A link transmission three-joint underactuated mechanism for finger rehabilitation

Abstract

The application relates to a connecting rod transmission three-joint underdrive mechanism for finger rehabilitation, which comprises a proximal phalanx sliding groove connecting rod mechanism and a middle phalanx sliding groove connecting rod mechanism. Through the proximal phalanx sliding groove and the proximal phalanx connecting rod system, the middle phalanx can keep following the proximal phalanx; in the same way, the distal phalanx can keep following the middle phalanx through the middle phalanx sliding groove connecting rod. Therefore, the mechanism can adopt one drive to synchronously control the angles of the three phalanges. The application can effectively reduce the driving quantity of a non-flexible hand rehabilitation medical robot, reduce the control difficulty, and solve the defects of poor control precision, high device cost and heavy weight of the existing non-underdrive manipulator.

Description

Technical Field

[0001] This invention relates to a finger underactuated mechanism, specifically a linkage-driven three-joint underactuated mechanism for finger rehabilitation. Background Technology

[0002] Compared to other parts of the body, the human hand can perform many gross motor skills and dexterity exercises, which play an irreplaceable role in daily life. Neurological damage can severely impair hand function, significantly reducing quality of life. Stroke is a leading cause of nerve damage in the hand. Globally, the incidence and disability rate of stroke in adults are high. For patients with hand injuries, in addition to medication, hand rehabilitation training is an effective treatment option.

[0003] Traditional hand rehabilitation training often involves rehabilitation physicians manually administering multiple courses of treatment to patients. This method is time-consuming and expensive for patients. Furthermore, limited by the physician's skill level and available time, it is often inefficient and fails to achieve satisfactory results. To address this challenge, many universities and research institutions have begun developing hand rehabilitation robots. These robots can effectively complete long-term, fewer-step hand rehabilitation training programs; and due to their high efficiency, ease of use, and low cost, they are widely favored.

[0004] Existing hand rehabilitation robots can be mainly categorized into flexible hand rehabilitation robots, multi-drive hand rehabilitation robots, and under-drive hand rehabilitation robots based on the number of drives. Flexible hand rehabilitation mechanisms have inconsistent finger joint flexion positions, resulting in poorer rehabilitation outcomes compared to non-flexible robots. Multi-drive hand rehabilitation robots, with each joint having its own drive, can have dozens of drives, significantly increasing control complexity and device cost, and making it difficult to control the device's weight and size. This invention uses a single drive to control the synchronous rotation of the three finger joints, greatly reducing the overall control complexity of the rehabilitation device while ensuring precise joint control. Summary of the Invention

[0005] The present invention aims to propose a linkage-driven three-joint underactuated mechanism for finger rehabilitation, which aims to solve the problems of large size and weight and high control difficulty of multi-drive finger rehabilitation mechanisms.

[0006] Embodiments of the present invention provide a three-joint underactuated linkage mechanism for finger rehabilitation, characterized by a proximal phalanx groove linkage mechanism and a middle phalanx groove linkage mechanism. The proximal phalanx groove linkage mechanism includes a left proximal phalanx roller pull-down linkage, a right proximal phalanx roller pull-down linkage, a proximal phalanx, a groove rod, a left middle phalanx control linkage, and a right middle phalanx control linkage. The middle phalanx groove linkage mechanism includes a middle phalanx roller pull-down linkage, a middle phalanx, a middle phalanx roller, a distal phalanx control linkage, and a distal phalanx.

[0007] To facilitate the description of the shapes of each part, the side of the underactuated mechanism that contacts the human hand is defined as the lower side of the underactuated mechanism, and vice versa. With the arm extended, the direction away from the human body is the front side of the underactuated mechanism, and vice versa. With the palm extended, the plane parallel to the palm and located in the middle of each finger joint is called the mid-plane of the underactuated fingers. The underactuated mechanism simulates a clenching motion called adduction, and the motion of spreading the fingers called abduction.

