Cooperative structure and robotic arm with adaptive gravity compensation

Abstract

The application relates to a self-adaptive gravity balance cooperation structure and a mechanical arm, which mainly comprises a connecting rod swing assembly, a first sliding block slidably arranged on an input rod of the connecting rod swing assembly, a second sliding block slidably arranged on an output rod of the connecting rod swing assembly, a balance motor for driving the first sliding block to move along the axial direction of the input rod, a first spring compensation assembly, a second spring compensation assembly, a pulley and a traction rope and the like. At least a part of the connecting rod swing assembly is coaxially provided with a pulley on a pivot shaft which is pivotally connected. One end of the traction rope is connected with the first sliding block, and the other end is connected with the second sliding block after being wound through the pulleys in sequence, and the traction rope is always in a tension state during the winding process. Compared with the prior art, the self-adaptive gravity balance cooperation structure and the mechanical arm can make up for the shortage that the spring compensation mechanism cannot effectively balance the gravity when the posture of the mechanical arm is changed.

Description

Technical Field

[0001] This invention relates to the field of mechanics, and more particularly to a cooperative structure and robotic arm with adaptive gravity balance. Background Technology

[0002] Robotic arms, such as multi-degree-of-freedom robotic arms, require appropriate mechanisms, such as springs or ropes with pulleys, or spring compensation mechanisms like swing rods and swing sliders, to balance the weight of the robotic arm's joints or the arm itself due to the gravity of its links. These mechanisms are connected to the designed connection points on each link. Figures 1 to 3 The mechanism shown is designed to precisely control the movement trajectory of the load end of the robotic arm.

[0003] However, in the prior art, all three structures have different drawbacks. In the first structure, for example... Figure 1 The equivalent zero-free-length spring shown only theoretically achieves a zero original length, meaning the spring's free length is zero when no force is applied. Therefore, when the linkage rotates to any angle, its resultant torque cannot be guaranteed to be zero based on the set original length of the spring. This results in the joint actuator needing to output a larger torque to overcome the influence of gravity. For example... Figure 1 As shown, assuming It is the mass of the connecting rod. It is the distance from the center of mass of the connecting rod to the joint axis. distance, It is the angular displacement of the connecting rod from the y-axis. and These are the endpoints of the spring on the base and the connecting rod, respectively, with gravity acting along the negative y-direction. The resultant torque of the connecting rod caused by gravity and the spring tension is given by the following formula:

[0004] (1)

[0005] in It is the spring stiffness. and They are distance and distance, It is the original length of the spring. The distance is defined as , Defined as According to the Law of Sines, we have the following formula:

[0006] (2)

[0007] Substituting it into equation (1), we get equation (3).

[0008] (3)

[0009] When assuming And by adjusting the design parameters, At that time, the resultant torque It is always zero, no matter what angle the link rotates to within the reachable range.

[0010] In the second structure, to avoid the defects of the first structure, a traction rope is used instead of an equivalent zero-free length spring. However, due to the limitation of the minimum bending radius of the traction rope, it is necessary to use pulleys to connect the corresponding connecting rod. This results in a certain degree of error between the position of the force point of the traction rope and the theoretically calculated connection point on the connecting rod.

[0011] In the third structure, a spring compensation component structure such as a connecting rod and a swing slider is used to replace the equivalent zero-free-length spring in order to overcome the above-mentioned defects.

[0012] Furthermore, in practical applications, all three structures can only balance a single joint. Moreover, when the posture of the robotic arm changes, the gravitational torque on each joint will change, making it difficult for any of the three structures to achieve a good balance.

[0013] Therefore, providing an adaptive gravity balance cooperative structure and robotic arm to compensate for the inability of the spring compensation mechanism to effectively balance gravity when the posture of the robotic arm changes or when the load at the end of the robotic arm changes, and to improve the gravity balance effect of the robotic arm, is the technical problem that this invention urgently needs to solve. Summary of the Invention

[0014] The purpose of this invention is to provide an adaptive gravity balance cooperative structure and robotic arm, which can compensate for the shortcomings of the spring compensation mechanism in effectively balancing gravity when the posture of the robotic arm changes, and improve the gravity balance effect of the robotic arm.

[0015] To achieve the above objectives, this invention proposes a cooperative structure for adaptive gravity balance, comprising:

[0016] The linkage swing assembly includes: an output lever for connecting to a wrist-mounted robotic arm;

[0017] The linkage swing assembly includes at least: an input rod parallel to the output rod and provided with a first driver, a first pivot shaft for connecting the first driver, and a second pivot shaft for connecting the second driver; wherein, the output rod is used to realize movement in three degrees of freedom through the rotational cooperation of the input rod, the first pivot shaft, and the second pivot shaft;

[0018] A first slider is slidably disposed on the input rod, wherein the first slider is connected to a first spring compensation assembly disposed on the connecting rod swing assembly;

[0019] A balancing motor for driving the first slider to move axially along the input rod;

[0020] A second slider is slidably disposed on the output rod, wherein the second slider is connected to a second spring compensation assembly disposed on the connecting rod swing assembly;

[0021] Several pulleys are mounted on the connecting rod swing assembly;

[0022] One end is connected to the first slider, and the other end, after being wound through each pulley in sequence, is connected to the traction rope of the second slider, wherein the traction rope is always in a taut state.

