Fusion system of a robot arm and a skilled hand and method for motion control therefor

Abstract

The invention relates to a fusion system of a robot arm and a dexterous hand, and to a method for controlling its motion. The fusion system comprises a robot arm with four degrees of freedom, a wrist of the dexterous hand, and a dexterous hand, wherein the wrist is a wrist with two orthogonal degrees of freedom integrated in a single joint space, wherein the wrist of the dexterous hand is attached to the end of the robot arm with four degrees of freedom, and wherein the palm of the dexterous hand is attached to the wrist of the dexterous hand.In the motion control method, the fusion system of a robot arm with four degrees of freedom and a dexterous hand is considered as a six-axis serial robot arm; according to the joint angles, the position of the wrist end of the dexterous hand can be determined using forward kinematic methods; according to the position of the wrist end of the dexterous hand, the joint angles are determined using backward kinematic numerical solution methods, and the control command is obtained from this. The present invention designs a wrist with two orthogonal degrees of freedom of the dexterous hand, uses a serial-parallel mechanism with six degrees of freedom, composed of a robot arm and a dexterous hand, to perform a fusion system for the robot arm and the dexterous hand, and proposes a solution method for determining the backward kinematic numerical solutions.

Description

[0001] This application claims priority to Chinese patent application No. 202210248880.9 filed with the Chinese Patent Office on March 14, 2022, with the invention titled “Fusing system of a robot arm and a dexterous hand and motion control method thereof,” the entire contents of which are incorporated herein by reference. Technical area

[0002] The invention belongs to the field of robot motion control and relates to a fusion system of a robot arm with four degrees of freedom and a dexter hand and a motion control method therefor. Background of the invention

[0003] As a component for executing interaction between the robot and its environment, a fully powered humanoid dexterous hand with large gripping force and multiple degrees of freedom plays a very important role in enhancing the robot's intelligence. A humanoid dexterous hand alone cannot perform fine operation tasks independently; a robot arm is required to support the dexterous hand. Therefore, the fusion system of a robot arm and dexterous hand and its motion control method are key technologies for realizing the robot's intelligence and dexterous operation.

[0004] The domestic development of fully powered humanoid dexterous hands with high gripping force and multiple degrees of freedom is still in its infancy. Most existing products are single-degree-of-freedom claws or underpowered dexterous hands with six or twelve degrees of freedom, which are unable to fully mimic the human hand for fine manipulation.

[0005] Currently, the arm-hand combination, consisting of a robot arm with six or seven degrees of freedom and an end claw or a dexterous hand with six or twelve degrees of freedom, is widely used at home and abroad. In this combination, the robot arm and the dexterous hand are controlled independently of each other, and neither joint control nor arm-hand fusion control is implemented.

[0006] Currently, the existing robot arm and claw assemblies generally lack wrist joints or use the robot arm's joints to replace the wrist function, which is neither aesthetically pleasing nor practical. There are no control methods for wrist joints with two orthogonal degrees of freedom in the current state of the art. There are no practical control methods for the four-degree-of-freedom plus two-degree-of-freedom serial-parallel fusion system consisting of a four-degree-of-freedom robot arm and the dexter hand. The four-degree-of-freedom robot arm and the wrist of the dexter hand can be reasonably regarded as the six-degree-of-freedom robot arm. However, for this type of arm, the three end axes are not orthogonal, and there is no analytical solution.

[0007] An urgent technical problem in this field that needs to be solved is to provide a fusion system of a robot arm with four degrees of freedom and a wrist of the dexter hand. Disclosure of the invention

[0008] The technical problem solved by the present invention is to overcome the drawbacks of the prior art and to propose the fusion system of a robot arm and a dexterous hand and methods for controlling the motion thereof.

[0009] The technical solution of the present invention is: A fusion system of a robot arm and a dexterous hand, comprising: a four-degree-of-freedom robot arm, a dexterous hand wrist, and a dexterous hand, wherein the dexterous hand wrist is attached to the end of the four-degree-of-freedom robot arm, the palm of the dexterous hand is attached to the wrist of the dexterous hand; and the dexterous hand wrist and the four-degree-of-freedom robot arm are connected by electronic circuits.