[0008] The lower half of the proximal knuckle component is a cuboid, and to improve wearing comfort, the contact surface between the component and the hand is designed with an arc. An arc-shaped pivot is located on the rear side of the cuboid, with a through hole in the center for easy pin connection to the robotic hand. The front side of the cuboid has a hollow center and two protruding arcs on both sides, with a hole at the center of each arc protrusion for easy pin connection to the pivot of the next knuckle. On the upper side of the cuboid, near the hand, there is a tall, slender cuboid protrusion perpendicular to the base plate. A vertical slot-shaped opening is located in the center of this protruding cuboid for easy connection to a connecting rod via a sliding pin. At the top of the component, there is a central slot with two protruding arcs on either side, with a hole in the center of each arc for easy connection between the proximal knuckle and a linear motor.

[0009] The lower half of the middle knuckle component is approximately cuboid, with a pivot on the rear side connecting to the front of the proximal knuckle. The front side features a hollowed-out structure with protruding sides for connecting to the rear of the distal knuckle. The surface in contact with the hand is designed with a rounded arc. The upper end near the proximal knuckle has a slender, tall cuboid protrusion with a vertical groove in the center for a sliding pin connection with a connecting rod, enabling linkage with the proximal knuckle.

[0010] The distal phalanx is rectangular in shape. The surface of the cuboid that contacts the hand is designed with a rounded arc. A pivot is located on the rear of this part for a pin-connection with the front of the middle phalanx. Two near-triangular protrusions are located on its upper side, with through holes for pin-connection with a connecting rod, enabling linkage with the middle phalanx.

[0011] All connecting rods are shaped like the number "7". To reduce stress concentration and deformation during use, the corners of the connecting rods are rounded with a large radius. The long straight end of the connecting rod has a hole drilled in the edge for easy insertion into the groove on the finger joint base plate for pin connection. The other end has a design with protruding sides and a hollow center, facilitating connection with the slide groove and inter-connection between connecting rods. The specific shape and function of each connecting rod are as follows: The left and right proximal finger joint roller pull-down connecting rods are slender inverted "7" shapes. The corners of these connecting rods have 90-degree angles to ensure unobstructed straight lines between the two fixed points, preventing interference between the connecting rod and the rear of the proximal finger joint during rotation. Both ends of the connecting rods have rounded corners, with holes at the center of the rounded corners for pin connection with the palm and proximal finger joint slide groove. The proximal finger joint roller pull-down connecting rod connects the palm and the roller in the proximal finger joint slide groove. When the linear motor drives the proximal joint to rotate, the roller in the proximal joint groove is pulled down along the groove by the proximal joint pull-down linkage, causing it to move downwards relative to the proximal joint. Simultaneously, the proximal joint roller pull-down linkage features a symmetrical design on both sides, enhancing force transmission and increasing the stability of the mechanism. The middle joint control linkage, except for its dimensions, is identical in shape to the proximal joint rod. To prevent interference between the rear tip of the middle joint and the middle joint control linkage during rotation, the middle joint control linkage has a 70-degree angle on both sides, creating a larger space between its two fixed points. One side of its long straight end is connected to the proximal joint groove and the proximal joint roller pull-down linkage via a roller and a pin, while the other end is fixed above the rotating shaft connecting the middle and proximal joints using a roller. The middle joint control linkage also features a symmetrical design on both sides. When the proximal knuckle rotates, the roller moves downward along the proximal knuckle groove under the action of the proximal knuckle roller pull-down linkage, simultaneously driving the middle knuckle control linkage downward. At this time, the middle knuckle control linkage applies a forward force through the opening on the upper side of the middle knuckle rotation axis, generating a rotational torque in the middle knuckle, thereby controlling the coordinated rotation of the middle knuckle. The angle between the two sides of the middle knuckle roller pull-down linkage is 90 degrees. One end has an arc-shaped opening in the middle for connecting with the middle knuckle, while the other end has a hollowed-out design with protruding fixing plates on both sides, used to connect the middle knuckle groove to the middle knuckle roller pull-down linkage via the roller. When the middle knuckle rotates, the middle knuckle roller pull-down linkage provides a pulling force for the roller in the middle knuckle groove to move downward along the middle knuckle groove. The distal knuckle control linkage and the middle knuckle pull-down linkage are identical in shape except for size. To prevent interference between the rear tip of the distal phalanx and the distal phalanx control link during rotation, the distal phalanx control link is angled at 70 degrees on both sides to create a larger space between the two fixed points. One of its hollowed-out ends is inserted into the middle phalanx groove and connected via rollers, the middle phalanx control link, and the middle phalanx groove; the other end is connected to the upper side of the distal phalanx rotation shaft via a pin.When the middle finger joint rotates, the roller in the middle finger joint groove moves downward along the groove under the pulling force of the middle finger joint roller pull-down linkage, simultaneously driving the distal finger joint control linkage to move downward in sync. The distal finger joint control linkage applies a forward force at the opening on the upper side of the distal finger joint rotation shaft, thereby generating a rotational torque to control the rotation of the distal finger joint.