[0023] Further, preferably, the linkage swing assembly further includes: a transmission rod parallel to the output rod; a first transmission rod assembly for connecting the input rod and the transmission rod to adjust one degree of freedom of the input rod; and a second transmission rod assembly for connecting the transmission rod and the output rod to adjust the distance between them; wherein at least one of the input rods is connected to a driver to form a first active joint, thereby controlling the motion state of the first transmission rod assembly; and at least one pivot shaft of the transmission rod is connected to the driver to form a second active joint, thereby controlling the motion state of the second transmission rod assembly.

[0024] Further, preferably, the linkage swing assembly consists of two parallelogram mechanisms connected in series and coaxially arranged via transmission rods; wherein the transmission rods, input rods, and output rods remain parallel to each other during the movement of the parallelogram mechanisms; wherein each transmission rod and input rod has at least one pivot axis for connecting a first driver and a second driver to form a first active joint and a second active joint respectively, and independently control the included angle of the corresponding parallelogram mechanisms.

[0025] Further, as a preferred embodiment, the linkage swing assembly further includes: a first link and a second link, which are pivotally connected to the input link at opposite ends via a first active joint and a second active joint, respectively; wherein the input link, the first link, the transmission link, and the second link are pivotally connected in sequence to form a parallelogram mechanism.

[0026] Further, as a preferred embodiment, the linkage swing assembly further includes: a third link and a fourth link pivotally connected to the second active joint at one end; wherein the transmission link, the third link, the output link, and the fourth link are pivotally connected in sequence to form a parallelogram mechanism.

[0027] Furthermore, as a preferred embodiment, each of the transmission rods is coaxially provided with a pulley on its pivot shaft.

[0028] Further, preferably, each connecting rod pivotally connected to the first spring compensation assembly is provided with a pulley; each connecting rod pivotally connected to the second spring compensation assembly is provided with a pulley; and, after the traction rope is wound around each pulley, at least a portion of it is parallel to the input rod and the output rod.

[0029] Further, preferably, both ends of the first spring compensation assembly and the second spring compensation assembly are pivotally connected to the corresponding slider and the connecting rod, respectively; the first spring compensation assembly and the second spring compensation assembly are zero-free-length springs or equivalent zero-free-length spring assemblies; wherein, the equivalent zero-free-length spring assembly includes: a rocker arm with one end pivotally connected to the corresponding slider and the other end passing through a positioning seat pivotally mounted on the connecting rod swing assembly, and a compensation spring sleeved on the rocker arm with one end abutting against the positioning seat and the other end connected to the end of the rocker arm.

[0030] This application also provides a robotic arm, comprising: the aforementioned adaptive gravity balance cooperative structure; a wrist robotic arm connected to the output rod; the wrist robotic arm having at least three degrees of freedom and a third slider slidably connected to the output rod; wherein the third slider is also connected to the traction rope; wherein the traction rope, starting from one end connected to the first slider, winds downward around a pulley disposed on the input rod, passes sequentially through pulleys disposed on pivot shafts of each connecting rod arranged parallel to the input rod, and then connects to the second slider; and, before connecting to the second slider, the traction rope passes around a pulley disposed on the output rod and connects to the third slider.

[0031] Further, preferably, it also includes: a first wrist fixing part rotatably connected to the third slider; a second wrist fixing part rotatably connected to the output rod and used to connect to the fourth driver; a swing rod connected to the second wrist fixing part and used to connect to the fifth driver; a load platform disposed on the swing rod and used to connect to the sixth driver; and a third spring compensation assembly with opposite ends used to pivotally connect the swing rod and the first wrist fixing part respectively; wherein, the load platform is used to rotate along the axial direction of the swing rod under the drive of the fifth driver; the third spring compensation assembly is a zero-free-length spring or an equivalent zero-free-length spring assembly; wherein, the equivalent zero-free-length spring assembly includes: a swing rod with one end pivotally connected to the first wrist fixing part and the other end passing through a fixed seat pivotally disposed on the second wrist fixing part; and a buffer spring sleeved on the swing rod, with one end abutting against the positioning seat and the other end connected to the end of the swing rod.

[0032] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in that it can make up for the inability of the spring compensation mechanism to effectively balance gravity when the posture of the robotic arm changes, and improve the gravity balance effect of the robotic arm. Attached Figure Description

[0033] Figure 1 This invention is a schematic diagram of the structure of a spring compensation assembly in the prior art. Figure 1 ;

[0034] Figure 2 This invention is a schematic diagram of the structure of a spring compensation assembly in the prior art. Figure 2 ;

[0035] Figure 3 This invention is a schematic diagram of the structure of a spring compensation assembly in the prior art. Figure 3 ;

[0036] Figure 4 : A schematic diagram of the adaptive gravity balance cooperative structure in the first embodiment of the present invention;

[0037] Figure 5 : A simplified diagram of the rope winding method of the adaptive gravity balance cooperative structure in the first embodiment of the present invention;

[0038] Figure 6 Schematic diagram of the mechanical analysis of the pulley and traction rope in the first embodiment of the present invention. Figure 1 ;

[0039] Figure 7 Schematic diagram of the mechanical analysis of the pulley and traction rope in the first embodiment of the present invention. Figure 2 ;

[0040] Figure 8: A schematic diagram of the force analysis of the adaptive gravity balance cooperative structure in the first embodiment of the present invention;