[0010] The wrist of the dexter hand is preferably a parallel two-degree-of-freedom mechanism that includes two motors, two pushrods, and two servo position controllers.

[0011] The two servo position controllers are respectively an active servo position controller and a slave servo position controller. The two motors comprise a first motor and a second motor. The two push rods comprise a first push rod and a second push rod. The active servo position controller is designed to drive the first motor, whose movement sets the first push rod in motion, and the slave servo position controller is designed to drive the second motor, whose movement sets the second push rod in motion. The end of the first push rod and the end of the second push rod are simultaneously connected to the palm of the dexter hand.

[0012] The two motors preferably use a synchronous differential control mode, and the two motors drive the two push rods in motion to realize the pitch movement and yaw rotation of the dexter hand.

[0013] When the two pushrods move in the same direction, the dexter hand performs a pitching motion, with a pitch angle range of -70 degrees to 70 degrees. When the two pushrods move in opposite directions, the dexter hand performs a yaw motion, with a yaw angle range of -45 degrees to 45 degrees.

[0014] A method of motion control for a fusion system of a robot arm and a dexterous hand, comprising: Consider the fusion system of a four-degree-of-freedom robot arm and a dexterous hand as a six-axis serial robot arm, the center point of the base of the four-degree-of-freedom robot arm is set as the origin, the robot coordinate system is constructed using DH method, and the DH parameters for respective joints and connecting rod of the robot arm are output.

[0015] According to the joint angles θ1, θ2, θ3, θ4 of the robot arm with four degrees of freedom and the joint angles θ5, θ6 of the wrist of the dexterous hand, the position pose matrix is ​​calculated using forward kinematics methods for the fusion system of a robot arm with four degrees of freedom and the dexterous hand. T=[RP01] of the wrist end of the dexter hand to realize the forward movement control for the fusion system, where R represents the rotation matrix of the wrist end of the dexter hand, and P represents the position matrix of the wrist end of the dexter hand;

[0016] If the position T=[RP01] of the wrist end of the dexter hand is known, the joint angles θ1, θ2, θ3, θ4, θ5, θ6 of the fusion system are determined using backward kinematics numerical solution methods for the fusion system of a robot arm with four degrees of freedom and the dexter hand, and according to the joint angles, the control command is obtained and sent to the servo position controller to drive the end of the wrist of the dexter hand so that the specified position posture is reached.

[0017] When the forward movement control for fusion system is preferred, the position of the wrist end of the skilled hand T=60T=10T*21T*32T*43T*54T*65T 10T is the coordinate transformation matrix from the base coordinate system of the robot arm to the first joint of the robot arm in the fusion system; 21T is the coordinate transformation matrix from the first joint of the robot arm to the second joint of the robot arm in the fusion system; 32T is the coordinate transformation matrix from the second joint of the robot arm to the third joint of the robot arm in the fusion system; 43T is the coordinate transformation matrix from the third joint of the robot arm to the fourth joint of the robot arm in the fusion system; 54T is the coordinate transformation matrix from the fourth joint of the robot arm to the first joint of the wrist of the dexter hand in the fusion system; 65T is the coordinate transformation matrix from the first joint of the wrist of the dexter hand to the second joint of the wrist of the dexter hand in the fusion system; 60T is the coordinate transformation matrix from the base coordinate system of the robot arm to the end of the wrist of the dexter hand in the fusion system. 10T=[c1−s100s1c10000100001] 21T=[c2−s200001d2−s2−c2000001] 32T=[c3−s30a2s3c300001d30001] 43T=[c4−s40000−1d4s4c4000001] 54T=[c5−s50000−1d5s5c5000001] 65T=[c6−s6000010−s6−c6000001] where, dj is the distance of the connecting rod between the j-th joint and the j-1-th joint, j=2, 3, 4, 5; a p is the length of the connecting rod of the p-th joint, p=2; si is the sine of the i-th joint angle, ci is the cosine of the i-th joint angle, i = 1, 2, 3, 4, 5, 6. si = sinθ i , ci = cosθ i .

[0018] The joint angle θ6 is preferably solved iteratively numerically.

