a linkage member, which is movably arranged in the first positioning assembly and has a third position and a fourth position. The first end of the linkage member is provided with a first oblique groove, and the second limiting member is slidably arranged in the first oblique groove at one end away from the second limiting groove; when the linkage member moves to the third position, the second limiting member is inserted into the second limiting groove; when the linkage member moves to the fourth position, the second limiting member withdraws from the second limiting groove. In one embodiment, the linkage mechanism further includes a pressing member, which is movably disposed in the first positioning assembly and has a fifth position and a sixth position. The pressing member is provided with a second inclined groove, and the second end of the linkage member is slidably disposed in the second inclined groove. When the pressing member is in the fifth position, the linkage member is located in the third position; when the pressing member is in the sixth position, the linkage member is located in the fourth position. In one embodiment, an extending direction of the first inclined slot is staggered with an extending direction of the second inclined slot. In one embodiment, the linkage mechanism further includes a fourth restoring member, which abuts against the linkage member and is used to provide elastic restoring force for the linkage member to drive the linkage member to remain in the third position. In one embodiment, when the first positioning assembly is used to connect with the second carrier body, the pressing member is in the fifth position, and the linking member is in the third position. In one embodiment, the positioning assembly further includes a rotational movement mechanism, and the first positioning assembly is slidingly connected to the second positioning assembly via the rotational movement mechanism, and the first positioning assembly simultaneously moves and turns relative to the sliding of the second positioning assembly. In one embodiment, the rotational movement mechanism includes a first track, a second track, a first sliding member and a second sliding member, the first track extends along the first direction, the second track is arranged to cross the first track, the first sliding member and the second sliding member are arranged at intervals in the first positioning assembly, the first sliding member is used to slide in the second track, and the second sliding member is used to slide in the first track. In one embodiment, the intersection of the first track and the second track forms an intersection point, and the distance between the intersection point and the end of the first track or the end of the second track is greater than or equal to the distance between the first sliding member and the second sliding member. In one embodiment, when the first sliding member is located at the intersection, the second sliding member is located in the first track, and the first positioning component is facing or facing away from the first direction relative to the second positioning component; when the second sliding member is located at the intersection, the first sliding member is located in the second track, and the first positioning component is set toward or facing away from the second direction relative to the second positioning component, and the second direction intersects with the first direction. In one embodiment, the second positioning assembly includes a second shell, the second shell has a second mounting cavity, and the second mounting cavity connects the first track and the second track; the rotational movement mechanism also includes a first slider and a second slider, the first slider is located in the second mounting cavity and connected to the first sliding member; the second slider is located in the second mounting cavity and connected to the second sliding member. In one embodiment, the positioning assembly further includes a first locking mechanism, which is disposed between the first positioning assembly and the second positioning assembly. The first locking mechanism has a first locking state and a first releasing state. When the first locking mechanism is in the first locking state, the first positioning assembly is restricted from rotating relative to the second positioning assembly. When the first locking mechanism is in the first releasing state, the first positioning assembly is allowed to rotate relative to the second positioning assembly. In one embodiment, the first locking mechanism includes: a locking assembly, which is movably disposed on one of the second positioning assembly and the first positioning assembly; and a locking recess, which is disposed on the other of the second positioning assembly and the first positioning assembly; wherein, when the locking assembly is inserted into the locking recess, the first positioning assembly is locked and engaged with the second positioning assembly to limit the rotation of the first positioning assembly relative to the second positioning assembly; when the locking assembly is withdrawn from the locking recess, the first positioning assembly can rotate relative to the second positioning assembly. In one embodiment, the locking assembly includes a first locking portion, which can be movably arranged in one of the second positioning assembly and the first positioning assembly along the first direction; when the first positioning assembly is rotated relative to the second positioning assembly to one of the first direction and the back of the first direction, the first locking portion can be locked and engaged with the locking recess. In one embodiment, the positioning assembly further includes a first lock releasing mechanism, which is operably connected to the first lock portion and is used to drive the first lock portion to withdraw from the locking recess. In one embodiment, the first locking portion is movably arranged on the second positioning assembly, the locking recess is arranged on the first positioning assembly, and the first unlocking mechanism includes: a first driving member, pivotally connected to the second positioning assembly and pivotally connected to the first locking portion; a first operating member, operably arranged on the second positioning assembly; and a first traction assembly, respectively connected to the first operating member and the first driving member; wherein, when the first operating member is operated, the first operating member drives the first driving member to pivot through the first traction assembly, so that the first driving member can drive the first locking portion to withdraw from the locking recess. In one embodiment, the locking assembly further includes a second locking portion, which is movably disposed on one of the second positioning assembly and the first positioning assembly, and the second locking portion and the first locking portion are disposed opposite to each other along the first direction; when the first positioning assembly is rotated relative to the second positioning assembly to the other of the first direction and the back direction, the second locking portion can be locked with the locking recess. In one embodiment, the first positioning assembly further includes a second driving member and a second transmission assembly, and the second transmission assembly is configured to drive the second driving member to move so that the second driving member drives the second locking portion to withdraw from the locking recess. In one embodiment, the locking recess is provided in the first positioning assembly, the second locking portion is provided in the second positioning assembly, and the second driving member can push the second locking portion to withdraw from the locking recess when driven by the second transmission assembly. In one embodiment, the second transmission assembly includes: a transmission member, which is movably arranged in the first positioning assembly and is configured to be driven and connected to the first transmission assembly provided on the first carrier body; a third driving member, which is pivotally connected to the first positioning assembly and one end of the third driving member is pivotally connected to the second driving member; and a third traction assembly, which is respectively connected to the other ends of the transmission member and the third driving member; when the transmission member is driven to move by the first transmission assembly, the transmission member drives the third driving member to pivot through the third traction assembly, so that the second driving member moves to be able to push the second locking portion to exit the locking recess. In one embodiment, the second positioning assembly includes a second shell, the upper surface of the second shell is provided with a protrusion, the protrusion forms a limiting protrusion, and a groove structure is formed between the limiting protrusion and the upper surface of the second shell. The first positioning assembly includes a first shell, and when the first positioning assembly is facing the first direction or facing away from the first direction relative to the second positioning assembly, a portion of the edge of the first shell is inserted into the groove structure. In one embodiment, the second shell includes a second top cover and a second bottom cover connected to each other, the upper surface of the second top cover is provided with the convex body, the convex body is formed with the limiting protrusion, and the groove structure is formed between the limiting protrusion and the upper surface of the second top cover. In one embodiment, the second positioning assembly includes a frame and at least one first support mechanism, the first support mechanism includes a first support member and a second support member, the first support member is fixed to the frame, and the second support member is supported by the first support member. When the first positioning assembly is facing the first direction or facing away from the first direction relative to the second positioning assembly, at least a portion of the second support member is located below the first positioning assembly. In one embodiment, the second support member includes two connecting pieces arranged opposite to each other and a connecting piece connected between the two connecting pieces. The two connecting pieces are supported on the first support member, and the connecting piece is located below the limiting protrusion. In one embodiment, the connecting piece includes a connecting body and a supporting protrusion protruding from the connecting body, and a snap-fit ​​groove is formed between the supporting protrusion and the connecting piece. The snap-fit ​​groove is located in the groove structure and is used to accommodate a portion of the edge of the first shell. In one embodiment, the second positioning assembly includes two first support structures arranged opposite to each other along the first direction, and when the first positioning assembly is facing the first direction or facing away from the first direction relative to the second positioning assembly, the second support member provides support force for the first positioning assembly. In one embodiment, the first positioning assembly further includes a second supporting mechanism, the second supporting mechanism includes a first sliding member and a second sliding member, the first positioning assembly includes a first shell, the second positioning assembly includes a second shell, and the first sliding member and the second sliding member are respectively connected to the first shell and the second shell. In one embodiment, the second positioning assembly further includes a third support mechanism and a second shell, the second shell includes a second top cover and a second bottom cover connected to each other, the third support mechanism includes a plurality of support columns, each of the support columns includes a bottom column provided on the second bottom cover and a top column provided on the second top cover, and the bottom column is connected to the top column. The present application also provides a positioning assembly for installing one of a first carrier body and a second carrier body to a car seat, comprising: a second positioning assembly, which is detachably mounted on the car seat; a first positioning assembly, which is rotatably disposed on the second positioning assembly, and the first positioning assembly is used to be detachably connected to one of the first carrier body and the second carrier body; a first limiting mechanism, which is disposed between the first positioning assembly and the second positioning assembly, and when the first positioning assembly is connected to the first carrier body, the first limiting mechanism selectively allows or limits the first carrier body to be detached from the first positioning assembly; and a second limiting mechanism, which is disposed between the first positioning assembly and the second positioning assembly, and when the first positioning assembly is connected to the second carrier body, the second limiting mechanism is used to selectively limit the angular range of rotation of the first positioning assembly relative to the second positioning assembly. In one embodiment, when the first positioning assembly is connected to the first carrier body and the first positioning assembly is rotated relative to the second positioning assembly to face a first direction, the first limiting mechanism is used to limit the first carrier body from separating from the first positioning assembly. In one embodiment, the first limiting mechanism includes: a first limiting groove, which is provided on a side of the second positioning component facing the first positioning component; and a first limiting member, which is movably provided on the first positioning component and can be inserted into or withdrawn from the first limiting groove; wherein, when the first positioning component is used to connect the first carrier body and is rotated relative to the second positioning component to face the first direction, the first limiting member is inserted into the first limiting groove to limit the first carrier body from separating from the first positioning component. In one embodiment, the first positioning assembly includes a first connecting mechanism for detachably connecting the first carrier body and having a locked state and an unlocked state. When the first connecting mechanism is in the locked state, the first carrier body is restricted from detaching from the first connecting mechanism; when the first connecting mechanism is in the unlocked state, the first carrier body is allowed to detach from the first connecting mechanism; the positioning assembly also has a locking and retaining mechanism, which is movably arranged in the first positioning assembly and is used to maintain the first connecting mechanism in the locked state; when the first limiting member retracts from the first limiting groove, the first limiting member is located in the moving path of the locking and retaining mechanism to limit the movement of the locking and retaining mechanism; when the first limiting member is inserted into the first limiting groove, the first limiting member deviates from the moving path of the locking and retaining mechanism to allow the locking and retaining mechanism to move. In one embodiment, the second limiting mechanism includes: a second limiting groove, which is provided in one of the second positioning component and the first positioning component; and a second limiting member, which is movably provided in the other of the second positioning component and the first positioning component and can be inserted into or withdrawn from the second limiting groove; wherein, when the first positioning component is used to connect the second carrier body, the second limiting member is inserted into the second limiting groove, and the first positioning component is restricted from rotating relative to the second positioning component to the first direction. In one embodiment, the positioning assembly further includes a rotational movement mechanism, and the first positioning assembly is slidingly connected to the second positioning assembly via the rotational movement mechanism, and the first positioning assembly simultaneously moves and turns relative to the sliding of the second positioning assembly. In one embodiment, the rotational movement mechanism includes a first track, a second track, a first sliding member and a second sliding member, the extension direction of the second track is arranged to cross the extension direction of the first track, the first sliding member and the second sliding member are arranged at intervals in the first positioning assembly, the first sliding member is used to slide in the second track, and the second sliding member is used to slide in the first track. In one embodiment, the intersection of the first track and the second track forms an intersection point, and the distance between the intersection point and the end of the first track or the end of the second track is greater than or equal to the distance between the first sliding member and the second sliding member. The present application also provides a carrier, comprising: the positioning assembly as described above; and a carrier body, detachably connected to the first positioning assembly of the positioning assembly, the carrier body being a first carrier body or a second carrier body. In one embodiment, it includes a positioning assembly as described above, wherein the first transmission assembly includes: a push member, movably arranged on the first carrier body and used to push the transmission member; and a second traction assembly, respectively connected to the push member and the second operating member; when the second operating member is operated, the second operating member drives the push member to push the transmission member through the second traction assembly. The present application also includes a positioning assembly, including: a first positioning assembly, having a rotation axis, the first positioning assembly is used to detachably connect a carrier body, the carrier body being a first carrier body or a second carrier body; a second positioning assembly; a rotation movement mechanism, the rotation movement mechanism including a track and a sliding member sliding in the track, the first positioning assembly is simultaneously displaced and rotated relative to the second positioning assembly through the rotation movement mechanism, the rotation axis is displaced along a straight line track perpendicular to the track with the displacement and rotation of the first positioning assembly, the track having a first slot section and a second slot section located on both sides of the intersection of the straight line track and the track; wherein, when the first positioning assembly is used to connect the first carrier body and the sliding member is located in the second slot section, the first positioning assembly restricts the first carrier body from disengaging from the first positioning assembly; when the first positioning assembly is used to connect the second carrier body, the sliding member is restricted from moving to the second slot section. In one embodiment, the sliding member is disposed on the first positioning component and deviates from the rotation axis, and the track is disposed on the second positioning component. In one embodiment, the first slot section is located in a first direction of the intersection, and the second slot section is located in a direction of the intersection opposite to the first direction. When the sliding member is located in the second slot section, the first positioning component is oriented toward the first direction relative to the second positioning component. The present application also provides a positioning assembly for installing a first carrier body or a second carrier body to a car seat, comprising: a third positioning assembly, detachably mounted on the car seat; a second positioning assembly, rotatably disposed on the third positioning assembly; a first positioning assembly, movably disposed on the second positioning assembly and having an extended state and a folded state, and the first positioning assembly is used to be detachably connected to the first carrier body or the second carrier body; and an extension mechanism, connected between the first positioning assembly and the second positioning assembly, for guiding the first positioning assembly to switch between the extended state and the folded state. In one embodiment, the extension mechanism includes a first main link, a second main link and a first auxiliary link, one of the first main link and the second main link is connected to the first positioning assembly, and the other is connected to the second positioning assembly, and the two ends of the first auxiliary link are respectively pivotally connected to the first main link and the second main link so that the first main link and the second main link can move closer to or away from each other; when the first main link and the second main link move closer to each other, the first positioning assembly is in the retracted state, and when the first main link and the second main link move away from each other, the first positioning assembly is in the extended state. In one embodiment, one end of the first main connecting rod and one end of the second main connecting rod are respectively provided with gears, the two gears are meshed with each other, and the two ends of the first auxiliary rod are respectively pivotally connected to the wheel centers of the two gears. In one embodiment, the extension mechanism further includes a first reinforcing rod and a third auxiliary rod, the first reinforcing rod is pivotally connected to the third auxiliary rod, and the end of the first reinforcing rod away from the third auxiliary rod is pivotally connected to the first auxiliary rod, and the end of the third auxiliary rod away from the first reinforcing rod is pivotally connected to the first main connecting rod, so that the first main connecting rod, the first auxiliary rod, the first reinforcing rod and the third auxiliary rod form a four-bar structure, and the third auxiliary rod is connected to the second positioning assembly. In one embodiment, the extending mechanism further includes a second auxiliary rod, both ends of which are pivotally connected to the wheel centers of the two gears, and the second auxiliary rod and the first auxiliary rod are respectively located on both sides of the gear. In one embodiment, the extension mechanism further includes a second reinforcing rod and a fourth auxiliary rod, the second reinforcing rod is pivotally connected to the fourth auxiliary rod, and the end of the second reinforcing rod away from the fourth auxiliary rod is connected to the second auxiliary rod, and the end of the fourth auxiliary rod away from the second reinforcing rod is pivotally connected to the second main connecting rod, so that the second main connecting rod, the second auxiliary rod, the second reinforcing rod and the fourth auxiliary rod form a four-bar structure, and the fourth auxiliary rod is connected to the first positioning assembly. In one embodiment, a second locking mechanism is further included, which is arranged between the first positioning component and the second positioning component. The second locking mechanism has a second locking state and a second releasing state. When the second locking mechanism is in the second locking state, the first positioning component is restricted from moving relative to the second positioning component. When the second locking mechanism is in the second releasing state, the first positioning component is allowed to move relative to the second positioning component. In one embodiment, the second locking mechanism includes a second locking member pivotally connected to the first positioning assembly, the second locking member has an operating end and a locking end, the second positioning assembly is provided with a locking mating portion, the second locking member can pivot between a locking position and an unlocking position, when the second locking member is in the locking position, the locking end can be locked and mated with the locking mating portion, when the second locking member is in the unlocking position, the locking end can be disengaged from the locking mating portion; the operating end can be operated to pivot the second locking member from the locking position to the unlocking position. To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below. Figures 1 to 5 schematically illustrate perspective views of a carrier 1000 according to some embodiments of the present invention. The carrier 1000 may include, for example, a first carrier body 500, a second carrier body 600, and a positioning assembly 100 according to some embodiments of the present invention. The first carrier body 500, the second carrier body 600, and the positioning assembly 100 will be described below together with the carrier 1000. Referring to Figures 1 to 3 , in some embodiments, the first carrier body 500 may be, for example, a child safety seat primarily designed to accommodate older children. Referring to Figures 4 to 6 , in some embodiments, the second carrier body 600 may be, for example, an infant safety carrier primarily designed to accommodate infants aged 0 to 15 months (approximately 10 kilograms). For safety reasons, when placed on a vehicle seat, the infant safety carrier is constrained to face the front of the vehicle, effectively facing forward in the vehicle's normal direction of travel. Figures 7 to 10 schematically show three-dimensional views of the positioning assembly 100 in different states in the first embodiment of the present invention. It should be noted that when the vehicle 1000 as a whole is a child safety seat, the positioning assembly 100 can be regarded as a vehicle base. Specifically, the positioning assembly 100 includes a first positioning assembly 110 and a second positioning assembly 120, and the first positioning assembly 110 can be rotatably arranged on the second positioning assembly 120. The second positioning assembly 120 is used for detachable connection with the car seat. Specifically, the second positioning assembly 120 is provided with a seat connection mechanism 125 (such as an ISOFIX connector) and a support leg 126. The seat connection mechanism 125 is mainly used to fix the second positioning assembly 120 to the car seat, and the support leg 126 is used to abut against the floor inside the vehicle. The first positioning assembly 110 can be detachably connected to one of the first carrier body 500 and the second carrier body 600. This is equivalent to the first positioning assembly 110 being detachably connected to the first carrier body 500 (see Figures 1-3 ), or the first positioning assembly 110 being detachably connected to the second carrier body 600 (see Figures 4 and 5 ). Specifically, when the first carrier body 500 is connected to the first positioning assembly 110, the first positioning assembly 110 can rotate relative to the second positioning assembly 120 toward a first direction F1. When the first positioning assembly 110 rotates relative to the second positioning assembly 120 toward the first direction F1, the first carrier body 500 is restricted from separating from the first positioning assembly 110 (the detailed principle will be described below). In other words, when the first carrier body 500 is connected to the first positioning assembly 110, the first positioning assembly 110 can rotate freely relative to the second positioning assembly 120, specifically in the first direction F1 (as shown in FIG1 ). However, when the first positioning assembly 110 rotates relative to the second positioning assembly 120 in the first direction F1, the first carrier body 500 connected to the first positioning assembly 110 cannot detach from the first positioning assembly 110. When the second carrier body 600 is connected to the first positioning assembly 110, the first positioning assembly 110 is restricted from rotating relative to the second positioning assembly 120 in the first direction F1 (the specific principle will be described below). It should be noted that, with reference to normal vehicle driving, the first direction F1 refers to the direction forward of the vehicle when the positioning assembly 100 is installed on the vehicle seat, which is equivalent to the direction toward the front of the vehicle. It should be noted that, in this article, the orientation of the carrier body 600 is consistent with the direction the infant or child faces after riding on the carrier body 600; the orientation of the first positioning element 110 relative to the second positioning element 120 is also consistent with the direction the infant or child faces after riding on the carrier body 600. 