[0041] Figure 9 : A schematic diagram of the robotic arm in the first embodiment of the present invention;

[0042] Figure 10 : A simplified structural diagram of the robotic arm in the first embodiment of the present invention;

[0043] Figure 11 Schematic diagram of mechanical analysis of the robotic arm in the first embodiment of the present invention. Figure 1 ;

[0044] Figure 12 Schematic diagram of mechanical analysis of the wrist-mounted robotic arm in the first embodiment of the present invention. Figure 1 ;

[0045] Figure 13 Schematic diagram of dynamic mechanical analysis of the robotic arm in the first embodiment of the present invention. Figure 1 ;

[0046] Figure 14 Schematic diagram of mechanical analysis of the constraint structure in the second embodiment of the present invention Figure 1 ;

[0047] Figure 15 Schematic diagram of mechanical analysis of the constraint structure in the second embodiment of the present invention Figure 2 ;

[0048] Figure 16 Schematic diagram of dynamic mechanical analysis of the robotic arm in the second embodiment of the present invention. Figure 1 ;

[0049] Figure 17 Schematic diagram of mechanical analysis of the constraint structure in the second embodiment of the present invention Figure 2 ;

[0050] Figure 18 Schematic diagram of mechanical analysis of the constraint structure in the second embodiment of the present invention Figure 3 ;

[0051] Figure 19 Schematic diagram of mechanical analysis of the wrist-mounted robotic arm in the second embodiment of the present invention. Figure 4 .

[0052] Reference numerals: Driver 1a, Driver 1b, Driver 1c, Link swing assembly 2, Driver 3a, Driver 3b, Driver 3c, Balance motor 5, First slider 6, Second slider 7, Third slider 8, Pulley 9a, Pulley 9b, Pulley 9c, Pulley 9d, Pulley 9e, First spring compensation assembly 10, Second spring compensation assembly 20, Input rod 21, First rod 22, Transmission rod 23, Second rod 24, Output rod 25, Third rod 27, Fourth rod 26, Traction rope 28, Third spring compensation assembly 30, Wrist robotic arm 3, First wrist fixing part 31, Second wrist fixing part 32, Swing rod 33, Load platform 35, Positioning seat 101, Swing rod 102, Compensation spring 103, Positioning seat 201, Swing rod 202, Compensation spring 203, Fixed seat 301, Swing rod 302, Buffer spring 303. Detailed Implementation

[0053] The parallel mechanism of the present invention will now be described in more detail with reference to the schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0054] Example 1

[0055] Please refer to Figures 1 to 8 In this embodiment, an adaptive gravity balance cooperative structure is provided for installation in the robotic arm of a robot. This adaptive gravity balance cooperative structure mainly consists of a linkage swing assembly 2, a first slider 6 slidably mounted on the input rod 21 of the linkage swing assembly 2, a second slider 7 slidably mounted on the output rod 25 of the linkage swing assembly 2, a balance motor 5 for driving the first slider 6 to move axially along the input rod 21, a first spring compensation assembly 10, a second spring compensation assembly 20, pulleys, and a traction rope 28. Furthermore, it is worth mentioning that the robotic arm can carry equipment such as drill bits, laser burners, or samplers, and its application scenarios include extraterrestrial exploration and field exploration. The traction rope 28 is preferably a steel wire rope.

[0056] The output rod 25 is used to connect to the wrist robotic arm 3.

[0057] The linkage swing assembly 2 includes at least: an input rod 21 parallel to the output rod 25 and equipped with a first actuator; a second pivot shaft for connecting to the first actuator; and a second pivot shaft for connecting to a third actuator. The input rod is used to rotate along the direction of gravity under the action of the first actuator. The output rod 25 is used to achieve movement in three degrees of freedom directions through the rotational cooperation of the input rod 21, the first pivot shaft, and the second pivot shaft.

[0058] The first slider 6 is connected to the first spring compensation assembly 10 disposed on the connecting rod swing assembly 2;

[0059] The second slider 7 is connected to the second spring compensation assembly 20 disposed on the connecting rod swing assembly 2;

[0060] At least a portion of the pivot shaft forming a pivot connection in the connecting rod swing assembly 2 is coaxially provided with a pulley.

[0061] One end of the traction rope 28 is connected to the first slider 6, while the other end is connected to the second slider 7 after being wound around each pulley in sequence, and is always in a taut state during the winding process.

[0062] Through the cooperation of the first slider 6, the second slider 7, the pulley set on part of the pivot axis in the linkage swing assembly 2, and the traction rope 28 wound around the pulley, the first slider 6, driven by the balance motor 5, adjusts its position on the input rod 21, thereby adjusting the position of the first constraint rod connected to the linkage swing assembly 2. Furthermore, by winding the traction rope 28 around the pulley and the second slider 7, the second slider 7 can synchronously drive the second spring compensation assembly 20 to move. Thus, when the posture of the robotic arm changes, for example, when the posture of the robotic arm is actively changed by the driver, the joint gravity torque after the posture change can be adapted automatically without adjusting the balance motor 5. Alternatively, when different weights of load are applied to the end effector, only one balancing motor 5 is needed to drive the movement of the first slider 6 and the second slider 7. This allows for synchronized fine-tuning of the connection points between the first spring compensation assembly 10 and the second spring compensation assembly 20 and the connecting rod in the linkage arm assembly. This ensures that the connection points of the first spring compensation assembly 10 and the second spring compensation assembly 20 are as close as possible to the length of the equivalent zero-free-length spring after the load on the robotic arm changes. This compensates for the inability of traditional spring compensation mechanisms to effectively balance gravity when the robotic arm's posture or load changes, improving the gravity balance effect on the robotic arm. Furthermore, when switching between different weights of loaded equipment, there is no need to manually adjust the positions of the corresponding constraint components. Therefore, by controlling the balancing motor, complete gravity balance for different end effector loads can be achieved. Moreover, it enables the synchronous adjustment of all gravity balance joints using only one balancing motor.