[0019] The k+1-th iteration formula of θ6 is as follows: θ6(k+1)=θ6(k)−f(θ6(k))(θ6(k)−θ6(k−1))f(θ6(k))−f(θ6(k−1))

[0020] θ 6(k+1) is the k+1-th iteration result of θ6, θ 6(k) is the k-th iteration result of θ6, θ 6(k-1) is the k-1-th iteration result of θ6, f(θ 6(k+1) ) is the inverse kinematics formula at θ 6(k+1) , f(θ 6(k) ) is the inverse kinematics formula at θ 6(k) , f(θ 6(k-1) ) is the inverse kinematics formula at θ 6(k-1 ).

[0021] Compared to the prior art, the advantageous effects of the present invention are: (1) The present invention is a wrist with two orthogonal degrees of freedom of the moving hand, which occupies only the space of a single joint and ensures high reliability by a redundant synchronous differential control with two motors. (2) The present invention uses a six-degree-of-freedom serial-parallel mechanism consisting of a four-degree-of-freedom robot arm and a two-degree-of-freedom dexterous hand to perform fusion control of the robot arm and the dexterous hand. The arm type consisting of a four-degree-of-freedom robot arm and a two-degree-of-freedom wrist does not meet the requirement that the three axes intersect at a point at the end, and there is no analytical solution for the inverse kinematics, only a numerical solution. Therefore, a method for numerically solving the inverse kinematics based on this arm type is developed, which is suitable for obtaining numerical solutions for all serial robot arms. (3) The present invention decouples the two coupled joints of the wrist of the dexter hand and regards them as two independent robot arm joints, joint 5 and joint 6. In this way, the control method of the present invention can integrate the complex parallel mechanism of the wrist of the dexter hand with the robot arm to control according to the control method for a serial robot arm with six degrees of freedom. (4) The six-degree-of-freedom serial-parallel mechanism of the present invention, which is composed of a four-degree-of-freedom robot arm and a two-degree-of-freedom wrist of a dexterous hand, has multi-degree-of-freedom redundancy, so that the robot arm can achieve the rotation of a five-finger dexterous hand without having to move over a large range. Short description of the drawing Fig. 1 shows a schematic control scheme of the wrist of the dexter hand; Fig. Figure 2 shows a wrist with two orthogonal degrees of freedom integrated into a single joint space; Fig. Figure 3 shows the arrangement of a robot arm with four degrees of freedom and a wrist with two degrees of freedom of a dexter hand. Embodiment(s) of the invention

[0022] The present invention is described in more detail below in conjunction with the accompanying drawings.

[0023] Without modifying the dexterous hand, the present invention designs a fusion system of a robot arm and a dexterous hand that is both aesthetic and practical, and can reduce the research and development cost and cycle; at the same time, a solution method for obtaining the reverse kinematics numerical solutions is proposed, and a motion control method for a fusion system of a robot arm and a dexterous hand is realized.

[0024] A fusion system of a robot arm and a skilled hand is in Fig. 3 and includes a four-degree-of-freedom robot arm, a dexterous hand wrist (the wrist with two orthogonal degrees of freedom integrated into a single joint space), and a dexterous hand. The two-degree-of-freedom wrist of the dexterous hand is attached to the end of the four-degree-of-freedom robot arm, and the two are connected by electronic circuits for communication and power supply. The palm of the dexterous hand is mounted on the wrist of the dexterous hand.The motion control method for a fusion system of a robot arm and a dexterous hand includes a control method for the wrist with two orthogonal degrees of freedom of the integrated in a single joint space, a forward kinematics method for a fusion system of the robot arm and the dexterous hand, and a backward kinematics method for a fusion system of the robot arm and the dexterous hand.

[0025] The wrist according to the invention with two orthogonal degrees of freedom of the integrated in a single joint space, as in Fig. The synchronous differential control system shown in Figure 2 uses two motors, m1 and m2. The two motors push two pushrods, L1 and L2, to realize the pitching and yaw rotation of the dexterous hand. When the two pushrods, L1 and L2, are driven in the same direction, the dexterous hand performs a pitching motion. The wrist joint can be regarded as joint J1, with a pitch angle range of -70 degrees to 70 degrees. When the two pushrods, L1 and L2, are driven in opposite directions, the dexterous hand performs a yaw motion. The wrist joint can be regarded as joint J2, with a yaw angle range of joint J2 from -45 degrees to 45 degrees. One of the two motors, m1, is driven by a servo positioning controller A (active), and the other motor, m2, is driven by a servo positioning controller B (slave).