[0012] Furthermore, in the three-joint underactuated mechanism, the proximal phalanx and the palm of the hand rehabilitation robot are connected by a pin. The upper part of the connection between the proximal phalanx and the palm is rectangular, while the lower part is arc-shaped, which allows the underactuated finger to rotate normally downwards while also achieving a hard limit on the upward rotation of the underactuated finger.

[0013] Furthermore, the connection between the middle phalanx and the proximal phalanx, and the connection between the distal phalanx and the middle phalanx, both adopt an upper rectangular shape and a lower circular arc design, thereby achieving overall hard limiting of the three-joint under-drive mechanism.

[0014] Furthermore, the roller connecting the proximal knuckle roller pull-down link and the middle knuckle control link can be inserted into the proximal knuckle slide groove, allowing the entire roller to move up and down along the proximal knuckle slide groove.

[0015] Furthermore, the roller connecting the middle finger joint roller pull-down linkage and the distal finger joint control linkage can be inserted into the middle finger joint slide groove, allowing the entire roller to move up and down along the middle finger joint slide groove.

[0016] Furthermore, when the three-joint under-drive mechanism retracts, the rollers in the proximal joint groove and the middle joint groove move downwards along the proximal joint groove and the middle joint groove, respectively. When the movement reaches the lowest end of the groove, the device reaches the limit position of retraction.

[0017] Furthermore, each link adopts a "7"-shaped design, which ensures that while meeting the tensile strength of the link, sufficient space is reserved between the two fixed points of the link to prevent interference between the link and each link when each joint reaches its limit position.

[0018] Furthermore, during use, the underside of the three-joint underactuated finger can be spatially separated from the human hand through a flexible material, ensuring that the mechanical finger provides bending driving torque to the human hand while preventing hand injury caused by joint misalignment during rotation.

[0019] Compared with existing technologies, the advantages of this invention are: This invention fully utilizes a linkage mechanism, enabling the synchronous movement of three joints in the rehabilitated finger through a single drive control. Compared to existing flexible devices, this structure can precisely control the angle of finger rotation, and the force sensor of the linear motor allows for feedback of the rehabilitated finger's force. Compared to existing non-flexible underactuated mechanisms and other transmission methods, this mechanism, employing only linkage mechanisms, effectively reduces the overall weight and complexity of the mechanism while meeting requirements, improving device stability, and reducing the failure rate. This invention aims to propose an underactuated mechanism for a rehabilitation robotic hand to solve the aforementioned existing problems. Attached Figure Description

[0020] Figure 1 This is an isometric drawing of the proximal joint sliding groove linkage mechanism of the present invention.

[0021] Figure 2 This is an isometric drawing of the finger joint sliding groove linkage mechanism in this invention.