[0063] The first and second spring compensation components described above can achieve gravity balance of the collaborative structure and the wrist robot, as well as actively eliminate joint gravitational torque caused by variable payloads, such as compensating for gravitational torque generated when actuators of different weights are mounted at the end of the robot arm.

[0064] Furthermore, it is worth mentioning that because the weight of the robotic arm and the load are balanced by the balancing mechanism, in this embodiment, all joint actuators can be disassembled or temporarily stopped during use, and the rotation of each link in the link swing assembly 2 can be manually pushed. In this way, when the load is loaded at the load end of the robotic arm, the operator can freely pull the entire robotic arm to reduce the physical burden of manually carrying the load and the potential human-machine collision injury.

[0065] Specifically, the linkage swing assembly 2 consists of two parallelogram mechanisms connected in series and coaxially arranged via a transmission rod 23. The transmission rod 23 remains parallel to the input rod 21 and the output rod 25 throughout the movement of the parallelogram mechanisms. Each of the transmission rod 23 and the input rod 21 has at least one pivot axis for connecting a first driver and a second driver, respectively forming a first active joint and a second active joint, and independently controlling the included angle of the corresponding parallelogram mechanisms. Through the parallelogram structure, two stable pitch angle adjustments can be achieved. Figure 4 The rope winding scheme shown prevents the slider from slipping due to the movement of the parallelogram mechanism.

[0066] In addition, such as Figure 6 and Figure 7 As shown, points Cs and Ce are the points of tangency where the traction rope first contacts and then disengages from pulley C, respectively, while point Cv is the lowest point of pulley C in the vertical direction. Similarly, points Ds and De are two points of tangency on pulley D, and point Dv is the lowest point on pulley D. Regardless of the parallelogram's movement, the spatial positions of points Cs and Cv relative to point C, and the spatial positions of points Dv and De relative to point D, remain unchanged. Points Ce and Ds are two points that slide on their respective pulleys as the parallelogram pitches. When the parallelogram is horizontal, the line connecting points C and D is horizontal, points Cv and Ce coincide, and points Dv and Ds coincide. When the parallelogram tilts upwards, the wrap angle of the traction rope on pulley C increases, and point Ce slides to the right of point Cv, while the wrap angle of the traction rope on pulley D decreases, and point Ds also slides to the right of point Dv. Because the two pulleys have equal diameters, the increase and decrease in the wrap angle are equal, i.e., the arc length. Furthermore, since the distance between pulleys C and D remains constant, the length of the common tangent between the two pulleys remains constant. Conversely, when the parallelogram tilts downwards, the change in the wrap angle on the pulleys is exactly the opposite of when the parallelogram tilts upwards. In summary, the path length of the rope between points Cs and De remains constant. The same conclusion applies when the rope passes through pulleys B and K. Because the distance between pulleys B and D remains constant, the length of their common tangent is also constant. Therefore, this rope-winding method achieves complete decoupling of the motion of the two parallelograms from the motion of the two sliders. This avoids the need for real-time adjustment of the gravity balance motor during robotic arm movement, greatly improving the robustness of the gravity balance system and enabling rapid robotic arm movement.

[0067] Further, as a preferred embodiment, the linkage swing assembly 2 further includes: a first link and a second link, which are pivotally connected to the input link 21 at opposite ends via a first active joint and a second active joint, respectively; wherein the input link 21, the first link, the transmission link 23, and the second link are pivotally connected in sequence to form a parallelogram mechanism.

[0068] Further, as a preferred embodiment, the linkage swing assembly 2 further includes: a third link and a fourth link that are pivotally connected to the second active joint at one end; wherein the transmission link 23, the third link, the output link 25 and the fourth link are pivotally connected in sequence to form a parallelogram mechanism.

[0069] Furthermore, as a preferred embodiment, each of the transmission rods 23 is coaxially provided with a pulley on its pivot shaft.

[0070] Furthermore, as a preferred embodiment, the connecting rods pivotally connected to the first spring compensation assembly 10 are all provided with the pulleys; the connecting rods pivotally connected to the second spring compensation assembly 20 are all provided with the pulleys.

[0071] Further, preferably, the opposite ends of the first spring compensation assembly 10 and the second spring compensation assembly 20 are pivotally connected to the corresponding slider and connecting rod, respectively; the first spring compensation assembly 10 and the second spring compensation assembly 20 are zero-free-length springs or equivalent zero-free-length spring assemblies; wherein, the equivalent zero-free-length spring assembly includes: a rocker arm with one end pivotally connected to the corresponding slider and the other end passing through a positioning seat pivotally mounted on the connecting rod swing assembly 2, and a compensation spring sleeved on the rocker arm with one end abutting against the positioning seat and the other end connected to the end of the rocker arm. It is worth mentioning that the two pivot points of the zero-free-length spring assembly can be interchanged. Furthermore, by adjusting the position of the endpoints of the zero-free-length spring, gravitational balance can be achieved for end loads of different masses. And the zero-free-length spring can be placed at any corner of the parallelogram mechanism.