[0026] The motion control method for the dexterous hand with two degrees of freedom is described in Fig. 1. The target position of the dexterous hand is input, and the fusion system calculates the control command according to the control law, sends the control command to servo positioning controller A (active) and servo positioning controller B (slave). The servo controller then combines the servo control command with the load transfer ratio KA and KB to obtain the drive command for the corresponding motor. The actual position of the joint passes through the position sensor, and then the result is fed back to the fusion system through the integrator operation, thus realizing large-scale closed-loop control.

[0027] A method for motion control for a fusion system of a robot arm with four degrees of freedom and a dexter hand with two degrees of freedom, the steps are as follows: (1) Consider the fusion system of a four-degree-of-freedom robot arm and a dexterous hand as a six-axis serial robot arm, the center point of the base of the robot arm is set as the origin, the coordinate system is established by DH method, and the DH parameters for respective connecting rod and joints of the robot arm are output, where the DH parameters of the joints include the joint angles θ1, θ2, θ3, θ4 of the four-degree-of-freedom robot arm and the joint angles θ5, θ6 of the wrist of the dexterous hand. (2) According to the detected joint angles θ1, θ2, θ3, θ4 of the robot arm with four degrees of freedom and the joint angles θ5, θ6 of the wrist of the dexterous hand, the position posture is determined using the forward kinematics method for the fusion system of a robot arm with four degrees of freedom and the dexterous hand. T=[RP01] of the wrist end of the dexter hand, thus implementing forward motion control for the fusion system. R represents the rotation matrix of the wrist end of the dexter hand, and P represents the position matrix of the wrist end of the dexter hand.

[0028] The transformation matrices between respective coordinate systems of the system for merging a robot arm with four degrees of freedom and a dexterous hand are: 10T=[c1−s100s1c10000100001] 21T=[c2−s200001d2−s2−c2000001] 32T=[c3−s30a2s3c300001d30001] 43T=[c4−s40000−1d4s4c4000001]T54=[c5−s50000−1d5s5c5000001]T65=[c6−s6000010−s6−c6000001] T60=T10∗T21∗T32∗T43∗T54∗T65 T10 is the coordinate transformation matrix from the base coordinate system of the robot arm to the first joint of the robot arm in the fusion system; T21 is the coordinate transformation matrix from the first joint of the robot arm to the second joint of the robot arm in the fusion system; T32 is the coordinate transformation matrix from the second joint of the robot arm to the third joint of the robot arm in the fusion system; T43 is the coordinate transformation matrix from the third joint of the robot arm to the fourth joint of the robot arm in the fusion system; T54 is the coordinate transformation matrix from the fourth joint of the robot arm to the first joint of the wrist of the dexter hand in the fusion system; T65 is the coordinate transformation matrix from the first joint of the wrist of the dexter hand to the second joint of the wrist of the dexter hand in the fusion system; T60 is the coordinate transformation matrix from the base coordinate system of the robot arm to the end of the wrist of the dexter hand in the fusion system.

[0029] dj is the distance of the connecting rod between the j-th joint and the j-1-th joint, j=2, 3, 4, 5; a p is the length of the connecting rod of the p-th joint, p=2; si is the sine of the i-th joint angle, ci is the cosine of the i-th joint angle, i=1, 2, 3, 4, 5, 6. si = sinθ i , ci = cosθ i , θ i is the i-th joint angle.

[0030] The first joint angle range is -90°<θ1 <90°. The second joint angle range is 0°<θ2 <90°. The third joint angle range is -120°<θ3 <0°. The fourth joint angle range is 0°<θ4 <180°. The fifth joint angle range is -70°<θ5 <70°. The sixth joint angle range is -45°<θ6 <45°.

[0031] (3) Since the three axes at the end of the system are not orthogonal, there is no analytical solution according to the known position [RP01] of the end of the system. Therefore, using backward kinematics numerical solution methods for the fusion system consisting of a robot arm with four degrees of freedom and the dexter hand, the joint angles θ1, θ2, θ3, θ4, θ5, θ6 of the system are determined, allowing the system's counter-directional motion to be controlled.