7 to 10 , in one embodiment, the first positioning assembly 110 includes a first housing 111 and a first connecting mechanism 112. The first connecting mechanism 112 is disposed within the first housing 111 and is configured to detachably connect to the first carrier body 500 or the second carrier body 600. The first connecting mechanism 112 has a locked state and an unlocked state. When the first connecting mechanism 112 is in the locked state, the first connecting mechanism 112 is connected to the carrier body. When the first connecting mechanism 112 is in the unlocked state, the first connecting mechanism 112 is detached from the carrier body. Specifically, the bottoms of the first carrier body 500 and the second carrier body 600 are provided with a latching member 610 (see FIG6 ). The latching member 610 may be, for example, a latching rod. Specifically, as shown in FIG11 to FIG13 , the first connecting mechanism 112 includes a latching hook 1121 and a latching slot 1122 provided in the first housing 111 . The latching slot 1122 is used to accommodate the latching member 610 of the first carrier body 500 or the second carrier body 600 . The latching hook 1121 is pivotally connected to the first housing 111 and has a locked position (see FIG12 ) and a released position (see FIG13 ). When in the locked position, the latching hook 1121 at least partially extends into the latching slot 1122 to engage and lock with the latching member 610 (see FIG36 and FIG37 ). In one embodiment, as shown in Figures 12 and 13, the engaging hook 1121 is provided with a receiving groove 11212 adapted to fit within the engaging member 610. The receiving groove 11212 is U-shaped and has a pushing wall 11213 adapted to be pushed by the engaging member 610 to drive the engaging hook 1121 to pivot from the unlocked position to the locked position. The first housing 111 has a first mounting cavity 1111. The groove wall of the engaging groove 1122 is provided with a through hole (not shown in the figures), which connects the first mounting cavity 1111 and the engaging groove 1122. Specifically, as shown in Figures 17 and 18, a support frame 123 is provided within the first mounting cavity 1111, and the engaging hook 1121 is pivotally connected to the support frame 123 via a pivot shaft 124. When the hook 1121 is in the locking position, the hook 1121 at least partially passes through the through hole and extends into the slot 1122 to engage and lock with the engaging member 610. When the hook 1121 is in the unlocking position, the hook 1121 withdraws from the slot 1122 through the through hole. Specifically, in this embodiment, as shown in Figures 6 and 7, the bottom of each of the first carrier body 500 and the second carrier body 600 is provided with two engaging members 610 along the front-to-back direction thereof. The first housing 111 is formed with two rows of engaging slots 1122, wherein each row of engaging slots 1122 includes at least one engaging slot 1122. Specifically, each row of engaging slots 1122 includes two engaging slots 1122. In other words, the first housing 111 is formed with four engaging slots 1122, which are arranged in a rectangular shape. The distance between the two rows of engaging slots 1122 arranged along the front and back of the first positioning assembly 110 is equal to the distance between the two engaging members 610 of the first carrier body 500 or the second carrier body 600. Correspondingly, the first housing 111 is pivotally connected with four engaging hooks 1121, with each engaging slot 1122 corresponding to one engaging hook 1121. 15 to 18 , in one embodiment, the positioning assembly 100 further includes a locking and retaining mechanism 150. The locking and retaining mechanism 150 is movably disposed within the first mounting cavity 1111. When the engaging hook 1121 is driven to the locked position, the locking and retaining mechanism 150 is used to lock the engaging hook 1121 in the locked position. Continuing with Figures 15 to 18 , in one embodiment, the locking and retaining mechanism 150 includes a first locking member 151. The first locking member 151 is movably disposed within the first mounting cavity 1111 and has a first position and a second position. Specifically, when the first positioning assembly 110 is oriented in the first direction F1 or the third direction F3, the movement direction of the first locking member 151 is parallel to the first direction F1 or the third direction F3. More specifically, one of the first locking member 151 and the engaging hook 1121 is provided with a locking groove 1511 (see Figure 13 ), and the other is provided with an engaging portion 11211. In other words, when the first locking member 151 is provided with the locking groove 1511, the engaging hook 1121 is provided with the engaging portion 11211; alternatively, when the engaging hook 1121 is provided with the locking groove 1511, the first locking member 151 is provided with the engaging portion 11211. Specifically, as shown in Figures 12 and 13, in this embodiment, the engaging hook 1121 is provided with an engaging portion 11211, and the first locking member 151 is provided with a locking recess 1511. More specifically, when the first locking member 151 is in the first position, the engaging portion 11211 engages with the locking recess 1511 to lock the engaging hook 1121 in the locked position (see Figure 12). When the first locking member 151 is in the second position, the engaging portion 11211 separates from the locking recess 1511, allowing the engaging hook 1121 to switch between the locked position and the unlocked position (see Figure 13). In one embodiment, as shown in Figures 15, 17, and 19, the locking and retaining mechanism 150 further includes a third restoring member 152 for providing an elastic restoring force to the first locking member 151, thereby maintaining the first locking member 151 in the first position. The third restoring member 152 is, for example, a spring. Thus, when the latching hook 1121 pivots from the unlocked position to the locked position, the third restoring member 152 automatically shifts the first locking member 151 to the first position, allowing the locking groove 1511 of the first locking member 151 to engage with the latching portion 11211 of the latching hook 1121, thereby locking the latching hook 1121 and maintaining the latching hook 1121 in the locked position. This improves the stability and reliability of the first carrier body 500 or the second carrier body 600 when mounted to the first positioning assembly 110. In one embodiment, the first connecting mechanism 112 further includes a second reset member (not shown). The second reset member is used to maintain the locking hook 1121 in the unlocked locked position. The second reset member is, for example, a torsion spring, which is mounted on the pivot shaft 124 and abuts against the locking hook 1121. Thus, when the first locking member 151 moves to the second position, the locking groove 1511 moves away from the engaging portion 11211, allowing the engaging portion 11211 to disengage from the locking groove 1511. The locking hook 1121 can then automatically rotate about the pivot shaft 124 to the unlocked position, thereby facilitating smooth unlocking and preventing the locking hook 1121 from becoming locked. The working principle and process of the first connecting mechanism 112 according to an embodiment of the present application will be described below with reference to Figures 6, 12, 13, 17 and 19. When the first carrier body 500 or the second carrier body 600 is not mounted on the first positioning assembly 110 , the engaging hook 1121 is kept in the unlocked position (see FIG. 13 ) by the second restoring member, and the engaging portion 11211 is withdrawn from the locking groove 1511 . When the first carrier body 500 or the second carrier body 600 needs to be installed on the first positioning assembly 110, that is, when the engaging member 610 needs to be connected to the first connecting mechanism 112, referring to Figures 12, 13, 17, and 18, the user can first place the engaging member 610 into the slot 1122 and abut against the abutting wall 11213 of the receiving slot 11212. Then, the user pushes the abutting wall 11213 of the receiving slot 11212 downward to drive the engaging hook 1121 to rotate about the pivot axis 124 (switching from Figure 13 to Figure 12), for example, rotating it clockwise from the perspective of Figure 13, until the engaging hook 1121 extends into the slot 1122 and blocks the notch of the slot 1122. At the same time, after the locking hook 1121 rotates, the locking portion 11211 is opposite to the locking groove 1511, and the third reset member 152 drives the first locking member 151 to move to the first position, so that the locking groove 1511 is locked outside the locking portion 11211, and finally the locking hook 1121 is maintained in the locked position, achieving a stable connection with the locking member 610. When it is necessary to separate the first carrier body 500 or the second carrier body 600 from the first positioning assembly 110, that is, to disengage the engaging member 610 from the first connecting mechanism 112, the user can move the first locking member 151 from the first position to the second position. During this process, the locking groove 1511 gradually moves away from the engaging portion 11211. During this movement, when the engaging portion 11211 completely withdraws from the locking groove 1511, the engaging hook 1121 automatically rotates about the pivot axis 124 (from FIG. 12 to FIG. 13 ) under the action of the second restoring member, for example, rotating counterclockwise from the perspective of FIG. 12 , so that the engaging hook 1121 withdraws from the engaging slot 1122, thereby opening the notch of the engaging slot 1122. Referring to Figures 14 to 18 , in one embodiment, the positioning assembly 100 further includes a first release member 160 movably disposed on the first positioning assembly 110 to facilitate user manipulation of the first locking member 151. The first release member 160 is drivingly connected to the first locking member 151. The first release member 160 is operable to drive the first locking member 151 from a first position to a second position. Thus, the user can switch the first locking member 151 from the first position to the second position by manipulating the first release member 160. Referring to Figure 18 , in one embodiment, the first release member 160 is provided with a driving slope 161. The first locking member 151 is further provided with a driving portion 1512. The driving portion 1512 is adapted to be pushed against and slide along the driving slope 161, thereby enabling the first locking member 151 to switch between the first position and the second position. Specifically, the first release member 160 moves within the first housing 111 along a fifth direction F5, which can be considered perpendicular to the bottom surface of the first housing 111. Referring to Figures 17 and 18 , the mating relationship between the first release member 160 and the first driving member 310 will be briefly described. Specifically, when the first locking member 151 is in the first position, the driving portion 1512 of the first locking member 151 abuts against the top of the driving slope 161 of the first release member 160. As shown in Figures 34 and 37 , when the first release member 160 is pushed upward in the fifth direction F5, guided by the driving slope 161, the driving portion 1512 gradually moves to the bottom of the driving slope 161, thereby moving the first locking member 151 to the second position, thereby disengaging the engaging portion 11211 from the locking recess 1511. Referring to Figures 15 and 17 , in one embodiment, the first housing 111 includes an indicator mechanism 113. This indicator mechanism 113 indicates whether the engaging hook 1121 is in the locked or released position based on the relative position of the first locking member 151 and the first housing 111. Specifically, as shown in Figure 15 , the first housing 111 includes a first top cover 1115 and a first bottom cover 1116 connected vertically. The first top cover 1115 and the first bottom cover 1116 together form a first mounting cavity 1111. A latching slot 1122 is formed in the first top cover 1115. Specifically, the indicator mechanism 113 includes a swinging member 1131, a color block 1132, and an observation hole 1133. The swinging member 1131 is pivotally connected to the side of the first bottom cover 1116 facing the first mounting cavity 1111, forming a third pivot point Q3. One end of the swinging member 1131 is pivotally connected to the first locking member 151, and the other end of the swinging member 1131 is provided with a color block 1132 (e.g., green). The first top cover 1115 is provided with an observation hole 1133. As will be appreciated from the foregoing, when the first release member 160 is operated (e.g., pushed upward in the fifth direction F5), the first locking member 151 moves from the first position to the second position. At this point, the end of the swinging member 1131 away from the color block 1132 moves along with the first locking member 151, causing the entire swinging member 1131 to pivot, thereby causing the end of the swinging member 1131 provided with the color block 1132 to move. In this way, a user can determine the position of the first locking member 151 by observing whether the color block 1132 is visible in the observation hole 1133, and thereby infer the position of the engaging hook 1121. Specifically, in this embodiment, when the first locking member 151 is in the first position, the color block 1132 is opposite to the viewing hole 1133, and the user can view the color block 1132 through the viewing hole 1133. However, when the first locking member 151 is in the second position, the color block 1132 is misaligned with the viewing hole 1133, and the user cannot view the color block 1132 through the viewing hole 1133. Therefore, when the color block 1132 is visible through the viewing hole 1133, it indicates that the engaging hook 1121 is in the locked position; when the color block 1132 is not visible through the viewing hole 1133, it indicates that the engaging hook 1121 is in the unlocked position. Of course, in other embodiments, when the first locking member 151 is in the first position, the color block 1132 is misaligned with the viewing hole 1133, and the user cannot see the color block 1132 through the viewing hole 1133. However, when the first locking member 151 is in the second position, the color block 1132 is aligned with the viewing hole 1133, and the user can see the color block 1132 through the viewing hole 1133. Alternatively, each swinging member 1131 is provided with two color blocks 1132 of different colors (e.g., red and green), and the two color blocks 1132 correspond to the first and second positions of the first locking member 151, respectively. The user observes the color of the color block 1132 through the viewing hole 1133 to determine whether the engaging hook 1121 is in the locked position or the released position. Referring to Figures 7, 8, 22, and 23, in one embodiment, the positioning assembly 100 further includes a rotational movement mechanism 190. The first positioning assembly 110 can be rotated relative to the second positioning assembly 120 via the rotational movement mechanism 190. Specifically, the example of a child riding in the first carrier body 500 will be used for illustration. When the positioning assembly 100 is mounted on a car seat, the first carrier body 500 is mounted on the first positioning assembly 110, and the child rides in the first carrier body 500, the rotational movement mechanism 190 can cause the first positioning assembly 110 (or the first carrier body 500) to face the first direction F1 (see Figure 7) or face away from the first direction F1 (i.e., the third direction F3) (see Figure 10). Of course, under the action of the rotating movement mechanism 190, the first positioning component 110 (which can also be the first carrier body 500) can also be oriented towards the second direction F2 (see Figure 8) or the fourth direction F4 (see Figure 9), so that it is convenient for the user to place the child into the first carrier body 500 or take the child out of the first carrier body 500. It should be noted that the first direction F1 and the third direction F3 are parallel and opposite to each other. In this embodiment, the third direction F3 can be considered to be toward the rear of the vehicle, that is, equivalent to the rear of the vehicle in the normal driving direction. The second direction F2 and the fourth direction F4 are parallel and opposite to each other, and can be considered to be the left and right directions of the vehicle in normal driving. The second direction F2 is toward the left door of the vehicle, and the fourth direction F4 is toward the right door of the vehicle. To further enhance the user's convenience in placing or retrieving a child when the first carrier body 500 is oriented in the second direction F2 or the fourth direction F4, in one embodiment, the first positioning assembly 110 is slidably connected to the second positioning assembly 120 via a rotational movement mechanism 190. The first positioning assembly 110 simultaneously moves and rotates relative to the sliding motion of the second positioning assembly 120. Thus, for example, when the user switches the first carrier body 500 from being oriented in the first direction F1 to being oriented in the second direction F2, the first carrier body 500 can simultaneously rotate relative to the second positioning assembly 120 to change its orientation and simultaneously be pulled outward relative to the second positioning assembly 120 to be closer to the vehicle door, making it easier to place or retrieve a child. Compared to conventional rotational mechanisms, this rotational movement mechanism 190 allows the first positioning assembly 110 to simultaneously rotate relative to the second positioning assembly 120 and simultaneously move laterally, eliminating the need for the conventional rotational movement and subsequent lateral pullout, thereby enhancing operational convenience. In one embodiment, as shown in Figures 14 and 22-24, the rotational movement mechanism 190 includes a first rail 191, a second rail 192, a first slider 194, and a second slider 195. The first rail 191 extends along a first direction F1, and the second rail 192 intersects the first rail 191. The intersection of the first rail 191 and the second rail 192 forms an intersection 193. Specifically, the second rail 192 is perpendicular to the first rail 191, which means that the second rail 192 extends in the second direction F2. More specifically, the first track 191 and the second track 192 are each divided into two segments by an intersection 193. One segment of the first track 191 (hereinafter referred to as the first segment) can be considered to extend from the intersection 193 in a first direction F1, while the other segment of the first track 191 (hereinafter referred to as the second segment) can be considered to extend from the intersection 193 in a third direction F3. One segment of the second track 192 (hereinafter referred to as the third segment) can be considered to extend from the intersection 193 in a second direction F2, while the other segment of the second track 192 (hereinafter referred to as the fourth segment) can be considered to extend from the intersection 193 in a fourth direction F4. In this embodiment, the four segments are of equal length. A first slider 194 and a second slider 195 are spaced apart from each other in the first positioning assembly 110. The first slider 194 is configured to slide within the second track 192, while the second slider 195 is configured to slide within the first track 191. Referring to Figures 14 and 22 , in one embodiment, the distance R1 between the intersection 193 and the ends of the first track 191 is greater than or equal to the distance R3 between the first slider 194 and the second slider 195, i.e., R1 ≥ R3. The distance R2 between the intersection 193 and the ends of the second track 192 is greater than or equal to the distance R3 between the first slider 194 and the second slider 195, i.e., R2 ≥ R3. Specifically, in this embodiment, R1 = R2 = R3. Specifically, when the first slider 194 is located at the intersection 193 and the second slider 195 is located within the first track 191, the first positioning assembly 110 is positioned toward or away from the first direction F1 relative to the second positioning assembly 120. This means that the first positioning assembly 110 can be positioned toward the first direction F1 relative to the second positioning assembly 120 (see FIG. 7 ), or the first positioning assembly 110 can be positioned toward the third direction F3 relative to the second positioning assembly 120 (see FIG. 10 ). When the second slider 195 is located at the intersection 193 and the first slider 194 is located within the second track 192, the first positioning assembly 110 is positioned toward or away from the second direction F2 relative to the second positioning assembly 120. This means that the first positioning assembly 110 can be positioned toward the second direction F2 relative to the second positioning assembly 120 (see FIG. 8 ), or the first positioning assembly 110 can be positioned toward the fourth direction F4 relative to the second positioning assembly 120 (see FIG. 9 ). In some non-limiting embodiments, the second slider 195 is located closer to the front of the first positioning assembly than the first slider 194. In some non-limiting embodiments, the first positioning assembly 110 is circular, and the first slider 194 is located at the center of the first positioning assembly 110. When the first positioning element 110 is oriented in the first direction F1 or the third direction F3 relative to the second positioning element 120, the intersection 193 overlaps with the center of the first positioning element 110 in a direction perpendicular to the plane of the first track 191 and the second track 192. 