[0022] Figure 3 This is an isometric drawing of the linkage-driven three-joint underactuated mechanism for finger rehabilitation according to the present invention.

[0023] Figure 4 This is a schematic front view of the outward extension limit position of the mechanism of the present invention.

[0024] Figure 5 This is a schematic front view of the inward limit position of the mechanism of the present invention.

[0025] Figure 6 This is an exploded view of the linkage-driven three-joint underactuated mechanism for finger rehabilitation of the present invention.

[0026] Figure 7 This is the overall assembly isometric drawing of the hand rehabilitation robot installed by our organization. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings. This description is not intended to limit the scope of the invention; any equivalent modifications or substitutions in function, method, or structure made by those skilled in the art based on this embodiment are within the protection scope of the present invention.

[0028] like Figures 1 to 7 As shown: Figure 1 This is an isometric drawing of the proximal finger joint slide linkage mechanism, which includes: part 1 proximal finger joint, part 2 middle finger joint, part 11 left proximal finger joint roller pull-down linkage, part 12 right proximal finger joint roller pull-down linkage, part 13 left middle finger joint control linkage, and part 14 right middle finger joint control linkage. Figure 2 This is an isometric drawing of the middle finger joint slide rail linkage mechanism, which includes: part 2 middle finger joint, part 3 distal finger joint, part 21 middle finger joint roller pull-down linkage, and part 22 distal finger joint control linkage.Figure 3 This is an isometric view of the three-joint underactuated linkage mechanism for finger rehabilitation of the present invention, which includes a proximal phalanx groove linkage mechanism and a middle phalanx groove linkage mechanism. Figure 4 This is a schematic diagram of the abduction limit position of the underactuated mechanism. The rotary joints of the proximal, middle, and distal phalanges are all equipped with hard limit mechanisms. When the three-joint underactuated mechanism abducts, its maximum extension is when the three fingers are on the same straight line. Figure 5 This is a schematic diagram of the inward limit position of the underactuated mechanism. When the underactuated mechanism retracts, the proximal joint roller and the middle joint roller move downwards along the proximal joint groove and the middle joint groove, respectively. When both reach the lowest end of the corresponding groove at the same time, this is the inward limit position of the device. Figure 6 This is an exploded view of the linkage-driven three-joint underactuated mechanism for finger rehabilitation of the present invention. Figure 7 This is a schematic diagram of the device being mounted on a hand rehabilitation robot. The hand rehabilitation robot consists of four underactuated devices and is driven by four linear motors. It can perform rehabilitation training on 12 joints of the four fingers of the hand: index finger, middle finger, ring finger, and little finger.

[0029] For ease of description, the side of the device closest to the body when the arm is fully extended is defined as the rear side. Using the corner as a boundary, the longer end of the connecting rod is called the straight side, and the shorter end is called the corner side. The following description will explain the principle of this device from the rear side to the front side according to the function of each connecting rod.

[0030] like Figure 7 As shown, the entire mechanism is connected to the palm of the finger rehabilitation robot via a pin on the rear side of the proximal phalanx. The left proximal phalanx roller pull-down link 11 and the right proximal phalanx roller pull-down link 12 are inserted into the groove on the upper surface of the palm at their corners, and connected to the palm via the pin. On the other side of the left proximal phalanx roller pull-down link 11 and the right proximal phalanx roller pull-down link 12, rollers connect the ends of the links to the proximal phalanx groove, forming a sliding and rotating joint, allowing the linear ends of the left proximal phalanx roller pull-down link 11 and the right proximal phalanx roller pull-down link 12 to move up and down along the direction of the groove. At the uppermost end of the proximal phalanx 1, a pin connects the output shaft of the linear motor to the proximal phalanx 1, using the forward thrust and backward pull of the motor to provide power to the entire mechanism.

