A method for actively controllable back-drive control of space manipulator joints

Abstract

This invention discloses an active and controllable reverse-drive control method for a space robotic arm joint. By actively applying output torque, the joint achieves reverse-drive control under the combined action of external force and joint output force. The method detects the torque at the joint output end and controls the reverse-drive stiffness and damping characteristics via a reverse-drive controller. A one-dimensional torque sensor measures the force at the joint output end, and this force, along with the desired reverse-drive torque, is input to the reverse-drive controller. Based on the desired reverse-drive torque requirement, the controller outputs the desired joint speed, and the speed and current are controlled by a speed controller and a current controller, thus achieving active control of the reverse-drive torque. The reverse-drive controller of this invention consists of torque hysteresis, a reverse-drive characteristic simulator, and a speed limiter, which can convert the desired reverse-drive torque and the actual torque into a controllable desired joint speed.

Description

Technical Field

[0001] The present invention relates to the field of space robots and can be applied to space mechanisms with back-drive requirements. Background Art

[0002] During the design and assembly process of the space manipulator joint, the forward drive torque will be designed and controlled, which can realize the torque characteristic control from the drive motor, transmission system to the output end, and the reverse drive torque can be obtained by measurement. However, in the space manipulator system, the joint reverse drive torque performance is required to achieve specific tasks. The reverse drive torque characteristic refers to the reverse motion characteristic from the output end external force, transmission system to the drive motor. Generally, there are large differences between the forward drive characteristic and the reverse drive characteristic of the transmission system such as the joint, especially in the transmission system using the planetary reducer, the difference is more obvious. This makes it impossible to control the transmission characteristics of the forward drive and reverse drive at the same time during the design of the transmission system. For some systems with reverse drive characteristic requirements, it can only be verified by testing whether the reverse drive characteristic meets the requirements, and it is impossible to achieve active control of the reverse drive characteristic. In addition, as the number of times the joint is used increases, the reverse drive characteristic changes, especially at the end of its life, the reverse drive torque characteristic will change significantly, and it is impossible to achieve full-cycle control of the reverse drive torque characteristic. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide a method for actively controllable back-drive control of joints of a space robot arm. By designing a method for actively controllable back-drive control of joints, the problem of uncontrollable back-drive torque of the joints is solved, thereby achieving the purpose of controlling the back-drive torque of the joints of the space robot arm throughout its life cycle.

[0004] The technical solution of the present invention is:

[0005] A space manipulator joint active controllable back-drive control method comprises the following steps:

[0006] 1) Use the torque sensor to obtain the actual joint torque M at the joint output end jI ;

[0007] 2) According to the absolute value of the actual joint torque |M jI |, determine the joint control torque M of the current k-th solution cycle j (k);

[0008] 3) According to step 2) the joint control torque M is obtained j (k), determine the expected joint velocity V of the current k-th solution cycle imp (k);

[0009] 4) The expected joint velocity V obtained in step 3) imp(k) Perform amplitude limiting processing to obtain the joint expected velocity V after amplitude limiting processing imp ′(k), the desired joint velocity V after clipping imp ′(k) is the expected rotation speed of the joint.

[0010] Preferably, step 2) determines the joint control torque M j The method is as follows:

[0011] The absolute value of the actual moment at the joint |M jI |In the process of increasing, if |M jI |≥M InDeadArea , then let the joint control torque M of the current k-th solution cycle be j (k) is equal to the actual joint torque value M jI Otherwise, let the joint control torque M of the current k-th solution cycle be j is 0;

[0012] Actual moment at the joint |M jI |During the process of reduction, if |M jI |<M OutDeadArea , then let the joint control torque M of the current k-th solution cycle be j (k) is 0, otherwise, let the joint control torque M of the current kth solution cycle be j (k) is equal to the actual joint torque value M jI ;

[0013] Among them, M InDeadArea To enter the effective torque value, M OutDeadArea It is the exit effective torque value.

[0014] Preferably, the effective torque value M is entered InDeadArea The method of determining is as follows:

[0015] If the middle value of the joint back-drive torque requirement range is less than or equal to 1 / 2 of the joint maximum output torque, then M InDeadArea Equal to the middle value of the joint back-drive torque requirement range;

[0016] On the contrary, let M InDeadArea Less than or equal to 1 / 2 of the maximum output torque of the joint.