14 and 21 to 23 , the principle and process of the simultaneous displacement and rotation of the first positioning assembly 110 by the sliding of the rotational movement mechanism 190 relative to the second positioning assembly 120 will be briefly described. In one embodiment, please refer to Figure 24. When the first positioning assembly 110 is set in the first direction F1 relative to the second positioning assembly 120, the first sliding member 194 is located at the intersection 193, that is, point M, and the second sliding member 195 is located at point N of the first track 191. When the user needs to switch the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented in the first direction F1 to being oriented in the second direction F2, this is equivalent to changing the first positioning assembly 110 from being oriented forward relative to the second positioning assembly 120 to being oriented to the left (switching from FIG. 7 to FIG. 8 ). The user can pull the first positioning assembly 110 to the left, and while doing so, the first positioning assembly 110 tends to rotate counterclockwise around the first sliding member 194. This allows the first sliding member 194 to move from point M to point M' within the second track 192, while simultaneously allowing the second sliding member 195 to move synchronously from point N to point N' within the first track 191. During this process, the first positioning assembly 110 gradually begins to rotate relative to the second positioning assembly 120, and can also move laterally (specifically, along the left direction) relative to the second positioning assembly 120. When the first sliding member 194 moves to point M', the second sliding member 195 is located at point N', i.e., intersection 193. At this point, the position of the first positioning assembly 110 relative to the second positioning assembly 120 is shown in FIG8 . It should be noted that the orientation and position of the first positioning assembly 110 relative to the second positioning assembly 120 from the state shown in FIG7 to the state shown in FIG8 is reversible, i.e., the orientation of the first positioning assembly 110 relative to the second positioning assembly 120 can also be switched from being in the second direction F2 to being in the first direction F1. When the user needs to switch the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented in the first direction F1 to being oriented in the fourth direction F4, this is equivalent to changing the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented forward to being oriented rightward (switching from FIG. 7 to FIG. 9 ). The user can pull the first positioning assembly 110 to the right, and while doing so, the first positioning assembly 110 tends to rotate clockwise around the first slider 194. This causes the first slider 194 to move from point M to point M'' within the second track 192, while simultaneously causing the second slider 195 to move synchronously from point N to point N' within the first track 191. During this process, the first positioning assembly 110 gradually begins to rotate relative to the second positioning assembly 120, while also being able to move laterally (specifically, to the right) relative to the second positioning assembly 120. When the first sliding member 194 moves to M'', the second sliding member 195 is located at point N', i.e., intersection 193. At this time, the position of the first positioning assembly 110 relative to the second positioning assembly 120 is shown in FIG9 . It should be noted that the orientation and position of the first positioning assembly 110 relative to the second positioning assembly 120 from the state shown in FIG7 to the state shown in FIG9 is reversible, that is, the orientation of the first positioning assembly 110 relative to the second positioning assembly 120 can also be switched from facing the fourth direction F4 to facing the first direction F1. Referring to Figures 8 and 10 , the user can switch the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented in the second direction F2 to being oriented in the third direction F3. Alternatively, referring to Figures 9 and 10 , the user can switch the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented in the fourth direction F4 to being oriented in the third direction F3. The following description will focus on switching the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented in the second direction F2 to being oriented in the third direction F3. Specifically, the user can pull the first positioning assembly 110, causing it to rotate counterclockwise around the first slider 194. This causes the second slider 195 to move from point N' to point N'' within the first track 191, while simultaneously causing the first slider 194 to move from point M' to point M within the second track 192. During this process, the first positioning assembly 110 gradually begins to rotate relative to the second positioning assembly 120, and at the same time, the rear end of the first positioning assembly 110 can move in the first direction F1 relative to the second positioning assembly 120. When the second sliding member 195 moves to N'', the first sliding member 194 is located at point M, that is, the intersection 193. At this time, the position of the first positioning assembly 110 relative to the second positioning assembly 120 is shown in Figure 10. It should be noted that the process of the orientation and position of the first positioning assembly 110 relative to the second positioning assembly 120 from the state of Figure 8 to the state of Figure 10 is reversible, that is, the orientation of the first positioning assembly 110 relative to the second positioning assembly 120 can also be switched from facing the third direction F3 to facing the second direction F2. When the user needs to switch the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented in the third direction F3 to being oriented in the fourth direction F4, this is equivalent to changing the first positioning assembly 110 from being oriented rearward to being oriented rightward relative to the second positioning assembly 120 (switching from FIG. 10 to FIG. 9 ). By directly pulling the first positioning assembly 110 and causing it to rotate counterclockwise around the first slider 194, the first slider 194 can be moved from point M to point M'' within the second track 192, causing the second slider 195 to synchronously move from point N'' to point N' within the first track 191. Similarly, when the user needs to switch the first positioning assembly 110 relative to the second positioning assembly 120 from being oriented in the fourth direction F4 to being oriented in the first direction F1, this is equivalent to changing the first positioning assembly 110 from being oriented rightward to being oriented forward relative to the second positioning assembly 120 (switching from FIG. 9 to FIG. 7 ). Directly pull the first positioning assembly 110 and make it rotate counterclockwise around the first sliding member 194. In this way, the second sliding member 195 can move from point N' to point N in the first track 191, so that the first sliding member 194 can synchronously move from point M'' to point M in the second track 192. In this embodiment, the shape of the projection of the first positioning component 110 on the second positioning component 120 is symmetrical about the rotation axis of the first positioning component 110. When the first positioning component 110 rotates relative to the second positioning component 120 to face the first direction F1, the overlapping area and range of the two are the same as the overlapping area and range of the two when the first positioning component 110 rotates relative to the second positioning component 120 to face the third direction F3. In this embodiment, the shape of the projection of the first positioning component 110 on the second positioning component 120 is circular. In other embodiments, the shape of the projection of the first positioning component 110 on the second positioning component 120 can also be other centrally symmetrical shapes that are symmetrical about the rotation axis of the first positioning component 110. Referring to Figures 23 to 28, in one embodiment, the second positioning assembly 120 includes a second housing 121 having a second mounting cavity 1211, which communicates with the first track 191 and the second track 192. Specifically, the second housing 121 includes a second top cover 1212 and a second bottom cover 1213 that are interconnected. The second mounting cavity 1211 is formed between the second top cover 1212 and the second bottom cover 1213. In this embodiment, the second top cover 1212 and the second bottom cover 1213 are arranged one above the other, each having a housing structure, and the second top cover 1212 and the second bottom cover 1213 are combined to form the second mounting cavity 1211. The first track 191 and the second track 192 are both formed in the second top cover 1212. Of course, in some other embodiments not shown, the second bottom cover 1213 may be a shell structure having an open second mounting cavity 1211 formed therein, and the second top cover 1212 may be a flat plate structure and cover the opening of the second mounting cavity 1211. The second top cover 1212 may be connected to the second bottom cover 1213 by screws or other connecting members. Referring to FIG. 28 , in one embodiment, the rotational movement mechanism 190 further includes a first slider 196 and a second slider 197. The first slider 196 is positioned within the second mounting cavity 1211 and connected to the first sliding member 194 (see FIG. 29 and FIG. 30 ). The first slider 196 is stopped by the inner wall of the second mounting cavity 1211, thereby retaining the first sliding member 194 within the second track 192. The second slider 197 is positioned within the second mounting cavity 1211 and connected to the second sliding member 195 (see FIG. 30 ). The second slider 197 is stopped by the inner wall of the second mounting cavity 1211, thereby retaining the second sliding member 195 within the first track 191. This prevents the first positioning assembly 110 from disengaging from the second positioning assembly 120 when sliding relative to the second positioning assembly 120. Specifically, the second mounting cavity 1211 further comprises a first channel 1216 and a second channel 1217. The first channel 1216 communicates with the first rail 191, along which the second slider 197 can slide, and the second slider 195 can slide. The second channel 1217 communicates with the second rail 192, along which the first slider 196 can slide, and the first slider 194 can slide. The length of the first channel 1216 intersects with the length of the second channel 1217. More specifically, in this embodiment, the length of the first channel 1216 (corresponding to the dimension in the first direction F1 or the third direction F3 in this embodiment) perpendicularly intersects with the length of the second channel 1217 (corresponding to the dimension in the second direction F2 or the fourth direction F4 in this embodiment). The width of the first channel 1216 intersects with the width of the second channel 1217. More specifically, in this embodiment, the width of the first channel 1216 (corresponding to the second direction F2 or the fourth direction F4 in this embodiment) intersects perpendicularly with the width of the second channel 1217 (corresponding to the first direction F1 or the third direction F3 in this embodiment). The length of the second slider 197 along the first channel 1216 is greater than the width of the second channel 1217, and the length of the first slider 196 along the second channel 1217 is greater than the width of the first channel 1216. This prevents the first slider 194 from sliding along the second track 192, thereby preventing the first slider 194 from sliding along the first track 191. It also prevents the second slider 195 from sliding along the first track 191, thereby preventing the second slider 195 from sliding along the second track 192. The first channel 1216 and the second channel 1217 are interconnected. In this embodiment, the length of the first channel 1216 is greater than the length of the first track 191, while the length of the second channel 1217 is greater than the length of the second track 192. In this embodiment, two opposing walls (or referred to as first walls) extend from the lower surface of the second top cover 1212 toward the second mounting cavity 1211, forming a first channel 1216 therebetween. Two further opposing walls (or referred to as second walls) extend from the lower surface of the second top cover 1212 toward the second mounting cavity 1211, forming a second channel 1217 therebetween. In some embodiments, the walls forming the first channel 1216 may extend from the second bottom cover 1213, and the walls forming the second channel 1217 may extend from the second bottom cover 1213, without limitation herein. Specifically, as shown in Figures 30, 34, and 37, a groove 1971 is provided on the side of the second slider 197 facing the second top cover 1212, and a sliding wheel 198 is mounted within the groove 1971. A portion of the sliding wheel 198 protrudes from the groove 1971 and slides against the wall of the second top cover 1212 where the first track 191 is located. The provision of the sliding wheel 198 improves the smooth movement of the second slider 195 within the first track 191. More specifically, the second slider 197 has four grooves 1971, each of which is mounted with a sliding wheel 198. Of course, the number of grooves 1971 and sliding wheels 198 on the second track 192 is not limited to four, and can be one, two, three, five, or more. More specifically, in this embodiment, the first slider 196 can be similar to the second slider 197, also having a groove 1971 and a sliding wheel 198. The specific location and number of the grooves 1971 and sliding wheels 198 can be referenced with reference to the grooves 1971 and sliding wheels 198 of the second slider 197. As described above, the first positioning assembly 110 is able to freely rotate relative to the second positioning assembly 120 under the action of the rotational movement mechanism 190. Specifically, the first positioning assembly 110 can rotate relative to the second positioning assembly 120 in any of the first direction F1, the second direction F2, the third direction F3, and the fourth direction F4. Therefore, when the first carrier body 500 (e.g., a child safety seat) is connected to the first positioning assembly 110, the first carrier body 500 can also rotate with the first positioning assembly 110 in any of the first direction F1, the second direction F2, the third direction F3, and the fourth direction F4. However, when a second carrier body 600 (e.g., an infant safety carrier) is connected to the first positioning assembly 110, for the safety of the infant, the second carrier body 600 can be oriented with the first positioning assembly 110 in any of the second, third, and fourth directions F2, F3, and F4, but cannot be rotated with the first positioning assembly 110 in the first direction F1. However, when the first positioning assembly 110 is connected to the first carrier body 500 and oriented in the first direction F1, if a user directly removes the first carrier body 500 from the first positioning assembly 110 and connects the second carrier body 600 to the first positioning assembly 110, the second carrier body 600 will be oriented in the first direction F1, posing a safety hazard. To prevent the user from inadvertently removing the first carrier body 500 oriented in the first direction F1 from the first positioning assembly 110, the positioning assembly 100 of the present application further includes a first limiting mechanism 140. The first limiting mechanism 140 is disposed between the first positioning assembly 110 and the second positioning assembly 120 , and is configured to selectively allow or limit the first carrier body 500 from being separated from the first positioning assembly 110 .Specifically, when the first positioning assembly 110 is rotated relative to the second positioning assembly 120 toward the first direction F1, the first limiting mechanism 140 is used to limit the first carrier body 500 from separating from the first positioning assembly 110. However, when the first positioning assembly 110 is rotated relative to the second positioning assembly 120 toward the second direction F2, the third direction F3, or the fourth direction F4, the first limiting mechanism 140 allows the first carrier body 500 to separate from the first positioning assembly 110. Therefore, when a user needs to remove the first carrier body 500 from the first positioning assembly 110, they must first rotate the first positioning assembly 110 to a direction other than the first direction F1, that is, toward the second direction F2, the third direction F3, or the fourth direction F4. The working principle of the first limiting mechanism 140 is briefly explained below with reference to the drawings. Referring to Figures 15, 16, and 22, in one embodiment, a first limiting mechanism 140 is disposed between the first positioning assembly 110 and the second positioning assembly 120, and is configured to selectively allow or limit the first connecting mechanism 112 from switching between a locked state and an unlocked state. In this embodiment, when the first positioning assembly 110 is connected to the first carrier body 500 and is oriented in the first direction F1, the first limiting mechanism 140 enters the movement path of the locking and retaining mechanism 150, restricting the movement of the locking and retaining mechanism 150 and thereby preventing the first connecting mechanism 112 from switching from the locked state to the unlocked state. Specifically, the first limiting mechanism 140 includes a first limiting groove 141 and a first limiting member 142. The first limiting groove 141 is provided on a side of the second positioning assembly 120 facing the first positioning assembly 110. Specifically, the first limiting groove 141 is provided on the second top cover 1212 of the second shell 121. The first limiting member 142 is movably provided on the first positioning assembly 110 and can be inserted into or withdrawn from the first limiting groove 141. Specifically, as shown in Figures 29 and 30, the first bottom cover 1116 of the first shell 111 is provided with a first limiting hole 1112, the first limiting hole 1112 is connected to the first mounting cavity 1111, the first limiting member 142 is movably provided in the first mounting cavity 1111 and at least part of the first limiting member 142 can extend out of the first mounting cavity 1111 through the first limiting hole 1112 (see Figure 34). When the first stopper 142 extends from the first mounting cavity 1111 through the first stopper hole 1112 and inserts into the first stopper groove 141, the first stopper 142 allows the first connection mechanism 112 to switch to an unlocked state, allowing the first carrier body 500 to be separated from the first positioning assembly 110. When the first stopper 142 withdraws from the first stopper groove 141, the first stopper 142 restricts the first connection mechanism 112 from switching to an unlocked state, restricting the first carrier body 500 from being separated from the first positioning assembly 110. Specifically, when the first positioning assembly 110 rotates relative to the second positioning assembly 120 toward the first direction F1, the first stopper 142 withdraws from the first stopper groove 141. This prevents the first carrier body 500 from being removed from the first positioning assembly 110 when facing the first direction F1. Specifically, the first positioning assembly 110 has a rotational axis, and the first limiting member 142 is positioned offset from the rotational axis. In this embodiment, a line passing through the rotational axis and perpendicular to the first direction F1 is defined as a reference line. When the first positioning assembly 110 is oriented in the first direction F1, the first limiting member 142 and the first limiting groove 141 are offset and located on either side of the reference line. More specifically, in this embodiment, if the first positioning assembly 110 is substantially circular, the rotational axis can be considered the center of the first positioning assembly 110. Specifically, the first limiting groove 141 is a semicircular groove (see FIG. 22 ), the radius of which is the distance between the first limiting member 142 and the center of the first positioning assembly 110. More specifically, the opening of the semicircular groove faces the third direction F3. When the first positioning assembly 110 is rotated relative to the second positioning assembly 120 away from the first direction F1 (i.e., toward the third direction F3), the first limiting member 142 is located at the midpoint of the first limiting groove 141. It should be noted that in this embodiment, the first sliding member 194 is disposed at the rotation axis of the first positioning assembly 110, and the second track 192 is provided for the displacement and sliding of the first sliding member 194. Therefore, the second track 192 in this embodiment also serves as a linear trajectory for the displacement of the rotation axis of the first positioning assembly 110. Of course, in other embodiments, the first positioning assembly 110 may have other symmetrical shapes (e.g., elliptical, rectangular, etc.), and the rotation axis may be at or offset from the geometric center of the first positioning assembly 110; alternatively, the first positioning assembly 110 may have an asymmetrical shape, and the rotation axis may be set according to actual needs. In this embodiment, the radius of the first retaining groove 141 is equal to half the distance between the first sliding member 194 and the second sliding member 195. In other words, the radius of the first retaining groove 141 is equal to one-quarter the radius of the first track 191 or the second track 192. The first retaining member 142 is located at the midpoint between the first sliding member 194 and the second sliding member 195. The center of the first retaining groove 141 is located at the intersection 193 between the first track 191 and the second track 192. The first retaining groove 141 and the second track 192 have two intersection points, located at the midpoint of the third groove section of the second track 192 and the midpoint of the fourth groove section of the second track 192, respectively. The first retaining groove 141 and the second track 192 have one intersection point, located at the midpoint of the first groove section of the first track 191. Of course, in other embodiments, the first retaining groove 141 may have other shapes, such as an elliptical shape, and the first retaining member 142 may be offset from the midpoint between the first sliding member 194 and the second sliding member 195. As described above, the first carrier body 500 is detachably connected to the first housing 111 via the first connecting mechanism 112. Specifically, when the first locking member 151 is in the first position, the latching hook 1121 is in the locked position, preventing the first carrier body 500 from being removed from the first connecting mechanism 112. When the first locking member 151 is in the second position, the latching hook 1121 is in the unlocked position, allowing the first carrier body 500 to be removed from the first connecting mechanism 112. Therefore, the position of the first locking member 151 is correlated with whether the first carrier body 500 can be removed from the first positioning assembly 110. Specifically, when the first locking member 151 is in the first position, the first carrier body 500 cannot be removed from the first positioning assembly 110; when the first locking member 151 is in the second position, the first carrier body 500 can be removed from the first positioning assembly 110. In this embodiment, when the first limiting member 142 withdraws from the first limiting groove 141, the first limiting member 142 is correspondingly located in the moving path of the first locking member 151, which can limit the first locking member 151 from moving from the first position to the second position, thereby limiting the locking hook 1121 from switching from the locked position to the unlocked position, and making the locking hook 1121 remain in the locked position, thereby blocking the notch of the locking groove 1122, and the locking member 610 of the first carrier body 500 cannot be removed from the locking groove 1122, which is equivalent to the first carrier body 500 not being removed from the first positioning assembly 110. When the first limiting member 142 is inserted into the first limiting groove 141, the first limiting member 142 deviates from the moving path of the first locking member 151 accordingly, which allows the first locking member 151 to move so that the engaging hook 1121 switches from the locking position to the releasing position, thereby opening the notch of the engaging slot 1122, and the engaging member 610 of the first carrier body 500 can be removed from the engaging slot 1122 to complete the removal of the first carrier body 500 from the first positioning assembly 110. 