[0032] The backward kinematics solution for robots can determine θ1, θ2, θ3, θ4, θ5, but no analytical solution of θ6 can be determined, therefore only a numerical solution can be determined.

[0033] The numerical solution essentially consists of an estimate and an iteration until the error is small enough, or until the solution must be abandoned. In this method, the common Newton-Raphson algorithm is used because it is conceptually simple and has a quadratic convergence rate if the initial estimate is "close enough" to the solution. In the Newton iteration method, the first derivative of f(x) at x k For complex functions, especially multivariate implicit functions, it is relatively time-consuming and complicated to calculate the derivatives or partial derivatives, so the secant method is used for approximate calculation, and the formula is as follows: xk+1=xk−f(xk)(xk−xk−1)f(xk)−f(xk−1)

[0034] However, there is no guarantee that the algorithm will converge or be fast enough to meet application requirements and return only a single solution. To provide solutions for different possible poses, different initial conditions must be used.

[0035] Therefore, in the present invention, the solution formula for the k+1-th joint angle θ6 is as follows: θ6(k+1)=θ6(k)−f(θ6(k))(θ6(k)−θ6(k−1))f(θ6(k))−f(θ6(k−1))

[0036] θ 6(k+1) is the k+1-th iteration result of θ6, θ 6(k) is the k-th iteration result of θ6, θ 6(k-1) is the k-1-th iteration result of θ6, f(θ 6(k+1) ) is the formula of the reverse kinematics at θ 6(k+1) , f(θ 6(k) ) is the formula for the reverse kinematics at θ 6(k) , f(θ 6(k-1) ) is the formula for the reverse kinematics at θ 6(k-1) .

[0037] The present invention uses a six-degree-of-freedom serial-parallel mechanism consisting of a four-degree-of-freedom robot arm and a two-degree-of-freedom dexterous hand to perform fusion control of the robot arm and dexterous hand. The arm type consisting of a four-degree-of-freedom robot arm and a two-degree-of-freedom wrist does not meet the requirement that the three axes intersect at a single point at the end, and there is no analytical solution for the inverse kinematics, only a numerical solution. Therefore, a method for numerically solving the inverse kinematics based on this arm type is developed, which is suitable for obtaining numerical solutions for all serial robot arms.

[0038] The six-degree-of-freedom serial-parallel mechanism of the present invention, which consists of a four-degree-of-freedom robot arm and a two-degree-of-freedom wrist of a dexterous hand, has multi-degree-of-freedom redundancy, so that the robot arm can achieve the rotation of a dexterous hand with five fingers without having to move over a large range. The contents not described in detail in the description of the present invention are well known to those skilled in the art.