[0017] Preferably, the exit effective torque value M OutDeadArea The method of determining is as follows:

[0018] M OutDeadArea Equal to 3-5 times the accuracy of the torque sensor or M InDeadArea 1 / 2 to 2 / 3 times.

[0019] Preferably, step 3) determines the expected joint velocity V of the current k-th solution cycle imp (k) method, specifically:

[0020]

[0021] Among them, T mf is the coefficient reflecting the joint back-drive damping, and C is the coefficient reflecting the joint back-drive friction.

[0022] Preferably, T mf The value range is 0 to 1.

[0023] Preferably, the value range of C is not greater than 10 -2 .

[0024] Preferably, in step 4), the desired joint velocity V after the amplitude limiting process is obtained. imp ′(k), specifically:

[0025]

[0026] Among them, V impULim is the upper limit of joint speed, V impDLim It is the lower limit of joint speed.

[0027] Preferably, V impULim Do not exceed 2 / 3 of the joint's maximum forward velocity.

[0028] Preferably, V impDLim Do not exceed 2 / 3 of the joint's maximum reverse velocity.

[0029] The advantages of the present invention compared with the prior art are:

[0030] The present invention can realize active control of the back-driving torque by establishing the friction and damping characteristic relationship between the joint torque and the speed according to the task requirements, improve the system stability through the torque hysteresis link, and meet the different back-driving torque usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Block diagram of active controllable backdrive control of space manipulator joints;

[0032] Figure 2 Backdrive controller block diagram;

[0033] Figure 3 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0034] According to the demand for active control of the back-drive torque of the space manipulator joint, the present invention actively controls the joint rotation speed so that the joint can achieve back-drive under the combined action of external force and the motor, and controls the back-drive friction and damping characteristics through the back-drive controller design; and realizes stable control of the back-drive force by setting a torque hysteresis link.

[0035] The principle block diagram of the present invention is as follows Figure 1 As shown in the figure, the backdrive controller outputs the desired joint speed according to the force at the joint output end and the desired backdrive stiffness and damping characteristics, controls the motor through the speed closed loop and current closed loop, and detects the actual joint torque through the joint one-dimensional torque sensor. The two elements of backdrive control are: external force detection and control of motor output torque. External force detection can be obtained through the torque sensor. Control the motor output torque and use the current-torque characteristics of the brushless DC motor for control.

[0036] The block diagram of the flyback controller is as follows: Figure 2 As shown in Figure 1, the backdrive controller consists of torque hysteresis, backdrive characteristic simulator and speed limiter. The input of the backdrive controller includes the joint expected backdrive torque and the joint actual torque, where the joint expected backdrive torque includes the effective torque value M. InDeadArea and exit effective torque value M OutDeadArea .

[0037] The present invention inputs the joint desired back-driving torque and the joint actual torque into the torque hysteresis link. The processing flow of the torque hysteresis link is as follows: Figure 3 As shown, the steps include:

[0038] 1) Use a one-dimensional torque sensor to obtain the actual joint torque M at the joint output end jI ;

[0039] 2) Absolute value of actual joint torque |M jI |In the process of increasing, if |M jI |≥M InDeadArea , then let the joint control torque M j (k) is equal to the actual joint torque value M jI Otherwise, let the joint control torque M j (k) is 0;

[0040] The absolute value of the actual moment at the joint |M jI |During the process of reduction, if |M jI |<M OutDeadArea , then let the joint control torque M j (k) is 0, otherwise, let the joint control torque M j (k) is equal to the actual joint torque value M jI ;

[0041] Enter the effective torque value MInDeadArea The method for determining M is as follows: according to the required range of joint back-drive torque for the task, if the middle value of the required range of joint back-drive torque is less than or equal to 1 / 2 of the maximum output torque of the joint, then M InDeadArea is equal to the middle value of the joint back-drive torque requirement range; otherwise, let M InDeadArea Less than or equal to 1 / 2 of the maximum output torque of the joint.