[0072] Alternatively, to meet the design requirements of practical applications, the linkage swing assembly 2 in this embodiment can also be composed of a transmission rod 23 parallel to the output rod 25, a first transmission rod assembly for connecting the input rod 21 and the transmission rod 23 to adjust one degree of freedom of the input rod 21, and a second transmission rod assembly for connecting the transmission rod 23 and the output rod 25 to adjust the distance between them. At least one of the input rods 21 is connected to the driver to form a first active joint, thereby controlling the motion state of the first transmission rod assembly; at least one pivot shaft of the transmission rod 23 is connected to the driver to form a second active joint, thereby controlling the motion state of the second transmission rod assembly. The first and second transmission rod assemblies can be composed of two intersecting links.

[0073] Example 2

[0074] This embodiment also provides a robotic arm; please refer to [reference needed]. Figures 9 to 19The system includes: a cooperative structure for adaptive gravity balance as described in the above embodiments; a wrist robotic arm 3 connected to the output rod 25; the wrist robotic arm 3 having at least three degrees of freedom and a third slider 8 slidably connected to the output rod 25; wherein the third slider 8 is also connected to the traction rope 28; wherein the traction rope 28 starts from one end connected to the first slider 6, winds downward around a pulley disposed on the input rod 21, passes sequentially through pulleys disposed on pivot shafts of each connecting rod parallel to the input rod 21, and then connects to the second slider 7; and, before connecting to the second slider 7, the traction rope 28 passes around a pulley disposed on the output rod 25 and connects to the third slider 8.

[0075] Through the cooperation of the first slider 6, the second slider 7, the third slider 8, the pulleys mounted on a portion of the pivot axis in the linkage swing assembly 2, and the traction rope 28 wound around the pulleys, the position of the first constraint rod connected to the linkage swing assembly 2 is adjusted by the first slider 6, driven by the balancing motor 5, adjusting its position on the input link 21. Furthermore, by winding the traction rope 28 around the pulleys of the second slider 7, the second slider 7 can synchronously drive the second spring compensation assembly 20 to move. Therefore, when the posture of the robotic arm changes, for example, by actively changing the posture of the robotic arm through the driver, it can adapt to the joint gravity torque after the posture change without adjusting the balancing motor 5. Alternatively, when different masses of load are applied to the end, only one balancing motor 5 is needed to drive the movement of the first slider 6, the second slider 7, and the third slider 8. This allows for the synchronous fine-tuning of the connection points between the first spring compensation component 10, the second spring compensation component 20, and the connecting rod in the linkage arm assembly. This ensures that the connection points of the first spring compensation component 10 and the second spring compensation component 20 are as close as possible to the length of the equivalent zero-free-length spring after the load on the robotic arm changes. This compensates for the inability of the spring compensation mechanism to effectively balance gravity when the posture or load of the robotic arm changes, thus improving the gravity balance effect on the robotic arm.

[0076] The first, second, and third spring compensation components are used to achieve gravity balance of the collaborative structure and the wrist robot, and to actively eliminate joint gravitational torque caused by variable payloads, such as compensating for gravitational torque generated when actuators of different weights are mounted at the end of the robot arm.

[0077] Furthermore, it is worth mentioning that because the weight of the robotic arm and the load are balanced by the balancing mechanism, in this embodiment, all joint actuators can be disassembled or disabled during use. The rotation of each link in the link swing assembly 2 can be achieved by manually pushing the link. In this way, when the load is loaded at the end of the robotic arm, the operator can freely pull the entire robotic arm to reduce the physical burden on the worker when manually carrying the load and the potential human-machine collision injury.

[0078] Further, preferably, the robotic arm also includes: a first wrist fixing part 31 rotatably connected to the third slider 8; a second wrist fixing part 32 rotatably connected to the output rod 25 and used to connect to the fourth driver; a swing rod 33 connected to the second wrist fixing part 32 and used to connect to the fifth driver; a load platform 35 disposed on the swing rod 33 and used to connect to the sixth driver; and a third spring compensation assembly 30 with opposite ends used to pivotally connect the swing rod 33 and the first wrist fixing part 31 respectively; wherein, the load platform 35 is used to rotate along the axial direction of the swing rod 33 under the drive of the fifth driver. Furthermore, it is worth mentioning that the load platform 35 can carry drill bits, laser burners, or samplers, etc., and the application scenarios can be extraterrestrial exploration and field exploration.

[0079] Through the above structure, under the action of the first to sixth actuators, the six active joints formed by the pivot shafts connected to them can be finely adjusted by the pulleys on the linkage arm assembly, the first slider 6, the second slider 7, and the third slider 8, while maintaining their positions and types. This allows for the fine adjustment of the spring compensation mechanisms corresponding to the three pitch-adjustment-related active joints, thereby achieving the corresponding gravity balance adjustment. In this embodiment, gravity balance of all three joints affected by gravity can be achieved using only one balancing motor 5.