Claims

[1] A fusion system of a robot arm and a dexterous hand, characterized by that the fusion system comprises a robot arm with four degrees of freedom, a wrist of the dexter hand and a dexter hand, wherein the wrist of the dexter hand is attached to the end of the robot arm with four degrees of freedom, wherein the dexter hand is attached to the wrist of the dexter hand; wherein the wrist of the dexter hand and the robot arm with four degrees of freedom are connected by electronic circuits. [2] A fusion system of a robot arm and a skilled hand according to claim 1, characterized by , that the wrist of the dexterous hand is a parallel mechanism with two degrees of freedom, and includes two motors, two pushrods and two servo position controllers, wherein the two servo position controllers are each an active servo position controller and a slave servo position controller, wherein the two motors comprise a first motor and a second motor, wherein the two push rods comprise a first push rod and a second push rod, wherein the active servo position controller is arranged to drive the first motor, the movement of which sets the first push rod in motion, and the slave servo position controller is arranged to drive the second motor, the movement of which sets the second push rod in motion; the end of the first push rod and the end of the second push rod are simultaneously connected to the palm of the dexter hand. [3] A fusion system of a robot arm and a skilled hand according to claim 2, characterized bythat the two motors use a synchronous differential control mode, whereby the two motors drive the two push rods in movement to realize the pitch movement and yaw rotation of the dexter hand. [4] A fusion system of a robot arm and a skilled hand according to claim 3, characterized by that the dexter hand performs a pitching movement when the two push rods move in the same direction, with the pitch angle range being -70 degrees to 70 degrees, and the dexter hand performs a yaw movement when the two push rods move in the opposite direction, with the yaw angle range being -45 degrees to 45 degrees. [5] A method for motion control for a fusion system of a robot arm and a dexterous hand, characterized by that the procedure includes: Consider the fusion system of a four-degree-of-freedom robot arm and a dexterous hand as a six-axis serial robot arm, the center point of the base of the four-degree-of-freedom robot arm is set as the origin, the robot coordinate system is created using a DH method, and the DH parameters for respective joints and connecting rod of the robot arm are output; According to the joint angles (θ1, θ2, θ3, θ4) of the four-degree-of-freedom robot arm and the joint angles (θ5, θ6) of the wrist of the dexterous hand, the position pose matrix is ​​calculated using forward kinematics methods for the fusion system of a four-degree-of-freedom robot arm and the dexterous hand. T=[RP01] of the wrist end of the dexter hand to realize the forward movement control for the fusion system, where R represents the rotation matrix of the wrist end of the dexter hand, and P represents the position matrix of the wrist end of the dexter hand; If the position T=[RP01] of the wrist end of the dexter hand is known, the joint angles θ1, θ2, θ3, θ4, θ5, θ6 of the fusion system are determined using backward kinematics numerical solution methods for the fusion system of a robot arm with four degrees of freedom and the dexter hand, and according to the joint angles, the control command is obtained and sent to the servo position controller to drive the wrist end of the dexter hand so that the specified position posture is reached. [6] A method of motion control for a fusion system of a robot arm and a skilled hand according to claim 5, characterized by that when the forward movement control for fusion system is used, the position and posture of the wrist end of the skilled hand T=60T=10T∗21T∗32T∗43T∗54T∗65T 10T is the coordinate transformation matrix from the base coordinate system of the robot arm to the first joint of the robot arm in the fusion system; 21T is the coordinate transformation matrix from the first joint of the robot arm to the second joint of the robot arm in the fusion system; 32T is the coordinate transformation matrix from the second joint of the robot arm to the third joint of the robot arm in the fusion system; 43T is the coordinate transformation matrix from the third joint of the robot arm to the fourth joint of the robot arm in the fusion system; 54T is the coordinate transformation matrix from the fourth joint of the robot arm to the first joint of the wrist of the dexter hand in the fusion system; 65T is the coordinate transformation matrix from the first joint of the wrist of the dexter hand to the second joint of the wrist of the dexter hand in the fusion system; 60T is the coordinate transformation matrix from the base coordinate system of the robot arm to the end of the wrist of the dexter hand in the fusion system. [7] A method of motion control for a fusion system of a robot arm and a skilled hand according to claim 6, characterized by , 10T=[c1−s100s1c10000100001]21T=[c2−s200001d2−s2−c2000001]32T=[c3−s30a2s3c300001d30001] 43T=[c4−s40000−1d4s4c4000001]54T=[c5−s50000−1d5s5c5000001]65T=[c6−s6000010−s6−c6000001] where, dj is the distance of the connecting rod between the j-th joint and the j-1-th joint, j=2, 3, 4, 5; a p is the length of the connecting rod of the p-th joint, p=2; si is the sine of the i-th joint angle, ci is the cosine of the i-th joint angle, i=1, 2, 3, 4, 5, 6. [8] A method of motion control for a fusion system of a robot arm and a skilled hand according to claim 7, characterized by , si = sin θ i , ci = cos θ i . [9] A method of motion control for a fusion system of a robot arm and a skilled hand according to claim 5, characterized by , the joint angle θ6 is solved iteratively numerically. [10] A method of motion control for a fusion system of a robot arm and a skilled hand according to claim 9, characterized by, the k+1-th iteration formula of θ6 is as follows: θ6(k+1)=θ6(k)−ƒ(θ6(k))(θ6(k)−θ6(k−1))ƒ(θ6(k))−ƒ(θ6(k−1)) θ 6(k+1) the k+1-th iteration result of θ6 is, θ 6(k) the k-th iteration result of θ6 is, θ 6(k-1) the k-1-th iteration result of θ6 is f(θ 6(k+1) ) the inverse kinematics formula at θ 6(k+1) is, f(θ 6(k) ) the inverse kinematics formula at θ 6(k) is, f(θ 6(k-1) ) the inverse kinematics formula at θ 6(k-1) is.

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