18 and 30 , in this embodiment, as described above, when the first carrier body 500 is connected to the first positioning assembly 110 and the first positioning assembly 110 is oriented in the first direction F1, the first limiting member 142 and the first limiting groove 141 are offset and located on either side of the reference line. At this point, the first limiting member 142 abuts against the second top cover 1212 of the second housing 121, and the first limiting member 142 is located in the movement path of the first locking member 151. Consequently, the movement of the first locking member 151 is blocked and maintained in the first position, ultimately preventing the first carrier body 500 from being removed from the first positioning assembly 110. Referring to FIG. 18 and 34 , when the first carrier body 500 is connected to the first positioning member 110 and the first positioning assembly 110 gradually rotates relative to the second positioning assembly 120 from the first direction F1 to the second direction F2 or the fourth direction F4, the first limiting member 142 rotates with the first positioning assembly 110 and gradually becomes aligned with the first limiting groove 141. When the first limiting member 142 is opposite to the first limiting groove 141, the first limiting member 142 can move downward to be inserted into the first limiting groove 141. In this way, the first limiting member 142 can deviate from the moving path of the first locking member 151, thereby allowing the first locking member 151 to move to the second position, so as to realize the removal of the first carrier body 500 from the first positioning assembly 110. It should be noted that when the first positioning component 110 is facing the second direction F2 or the fourth direction F4, the first limiting member 142 is opposite to the end of the first limiting groove 141 and is inserted at the end; when the first positioning component 110 switches from the second direction F2 or the fourth direction F4 to the third direction F3, the first limiting member 142 will move in the first limiting groove 141 which is a semicircular groove to the midpoint of the first limiting groove 141. Referring to Figures 30, 34 and 37, in one embodiment, a sliding slope 1421 is provided at one end of the first limiting member 142 facing the second positioning component 120, and the sliding slope 1421 can push the groove walls at both ends of the first limiting groove 141 to move the first limiting member 142 out of the first limiting groove 141 in a direction away from the second positioning component 120, so that when the first positioning component 110 slides relative to the second positioning component 120, it is automatically inserted into or withdrawn from the first limiting groove 141 according to the direction of the first positioning component 110. Continuing with Figures 30, 34, and 37, in one embodiment, the first limiting mechanism 140 further includes a first return member 143. The first return member 143 is configured to provide an elastic restoring force to the first limiting member 142, thereby driving the first limiting member 142 into the first limiting groove 141. Specifically, as shown in Figures 16 and 18, a support rod 116 and two support plates 115 are disposed within the first mounting cavity 1111. The two support plates 115 are located on opposite sides of the first limiting hole 1112. The first limiting member 142 is provided with a strip-shaped hole 1422, through which the support rod 116 passes and is connected to the two support plates 115. More specifically, the first limiting member 142 has a cavity defined therein. The first return member 143, such as a spring, is housed within the cavity, with its ends abutting the support rod 116 and the bottom wall of the cavity of the first limiting member 142, respectively (see Figures 30, 34, and 37). When the first limiting member 142 withdraws from the first limiting groove 141, the first limiting member 142 abuts against the surface of the second positioning assembly 120, causing the first restoring member 143 to be squeezed and in a compressed state; when the first limiting member 142 moves above the first limiting groove 141, the first restoring member 143 resets to drive the first limiting member 142 to move downward and insert into the first limiting groove 141. As described above, the first positioning assembly 110 is able to freely rotate relative to the second positioning assembly 120 under the action of the rotational movement mechanism 190. Therefore, the carrier body connected to the first positioning assembly 110 can also freely rotate with the first positioning assembly 110. However, for safety reasons, some carrier bodies, such as the second carrier body 600 (e.g., an infant safety carrier), cannot be positioned forward (i.e., facing the first direction F1). In other words, when the first positioning assembly 110 is connected to the second carrier body 600, the first positioning assembly 110 is restricted from facing the first direction F1, which is equivalent to being restricted to facing the front of the vehicle. In this embodiment, the positioning assembly 100 further includes a second limiting mechanism 170 and a linkage mechanism 180 to restrict the first positioning assembly 110 from rotating in the first direction F1 when the second carrier body 600 is connected to the first positioning assembly 110. The second limiting mechanism 170 is used to limit the angular range of rotation of the first positioning assembly 110 relative to the second positioning assembly 120, while the linkage mechanism 180 ensures that the second limiting mechanism 170 only functions when the second carrier body 600 is connected to the first positioning assembly 110. The operating principles of the second limiting mechanism 170 and the linkage mechanism 180 are described in detail below. The second limiting mechanism 170 has a first state and a second state. When the second limiting mechanism 170 is in the first state, it limits the first positioning component 110 from rotating relative to the second positioning component 120 to the first direction F1. When the second limiting mechanism 170 is in the second state, it allows the first positioning component 110 to rotate relative to the second positioning component 120 to the first direction F1. Specifically, the second limiting mechanism 170 is arranged between the first positioning assembly 110 and the second positioning assembly 120. The second limiting mechanism 170 is used to limit the angular range of rotation of the first positioning assembly 110 relative to the second positioning assembly 120 when the second carrier body 600 is connected to the first positioning assembly 110, so as to prevent the second carrier body 600 from rotating toward the first direction F1. Referring to Figures 15, 16, and 22, in one embodiment, the second limiting mechanism 170 includes a second limiting groove 171 and a second limiting member 172. The second limiting groove 171 can be provided in one of the second positioning assembly 120 and the first positioning assembly 110, while the second limiting member 172 is movably provided in the other of the two, and the second limiting member 172 can be inserted into and removed from the second limiting groove 171. For example, when the second limiting groove 171 is provided in the first positioning assembly 110, the second limiting member 172 is movably provided in the second positioning assembly 120. Alternatively, in this embodiment, the second limiting groove 171 is provided in the second positioning assembly 120, and the first limiting member 172 is movably provided in the first positioning assembly 110. More specifically, in this embodiment, the second limiting groove 171 is provided on the side of the second positioning assembly 120 facing the first positioning assembly 110. Specifically, as shown in Figures 29 and 30, the first bottom cover 1116 of the first housing 111 is provided with a second limiting hole 1113, which is in communication with the first mounting cavity 1111. The second limiting member 172 is movably disposed within the first mounting cavity 1111, and at least a portion of the second limiting member 172 can extend out of the first mounting cavity 1111 through the second limiting hole 1113 (see Figure 37). When the second limiting member 172 is inserted into the second limiting groove 171, the first positioning assembly 110 is restricted from rotating relative to the second positioning assembly 120 in the first direction F1 (this can be considered as the second limiting mechanism 170 being in the first state). When the second limiting member 172 is removed from the second limiting groove 171, the first positioning assembly 110 is allowed to rotate relative to the second positioning assembly 120 in the first direction F1 (this can be considered as the second limiting mechanism 170 being in the second state). Specifically, when the first carrier body 500 is connected to the first positioning assembly 110, the second limiting member 172 retracts from the second limiting groove 171 and remains in the retracted state, thereby enabling the first positioning assembly 110 to rotate toward the first direction F1. In this embodiment, the first positioning assembly 110 can rotate 360° relative to the second positioning assembly 120. When the second carrier body 600 is connected to the first positioning assembly 110, the second limiting member 172 is inserted into the second limiting groove 171. The length of the second limiting groove 171 limits the range of movement of the second limiting member 172, thereby preventing the first positioning assembly 110 from rotating toward the first direction F1. In one embodiment, the second stopper 172, like the first stopper 142, is offset from the rotational axis of the first positioning assembly 110. When the first positioning assembly 110 is oriented in the first direction F1, the second stopper 172 and the second stopper groove 171 are offset and located on opposite sides of the reference line. Specifically, as shown in Figures 15 to 18, the second stopper groove 171 is a semicircular groove (see Figure 22), with a radius equal to the distance between the second stopper 172 and the center of the first positioning assembly 110. More specifically, the opening of the semicircular groove faces the third direction F3. When the first positioning assembly 110 is rotated relative to the second positioning assembly 120 away from the first direction F1, the second stopper 172 is located at the midpoint of the second stopper groove 171. When the first positioning assembly 110 is rotated relative to the second positioning assembly 120 in the second direction F2 and the fourth direction F4, respectively, the second stopper 172 is located at the two ends of the second stopper groove 171 in Figure 22. In this embodiment, the radius of the second retaining groove 171 is equal to half the distance between the first sliding member 194 and the second sliding member 195. In other words, the radius of the second retaining groove 171 is equal to one-quarter the radius of the first or second track. The second retaining member 172 is located at the midpoint between the first sliding member 194 and the second sliding member 195. The center of the second retaining groove 171 is located at the intersection 193 between the first and second tracks. The second retaining groove 171 and the second track 192 have two intersection points, located at the midpoint of the third and fourth groove segments of the second track 192, respectively. The second retaining groove 171 and the second track 192 have one intersection point, located at the midpoint of the first groove segment of the first track 191. Of course, in other embodiments, the first retaining groove 171 may have other shapes, such as an elliptical shape, and the second retaining member 172 may be offset from the midpoint between the first and second sliding members 194 and 195. Referring to Figures 15 to 19 , in one embodiment, the linkage mechanism 180 is disposed within the first mounting cavity 1111 and is configured to be drivingly coupled to the second retaining member 172. The linkage mechanism 180 can drive the second retaining member 172 to retract from or retract into the second retaining groove 171. Thus, the state of the second retaining member 172 can be controlled by the linkage mechanism 180. Continuing with Figures 15 to 19 , in one embodiment, the linkage mechanism 180 includes a linkage member 181 movably disposed within the first mounting cavity 1111 and having a third position and a fourth position. Specifically, the linkage member 181 moves parallel to the first direction F1 or the third direction F3. Specifically, a first inclined slot 1811 (see Figure 16 ) is defined at the first end of the linkage member 181. The end of the second retaining member 172 facing away from the second retaining groove 171 slides within the first inclined slot 1811, while the end of the second retaining member 172 proximal to the second retaining groove 171 is inserted into the second retaining groove 171 through the second retaining hole 1113. More specifically, when the linkage member 181 moves to the third position, the second retaining member 172 is inserted into the second retaining groove 171. When the linkage member 181 moves to the fourth position, the second retaining member 172 retracts from the second retaining groove 171. In other words, when the linkage 181 switches between the third position and the fourth position, the first inclined slot 1811 drives the second limiting member 172 to be inserted into or withdrawn from the second limiting groove 171. In this way, whether the second limiting member 172 is inserted into the second limiting groove 171 can be controlled by changing the position of the linkage 181. It should be noted that the second stopper 172 can be slidably disposed in the first inclined slot 1811 via a connecting member such as a pin. Alternatively, as shown in FIG16 , a guide protrusion 1721 is provided on the sidewall of the second stopper 172 , and the guide protrusion 1721 is inserted into the first inclined slot 1811 . Referring again to Figures 15 to 19 , in one embodiment, the linkage mechanism 180 further includes a pressing member 182, which is movably disposed within the first mounting cavity 1111 and has a fifth position and a sixth position. Specifically, a movable stopper 114 (see Figures 17 and 19 ) is provided on the side of the first bottom cover 1116 facing the first mounting cavity 1111. The movable stopper 114 has a movable cavity 1141. A first opening 1142 is provided on the side of the movable stopper 114 facing the second stopper 172, and the first opening 1142 communicates with the movable cavity 1141. The pressing member 182 is accommodated within the movable cavity 1141 and is movable up and down within the movable cavity 1141 along a fifth direction F5. The pressing member 182 defines a second slanted slot 1821 (see Figures 20 and 21 ). The second end of the linkage member 181 passes through the first opening 1142 and slides within the second slanted slot 1821. The extension direction of the first inclined groove 1811 intersects with the extension direction of the second inclined groove 1821. Specifically, when the pressing member 182 is in the fifth position, the connecting member 181 is in the third position; when the pressing member 182 is in the sixth position, the connecting member 181 is in the fourth position. In this way, the position of the connecting member 181 can be changed by changing the position of the pressing member 182, thereby controlling whether the second limiting member 172 can be inserted into the second limiting groove 171. In this embodiment, as shown in Figure 21, a portion of the pressing member 182 is a quadrilateral hollow cylindrical structure, the second inclined groove 1821 is provided on the side wall of the hollow cylindrical structure, and the second end of the connecting member 181 enters the hollow cylindrical structure; as shown in Figure 19, the other portion of the pressing member 182 is a circular convex column structure. In this embodiment, the distance between the bottom end of the first inclined groove 1811 and the bottom end of the second inclined groove 1821 is smaller than the distance between the top end of the first inclined groove 1811 and the top end of the second inclined groove 1821. When the pressing member 182 is in the fifth position within the movable cavity 1141, the second end of the linkage member 181 is located at the bottom end of the second inclined groove 1821, and the guide protrusion 1721 of the second limiting member 172 is located at the bottom end of the first inclined groove 1811. When the pressing member 182 is in the sixth position within the movable cavity 1141, the second end of the linkage member 181 is located at the top end of the second inclined groove 1821, and the guide protrusion 1721 of the second limiting member 172 is located at the top end of the first inclined groove 1811. Specifically, in one embodiment, as shown in FIG. 20 , the linkage mechanism 180 further includes a fourth restoring member 183 , which abuts against the linkage member 181 and is used to provide elastic restoring force for the linkage member 181 to drive the linkage member 181 to remain in the third position. The following will briefly explain, with reference to the accompanying diagrams, the principle that when the first positioning assembly 110 is connected to the first carrier body 500, the first positioning assembly 110 can rotate relative to the second positioning assembly 120 toward the first direction F1, while when the first positioning assembly 110 is connected to the second carrier body 600, the first positioning assembly 110 is restricted from rotating relative to the second positioning assembly 120 toward the first direction F1. In other words, the working principle of the second limiting mechanism 170 can be briefly explained with reference to the accompanying diagrams; or, in layman's terms, the principle that when the second limiting member 172 is inserted into the second limiting groove 171, the first positioning assembly 110 is restricted from rotating relative to the second positioning assembly 120 toward the first direction F1, and when the second limiting member 172 is removed from the second limiting groove 171, the first positioning assembly 110 is allowed to rotate relative to the second positioning assembly 120 toward the first direction F1. Referring to Figures 15 and 31 , in one embodiment, the first housing 111 is provided with a push hole 1114 communicating with the first mounting cavity 1111. Specifically, the first top cover 1115 is provided with the push hole 1114, and the top of the movable limit seat 114 is provided with a second opening 1143 (see Figures 19 and 31 ), with the second opening 1143 and the push hole 1114 being arranged opposite each other along the fifth direction F5. A push member 520 is provided on the side of the first carrier body 500 facing the first positioning assembly 110 (see Figure 31 ). When the first carrier body 500 is connected to the first connecting mechanism 112, i.e., when the first carrier body 500 is mounted to the first positioning assembly 110, the push member 520 passes through the push hole 1114 and abuts against the pressing member 182, causing the pressing member 182 to be in the sixth position. As described above, when the pressing member 182 is in the sixth position, the linkage member 181 is in the fourth position, and the second limiting member 172 is lifted to retreat from the second limiting groove 171. Specifically, when the second limiting member 172 is lifted, it does not extend out of the second limiting hole 1113. When the first carrier body 500 remains installed on the first positioning assembly 110, the pushing action of the pushing member 520 can keep the pressing member 182 in the sixth position, so that the second limiting member 172 can always remain in the lifted state (see Figures 31 and 33), and the second limiting member 172 retreats from the second limiting groove 171. Therefore, when the first positioning assembly 110 slides relative to the second positioning assembly 120 through the rotation and movement mechanism 190, the second limiting member 172 will not interfere with the second positioning assembly 120, and the first positioning assembly 110 can slide freely relative to the second positioning assembly 120, for example, the first positioning assembly 110 can be oriented in the first direction F1 (see Figures 1 and 29); or the first positioning assembly 110 can be oriented in the third direction F3 (see Figures 2 and 32). However, when the first carrier body 500 is removed from the first positioning assembly 110, the pressing member 182 is no longer subjected to the resisting force from the pushing member 520. Under the elastic action of the fourth restoring member 183, the connecting member 181 can move and remain in the third position, and under the driving action of the first inclined groove 1811 and the second inclined groove 1821, the pressing member 182 is restored to the fifth position, and the second limiting member 172 moves downward to extend out of the second limiting hole 1113 and insert into the second limiting groove 171. Referring to Figures 35 and 36 , since the push member 520 is not provided on the side of the second carrier body 600 facing the first positioning assembly 110, when the second carrier body 600 is mounted to the first positioning assembly 110, the top of the pressing member 182 remains unaffected by external thrust and can remain in the fifth position. Simultaneously, the linkage member 181 remains in the third position, and the second limiting member 172 remains extended out of the second limiting hole 1113 and inserted into the second limiting groove 171. Specifically, in this embodiment, the second limiting groove 171 is a semicircular groove that communicates with the first rail 191 and the second rail 192, with the notch of the semicircular groove facing the third direction F3. Therefore, after being inserted into the second limiting groove 171, the second limiting member 172 can only move within the extended range of the semicircular groove. When the first positioning assembly 110 is oriented toward the third direction F3, the second limiting member 172 is located at the midpoint of the semicircular groove; when the first positioning assembly 110 is oriented toward the second direction F2 or the fourth direction F4, the second limiting member 172 is located at the end of the semicircular groove and abuts against the groove wall at the end, and the end of the second limiting groove 171 limits the second limiting member 172 from continuing to rotate, thereby limiting the first positioning assembly 110 from rotating relative to the second positioning assembly 120 to the first direction F1. In one embodiment, the radius of the first limiting groove 141 and the radius of the second limiting groove 171 can be the same or different. When the radius of the first limiting groove 141 is the same as the radius of the second limiting groove 171, the first limiting groove 141 can be regarded as the second limiting groove 171, and correspondingly, the first limiting hole 1112 can be regarded as the second limiting hole 1113. More specifically, as shown in Figures 16 and 30, the second limiting member 172 is roughly a cylindrical structure with two ends open, and the second limiting member 172 is sleeved on the outside of the first limiting member 142. Of course, in other embodiments, when the radius of the first limiting groove 141 is different from the radius of the second limiting groove 171, the first limiting groove 141 and the second limiting groove 171 can be regarded as concentric structures. As described above, in this embodiment, the second limiting member 172 of the second limiting mechanism 170 is inserted into the second limiting groove 171 to prevent the second carrier body 600 from rotating toward the first direction F1. Therefore, the second limiting mechanism 170 can be referred to as an anti-misuse structure. In this embodiment, the fourth restoring member 183 functions as an elastic member. The elastic force of the fourth restoring member 183 constantly maintains the second limiting mechanism 170 in the first state, i.e., the linkage mechanism 180 constantly drives the second limiting member 172 into the second limiting groove 171. The pushing member 520 of the first carrier body 500 overcomes the elastic force of the fourth restoring member 183, placing the second limiting mechanism 170 in the second state. Therefore, when the first positioning assembly 110 is connected to the first carrier body 500 or the second carrier body 600, the user can release the second limiting mechanism 170 from limiting the rotational range of the first positioning assembly 110 or activate the second limiting mechanism 170 to limit the rotational range of the first positioning assembly 110 without manual operation. It should be noted that in other embodiments, the second limiting mechanism 170 can be constantly maintained in the second state by an elastic member. When the first positioning assembly 110 is used to connect to the second carrier body 600, the second limiting mechanism 170 is in the first state by the second carrier body 600 overcoming the elastic force of the elastic member. In other embodiments, the linkage mechanism 180 can be omitted. For example, an elastic member is located within the second limiting member 172 and abuts against the second limiting member 172. The elastic force of the elastic member constantly disengages the second limiting member 172 from the second limiting groove 171. The second carrier body 600 is provided with a pushing structure similar to the pushing member 520. When the second carrier body 600 is connected to the first positioning assembly 110, the pushing structure overcomes the elastic force of the elastic member and pushes the second limiting member 172 to move and insert into the second limiting groove 171, thereby limiting the rotation angle range of the first positioning assembly 110. Alternatively, the positioning assembly 100 may also be provided with an anti-misuse mechanism (not shown in the figure), and the anti-misuse mechanism is provided with an anti-misuse button for manual operation by the user. The anti-misuse button can be operated to move to different positions. When the user manually operates the anti-misuse button to move to one of the positions, it can drive the second limit member 172 to insert into the second limit groove 171. To prevent the first positioning assembly 110 from rotating freely relative to the second positioning assembly 120, in one embodiment, the positioning assembly 100 further includes a first locking mechanism disposed between the first positioning assembly 110 and the second positioning assembly 120. The first locking mechanism has a first locked state and a first unlocked state. When the first locking mechanism is in the first locked state, the first positioning assembly 110 is restricted from rotating relative to the second positioning assembly 120. When the first locking mechanism is in the first unlocked state, the first positioning assembly 110 is allowed to rotate relative to the second positioning assembly 120. In this embodiment, when the first locking mechanism is in the first locked state, the side surface of the first positioning assembly 110 is locked with the second positioning assembly 120, i.e., the first positioning assembly 110 and the second positioning assembly 120 are laterally locked. 