[0080] Furthermore, by using the aforementioned winding method, the slack in the rope connecting the first slider 6, the second slider 7, and the third slider 8 during the pitching motion of the parallelogram mechanism can be avoided. This would prevent the first slider 6, the second slider 7, and the third slider 8 from becoming entangled due to the movement position of the parallelogram, thus affecting the accuracy of gravity compensation. This ensures that the first slider 6, the second slider 7, and the third slider 8 maintain synchronous movement with the change in the attitude of the parallelogram mechanism when there is no load change.

[0081] Furthermore, it is worth mentioning that the third spring compensation assembly 30 is a zero-free-length spring or an equivalent zero-free-length spring assembly; wherein, the equivalent zero-free-length spring assembly includes: a swing rod with one end pivotally connected to the first wrist fixing part 31 and the other end passing through a fixing seat pivotally mounted on the second wrist fixing part 32, and a compensation spring sleeved on the swing rod, with one end abutting against the positioning seat and the other end connected to the end of the swing rod. The two pivot points of the zero-free-length spring assembly can be interchanged.

[0082] Furthermore, to better illustrate the above principles, the following explanation is provided:

[0083] like Figure 11 As shown, the robotic arm in this embodiment consists of a 3-DOF arm and a 3-DOF wrist. The entire structure is composed of rotary joints, with two overlapping rotary joints at points B and D. All active joints of the robotic arm are labeled "aj i" (i=1,2,...,6) and are listed in Table 1. In particular, link BK is actively controlled by an actuator mounted on link BD. The three springs are represented by broken lines, with endpoints Ii and Ji (i=1,2,3) respectively.

[0084] Table 1

[0085]

[0086] The robotic arm consists of two cascaded parallelogram mechanisms that can rotate about axis CA, responsible for positioning the wrist to any position in space. The wrist, in turn, points the distal end of the robotic arm in a given direction. Finally, the axes of the three active joints intersect at a single point, facilitating the analytical solution to the inverse kinematics problem of the robotic hand. In the following text, the three pitch joints affected by gravity are denoted by θ1, θ2, and θ=, with the direction of gravity being the negative y-axis. Additionally, the following definitions apply:

[0087] ● The symbol lij represents the distance between points i and j;

[0088] ● The symbol mij represents the link mass specified by points i and j.

[0089] Furthermore, the robotic arm in this embodiment employs a parallelogram mechanism to decouple the gravitational torques of each joint, thus solving the gravity compensation problem for multiple pitch joints. Due to the parallelism of the parallelogram, axis QJ3 is always vertical, which means that the gravity balance of the third pitch joint can be independent of the arm's posture.

[0090] like Figure 12As shown, the total mass of the part within the dashed box is specified as m3. Since its center of mass R does not change with the rotation of the roll joint, it is clear that the gravitational torque at joint Q is only related to θ3. The spring stiffness and free length of endpoints I3 and J3 are K= and l0, respectively, and the angle J3I3Q is specified as φ. Then, the resultant torque of the pitch joint Q, affected by the actuator, gravity, and spring tension, is expressed as:

[0091] (1)

[0092] In the formula, Tatr3 is the output torque of the third pitch joint actuator. Equation (2) can be obtained according to the sine law.

[0093] (2)

[0094] Substituting (2) into (1) yields the equation ( 3)(3)

[0095] Assume l0=0, and adjust the structural parameters to make Even if the joint actuator fails, the resultant torque T remains zero regardless of the angle of rotation of the link within its reach. Although the free length of a spring cannot actually be zero, an equivalent zero-free-length spring can be achieved using a wire rope or link and a swing slider, such as... Figure 2 and Figure 3 As shown. This invention selects... Figure 3 A method for realizing a zero-freedom long spring.

[0096] For the equilibrium of parallelogram BKLD, the mass of the wrist (the part within the blue dashed box) is denoted by m², as follows: Figure 13 As shown, the force acting on this parallelogram can be Figure 14 The following is an explanation. A zero-free length spring with stiffness K2 is fixed at points I2 and J2. Points O and P are the centers of mass of connecting rods BK and DL, while the center of mass of mass m2 falls at point N.

[0097] θ is actively controlled by the joint actuator, and Tatr2 is the driving torque required to maintain the current posture. Based on the principle of virtual work,

[0098] (4)

[0099] in, (5)

[0100] (6)

[0101] (7)

[0102] Based on the Law of Cosines, we have

[0103] (8)

[0104] Differentiating both sides of equation (8) yields equation (9).

[0105] Substituting formula (9) into formula (4), we have

[0106] (10)

[0107] Under ideal gravity compensation, Tatr2 is expected to always be zero and independent of θ2. It is easy to verify that the required actuator torque is zero when the zero-free-length spring stiffness satisfies (11).

[0108] (11)

[0109] As can be seen from (4), the position of the wrist's center of mass (i.e., point N) is irrelevant. This means that no matter what posture the wrist is in, as long as the total mass m2 remains unchanged, the equilibrium state of the parallelogram BKLD will not change.

[0110] Furthermore, the parallelogram ABCD within the dashed box and the wrist can be considered as a single unit with a total mass of m1. A zero-freedom long spring with stiffness K1 is fixed at points I1 and J1, as follows. Figure 13 As shown. Similarly, the derivation of the stiffness required for balancing this zero-free-length spring is as follows:

[0111] (12)

[0112] Regardless of where the center of mass of the part is, the equilibrium state of parallelogram ABCD remains unchanged.