[0042] Exit effective torque value M OutDeadArea The determination method is based on the effective torque value M InDeadArea The setting value and the accuracy of the one-dimensional torque sensor are used to determine the value. It is recommended to set the value to 3-5 times the accuracy of the one-dimensional torque sensor or M InDeadArea 1 / 2 to 2 / 3 times;

[0043] 3) Torque hysteresis link outputs joint control torque M j (k), which is input into the back-drive characteristic simulator to determine the joint expected velocity V in the current k-th solution cycle imp (k);

[0044] The reverse drive characteristic simulator is described as:

[0045]

[0046] Among them, V imp (k) is the expected joint velocity, T mf and C are coefficients reflecting the joint back-drive damping and friction, which are set according to the characteristics of the joint back-drive process of the task, or according to the test results of the joint at normal temperature and pressure. mf The value range is 0 to 1; the value range of C is no more than 10 -2 .

[0047] 4) After the joint expected speed is limited, the output is the joint expected speed after limiting V imp ′(k), described as:

[0048]

[0049] Among them, V impULim The upper limit of the joint speed limit shall not exceed 2 / 3 of the maximum forward speed of the joint. impDLim It is the lower limit of the joint speed, which shall not exceed 2 / 3 of the maximum reverse speed of the joint.

[0050] like Figure 1 As shown, the desired joint velocity V after limiting imp ′(k) is used as the input of the joint velocity closed loop, and the desired joint velocity is tracked through the velocity closed loop.

[0051] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall belong to the protection scope of the technical solution of the present invention. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0052] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A space manipulator joint active controllable back-drive control method, characterized in that: include: The actual joint torque M at the joint output end is obtained by using the torque sensor jI ; According to the absolute value of the actual joint torque M jI |, determine the joint control torque M of the current k-th solution cycle j (k); According to the obtained joint control torque M j (k), determine the expected joint velocity V of the current k-th solution cycle imp (k); The expected joint velocity V is obtained imp (k) Perform amplitude limiting processing to obtain the joint expected velocity V after amplitude limiting processing imp ′(k), the desired joint velocity V after clipping imp ′(k) is the desired rotation speed of the joint; Determine the joint control torque M j (k) method, specifically: The absolute value of the actual moment at the joint M jI |In the process of increasing, if |M jI |≥M InDeadArea , then let the joint control torque M of the current k-th solution cycle be j (k) is equal to the actual joint torque value M jI Otherwise, let the joint control torque M of the current k-th solution cycle be j (k) is 0; Actual moment at the joint |M jI |During the process of reduction, if |M jI |<M OutDeadArea , then let the joint control torque M of the current k-th solution cycle be j (k) is 0, otherwise, let the joint control torque M of the current kth solution cycle be j (k) is equal to the actual joint torque value M jI ; Among them, M InDeadArea To enter the effective torque value, M OutDeadArea is the exit effective torque value; Determine the expected joint velocity V of the current k-th solution cycle imp (k) method, specifically: Among them, T mf is the coefficient reflecting the joint back-drive damping, C is the coefficient reflecting the joint back-drive friction; The desired joint velocity V after the amplitude limiting process is obtained imp ′(k), specifically: Among them, V impULim is the upper limit of joint speed, V impDLim It is the lower limit of joint speed.

2. The method for actively controllable back-drive control of a space manipulator joint according to claim 1, characterized in that: The effective torque value M InDeadArea The method of determining is as follows: If the middle value of the joint back-drive torque requirement range is less than or equal to 1 / 2 of the joint maximum output torque, then M InDeadArea Equal to the middle value of the joint back-drive torque requirement range; On the contrary, let M InDeadArea Less than or equal to 1 / 2 of the maximum output torque of the joint.

3. The method for actively controllable back-drive control of a space manipulator joint according to claim 1, characterized in that: The exit effective torque value M OutDeadArea The method of determining is as follows: M OutDeadArea Equal to 3-5 times the accuracy of the torque sensor or M InDeadArea 1 / 2 to 2 / 3 times.

4. The method for actively controllable back-drive control of a space manipulator joint according to claim 1, characterized in that: The T mf The value range is 0 to 1.

5. The method for actively controllable back-drive control of a space manipulator joint according to claim 1, characterized in that: The value range of C is not greater than 10 -2 .

6. The method for actively controllable back-drive control of a space manipulator joint according to claim 1, characterized in that: The V impULim Do not exceed 2 / 3 of the joint's maximum forward velocity.

7. The method for actively controllable back-drive control of a space manipulator joint according to claim 1, characterized in that: The V impDLim Do not exceed 2 / 3 of the joint's maximum reverse velocity.

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