9 , 22 , and 23 , in one embodiment, the first locking mechanism includes a locking assembly 211 and a locking recess 212. The locking assembly 211 is movably disposed on one of the second positioning assembly 120 and the first positioning assembly 110, while the locking recess 212 is disposed on the other of the second positioning assembly 120 and the first positioning assembly 110. For example, when the locking assembly 211 is movably disposed on the first positioning assembly 110, the locking recess 212 is disposed on the second positioning assembly 120. Alternatively, when the locking assembly 211 is movably disposed on the second positioning assembly 120, the locking recess 212 is disposed on the first positioning assembly 110. When the locking assembly 211 is inserted into the locking recess 212, the first positioning assembly 110 and the second positioning assembly 120 are locked and engaged, thereby restricting the first positioning assembly 110 from rotating relative to the second positioning assembly 120. When the locking assembly 211 withdraws from the locking recess 212 , the first positioning assembly 110 can rotate relative to the second positioning assembly 120 . It should be noted that in this embodiment, when the first positioning assembly 110 is oriented in the first direction F1 or the third direction F3 relative to the second positioning assembly 120, the locking assembly 211 can lock with the locking recess 212 to restrict the first positioning assembly 110 from rotating relative to the second positioning assembly 120. However, when the first positioning assembly 110 is oriented in the second direction F2 or the fourth direction F4 relative to the second positioning assembly 120, the locking assembly 211 and the locking recess 212 are not locked with each other, allowing the first positioning assembly 110 to rotate relative to the second positioning assembly 120. In this embodiment, the locking recess 212 is provided on a side surface of the first positioning assembly 110; in other embodiments, the locking recess 212 may be provided on the bottom of the first positioning assembly 110, so that the bottom of the first positioning assembly 110 is locked with the second positioning assembly 120. In this embodiment, as shown in Figures 22, 23, 25, and 27, the locking assembly 211 includes a first locking portion 2111. The first locking portion 2111 is movably disposed in the first direction F1 at either the second positioning assembly 120 or the first positioning assembly 110. Specifically, in this embodiment, the first locking portion 2111 is movably disposed in the second positioning assembly 120. A protrusion is provided on the upper surface of the second housing. Specifically, the second top cover 1212 is provided with two protrusions 1214 spaced apart along the first direction F1 or the third direction F3 (see Figures 22 and 23). The space between the two protrusions 1214 is used to accommodate the first positioning assembly 110. Optionally, the first locking portion 2111 can be movably disposed at the front or rear end of the second positioning assembly 120 along the first direction F1, equivalent to being movably disposed at one of the two protrusions 1214 disposed at the front and rear ends. Specifically, the two protrusions 1214 are respectively provided with a through-hole, and both through-holes are connected to the second mounting cavity 1211. Among them, the first locking portion 2111 corresponds to one of the through-holes and is movably arranged in the second mounting cavity 1211, and at least part of the first locking portion 2111 can extend out of the second mounting cavity 1211 through the corresponding through-hole. More specifically, as shown in Figures 22 and 25, along the first direction F1, the first locking portion 2111 is located at the rear end of the second positioning assembly 120, that is, it is equivalent to the first locking portion 2111 being movably inserted into the through-hole of the protrusion 1214 located at the rear. It should be noted that the protrusion 1214 protrudes upward relative to the first track 191 and the second track 192. In this embodiment, the first track 191 and the second track 192 are arranged on the upper surface of the second top cover 1212, so the protrusion 1214 protrudes upward relative to the upper surface of the second top cover 1212. In other embodiments, if the first rail 191 and the second rail 192 are not disposed on the upper surface of the second top cover 1212 but are instead sunken relative to the upper surface of the second top cover 1212, the protrusion 1214 may not protrude upward relative to the upper surface of the second top cover 1212. For example, the protrusion 1214 may be flush with the upper surface of the second top cover 1212. In this embodiment, the protrusion 1214 is disposed on the second top cover 1212. In other embodiments, the protrusion 1214 may also be disposed elsewhere on the second housing 121. In some non-limiting embodiments, there may be only one protrusion 1214 or more than two protrusions 1214. Furthermore, in this embodiment, as shown in FIG23 , the locking assembly 211 further includes a second locking portion 2112. The second locking portion 2112 is movably disposed in one of the second positioning assembly 120 and the first positioning assembly 110 along the first direction F1. Specifically, in this embodiment, the second locking portion 2112 and the first locking portion 2111 are both movably disposed in the second positioning assembly 120, and the second locking portion 2112 and the first locking portion 2111 are disposed opposite each other along the first direction F1. Specifically, as shown in FIG23 and FIG25 , the second locking portion 2112 is movably disposed at the front end of the second positioning assembly 120, which is equivalent to the second locking portion 2112 being movably disposed in the through-hole of the protrusion 1214 located in the front. Specifically, in this embodiment, as shown in FIG9 , a locking recess 212 is provided only on one side of the first positioning assembly 110, and the number of locking recesses 212 on that side is set to one. When the first positioning assembly 110 is oriented in the first direction F1, the locking recess 212 is oriented in the first direction F1 and rotates synchronously with the rotation of the first positioning assembly 110. Therefore, when the first positioning assembly 110 is oriented in the first direction F1, the second locking portion 2112 can be inserted into the locking recess 212 and locked with the locking recess 212, thereby maintaining the first positioning assembly 110 in the first direction F1. When the first positioning assembly 110 is oriented in the third direction F3, the locking recess 212 rotates synchronously to the third direction F3, and the first locking portion 2111 can be inserted into the locking recess 212 and locked with the locking recess 212, thereby maintaining the first positioning assembly 110 in the third direction F3. Alternatively, in other embodiments, locking recesses 212 may be provided on both sides of the first positioning assembly 110. In this case, the locking assembly 211 may include both the first locking portion 2111 and the second locking portion 2112, or may include only the first locking portion 2111 or the second locking portion 2112. For example, in the case where both sides of the first positioning assembly 110 are provided with locking recesses 212, and the locking assembly 211 includes only the first locking portion 2111, when the first positioning assembly 110 is oriented in the first direction F1 or the third direction F3, the locking recess 212 on one side faces the first direction F1, while the locking recess 212 on the other side faces the third direction F3. Thus, when the first positioning assembly 110 is rotated to the first direction F1 or the third direction F3, the first locking portion 2111 can be inserted into the corresponding locking recess 212 to achieve a locked engagement, thereby maintaining the first positioning assembly 110 in the first direction F1 or the third direction F3. In this embodiment, the first locking portion 2111 and the second locking portion 2112 each include only one inserting tongue, and the number of locking recesses 212 on the corresponding side of the first positioning component 110 is also correspondingly set to one; in other embodiments, the number of inserting tongues of the first locking portion 2111 and the second locking portion 2112 can be two or more, and the number of locking recesses 212 on the corresponding side of the first positioning component 110 is also correspondingly set to two or more. Referring to Figures 22 and 23 , in one embodiment, the second top cover 1212 includes two protrusions 1214 spaced apart along the first direction F1 or the third direction F3, each formed with a retaining protrusion 1215. Both retaining protrusions 1215 project toward the space housing the first positioning assembly 110. A slot-shaped structure with an opening is formed between each retaining protrusion 1215 and the upper surface of the second housing 121 (in this embodiment, the upper surface of the second top cover 1212). This allows a portion of the edge 1118 of the first housing 111 (see Figures 11 and 14 ) to be inserted into the two slots when the first positioning assembly 110 is accommodated in the space between the two protrusions 1214. Specifically, the first housing 111 is circular in shape, and when the first positioning assembly 110 is accommodated in the space between the two protrusions 1214, a portion of the circumferential edge 1118 of the first housing 111 can be inserted into the two slots. When the carrier body is mounted on the first positioning assembly 110, the center of gravity of the carrier body is generally biased toward the rear side of the carrier body, that is, the side of the carrier body close to its backrest. Taking the first carrier body 500 as an example, as shown in FIG2 , when the first carrier body 500 is arranged in a rearward direction, that is, when the first positioning assembly 110 is arranged toward the third direction F3, the portion of the edge 1118 of the first shell 111 facing the third direction F3 may have a tendency to tilt upward. The above-mentioned arrangement of inserting the portion of the edge 1118 of the first shell 111 into the two groove-shaped structures can prevent the first positioning assembly 110 from arbitrarily separating from the second positioning assembly 120 under the action of the gravity of the carrier body. In some non-limiting embodiments, there can be only one or more than two groove-shaped structures. Furthermore, a first support mechanism 127 may be provided within the second mounting cavity 1211. On one hand, when a carrier body (such as the first carrier body 500 or the second carrier body 600) is connected to the first positioning assembly 110 and the first positioning assembly 110 is rotated relative to the second positioning assembly 120 toward the first direction F1 or the third direction F3, the first support mechanism 127 is used to auxiliary support the carrier body, thereby improving the stability of the carrier body installed on the first positioning assembly 110. On the other hand, the first support mechanism 127 of this embodiment is at least partially located within the groove structure of the protrusion 1214. The first support mechanism 127 of this embodiment can be used to strengthen the groove wall strength of the groove structure used to engage the partial edge 1118 of the first shell 111 as described above. In this embodiment, two first support mechanisms 127 are provided, one each disposed on the two protrusions 1214. The following describes the structure of the first support mechanism 127 located at the rear end of the second positioning assembly 120 in detail, taking the first support mechanism 127 located at the rear end of the second positioning assembly 120 as an example. The first support mechanism 127 may include a first support member 1271 and a second support member 1272. In this embodiment, as shown in FIG38 , the second positioning assembly 120 further includes a skeleton 128 disposed within the second mounting cavity 1211. The skeleton 128 is generally U-shaped and includes a first straight rod 1281 and a second straight rod 1282 extending along the front-to-back direction of the positioning assembly 100 and spaced apart along the left-to-right direction, as well as an arc-shaped rod 1283 whose ends are respectively connected to the first straight rod 1281 and the second straight rod 1282. In this embodiment, the first support member 1271 located at the rear end of the second positioning assembly 120 is a U-shaped rod, and the two ends of the first support member 1271 are respectively fixed to the upper surfaces of the first straight rod 1281 and the second straight rod 1282. There are two second support members 1272, which are spaced apart and disposed on the upper surface of the first support member 1271. Of course, in other embodiments, the first support member 1271 may also be in other shapes such as a straight structure, and the number of the second support members 1272 may be more than two or less than two. The structure of one of the second support members 1272 will be described in detail below, taking one of the second support members 1272 as an example. Referring to Figures 38 and 39 , the second support member 1272 is generally a U-shaped frame structure and includes two connecting pieces 12721 arranged opposite to each other, and a connecting piece 12722 connected between the two connecting pieces 12721. Each connecting piece 12721 includes a connecting body 12721a and a supporting protrusion 12721b protruding from the connecting body 12721a. The supporting protrusion 12721b is connected to the approximate middle portion of the connecting body 12721a. In this embodiment, the connecting pieces 12721 are all integrally formed structures. In other embodiments, the connecting pieces 12721 can also be formed by connecting the connecting body 12721a and the supporting protrusion 12721b by welding, riveting, or the like. The lower surfaces of the connecting body 12721a and the supporting protrusion 12721b form a fixing groove 12721c, into which the first support member 1271 is at least partially engaged, thereby supporting the second support member 1272 on the first support member 1272. Furthermore, to enhance the stability of the connection between the first and second support members 1271 and 1272, the portion of the connecting body 12721a below the supporting protrusion 12721b and the lower surface of the supporting protrusion 12721b are fixedly connected to this portion of the first support member 1271. The upper surface of the supporting protrusion 12721b, the connecting body 12721a, and the connecting piece 12722 form an engaging groove 12721d. Specifically, the connecting piece 12722 has a generally square sheet-like structure, and the approximately middle portion of the connecting piece 12722 is arched upward, that is, arched in a direction away from the first support member 1271 to form an arched portion 12722a. The side of the arched portion 12722a facing the first support member 1271 forms a receiving groove 12722b. A fastening hole 12722c is also defined in the approximately middle portion of the arched portion 12722a and communicates with the receiving groove 12722b. In this embodiment, referring to Figures 22 and 23 , a connecting hole (not shown) is provided on the side of the protrusion 1214 facing the space housing the first positioning assembly 110, communicating with the second mounting cavity 1211. The connecting hole is specifically located at the bottom of the groove structure. The first support member 1271 is located within the second mounting cavity 1211. The portion of the second support member 1272 located below the upper surface of the supporting protrusion 12721b is located within the second mounting cavity 1211. The portion of the second support member 1272 located above the upper surface of the supporting protrusion 12721b extends out of the second mounting cavity 1211 through the connecting hole and protrudes above the upper surface of the second top cover 1212. The arched portion 12722a of the connecting piece 12722 is located below the limiting protrusion 1215; more specifically, the arched portion 12722a of the connecting piece 12722 can be supported below the limiting protrusion 1215. In this embodiment, the limiting protrusion 1215 (or protrusion 1214) is generally made of a plastic material, while the second support member 1272 is made of a rigid material (e.g., sheet metal). Therefore, the second support member 1272 can enhance the structural strength of the limiting protrusion 1215 (or protrusion 1214). When the first positioning assembly 110 is accommodated in the space between the two protrusions 1214, a portion of the edge 1118 of the first housing 111 (see Figures 11 and 14) can be inserted into the two groove structures, namely, the two engaging grooves 12721d located at the front and rear ends of the second positioning assembly 120, further preventing the first positioning assembly 110 from being detached from the second positioning assembly 120. Furthermore, referring to Figures 40 and 41 , a support pad 1273 may be disposed within the receiving groove 12722b of each second support member 1272. The support pad 1273 may be secured to the side of the arched portion 12722a facing the first support member 1271 via fasteners, such as screws, passing through the fastening holes 12722c and the support pad 1273. The support pad 1273 may increase the contact area between the second support member 1272 and the edge 1118, thereby further enhancing the structural strength of the limiting protrusion 1215 and preventing damage to the limiting protrusion 1215 or failure to limit the first positioning assembly 110. Furthermore, as shown in Figures 40 and 41, the first support mechanism 127 may further include an auxiliary support piece 1274 having a generally C-shaped cross-section. For example, the auxiliary support piece 1274 may include a first auxiliary piece 12741, a second auxiliary piece 12742, and a third auxiliary piece 12743, which are sequentially connected and arranged at an angle. The third auxiliary piece 12743 is shorter than the first auxiliary piece 12741 and the second auxiliary piece 12742, and the third auxiliary piece 12743 is connected to the middle of the second auxiliary piece 12742. In this embodiment, the first auxiliary piece 12741 and the second auxiliary piece 12742 are perpendicular to each other, and the second auxiliary piece 12742 and the third auxiliary piece 12743 are perpendicular to each other. In other embodiments, the angle between the first auxiliary piece 12741 and the second auxiliary piece 12742, and the angle between the second auxiliary piece 12742 and the third auxiliary piece 12743 may also be greater than 90 degrees or less than 90 degrees. When the auxiliary support pieces 1274 are disposed on the second support members 1272, the first auxiliary piece 12741 is disposed generally horizontally and positioned above the upper surfaces of the support protrusions 12721b of the two second support members 1272. The second auxiliary piece 12742 is disposed generally vertically and abuts the bottoms of the engagement grooves 12721d of the two second support members 1272, that is, the portion of the connecting body 12721a of the two second support members 1272 located above the support protrusions 12721b. The third auxiliary piece 12743 is interposed between the two second support members 1272 and is capable of abutting against the two connecting pieces 12722. More specifically, in this embodiment, the support pads 1273 disposed within the receiving grooves 12722b of each second support member 1272 can be considered part of the auxiliary support piece 1274. The two support pads 1273 are disposed on the second auxiliary piece 12742 and are located at both ends of the third auxiliary piece 12743. In this embodiment, the auxiliary support piece 1274 is an integrally formed structure, that is, the first auxiliary piece 12741, the second auxiliary piece 12742, the third auxiliary piece 12743, and the support pad 1273 are integrally formed. Of course, in other embodiments, the first auxiliary piece 12741, the second auxiliary piece 12742, the third auxiliary piece 12743, and the support pad 1273 can also be connected by welding, riveting, etc. to form the auxiliary support piece 1274. More specifically, the second auxiliary piece 12742 is provided with an orifice 12744, which communicates with the second mounting cavity 1211 and the connecting hole of the protrusion 1214, allowing the first locking portion 2111 or the second locking portion 2112 to pass through.When the first positioning assembly 110 is accommodated in the space between the two protrusions 1214, a partial edge 1118 of the first shell 111 (see Figures 11 and 14) can be supported by the first auxiliary piece 12741 of the auxiliary support piece 1274. Compared with being directly supported by the upper surface of the supporting protrusions 12721b of the two second support members 1272, its supporting area is greatly increased, which plays a certain force-relieving role and reduces the pressure borne by the unit supporting area, thereby further assisting in supporting the first positioning assembly 110, that is, assisting in supporting the carrier body, so as to improve the stability of the carrier body installed on the first positioning assembly 110. It is worth noting that the structure of the first support mechanism 127 located at the front end of the second positioning assembly 120 is roughly similar to the structure of the first support mechanism 127 located at the rear end of the second positioning assembly 120 mentioned above. The only difference is that since the second positioning assembly 120 as a whole presents a low front and high back structure, the first support member 1271 of the first support mechanism 127 located at the front end of the second positioning assembly 120 is a straight rod rather than a U-shaped rod. Furthermore, as shown in FIG42 , the first positioning assembly 110 further includes a second support mechanism 117. Specifically, the second support mechanism 117 includes the first sliding member 194 and the second sliding member 195 described above. The two ends of the first sliding member 194 are respectively connected to the first positioning assembly 110 and the first slider 196 provided on the second positioning assembly 120, and the two ends of the second sliding member 195 are respectively connected to the first positioning assembly 110 and the second slider 197 provided on the second positioning assembly 120. Referring to FIG8 and FIG9 , when the first positioning assembly 110 rotates relative to the second positioning assembly 120 toward the second direction F2 or the fourth direction F4, the projection of at least a portion of the first positioning assembly 110 in the fifth direction F5 will exceed the projection of the second positioning assembly 120 in the fifth direction F5, that is, the first positioning assembly 110 of this portion will be suspended. The first sliding member 194 and the second sliding member 195 are always located within the projection range of the second positioning component 120 in the fifth direction F5. Therefore, the first sliding member 194 and the second sliding member 195 can support the first positioning component 110 and the carrier body installed on the first positioning component 110, and can also generate a certain pulling force on the non-suspended part of the first positioning component 110 to prevent it from tilting upward due to the gravity of the suspended part of the first positioning component 110. Furthermore, please refer to Figures 25, 28 and 42. The second positioning assembly 120 may also include a third support mechanism 129. The third support mechanism 129 includes a plurality of support column assemblies arranged in the second mounting cavity 1121. In this embodiment, the third support mechanism 129 includes six groups of support column assemblies, and the six groups of support column assemblies are arranged at intervals along the extension direction of the second rail 192. Specifically, each group of support column assemblies includes a first support column 1291 and a second support column 1292 respectively located on both sides of the second rail 192. The first support column 1291 includes a first bottom column 1291a fixed to the second bottom cover 1213 and a first top column 1291b fixed to the second top cover 1212. The first bottom column 1291a and the first top column 1291b are in contact with each other to form a support structure. The second support column 1292 includes a second bottom column 1292a fixed to the second bottom cover 1213 and a second top column 1292b fixed to the second top cover 1212. The second bottom column 1292a and the second top column 1292b abut against each other to form a support structure. In this manner, the six support column assemblies further enhance the structural strength of the second positioning assembly 120 and provide auxiliary support for the first positioning assembly 110. In this embodiment, as shown in Figures 25 and 28, two groups of support column assemblies (hereinafter referred to as the first support column assemblies) are located near the two ends of the first track 192; two additional groups of support column assemblies (hereinafter referred to as the second support column assemblies) are located near the intersection 193; and two additional groups of support column assemblies (hereinafter referred to as the third support column assemblies) are located farther from the second track 192 along the first direction F1 relative to the second support column assemblies and farther from the first track 191 along the second direction F2 relative to the second support column assemblies. When the first positioning assembly 110 is rotated to the second or fourth direction relative to the second positioning assembly 120, the first slider 194 and the second slider 195 assist in receiving force. The first and second support column assemblies can provide support for the first positioning assembly 110 at locations adjacent to the first and second sliders 194 and 195. Furthermore, the third support column assembly can further expand the support range, thereby providing support for the carrier body connected to the first positioning assembly 110 and increasing the structural strength of the second positioning assembly 120, thereby preventing the second positioning assembly 120 from being damaged by compression. Of course, in other embodiments, the number and location of the support column assemblies can also be adjusted as needed. 