[0031] like Figure 1As shown, the top ends of the left middle finger joint control link 13 and the right middle finger joint control link 14 on their straight sides are secured by pins to ensure that the top ends of the left middle finger joint control link 13 and the right middle finger joint control link 14 are concentric with the top openings on the straight sides of the left proximal finger joint roller pull-down link 11 and the right proximal finger joint roller pull-down link 12, respectively, and move synchronously in a straight line along the slide groove. The corner ends of the left middle finger joint control link 13 and the right middle finger joint control link 14 form a rotary joint with the middle finger joint 2. This ensures that when the left middle finger joint control link 13 and the right middle finger joint control link 14 apply a forward force to the middle finger joint 2, this force generates a rotational torque about the rotation axis of the middle finger joint 2, causing the middle finger joint 2 to rotate.

[0032] like Figure 2 As shown, the straight end of the middle finger joint roller pull-down link 21 is inserted into the groove on the upper surface of the proximal finger joint 1, forming a revolute joint. The corner end of the middle finger joint roller pull-down link 21 forms a sliding joint with the slide groove of the middle finger joint 2. The straight end of the distal finger joint control link 22 forms a revolute joint with the corner end of the middle finger joint roller pull-down link 21, allowing their ends to rotate relative to each other and move up and down synchronously along the slide groove of the middle finger joint 2. The corner end of the distal finger joint control link 22 is inserted into the groove of the distal finger joint 3, forming a revolute joint. This ensures that when the middle finger joint rotates relative to the proximal finger joint, the roller in the middle finger joint slide groove can drive the straight end of the distal finger joint control link 22 to move downward along the slide groove under the pulling force of the middle finger joint roller pull-down link 21. When the corner end of the distal finger joint control link 22 moves forward, a rotational torque is generated on the upper side of the distal finger joint 3, causing the distal finger joint 3 to rotate.

[0033] like Figure 4 As shown, when the linear motor retracts, the three-joint underdriven mechanism will extend outwards. When the upper surfaces of the three joints are parallel to each other, the two rollers will simultaneously reach the top of the corresponding groove, i.e., the extension limit position of the device. Figure 7 As shown, when the linear motor extends, the tip of the proximal phalanx 1 will be subjected to a forward force, forming a rotational torque around the rotation axis of the proximal phalanx 1. At this time, the proximal phalanx 1 will rotate relative to the palm.

[0034] Furthermore, when the proximal phalanx 1 rotates, the left proximal phalanx roller pull-down link 11 and the right proximal phalanx roller pull-down link 12 will exert a force on the roller in the groove of the proximal phalanx 1 in a straight downward direction along the two fixed points passing through the left proximal phalanx roller pull-down link 11 and the right proximal phalanx roller pull-down link 12. The component of this force will pull the roller to slide downward along the groove direction.

[0035] Furthermore, when the roller in the groove of the proximal finger joint 1 moves downward, it will drive the top ends of the left middle finger joint control link 13 and the right middle finger joint control link 14 to move downward synchronously. At this time, at the opening on the corner side of the left middle finger joint control link 13 and the right middle finger joint control link 14, the link generates a force on the middle finger joint 2 along the straight line passing through the two fixed points of the left middle finger joint control link 13 and the right middle finger joint control link 14 and in the forward direction. The component of this force will generate a rotational torque on the middle finger joint 2 about the rotation axis of the middle finger joint 2, thereby causing the middle finger joint 2 to rotate, thus realizing the linkage effect of the movement of the proximal and middle fingers.

[0036] Furthermore, when the middle finger joint 2 rotates, the middle finger joint roller pull-down linkage 21 will generate a downward force on the roller located in the middle finger joint groove along the two fixed points of the middle finger joint roller pull-down linkage 21. The component of this force can cause the roller in the middle finger joint 2 groove to move downward along the groove.