[0113] In other words, the gravitational torque in each parallelogram is independent of the wrist or the posture of the other parallelograms. This crucial decoupling property allows for independent gravity compensation for each pitch joint.

[0114] Therefore, all joints in the robotic arm affected by gravity are in balance, and Table 2 summarizes the necessary conditions for balance.

[0115] Table 2

[0116]

[0117] However, when a load is applied to the end effector of the robotic arm, the gravitational torque within the joints is no longer balanced. Load capacity will be limited by the capabilities of the joint motors and the reach of the robotic arm. To achieve complete balance of the parallelogram mechanism for different loads, a zero-free-length spring is used. one end is like Figure 16 As shown, it is fixed to the slider.

[0118] Additionally, it is worth mentioning that when the endpoint of a zero-free-length spring changes, it remains a zero-free-length spring; only the amount of stretching changes.

[0119] When there is no load at the far end of the parallelogram, and the parallelogram mechanism is only affected by its own weight, the initial length is... , and zero free length spring stiffness They are chosen so that their product satisfies equation (13), which is a necessary condition for perfect gravitational equilibrium.

[0120] (13)

[0121] in , and These are connecting rods ,link and connecting rod The quality.

[0122] When a load is applied to the far end of the parallelogram At that moment, to balance the increased gravitational torque, the slider is pulled upward by the rope a distance. At this point, the zero-free length spring is shown by the dashed line in Figure 17, and its endpoint... Move to point According to the necessary condition for equilibrium (13), we have equation (14).

[0123] (14)

[0124] Substituting equation (13) into equation (14), the distance It can be obtained in equation (15).

[0125] (15)

[0126] Similarly, such as Figure 18 The zero-free-length spring shown endpoints When fixed to the slider, it will move along the connecting rod. The mass assignment of the translation slider is According to the necessary condition for equilibrium, we have equation (16).

[0127] (16)

[0128] When a load is applied to the far end of the parallelogram At this point, the slider should be pulled down a certain distance. , to reach a new equilibrium in equation (17).

[0129] (17)

[0130] By combining equations (16) and (17), we obtain equation (18).

[0131] (18)

[0132] Regarding the adaptive gravity balance of the wrist's pitch joint, such as Figure 19 As shown, the zero-free length spring is before loading at the end of the robotic arm. The equilibrium condition is given by equation (19).

[0133] (19)

[0134] When loading load at the end At this time, the slider needs to be pulled upwards by a distance. Its endpoints Move to point , thus achieving a new equilibrium in equation (20).

[0135] (20)

[0136] By combining equations (19) and (20), the distance can be obtained. As shown in equation (21).

[0137] (twenty one)

[0138] like Figures 9 to 19 As shown, the positions and types of the six active joints remain unchanged, but the gravity compensation mechanism of the three pitch joints is altered: the three zero-free long springs adopt a structure of lightweight connecting rods and oscillating sliders, but the endpoints... (i=1, 2, 3) are hinged to the first slider 6, the second slider 7, and the third slider 9, respectively. The three sliders are pulled vertically by a steel wire (the wire is not shown). It is worth mentioning the zero-freedom long spring. endpoints It is not directly hinged to the corresponding slider; there is a passive yaw joint in the middle, i.e. Figure 9 The output shaft of the first wrist fixing part 31 shown is coaxial with the active yaw joint below point Q.

[0139] like Figure 16As shown, the total mass of the portion within the largest dashed box is assigned as m3, with its center of mass located at point R. The total mass of the portion within the second largest dashed box is assigned as m2, and the total mass of the portion within the smallest dashed box is assigned as m1. The positions of the centers of mass for masses m1 and m2 are irrelevant. Points G, O, H, and P are the centers of mass for links AB, BK, CD, and DL, respectively (the masses of oscillating sliders I1 and I2 are included in links CH and BK).

[0140] The gravity balance of this 6-DOF robotic arm is attitude-independent. Whether there is no load or different loads are applied at point S, only the positions of the sliders need to be adjusted to achieve complete gravity balance. As long as the load does not change, no further adjustment of the slider positions is required regardless of the robotic arm's pose.

[0141] The initial equilibrium conditions of the three zero-free long springs, and the relationship between the slider displacement and the end load are summarized in Table 3.

[0142] Table 3

[0143]

[0144] To reduce the number of actuators used to adjust the zero-free length spring end, a single steel wire rope is used to pull three sliders simultaneously. Due to the inextensibility of the steel wire rope, the displacement increments of the three sliders are always equal. This characteristic requires that when a load is applied to the end of the robotic arm, the ideal displacement increments of the three sliders should be equal to achieve a new equilibrium, i.e., equation (22).

[0145] (twenty two)

[0146] Further, we can derive equation (23).

[0147] (twenty three)

[0148] Therefore, equation (23) and the three initial equilibrium conditions constitute five constraints, which are used to guide the process. The selection of nine balancing parameters. The balancing parameters are under-constrained, bringing great flexibility and convenience to physical design.