25 to 27 , in one embodiment, the carrier 1000 further includes a first release mechanism 300 . The first release mechanism 300 can be operably connected to the first lock portion 2111 or the second lock portion 2112 and can be used to drive the first lock portion 2111 or the second lock portion 2112 to withdraw from the locking recess 212 . Specifically, in this embodiment, as shown in Figures 25 to 27 , the first release mechanism 300 is operably connected to the first lock portion 2111. Therefore, the release mechanism and process of the first release mechanism 300 will be described below using the interlocking interaction between the first release mechanism 300 and the first lock portion 2111. Specifically, the first release mechanism 300 includes a first drive member 310, a first operating member 320, and a first pulling assembly 330. The first drive member 310 is pivotally connected to the second positioning assembly 120 and to the first lock portion 2111. The first operating member 320 is operably disposed on the second positioning assembly 120 and is exposed therefrom. This facilitates user operation of the first operating member 320. The first pulling assembly 330 is connected to both the first operating member 320 and the first drive member 310. When the first operating member 320 is operated (e.g., pressed or pushed), the first operating member 320 drives the first driving member 310 to pivot via the first pulling assembly 330, thereby enabling the first driving member 310 to drive the first locking portion 2111 to withdraw from the locking recess 212. In some non-limiting embodiments, because the first locking portion 2111 is located at the rear end of the second positioning assembly 120 and the locking recess 212 is located at the front end of the first positioning assembly 110, the first locking portion 2111 can only be locked with the locking recess 212 when the first positioning assembly 110 is rotated relative to the second positioning assembly 120 toward the third direction F3 (i.e., away from the first direction F1), and the first locking portion 2111 can then be controlled to withdraw from the locking recess 212 by the first release mechanism 300. In one embodiment, as shown in Figures 25 to 27 , two first release mechanisms 300 are provided. These two first release mechanisms 300 are located on the left and right sides of the second positioning assembly 120, respectively. Both first release mechanisms 300 are operably connected to the first locking portion 2111. Thus, a user can operate either first operating member 320 to disengage the first locking portion 2111 from the locking recess 212. Referring to Figures 25 to 27 , in one embodiment, the first traction assembly 330 includes a first traction rope 331. One end of the first traction rope 331 is connected to the first driver 310, and the other end of the first traction rope 331 is connected to the first operating member 320. Specifically, the positioning assembly 100 is mounted on a vehicle seat. The operating principle of the first release mechanism 300 near the right door is described as an example. The first driver 310 in the first release mechanism 300 is pivotally connected to the second bottom cover 1213 at a first pivot point Q1. The pivot point between the first driver 310 and the first lock portion 2111 and the connection point between the first driver 310 and the first traction rope 331 are located on either side of the first pivot point Q1. More specifically, the first operating member 320 is movably mounted on the second housing 121. Therefore, when it is necessary to release the first lock portion 2111, the first operating member 320 near the right door can be moved, driving the first pulling rope 331 to pull the first driving member 310 in a counterclockwise direction about the first pivot point Q1. This in turn causes the first driving member 310 to move the first lock portion 2111 in the third direction F3, allowing the first lock portion 2111 to exit the locking recess 212. It should be noted that when the first driving member 310 near the right door rotates counterclockwise about the first pivot point Q1, since the first driving member 310 near the left door is also connected to the first locking member 2111, the first locking member 2111 drives the first driving member 310 near the left door to rotate clockwise about its first pivot point Q1. In other words, the left and right first driving members 310 in this embodiment are interlocked. Operating one of the first operating members 320 can release the first lock portion 2111 and cause both first driving members 310 to pivot. Continuing with Figures 25 to 27 , in one embodiment, the locking assembly 211 further includes a fifth reset member 2113. The fifth reset member 2113 abuts between the second bottom cover 1213 and the first locking portion 2111, and is used to reset the first locking portion 2111, thereby constantly ensuring that the first locking portion 2111 tends to be inserted into the locking recess 212. The fifth reset member 2113 is, for example, a spring. Thus, when the locking recess 212 rotates with the first positioning assembly 110 to face the first locking portion 2111, the wall of the first housing 111 releases its contact with the first locking portion 2111. Under the elastic action of the fifth reset member 2113, the first locking portion 2111 automatically inserts into the locking recess 212. As described above, since the first positioning assembly 110 is restricted from aligning in the first direction F1 when connected to the second carrier body 600, in this embodiment, only the first locking portion 2111 can perform a locking function when the first positioning assembly 110 is connected to the second carrier body 600, while the second locking portion 2112 does not engage with the locking recess 212. Specifically, when the first positioning assembly 110 is oriented in the third direction F3, the first locking portion 2111, under the action of the fifth return member 2113, automatically inserts into the locking recess 212 for locking engagement. Simultaneously, the second locking portion 2112 is abutted by the wall of the first housing 111 and accommodated within the second mounting cavity 1211. When the user desires to switch the first positioning assembly 110 from the third direction F3 to the second direction F2 or the fourth direction F4, the user can operate the first release mechanism 300 to retract the first locking portion 2111 from the locking recess 212. Therefore, when the first positioning assembly 110 is connected to the second carrier body 600 , the first locking portion 2111 can be operated only through the first release mechanism 300 . As described above, when the first positioning assembly 110 is connected to the first carrier body 500, the first positioning assembly 110 can freely rotate relative to the second positioning assembly 120. That is, the first positioning assembly 110 can be oriented in any of the first direction F1, the second direction F2, the third direction F3, and the fourth direction F4. In one embodiment, as shown in Figures 25 to 27, the locking assembly 211 further includes a seventh return member 2114. The seventh return member 2114 abuts between the second bottom cover 1213 and the second locking portion 2112, and is used to cause the second locking portion 2112 to be inserted into the locking recess 212. Therefore, when the first positioning assembly 110 is oriented in the first direction F1, the locking recess 212 and the second locking portion 2112 are opposite each other. Under the elastic action of the seventh return member 2114, the second locking portion 2112 can be inserted into the locking recess 212 to lock with the locking recess 212. At this time, the first locking portion 2111 is abutted by the shell wall of the first housing 111 and is accommodated in the second mounting cavity 1211. When it is necessary to switch the first positioning assembly 110 from the first direction F1 to another direction (for example, the second direction F2, the fourth direction F4, etc.), the user can first retract the second locking portion 2112 from the locking recess 212 and then change the orientation of the first positioning assembly 110 using the rotational movement mechanism 190. 19 and 21 , in one embodiment, the carrier 1000 further includes a second lock releasing mechanism 400 . The second lock releasing mechanism 400 is mainly configured to be operably connected to the second lock portion 2112 and configured to drive the second lock portion 2112 to exit from the locking recess 212 . Referring to FIG. 19 , in one embodiment, the locking recess 212 is a locking hole that is communicable with the first mounting cavity 1111. Specifically, as shown in FIG. 19 and FIG. 29 , the second release mechanism 400 includes a second driver 410, a second operating member 420, and a transmission unit. The second driver 410 is movably disposed within the first mounting cavity 1111 and is capable of driving the second locking portion 2112 out of the locking recess 212. Specifically, when the first positioning assembly 110 is facing toward or away from the first direction F1, the movement direction of the second driver 410 is parallel to the first direction F1 or the third direction F3. Thus, when the second driver 410 moves, it contacts and abuts against the second locking portion 2112, thereby pushing the second locking portion 2112 out of the locking recess 212. Specifically, the second driving member 410 is provided with an elastic arm 411, which is used to abut against the sidewall of the first bottom cover 1116 or the first top cover 1115 to assist in resetting the second driving member 410. The second operating member 420 is operably disposed on the first carrier body 500 (see Figures 29 and 49). A transmission unit is respectively connected to the second operating member 420 and the second driving member 410. When the second operating member 420 is operated, the second operating member 420 drives the second driving member 410 to move via the transmission unit, so that the second driving member 410 drives the first locking portion 2111 to withdraw from the locking recess 212. 30 and 34 , in one embodiment, the transmission unit includes a first transmission assembly 430 and a second transmission assembly 440. The first transmission assembly 430 is disposed in the first carrier body 500, and the second transmission assembly 440 is disposed in the first mounting cavity 1111. The first transmission assembly 430 and the second transmission assembly 440 are drivingly connected. With reference to Figures 30, 34, and 43-44, in one embodiment, the second transmission assembly 440 includes a transmission member 441, a third drive member 442, and a third traction assembly 443. The transmission member 441 is movably disposed within the first mounting cavity 1111 and is drivingly connected to the first transmission assembly 430 (see Figures 30 and 34). The third drive member 442 is pivotally connected to the bottom wall of the first mounting cavity 1111 and is also pivotally connected to the second drive member 410. Specifically, the third drive member 442 is pivotally connected to the first bottom cover 1116 at a second pivot point Q2 (see Figures 41 and 46). The third traction assembly 443 is connected to the transmission member 441 and the third drive member 442, respectively (see Figures 43 and 44). When the first transmission assembly 430 drives the transmission member 441 to move, the transmission member 441 drives the third driving member 442 to pivot through the third traction assembly 443 , so that the second driving member 410 moves to push the second locking portion 2112 to exit from the locking recess 212 . Specifically, as shown in Figures 47 and 48, the third traction assembly 443 is a flexible element comprising a third traction rope 4431 and a third traction sleeve 4432 disposed over the third traction rope 4431. When the transmission member 441 moves, the third traction sleeve 4432 deforms, causing the third traction rope 4431 to pivot by pulling the third driving member 442, thereby driving the second driving member 410 to move against the second locking portion 2112. Specifically, the third traction sleeve 4432 has a first sleeve end 44321 and a second sleeve end 44322. The third traction rope 4431 has a first rope end 44311 adjacent to the first sleeve end 44321 and a second rope end 44312 adjacent to the second sleeve end 44322. More specifically, as shown in FIG30 , the transmission member 441 includes a fixed seat 4411 and a movable resisting seat 4412. The fixed seat 4411 is fixedly disposed within the first mounting cavity 1111, and the movable resisting seat 4412 is movably disposed on the fixed seat 4411 along the fifth direction F5. In other words, the movable resisting seat 4412 is movable along the fifth direction F5 relative to the fixed seat 4411. The first end 44311 of the third traction rope 4431 is connected to the first connecting portion 44111 of the fixed seat 4411 (see FIG30 ), and the second end 44312 of the third traction rope 4431 is connected to the third driving member 442 (see FIG43 and FIG44 ). The connection point between the second end 44312 of the third traction rope 4431 and the third driving member 442 and the pivot point between the third driving member 442 and the second driving member 410 are located on either side of the second pivot point Q2, respectively. The first end 44321 of the third traction sleeve 4432 is connected to the second connection portion 44121 of the movable push seat 4412 (see Figure 30). Along the fifth direction F5, the second connection portion 44121 is located below the first connection portion 44111. The second end 44322 of the third traction sleeve 4432 is connected to the first top cover 1115 or the first bottom cover 1116 (see Figures 43 and 44). Specifically, the first bottom cover 1116 or the second top cover 1212 is provided with a third connection portion 4413 on the side facing the first mounting cavity 1111 (see Figure 21). The second end 44322 of the third traction sleeve 4432 is connected to the third connection portion 4413. Specifically, the third traction sleeve 4432 is a flexible wire sleeve. It should be noted that the third traction sleeve 4432 should be made of a rigid but flexible material, such as a flexible tubular structure made of metal (e.g., steel) or plastic (e.g., PVC). Similarly, the third traction rope 4431 can also be made of a hard but bendable material. The working principle and process of the second transmission assembly 440 will be described below with reference to FIG29 and FIG30. When it is necessary to withdraw the second locking portion 2112 from the locking recess 212 to allow the first positioning assembly 110 to slide relative to the second positioning assembly 120, the user can move the movable push seat 4412 downward in the fifth direction F5. This causes the second connecting portion 44121 to move the first sleeve end 44321, and simultaneously compresses and bends the third traction sleeve 4432, causing the third traction rope 4431 to bend along with the third traction sleeve 4432. Because the first rope end 44311 of the third traction rope 4431 is fixed to the first connecting portion 44111, when the movable push seat 4412 moves downward in the fifth direction F5, the first sleeve end 44321 moves downward in the fifth direction F5 along with the second connecting portion 44121, and the length of the section L1 of the third traction rope 4431 between the first sleeve end 44321 and the first rope end 44311 increases (as seen from FIG. 47 to FIG. 48 ). Since the total length of the third traction rope 4431 remains unchanged, under the transmission action of the third traction sleeve 4432, the length of the section L2 of the third traction rope 4431 between the second rope end 44312 and the second sleeve end 44322 is reduced (changing from Figure 47 to Figure 48). In this way, it can be regarded that the second rope end 44312 will pull the third driving member 442 to pivot around the second pivot point Q2 in the clockwise direction, and then the third driving member 442 can push the second driving member 410 to move to push the second locking part 2112 to withdraw from the locking hole (switching from Figure 43 to Figure 45). Referring to FIG. 30 , in one embodiment, the second transmission assembly 440 further includes an eighth reset member 444, which can be, for example, an elastic member such as a spring. The eighth reset member 444 abuts between the fixed seat 4411 (or the surface of the first bottom cover 1116 facing away from the second positioning assembly 120) and the movable push seat 4412, and is configured to drive the movable push seat 4412 to move upward in the fifth direction F5. When the movable push seat 4412 is not being pushed, the eighth reset member 444 can reset the movable push seat 4412, thereby resetting the third traction sleeve 4432 and the third traction rope 4431. Driven by the third traction rope 4431, the third driving member 442 can pivot counterclockwise about the second pivot point Q2 to assist in resetting the second driving member 410. Referring to Figures 29 and 30, in one embodiment, the first transmission assembly 430 includes a push member 431 and a second traction assembly 432. The push member 431 is movably disposed on the first carrier body 500 and is used to push the transmission member 441. Specifically, the push member 431 is movable along the fifth direction F5. The first top cover 1115 is provided with a push hole 1117. Thus, when the first carrier body 500 is mounted on the first housing 111, the push member 431 can pass through the push hole 1117 and abut against the movable push seat 4412. More specifically, the second traction assembly 432 is connected to the push member 431 and the second operating member 420, respectively. Thus, when the second operating member 420 is operated, the second operating member 420 can drive the push member 431, via the second traction assembly 432, to push against the movable push seat 4412 of the transmission member 441. Referring to Figure 29 , in one embodiment, the second traction assembly 432 includes a second traction rope 4321. One end of the second traction rope 4321 is connected to the second operating member 420, and the other end of the second traction rope 4321 is connected to the push member 431. Specifically, the second operating member 420 is movably mounted on the first carrier body 500. A linkage block 433 (see Figures 30, 50, and 51) is disposed on top of the push member 431. The linkage block 433 and the first operating member 320 are spaced apart in the front-to-back direction of the first carrier body 500. More specifically, a guide wheel 434 (see Figures 30, 50, and 51) is disposed within the first carrier body 500. The ends of the second traction rope 4321 pass over the guide wheel 434 and are connected to the linkage block 433 and the first operating member 320, respectively. Thus, when the second operating member 420 is operated (e.g., rotated, pressed, or moved), the second traction rope 4321, guided by the guide wheel 434, pulls the linkage block 433 to push the resisting member 431 downward in the fifth direction F5. This causes the resisting member 431 to pass through the resisting hole 1117 and extend into the first mounting cavity 1111, thereby pushing the movable resisting seat 4412 downward in the fifth direction F5. Specifically, a sixth return member 530 (see Figures 50 and 51) is provided within the first carrier body 500. The sixth return member 530 abuts between the first carrier body 500 and the linkage block 433. When the user releases the second operating member 420, the sixth return member 530 is used to reset the resisting member 431, i.e., to drive the resisting member 431 out of the first mounting cavity 1111. In this embodiment, the linkage block 433 is connected to the push member 431 via fasteners such as screws or rivets, so that when the second traction rope 4321 pulls the linkage block 433, the push member 431 can be driven to move. In other embodiments, the linkage block 433 can be omitted, and the second traction rope 4321 can be directly connected to the push member 431 to directly pull the push member 431 to move. The working principle and process of the second release mechanism 400 will be briefly described below with reference to relevant diagrams. 29-31 , when the first carrier body 500 is connected to the first positioning assembly 110, the push member 431 is positioned opposite the transmission member 441. When the first positioning assembly 110 is oriented in the first direction F1 relative to the second positioning assembly 120, the locking recess 212 (locking hole) faces the first direction F1 and opposes the second locking portion 2112. At this point, the second locking portion 2112 automatically inserts into the locking hole of the first positioning assembly 110 under the action of the seventh return member 2114, thereby locking the first positioning assembly 110 in the first direction F1. With reference to Figures 29 to 31 and 43 to 48 , when the orientation of the first carrier body 500 needs to be changed, the user can operate the second operating member 420 so that the second operating member 420 pulls the push member 431 downward along the fifth direction F5 via the second traction rope 4321. During the downward movement, the push member 431 gradually passes through the push hole 1114 and extends into the first mounting cavity 1111, where it abuts against the movable push seat 4412. When the top of the movable push seat 4412 is subjected to a downward push force along the fifth direction F5, the movable push seat 4412 moves downward, causing the second connecting portion 44121 to drive the first sleeve end 44321 to move, thereby further bending and deforming the third traction sleeve 4432. As the third traction sleeve 4432 further bends and deforms, the length of the section L1 of the third traction rope 4431 between the first rope end 44311 and the first sleeve end 44321 increases, and the length L2 of the section of the third traction rope 4431 between the second rope end 44312 and the second sleeve end 44322 decreases. In this way, it can be regarded as the second rope end 44312 moving toward the direction close to the second sleeve end 44322, thereby pulling the third drive member 442 to pivot in a clockwise direction around the second pivot point Q2, so that the third drive member 442 pushes the second drive member 410 to move toward the direction close to the locking hole to push the second locking part 2112 to withdraw from the locking hole. In this embodiment, the second release mechanism 400 can also be used to release the first lock portion 2111. Specifically, when the first carrier body 500 is mounted on the first positioning assembly 110 and the first positioning assembly 110 is oriented in the third direction F3 relative to the second positioning assembly 120, the first lock portion 2111 is aligned with the locking hole. Under the action of the fifth return member 2113, the first lock portion 2111 can be automatically inserted into the locking hole. At this point, the user can selectively release the first lock portion 2111 using either the second release mechanism 400 or the first release mechanism 300. The following describes the operation of the positioning assembly 100 in the first embodiment, using the example of a removable connection between the first carrier body 500 and the first positioning assembly 110. The positioning assembly 100 is connected to a vehicle seat, and the first carrier body 500 is connected to the first positioning assembly 110. When the first carrier body 500 and the first positioning assembly 110 are oriented in the first direction F1 (equivalent to the front of the vehicle), the first limiting mechanism 140 restricts the first carrier body 500 from being removed from the first positioning assembly 110 (the specific principle is described above). In other words, when the first carrier body 500 is connected to the first positioning assembly 110 and oriented in the first direction F1, the first carrier body 500 cannot be removed to replace the second carrier body 600. When the first carrier body 500 is oriented in the first direction F1 along with the first positioning assembly 110, the second locking portion 2112 is inserted into the locking recess 212 of the first positioning assembly 110, restricting rotation of the first positioning assembly 110 relative to the second positioning assembly 120 and maintaining the first carrier body 500 in the first direction F1. To change the orientation of the first carrier body 500, the user can operate the second release mechanism 400 (operating the second operating member 420) to disengage the second locking portion 2112 from the locking recess 212. Subsequently, the rotational movement mechanism 190 can be used to rotate the first positioning assembly 110 toward any of the second direction F2, the third direction F3, or the fourth direction F4. It should be noted that when the first carrier