[0037] Furthermore, as the rollers within the groove of the middle finger joint 2 move downwards along the groove, they will synchronously drive the top end of the distal finger joint control link 22 on the straight side to move downwards. At this time, at the top end of the distal finger joint control link 22 on the corner side, the distal finger joint control link 22 will generate a force that moves forward along a straight line passing through the two openings of the distal finger joint control link 22. Its component force can generate a torque on the distal finger joint 3, causing the distal finger joint 3 to rotate around its rotation axis, thereby achieving the linkage effect of the movement of the middle finger joint and the distal finger joint.

[0038] Furthermore, based on the above analysis, this device can achieve an underactuated effect by applying a single drive to control the synchronous rotation of three joints. For example... Figure 5 As shown, when the linear motor extends, the rollers in both chutes will move downwards along the direction of the chutes, and the entire device will retract. When the two rollers reach the bottom of the chutes simultaneously, the device will lock to achieve a hard downward limit, which is the retraction limit position of the device.

[0039] Furthermore, when the entire device is in use, flexible materials such as springs or rubber should be used to isolate the human finger from the underdriven finger, providing sufficient rotation space for the human finger to prevent hand injury caused by misalignment of the human hand joint and mechanical joint during rotation.

[0040] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. The present invention will now be described in detail with reference to the various embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention, and any equivalent functional, methodological, or structural modifications or substitutions made by those skilled in the art based on these embodiments are within the scope of protection of the present invention.

Claims

1. A link transmission three-joint underactuated mechanism for finger rehabilitation, characterized in that, It comprises proximal interphalangeal slot link mechanism and middle interphalangeal slot link mechanism, and joint adduction and abduction hard limit design; The proximal interphalangeal slot link mechanism comprises proximal interphalangeal, left proximal interphalangeal roller downlink, right proximal interphalangeal roller downlink, proximal interphalangeal roller and middle interphalangeal control link; the middle interphalangeal slot link mechanism comprises middle interphalangeal, distal interphalangeal, middle interphalangeal roller downlink, middle interphalangeal roller and distal interphalangeal control link; The left proximal interphalangeal roller downlink and the right proximal interphalangeal roller downlink are inserted into the palm upper surface groove on the corner side, the palm groove is punched, and the left proximal interphalangeal roller downlink, the right proximal interphalangeal roller downlink and the palm are connected through the bolt; on the other side of the left proximal interphalangeal roller downlink and the right proximal interphalangeal roller downlink, the roller is used to connect the link end and the proximal interphalangeal slot, forming a moving pair and a rotating pair, so that the linear side end of the left proximal interphalangeal roller downlink and the right proximal interphalangeal roller downlink can move up and down along the direction of the slot; at the uppermost end of the proximal interphalangeal, the linear motor output shaft and the proximal interphalangeal are connected by using the bolt, and the forward thrust and the backward pull of the motor provide power for the whole mechanism; The linear side top end of the left middle interphalangeal control link and the right middle interphalangeal control link uses the bolt to make the left middle interphalangeal control link and the right middle interphalangeal control link respectively and the left proximal interphalangeal roller downlink and the right proximal interphalangeal roller downlink linear side top end hole keep concentric, so that their top ends form rotating pairs with each other and moving pairs with the proximal interphalangeal slot; the corner side end hole of the left middle interphalangeal control link and the right middle interphalangeal control link is fixed in the hole on the upper side of the middle interphalangeal and the proximal interphalangeal rotating shaft by using the bolt, so as to form a rotating pair connection; to ensure that when the left middle interphalangeal control link and the right middle interphalangeal control link exert a forward force on the middle interphalangeal, the force can generate a rotating torque around the middle interphalangeal rotating shaft, so that the middle interphalangeal rotates; The linear end of the middle interphalangeal roller downlink is inserted into the groove on the upper surface of the proximal interphalangeal, and is connected by using the bolt, forming a rotating pair; the corner side top end hole of the middle interphalangeal roller downlink is aligned with the slot hole of the middle interphalangeal after being connected by using the roller, so that the top end of the middle interphalangeal roller downlink can move up and down along the slot, forming a moving pair; the linear side top end hole of the distal interphalangeal control link is aligned with the corner side top end hole of the middle interphalangeal roller downlink and is connected by using the roller, so that the top ends thereof can rotate relative to each other and can move up and down along the middle interphalangeal slot in synchronization; the corner side of the distal interphalangeal control link is inserted into the groove of the distal interphalangeal, and the top end hole thereof is connected with the hole above the distal interphalangeal rotating shaft by using the bolt, forming a rotating pair; to ensure that when the middle interphalangeal rotates relative to the proximal interphalangeal, the roller in the middle interphalangeal slot can drive the linear side of the distal interphalangeal control link to move downward along the middle interphalangeal slot; when the corner side of the distal interphalangeal control link moves forward, a rotating torque that makes the distal interphalangeal rotate can be generated on the upper side of the distal interphalangeal; When the linear motor contracts, the three-joint underactuated mechanism will be extended; when the upper surfaces of the three joints are parallel to each other, the two rollers will reach the top of the corresponding sliding grooves at the same time, i.e. the extreme position of the extension of the device; when the linear motor extends, the top of the proximal joint will be subjected to a forward force, forming a rotational torque around the rotation axis of the proximal joint, and at this time the proximal joint will rotate relative to the palm; When the proximal joint rotates, the left proximal joint roller downlink and the right proximal joint roller downlink will generate a force on the roller in the proximal joint sliding groove, the force being directed downward along a straight line passing through the two fixed points of the proximal joint roller downlink, and the component of the force will pull the roller to slide downward along the sliding groove; When the roller in the proximal joint sliding groove moves downward, the left middle joint control link and the right middle joint control link will move downward synchronously; at this time, the links will generate a force on the middle joint, the force being directed forward along a straight line passing through the two fixed points of the left middle joint control link and the right middle joint control link, and the component of the force will generate a rotational torque on the middle joint around the rotation axis of the middle joint, so that the middle joint rotates, thereby realizing the linkage effect of the proximal joint and the middle joint; When the middle joint rotates, the middle joint roller downlink will generate a force on the roller in the middle joint sliding groove, the force being directed downward along a straight line passing through the two fixed points of the middle joint roller downlink, and the component of the force will move the roller in the middle joint sliding groove downward along the sliding groove; When the roller in the middle joint sliding groove moves downward along the sliding groove, the linear side top of the distal joint control link will move synchronously; at this time, the distal joint control link will generate a force on the distal joint, the force being directed forward along a straight line passing through the two openings of the distal joint control link, and the component of the force will generate a torque on the distal joint to rotate the distal joint around its rotation axis.