[0149] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A cooperative structure for adaptive gravity balance, characterized in that, include: The linkage swing assembly includes: an output lever for connecting to a wrist-mounted robotic arm; The linkage swing assembly includes at least: an input rod parallel to the output rod and provided with a first driver, a first pivot shaft for connecting a second driver, and a second pivot shaft for connecting a third driver; wherein, the output rod is used to realize movement in three degrees of freedom through the rotational cooperation of the input rod, the first pivot shaft, and the second pivot shaft; A first slider is slidably disposed on the input rod, wherein the first slider is connected to a first spring compensation assembly disposed on the connecting rod swing assembly; A balancing motor for driving the first slider to move axially along the input rod; A second slider is slidably disposed on the output rod, wherein the second slider is connected to a second spring compensation assembly disposed on the connecting rod swing assembly; Several pulleys are mounted on the connecting rod swing assembly; One end is connected to the first slider, and the other end, after being wound through each pulley in sequence, is connected to the traction rope of the second slider, wherein the traction rope is always in a taut state.

2. The adaptive gravity balance cooperative structure as described in claim 1, characterized in that, The linkage swing assembly further includes: a transmission rod parallel to the output rod; a first transmission rod assembly for connecting the input rod and the transmission rod to adjust one degree of freedom of the input rod; and a second transmission rod assembly for connecting the transmission rod and the output rod to adjust the distance between them; wherein at least one of the input rods is connected to a driver to form a first active joint, thereby controlling the motion state of the first transmission rod assembly; and at least one pivot shaft of the transmission rod is connected to the driver to form a second active joint, thereby controlling the motion state of the second transmission rod assembly.

3. The adaptive gravity balance cooperative structure as described in claim 1, characterized in that, The linkage swing assembly consists of two parallelogram mechanisms connected in series and coaxially arranged via transmission links; wherein the transmission links, input links, and output links remain parallel to each other during the movement of the parallelogram mechanisms; wherein each of the transmission links and the input links has at least one pivot axis for connecting the first driver and the second driver to form the first active joint and the second active joint respectively, and independently controlling the included angle of the corresponding parallelogram mechanisms.

4. The adaptive gravity balance cooperative structure as described in claim 3, characterized in that, The linkage swing assembly further includes: a first link and a second link, which are pivotally connected to the input link at opposite ends via a first active joint and a second active joint, respectively; wherein the input link, the first link, the transmission link, and the second link are pivotally connected in sequence to form a parallelogram mechanism.

5. The adaptive gravity balance cooperative structure as described in claim 4, characterized in that, The linkage swing assembly further includes a third link and a fourth link that are pivotally connected to the second active joint at one end; wherein the transmission link, the third link, the output link, and the fourth link are pivotally connected in sequence to form a parallelogram mechanism.

6. The adaptive gravity balance cooperative structure as described in claim 2, characterized in that, The pulleys are coaxially arranged on the pivot shafts of the transmission rods; and, after the traction rope is wound around each pulley, at least a portion of it is parallel to the input rod and the output rod.

7. The adaptive gravity balance cooperative structure as described in any one of claims 1 to 6, characterized in that, The connecting rods pivotally connected to the first spring compensation assembly are all equipped with the pulleys; the connecting rods pivotally connected to the second spring compensation assembly are all equipped with the pulleys.

8. The adaptive gravity balance cooperative structure as described in claim 7, characterized in that, The first spring compensation assembly and the second spring compensation assembly are pivotally connected at their respective ends to the corresponding slider and the connecting rod; the first spring compensation assembly and the second spring compensation assembly are zero-free-length springs or equivalent zero-free-length spring assemblies; wherein, the equivalent zero-free-length spring assembly includes: a rocker arm with one end pivotally connected to the corresponding slider and the other end passing through a positioning seat pivotally mounted on the connecting rod swing assembly, and a compensation spring sleeved on the rocker arm with one end abutting against the positioning seat and the other end connected to the end of the rocker arm.

9. A robotic arm, characterized in that, include: The adaptive gravity balance cooperative structure according to any one of claims 1 to 8; A wrist-mounted robotic arm connected to the output rod; the wrist-mounted robotic arm has at least three degrees of freedom and a third slider slidably connected to the output rod; wherein the third slider is also connected to the traction rope; wherein the traction rope starts from one end connected to the first slider, winds downward around a pulley disposed on the input rod, passes sequentially through pulleys disposed on pivot shafts of each connecting rod arranged parallel to the input rod, and then connects to the second slider; and, before connecting to the second slider, the traction rope passes around a pulley disposed on the output rod and connects to the third slider.

10. The robotic arm according to claim 9, characterized in that, The system comprises a first wrist fixing part rotatably connected to the third slider, a second wrist fixing part rotatably connected to the output rod and used to connect to the fourth driver, a swing rod connected to the second wrist fixing part and used to connect to the fifth driver, a load platform disposed on the swing rod and used to connect to the sixth driver, and a third spring compensation assembly at opposite ends used to pivotally connect the swing rod and the first wrist fixing part, respectively; wherein, the load platform is used to rotate along the axial direction of the swing rod under the drive of the fifth driver; the third spring compensation assembly is a zero-free-length spring or an equivalent zero-free-length spring assembly; wherein, the equivalent zero-free-length spring assembly includes: a swing rod with one end pivotally connected to the first wrist fixing part and the other end passing through a fixed seat pivotally disposed on the second wrist fixing part, and a compensation spring sleeved on the swing rod with one end abutting against a positioning seat and the other end connected to the end of the swing rod.

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