body 500 is rotated toward the third direction F3 along with the first positioning assembly 110, the first locking portion 2111 is inserted into the locking recess 212, maintaining the first carrier body 500 in the third direction F3. When the orientation of the first carrier body 500 needs to be changed again, the user operates the second release mechanism 400 or the first release mechanism 300 to move the first locking portion 2111 away from the locking recess 212 . Suppose it is necessary to remove the first carrier body 500 from the first positioning assembly 110 and connect the second carrier body 600 to the first positioning assembly 110. As described above, the orientation of the first positioning assembly 110 can be changed to face any of the second direction F2, the third direction F3, or the fourth direction F4. When the first positioning assembly 110 faces a direction other than the first direction F1, the first limiting mechanism 140 allows the first carrier body 500 to be removed from the first positioning assembly 110 (the specific principles are described above). When the second carrier body 600 is connected to the first positioning assembly 110, the second limiting mechanism 170 limits the angular range of rotation of the first positioning assembly 110 relative to the second positioning assembly 120, preventing the first positioning assembly 110 from rotating toward the first direction F1 (the specific principles are described above). When the first positioning assembly 110 is oriented in the third direction F3, the first locking portion 2111 automatically inserts into the locking recess 212 of the first positioning assembly 110, thereby maintaining the second carrier body 600 in the third direction F3. To change the orientation of the second carrier body 600, the user can only operate the first release mechanism 300 to retract the first locking portion 2111 from the locking recess 212, thereby releasing the first positioning assembly 500 and the second positioning assembly 600. Referring to Figures 52 to 54 , a second embodiment of the present application provides another positioning assembly 100 for attaching a first carrier body 500 or a second carrier body 600 to a car seat. Specifically, the positioning assembly 100 includes a first positioning assembly 110, a second positioning assembly 120, a third positioning assembly 130, and an extension mechanism 230. The third positioning assembly 130 is removably attachable to the car seat and includes a seat connection plug 125 and a support leg 126. The seat connection plug 125 is primarily used to secure the third positioning assembly 130 to the car seat, while the support leg 126 is designed to rest against the vehicle floor. The second positioning assembly 120 is rotatably mounted on the third positioning assembly 130. The first positioning assembly 110 is movably mounted on the second positioning assembly 120 and has both an extended and retracted state. The first positioning assembly 110 is designed to be removably attached to the first carrier body 500 or the second carrier body 600. Thus, by rotating the second positioning assembly 120, the first positioning assembly 110 can be oriented in any of the following directions: the first direction F1 (see Figure 52), the second direction F2 (see Figure 54), the third direction F3 (see Figure 53), and the fourth direction F4 (see Figure 57). Specifically, in this embodiment, the second positioning assembly 120 and the third positioning assembly 130 are both generally circular in structure, with approximately the same radius. When the first positioning assembly 110 is in the retracted state, the first positioning assembly 110 and the second positioning assembly 120 overlap below (see Figures 52 to 54). When the first positioning assembly 110 is in the extended state, the first positioning assembly 110 is offset from the second positioning assembly 120 below (see Figures 55 and 57). The extension mechanism 230 is connected between the first positioning assembly 110 and the second positioning assembly 120 and is used to guide the first positioning assembly 110 between the extended and retracted states. It should be noted that in this embodiment, "the second positioning assembly 120 is rotatably disposed on the third positioning assembly 130" means that the second positioning assembly 120 can rotate about an axis on the third positioning assembly 130. In this embodiment, the second positioning assembly 120 is circular, with the axis being its center. In other embodiments, the second positioning assembly 120 can have other symmetrical shapes (e.g., elliptical, rectangular, etc.), and the axis can be at or offset from the geometric center of the second positioning assembly 120. Alternatively, the second positioning assembly 120 can have an asymmetrical shape, and the axis can be set according to actual needs. 55 and 56 , in one embodiment, the extension mechanism 230 includes a first main link 231, a second main link 232, and a first auxiliary link 233. One of the first main link 231 and the second main link 232 is connected to the first positioning assembly 110, and the other is connected to the second positioning assembly 120. The first auxiliary link 233 is pivotally connected to the first main link 231 and the second main link 232 at both ends, respectively, to enable the first main link 231 and the second main link 232 to move closer to or further away from each other. Specifically, when the first main link 231 and the second main link 232 move closer to each other, the first positioning assembly 110 is in a retracted state. When the first main link 231 and the second main link 232 move further away from each other, the first positioning assembly 110 is in an extended state. 56 , in one embodiment, a gear 234 is provided at one end of the first main connecting rod 231 and one end of the second main connecting rod 232, and the two gears 234 are meshed with each other. The first auxiliary rod 233 has its two ends pivotally connected to the hubs of the two gears 234. Continuing with FIG56 , in one embodiment, the extension mechanism 230 further includes a second auxiliary rod 237. The ends of the second auxiliary rod 237 are pivotally connected to the centers of the two gears 234. The second auxiliary rod 237 and the first auxiliary rod 233 are located on either side of the gears 234. This improves the stability of the first main connecting rod 231 and the second main connecting rod 232 during their movement toward or away from each other. 56 , in one embodiment, the extension mechanism 230 further includes a first reinforcing rod 235, a second reinforcing rod 238, a third auxiliary rod 236, and a fourth auxiliary rod 239. The first reinforcing rod 235 and the third auxiliary rod 236 are pivotally connected, with the end of the first reinforcing rod 235 away from the third auxiliary rod 236 pivotally connected to the first auxiliary rod 233, and the end of the third auxiliary rod 236 away from the first reinforcing rod 235 pivotally connected to the first main link 231. Thus, the first main link 231, the first auxiliary rod 233, the first reinforcing rod 235, and the third auxiliary rod 236 form a four-bar linkage (hereinafter referred to as the first linkage assembly). The second reinforcement rod 238 is pivotally connected to the fourth auxiliary rod 239. The end of the second reinforcement rod 238 away from the fourth auxiliary rod 239 is connected to the second auxiliary rod 237. The end of the fourth auxiliary rod 239 away from the second reinforcement rod 238 is pivotally connected to the second main link 232. Therefore, the second main link 232, the second auxiliary rod 237, the second reinforcement rod 238, and the fourth auxiliary rod 239 also form a four-bar linkage structure (hereinafter referred to as the second linkage assembly). Specifically, the third auxiliary rod 236 is connected to the second positioning assembly 120, and the fourth auxiliary rod 239 is connected to the first positioning assembly 110. Referring to Figures 54 and 55 , before the first positioning assembly 110 is stretched outward, the first link assembly is rectangular, the second link assembly is rectangular, and the first and second link assemblies overlap. During the outward stretching of the first positioning assembly 110, the first link assembly deforms into a parallelogram, and the angles of the four interior angles of the parallelogram formed by the first link assembly gradually change. Similarly, the second link assembly deforms into a parallelogram, and the angles of the four interior angles of the parallelogram formed by the second link assembly gradually change. In this embodiment, during the outward stretching of the first positioning assembly 110, the first and second link assemblies transition from overlapping to mirror-symmetric. In one embodiment, as shown in Figure 55, the positioning assembly 100 includes at least one extending mechanism 230. Specifically, in this embodiment, the positioning assembly 100 includes two extending mechanisms 230, and the two extending mechanisms 230 are arranged in parallel. Referring to FIG. 58 , in one embodiment, the positioning assembly 100 further includes a second locking mechanism 240. The second locking mechanism 240 is disposed between the first positioning assembly 110 and the second positioning assembly 120. The second locking mechanism 240 has a second locked state and a second unlocked state. When the second locking mechanism 240 is in the second locked state, the first positioning assembly 110 is restricted from moving relative to the second positioning assembly 120, which means that the first positioning assembly 110 cannot switch between the extended state and the retracted state. When the second locking mechanism 240 is in the second unlocked state, the first positioning assembly 110 is allowed to move relative to the second positioning assembly 120, which means that the first positioning assembly 110 can switch between the extended state and the retracted state. Continuing with FIG. 58 , in one embodiment, the second locking mechanism 240 includes a second locking member 241 pivotally connected to the first positioning assembly 110 . The second locking member 241 has an operating end 2411 and a locking end 2412 . The second positioning assembly 120 is provided with a locking engagement portion 122 (e.g., a mating hole). The second locking member 241 is pivotable between a locked position and an unlocked position. When the second locking member 241 is in the locked position, the locking end 2412 can be locked and engaged with the locking engagement portion 122. When the second locking member 241 is in the unlocked position, the locking end 2412 can be disengaged from the locking engagement portion 122. The operating end 2411 can be operated to pivot the second locking member 241 from the locked position to the unlocked position. Specifically, the pivot point between the second locking member 241 and the first positioning assembly 110 is located between the operating end 2411 and the locking end 2412, so that the second locking member 241 roughly presents a "seesaw" structure when the first positioning assembly 110 pivots, that is, when the operating end 2411 is pressed, the locking end 2412 is tilted to be able to disengage the locking mating portion 122. 58 , the second locking mechanism 240 further includes a button 242 configured to abut against the operating end 2411. When the second locking member 241 needs to be released, the user can push the button 242 to pivot the second locking member 241 to the unlocked position. Of course, in other embodiments not shown, the second locking mechanism 240 may also be a locking structure. For example, the locking structure may include a male buckle and a female buckle that can be engaged with each other, with one of the male buckle and the female buckle being disposed on the first positioning assembly 110 and the other on the second positioning assembly 120. For another example, the second locking member 241 may be a locking column that can be operated to move in the vertical direction. The first positioning assembly 110 and the second positioning assembly 120 may be locked or released by inserting or disengaging the second locking member 241 into or out of the locking engagement portion 122. The following describes the operation of the second embodiment using the example of a removable connection between the first carrier body 500 and the first positioning assembly 110. The positioning assembly 100 is connected to the interior of a vehicle, and the first carrier body 500 is connected to the first positioning assembly 110. Assuming the first carrier body 500 is used facing the first direction F1, when a child needs to be removed from the first carrier body 500, the user rotates the first positioning assembly 110 relative to the second positioning assembly 120 toward the second direction F2 or the fourth direction F4, positioning the first positioning assembly 110 toward the vehicle's side door, with the child facing the vehicle's side door. The user then operates the button 242, releasing the second locking member 241 from the locking engagement portion 122. The user then pulls the first positioning assembly 110 toward the second direction F2 or the fourth direction F4, causing the extension mechanism 230 to stretch and deform, and the first carrier body 500 to face the second direction F2 or the fourth direction F4. The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be based on the appended claims. 1000: Carrier 100: Positioning assembly 110: First positioning assembly 111: First shell 1111: First mounting cavity 1112: First limiting hole 1113: Second limiting hole 1114: Push hole 1115: First top cover 1116: First bottom cover 1117: Push hole 1118: Edge 112: First connecting mechanism 1121: Engaging hook 11211: Engaging portion 11212: Accommodating groove 11213: Push wall 1122: Slot 113: Indicating mechanism 1131: Swinging member 1132: Color block 1133: Observation hole 114: Movable limiting seat 1141: Active cavity 1142: First opening 1143: Second opening 11 5: Support plate 116: Support rod 117: Second support mechanism 120: Second positioning assembly 121: Second housing 1211: Second mounting cavity 1212: Second top cover 1213: Second bottom cover 1214: Protrusion 1215: Position-limiting protrusion 1216: First channel 1217: Second channel 122: Locking mating portion 12​​3: Support frame 124: Pivot shaft 125: Seat connection plug 126: Support leg 127: First support mechanism 1271: First support member 1272: Second support member 12721: Connecting piece 12721a: Connecting body 12721b: Support protrusion 12721c: Fixing groove 12721d: Snap-fit Slot 12722: Connecting piece 12722a: Arched portion 12722b: Accommodating slot 12722c: Fastening hole 1273: Support pad 1274: Auxiliary support piece 12741: First auxiliary piece 12742: Second auxiliary piece 12743: Third auxiliary piece 12744: Orifice 128: Skeleton 1281: First straight rod 1282: Second straight rod 1283: Arc rod 129: Third supporting mechanism 1291: First supporting column 1291a: First bottom column 1291b: First top column 1292: Second supporting column 1292a: Second bottom column 1292b: Second top column 130: Third positioning component 140: First limiting mechanism 14 1: First limiting groove 142: First limiting member 1421: Sliding inclined surface 1422: Bar-shaped hole 143: First reset member 150: Locking and holding mechanism 151: First locking member 1511: Locking groove 1512: Driving portion 152: Third reset member 160: First release member 161: Driving inclined surface 170: Second limiting mechanism 171: Second limiting groove 172: Second limiting member 1721: Guide protrusion 180: Linking mechanism 181: Linking member 1811: First inclined groove 182: Pressing member 1821: Second inclined groove 183: Fourth reset member 190: Rotational movement mechanism 191: First track 192: Second track 193: Intersection194: First sliding member 195: Second sliding member 196: First slider 197: Second slider 1971: Groove 198: Sliding wheel 211: Locking assembly 2111: First locking portion 2112: Second locking portion 2113: Fifth reset member 2114: Seventh reset member 212: Locking recess 230: Extension mechanism 231: First main connecting rod 232: Second main connecting rod 233: First auxiliary rod 234: Gear 235: First reinforcement rod 23 6: Third auxiliary rod 237: Second auxiliary rod 238: Second reinforcement rod 239: Fourth auxiliary rod 240: Second locking mechanism 241: Second locking member 2411: Operating end 2412: Locking end 242: Button 300: First release mechanism 310: First driving member 320: First operating member 330: First traction assembly 331: First traction rope 400: Second release mechanism 410: Second driving member 411: Elastic arm 420: Second operating member Working member 430: First transmission assembly 431: Pushing member 432: Second traction assembly 4321: Second traction rope 433: Linking block 434: Guide wheel 440: Second transmission assembly 441: Transmission member 4411: Fixed seat 44111: First connecting portion 4412: Movable pushing seat 44121: Second connecting portion 4413: Third connecting portion 442: Third driving member 443: Third traction assembly 4431: Third traction rope 44311: First rope end 44312: Second rope end 4432: Third traction sleeve 44321: First sleeve end 44322: Second sleeve end 444: Eighth restoration member 500: First carrier body 520: Pushing member 530: Sixth restoration member 600: Second carrier body 610: Engaging member F1: First direction F2: Second direction F3: Third direction F4: Fourth direction F5: Fifth direction Q1: First pivot point Q2: Second pivot point Q3: Third pivot point The drawings constituting a part of this application are used to provide further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute improper limitations on this application. In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the diagrams required for use in the description of the embodiments. Obviously, the diagrams described below are only some embodiments of the present application. For ordinary technicians in this field, other diagrams can be obtained based on these diagrams without any creative work. In addition, the drawings are not drawn to a 1:1 scale, and the relative sizes of the various elements are drawn only for illustrative purposes and are not necessarily drawn to true scale. FIG1 is a schematic diagram of a three-dimensional structure of a carrier according to an embodiment of the present application, wherein a first carrier body is connected to a first positioning assembly, and the first positioning assembly faces a first direction; FIG2 is a schematic diagram of a three-dimensional structure of a carrier according to an embodiment of the present application, wherein a first carrier body is connected to a first positioning assembly, and the first positioning assembly faces a third direction; FIG3 is a schematic diagram of a three-dimensional structure of a carrier according to an embodiment of the present application, wherein a first carrier body is connected to a first positioning assembly, and the first positioning assembly faces a fourth direction; FIG4 is a schematic diagram of a three-dimensional structure of a carrier according to an embodiment of the present application, wherein the second carrier body is connected to the first positioning assembly, and the first positioning assembly faces a third direction; FIG5 is a schematic diagram of a three-dimensional structure of a carrier according to an embodiment of the present application, wherein the second carrier body is connected to the first positioning assembly, and the first positioning assembly faces the fourth direction; FIG6 shows a perspective view of the second carrier body in FIG5 ; FIG7 is a schematic diagram of the three-dimensional structure of the positioning assembly in the first embodiment of the present application, wherein the first positioning assembly faces the first direction; FIG8 is a schematic diagram of the three-dimensional structure of the positioning assembly in the first embodiment of the present application, wherein the first positioning assembly faces the second direction; FIG9 is a schematic diagram of the three-dimensional structure of the positioning assembly in the first embodiment of the present application, wherein the first positioning assembly faces the fourth direction; FIG10 is a schematic diagram of the three-dimensional structure of the positioning assembly in the first embodiment of the present application, wherein the first positioning assembly faces the third direction; FIG11 is a schematic diagram of the three-dimensional structure of the first positioning assembly in the positioning assembly in FIG7 ; FIG12 shows a cross-sectional view taken along line U1-U1 of FIG11 , with the latch hook in a locked position; FIG13 shows a cross-sectional view taken along line U1-U1 of FIG11 , with the latch hook in a released position; FIG14 is a schematic diagram of the three-dimensional structure of the first positioning assembly in the positioning assembly in FIG7 from another perspective; FIG15 is an exploded view of the first positioning assembly in FIG14; FIG16 is an enlarged view of circle A in FIG15 ; FIG17 is a schematic diagram of a portion of the structure of the first positioning assembly in FIG15 , wherein the first top cover is omitted; FIG18 is an enlarged view of circle B in FIG17 ; FIG19 is an enlarged view of circle C in FIG17 ; FIG20 is a schematic diagram of a portion of the structure of the first positioning assembly in FIG15 , wherein the first bottom cover is omitted; FIG21 is an enlarged view of circle D in FIG20 ; FIG22 is a schematic diagram of the three-dimensional structure of the second positioning assembly in the positioning assembly in FIG7; FIG23 is a schematic diagram of the three-dimensional structure of the second positioning assembly in the positioning assembly in FIG7 from another perspective; FIG24 is a top view of the second positioning assembly in the positioning assembly of FIG7 ; FIG25 is a top view of the second positioning assembly in the positioning assembly of FIG7 , wherein the second top cover is omitted; FIG26 is an enlarged view of circle O in FIG25 ; FIG27 is an enlarged view of circle P in FIG25 ; FIG28 shows a bottom view of the second top cover of the second positioning assembly; FIG29 shows a cross-sectional view taken along line U2-U2 of FIG1 ; FIG30 is an enlarged view of circle E in FIG29; FIG31 is an enlarged view of circle F in FIG29 ; FIG32 shows a cross-sectional view taken along line U3-U3 of FIG2 ; FIG33 is an enlarged view of circle G in FIG30 ; FIG34 is an enlarged view of circle H in FIG30 ; FIG35 shows a cross-sectional view taken along line U4-U4 of FIG4 ; FIG36 is an enlarged view of circle J in FIG33 ; FIG37 is an enlarged view of circle K in FIG33 ; FIG38 is a partial structural diagram of a second positioning assembly according to an embodiment of the present application; FIG39 is a schematic structural diagram of a second support member in the second positioning assembly in FIG38; FIG40 is a partial structural diagram of a second positioning assembly according to another embodiment of the present application; FIG41 is a schematic diagram of the structure of FIG40 from another perspective; FIG42 is a cross-sectional view taken along line U5-U5 in FIG9 ; FIG43 is a schematic diagram of the three-dimensional structure of the positioning assembly in the first embodiment of the present application, wherein the first top cover and the second top cover are omitted; FIG44 is an enlarged view of the circle S in FIG43 ; FIG45 is a schematic diagram of the three-dimensional structure of the positioning assembly in the first embodiment of the present application, wherein the first top cover, the first bottom cover, and the second top cover are omitted; FIG46 is an enlarged view of circle T in FIG45 ; FIG47 is a schematic structural diagram of the third traction assembly in FIG43 , wherein the third traction assembly is not deformed; FIG48 is a schematic structural diagram of the third traction assembly in FIG43 , wherein the third traction assembly has been deformed; FIG49 shows a front view of the first carrier body in FIG1 ; FIG50 shows a cross-sectional view taken along line U6-U6 of FIG49 , wherein the push member is not pressed downward; FIG51 shows a cross-sectional view taken along line U6-U6 of FIG49 , wherein the push member is pressed downward; FIG52 is a schematic diagram of the three-dimensional structure of the positioning assembly in the second embodiment of the present application, wherein the first positioning assembly faces the first direction; FIG53 is a schematic diagram of the three-dimensional structure of the positioning assembly in the second embodiment of the present application, wherein the first positioning assembly faces the third direction; FIG54 is a schematic diagram of the three-dimensional structure of the positioning assembly in the second embodiment of the present application, wherein the first positioning assembly faces the second direction and is in a retracted state; FIG55 is a schematic diagram of the three-dimensional structure of the positioning assembly in the second embodiment of the present application, wherein the first positioning assembly is facing the second direction and is in an extended state; FIG56 is an enlarged view of circle L in FIG55 ; FIG57 is a schematic diagram of the three-dimensional structure of the positioning assembly in the second embodiment of the present application, wherein the first positioning assembly faces the fourth direction; Figure 58 is a cross-sectional view of the positioning assembly in the second embodiment of the present application. 100: Positioning component 110: first positioning component 111: First shell 112: First connecting mechanism 1122:Card slot 113: Instruction Agency 1133: Observation hole 125: Seat connection plug 126: Support Leg F1: First direction F2: Second direction F3: Third direction F4: Fourth direction