2. The link actuated three joint underactuated mechanism for finger rehabilitation according to claim 1, characterized in that The shape of the joint connecting shaft is designed as a rectangular design on the upper side of the shaft and a circular arc design on the lower side of the shaft; when the manipulator retracts, it can work normally, and when it reaches the extreme position of extension, it realizes mechanical limiting.

3. The link actuated three joint underactuated mechanism for finger rehabilitation according to claim 1, wherein The force transmission between the joints is carried out through the links, and sliding grooves are designed above the proximal joint and above the distal joint, and the joint connecting nodes can be translated up and down along the sliding grooves through the rollers.

4. The link actuated three joint underactuated mechanism for finger rehabilitation of claim 1, wherein When the device reaches the maximum extension degree, the two rollers reach the top of the corresponding sliding grooves respectively; when the device reaches the maximum retraction degree, the two rollers reach the bottom of the corresponding sliding grooves respectively; through the rollers, the mechanical limiting of the two extreme positions of the device is realized at the same time.

5. The link actuated three joint underactuated mechanism for finger rehabilitation according to claim 1, wherein When the driving force pushes the proximal joint to rotate, the force is transmitted to the middle joint through the links to make the middle joint rotate; when the middle joint rotates, the force can be transmitted to the distal joint through the links to make the distal joint rotate; the force can be transmitted through the links in the direction of the proximal joint to the middle joint to the distal joint.

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