Claims

1. A positioning component, comprising a first positioning component and a second positioning component, wherein the first positioning component is rotatably disposed on the second positioning component, and the first positioning component is used for detachably connecting to a vehicle body, wherein the vehicle body is a first vehicle body or a second vehicle body; wherein, When the first positioning component is used to connect with the first vehicle body and rotates relative to the second positioning component to face a first direction, the first positioning component can restrict the first vehicle body from disengaging from the first positioning component; when the first positioning component is used to connect with the second vehicle body, the first positioning component is restricted to rotate relative to the second positioning component to face the first direction.

2. The positioning component according to claim 1, wherein, It also includes: a first connecting mechanism disposed on the first positioning component and having a locked state and an unlocked state, wherein when the first connecting mechanism is in the locked state, the first connecting mechanism is connected to the vehicle body, and when the first connecting mechanism is in the unlocked state, the first connecting mechanism is disassembled from the vehicle body; and a first restricting mechanism disposed between the first positioning component and the second positioning component for selectively allowing or restricting the first connecting mechanism to switch between the locked state and the unlocked state.

3. The positioning component according to claim 2, wherein, It also includes: a locking and retaining mechanism, movably disposed on the first positioning component, and used to maintain the connection between the first connecting mechanism and the vehicle body; wherein, when the first positioning component is used to connect the first vehicle body and is oriented toward the first direction, the first restricting mechanism enters the movement path of the locking and retaining mechanism, restricting the movement of the locking and retaining mechanism, so as to restrict the first connecting mechanism from switching from the locked state to the unlocked state.

4. The positioning component according to claim 2 or 3, wherein, The first limiting mechanism includes: a first limiting groove disposed on the side of the second positioning component facing the first positioning component; and a first limiting member movably disposed on the first positioning component and capable of being inserted into or retracted from the first limiting groove; wherein, when the first limiting member is inserted into the first limiting groove, the first limiting member allows the first connecting mechanism to switch to the unlocked state; when the first limiting member retracts from the first limiting groove, the first limiting member restricts the first connecting mechanism from switching to the unlocked state; and when the first positioning component rotates relative to the second positioning component to face the first direction, the first limiting member retracts from the first limiting groove.

5. The positioning component according to claim 4, wherein, The first positioning component has a rotation axis, and the first limiting member is offset from the rotation axis. A straight line passing through the rotation axis and perpendicular to the first direction is defined as a reference line. When the first positioning component is facing the first direction, the first limiting member and the first limiting groove are misaligned and located on both sides of the reference line.

6. The positioning component according to claim 5, wherein, The first positioning component has a circular structure, the rotation axis is the center of the first positioning component, the first limiting groove is a semi-circular groove, the radius of the semi-circular groove is the distance between the center of the first limiting member and the center of the first positioning component, and when the first positioning component rotates relative to the second positioning component to face away from the first direction, the first limiting member is located at the midpoint of the first limiting groove.

7. The positioning component according to claim 4, wherein, The first limiting member has a sliding inclined surface at one end facing the second positioning component. The sliding inclined surface can push against the first limiting groove so that the first limiting member moves away from the first limiting groove in a direction away from the second positioning component.

8. The positioning component according to claim 7, wherein, The first positioning component includes a first housing, and the first connecting mechanism includes a locking hook, which is pivotally connected to the first housing and has a locked position and an unlocked position; when the locking hook is in the locked position, the locking hook is used to engage and lock with the vehicle body.

9. The positioning component according to claim 8, wherein, The first housing has a first mounting cavity, and the positioning component further includes: a locking and retaining mechanism, which is movably disposed within the first mounting cavity, and when the engaging hook is driven to the locking position, the locking and retaining mechanism is used to lock the engaging hook in the locking position.

10. The positioning component according to claim 9, wherein, The locking and retaining mechanism includes a first locking member, which is movably disposed within the first mounting cavity and has a first position and a second position. One of the first locking member and the engaging hook has a locking groove, and the other has an engaging portion. When the first locking member is in the first position, the locking groove engages with the engaging portion to lock the engaging hook in the locked position. When the first locking member is in the second position, the locking groove disengages from the engaging portion to allow the engaging hook to switch between the locked position and the unlocked position.

11. The positioning component according to claim 10, wherein, When the first limiting member retracts from the first limiting groove, the first limiting member is located in the movement path of the first locking member to restrict the first locking member from switching from the first position to the second position; When the first limiting member is inserted into the first limiting groove, the first limiting member deviates from the movement path of the first locking member to allow the first locking member to switch from the first position to the second position.

12. The positioning component according to claim 1, wherein, It also includes a second limiting mechanism, which is disposed between the first positioning component and the second positioning component, for selectively limiting the angular range of rotation of the first positioning component relative to the second positioning component.

13. The positioning component according to claim 12, wherein, The second limiting mechanism has a first state and a second state. When the second limiting mechanism is in the first state, it restricts the first positioning component from rotating relative to the second positioning component toward the first direction. When the second limiting mechanism is in the second state, it allows the first positioning component to rotate relative to the second positioning component toward the first direction. The positioning component further includes an elastic element. The elastic element always keeps the second limiting mechanism in the first state. When the first positioning component is used to connect to the first vehicle body, the second limiting mechanism is in the second state by overcoming the elastic force of the elastic element through the first vehicle body. Alternatively, the elastic element always keeps the second limiting mechanism in the second state. When the first positioning component is used to connect to the second vehicle body, the second limiting mechanism is in the first state by overcoming the elastic force of the elastic element through the second vehicle body.

14. The positioning component according to claim 13, wherein, The second limiting mechanism includes: a second limiting groove disposed in one of the second positioning component and the first positioning component; and a second limiting member movably disposed in the other of the second positioning component and the first positioning component and capable of being inserted into or retracted from the second limiting groove; wherein, when the first positioning component is used to connect the second carrier body, the second limiting member is inserted into the second limiting groove, and the first positioning component is restricted to rotate relative to the second positioning component toward the first direction.

15. The positioning component according to claim 14, wherein, The first positioning component has a rotation axis, and the second limiting member is offset from the rotation axis. A straight line passing through the rotation axis and perpendicular to the first direction is defined as a reference line. When the first positioning component is facing the first direction, the second limiting member and the second limiting groove are misaligned and located on both sides of the reference line.

16. The positioning component according to claim 15, wherein, The first positioning component has a circular structure, the rotation axis is the center of the first positioning component, the second limiting groove is a semi-circular groove, the radius of the semi-circular groove is the distance between the center of the second limiting member and the center of the first positioning component, and when the first positioning component rotates relative to the second positioning component to face away from the first direction, the second limiting member is located at the midpoint of the second limiting groove.

17. The positioning component according to claim 14, wherein, It also includes a linkage mechanism, which is disposed in the first positioning component and is used to drive the second limiting member. The linkage mechanism can drive the second limiting member to retract or insert into the second limiting groove.

18. The positioning component according to claim 17, wherein, The linkage mechanism includes a linkage member, which is movably disposed in the first positioning assembly and has a third position and a fourth position. A first inclined groove is formed at the first end of the linkage member, and the end of the second limiting member opposite to the second limiting groove is slidably disposed in the first inclined groove. When the linkage member moves to the third position, the second limiting member is inserted into the second limiting groove. When the linkage member moves to the fourth position, the second limiting member is retracted from the second limiting groove.

19. The positioning component according to claim 18, wherein, The linkage mechanism further includes a pressing member, which is movably disposed in the first positioning component and has a fifth position and a sixth position. The pressing member has a second inclined groove, and the second end of the linkage member is slidably disposed in the second inclined groove. When the pressing member is in the fifth position, the linkage member is in the third position; when the pressing member is in the sixth position, the linkage member is in the fourth position.

20. The positioning component according to claim 19, wherein, When the first positioning component is used to connect with the second vehicle body, the pressing member is in the fifth position and the linkage member is in the third position.

21. The positioning component according to claim 1, wherein, The positioning component further includes a first locking mechanism disposed between the first positioning component and the second positioning component. The first locking mechanism has a first locked state and a first unlocked state. When the first locking mechanism is in the first locked state, the first positioning component is restricted from rotating relative to the second positioning component. When the first locking mechanism is in the first unlocked state, the first positioning component is allowed to rotate relative to the second positioning component.

22. The positioning component according to claim 21, wherein, The first locking mechanism includes: a locking component movably disposed on one of the second positioning component and the first positioning component; and a locking recess disposed on the other of the second positioning component and the first positioning component; wherein, when the locking component is inserted into the locking recess, the first positioning component and the second positioning component are locked together to restrict the first positioning component from rotating relative to the second positioning component; when the locking component is disengaged from the locking recess, the first positioning component can rotate relative to the second positioning component.

23. The positioning component according to claim 22, wherein, The locking assembly includes a first locking part, which is movably disposed in either the second positioning assembly or the first positioning assembly along the first direction; when the first positioning assembly rotates relative to the second positioning assembly to either facing the first direction or facing away from the first direction, the first locking part can lock into the locking recess.

24. The positioning component according to claim 23, wherein, The positioning component further includes a first release mechanism, which is operably connected to the first lock and used to drive the first lock out of the locking recess.

25. The positioning component according to claim 24, wherein, The first locking part is movably disposed on the second positioning component, and the locking recess is disposed on the first positioning component. The first unlocking mechanism includes: a first driving member, pivotally connected to the second positioning component and pivotally connected to the first locking part; a first operating member, operably disposed on the second positioning component; and a first traction component, respectively connected to the first operating member and the first driving member; wherein, when the first operating member is operated, the first operating member drives the first driving member to pivot through the first traction component, so that the first driving member can drive the first locking part to exit from the locking recess.

26. The positioning component according to any one of claims 23 to 25, wherein, The locking assembly further includes a second locking part, which is movably disposed on one of the second positioning assembly and the first positioning assembly, and the second locking part and the first locking part are disposed opposite to each other along the first direction; when the first positioning assembly rotates relative to the second positioning assembly to either facing the first direction or facing away from the first direction, the second locking part can lock into the locking recess.

27. The positioning component according to claim 1, wherein, The second positioning component includes a second housing. A protrusion is provided on the upper surface of the second housing, which is connected to each other. The protrusion forms a limiting protrusion. A groove structure is formed between the limiting protrusion and the upper surface of the second housing. The first positioning component includes a first housing. When the first positioning component is facing the first direction or away from the first direction relative to the second positioning component, a portion of the edge of the first housing is inserted into the groove structure.

28. The positioning component according to claim 27, wherein, The second positioning component includes a frame and at least one first support mechanism. The first support mechanism includes a first support member and a second support member. The first support member is fixed to the frame, and the second support member is supported on the first support member. When the first positioning component is facing the first direction or away from the first direction relative to the second positioning component, at least a portion of the second support member is located below the first positioning component.

29. The positioning component according to claim 1, wherein, The second positioning component further includes a third support mechanism and a second housing. The second housing includes a second top cover and a second bottom cover that are connected to each other. The third support mechanism includes a plurality of support columns. Each support column includes a bottom column disposed on the second bottom cover and a top column disposed on the second top cover. The bottom column and the top column are connected.

30. A vehicle comprising: The positioning component according to any one of claims 1-29; And a vehicle body, detachably connected to the first positioning component of the positioning assembly, wherein the vehicle body is a first vehicle body or a second vehicle body.

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