A compliant control method for master-slave teleoperated robots

Abstract

The application discloses a compliant control method of master-slave teleoperation robot, specifically comprising the following steps: introducing a double adaptive admittance controller based on a self-disturbance control into a slave robot control system; after initializing the pose of the master-slave robot, performing motion mapping of the master-slave robot, collecting and processing the force / torque data of the six-dimensional force / torque sensor of the master-slave robot, and calculating the actual external force to determine whether to run the admittance controller; if it is determined to run, the position in the Z-axis direction of the slave robot is controlled by the admittance controller through the expected force set by the admittance controller, and the positions in other orthogonal directions are continuously controlled by the master robot, so that accurate interactive force control is realized. The double adaptive admittance control algorithm based on the self-disturbance control adjusts the parameters of the admittance model in real time through the construction of a double adaptive update law, and further improves the force tracking accuracy and robustness of the robot by introducing the self-disturbance control.

Description

Technical Field

[0001] This invention belongs to the field of teleoperated robot technology and relates to a compliant control method for a master-slave teleoperated robot. Background Technology

[0002] Master-slave teleoperated robots allow operators to control the slave robot to complete tasks in a safe environment, making them suitable for complex or harsh scenarios, such as space or deep-sea exploration, remote minimally invasive surgery, and nuclear power plant maintenance.

[0003] Traditional position control cannot meet the needs of tasks where robots interact with their environment through force, such as grinding and polishing, constant force assembly, and medical ultrasound inspection. When a secondary robot moves according to the instructions of the primary robot, if the secondary robot comes into contact with the environment or an object, a force will be generated between the two. The introduction of force feedback allows the operator to feel the interactive force, but it cannot control the interactive force.

[0004] Force-position control structures are widely used in master-slave teleoperated robot systems due to their advantages such as simple structure, ease of implementation, and ability to realistically feedback external forces. However, in high-stiffness environments, due to the large interaction forces, the master robot may experience impact-induced movements under the influence of feedback forces, making it difficult to maintain a stable posture. This, in turn, causes the slave robot to produce unexpected following movements, thus preventing the slave robot from achieving stable and compliant interaction with the environment or objects. Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, this invention proposes a compliant control method for a master-slave teleoperated robot, the specific technical solution of which is as follows:

[0006] A compliant control method for a master-slave teleoperated robot introduces an admittance controller based on a dual adaptive admittance control algorithm with active disturbance rejection control into the slave robot control system. After initializing the poses of the master and slave robots, motion mapping is performed. Force / torque data from the six-dimensional force / torque sensors of the master and slave robots are collected and processed to calculate the actual external force. This is used to determine whether the admittance controller should be activated. If activation is determined, the admittance controller controls the position of the slave robot in the Z-axis direction by setting and tracking the desired force. The position in other orthogonal directions is controlled by the master robot, thereby achieving accurate interactive force control.

[0007] Furthermore, after the master-slave robot motion mapping begins, the slave robot follows the master robot's motion within the free motion space.

[0008] Furthermore, the aforementioned dual adaptive admittance control algorithm based on active disturbance rejection control is specifically as follows:

[0009] A steady-state error-free admittance model incorporating uncertainties in environmental location information is derived from the traditional second-order admittance model:

[0010]

[0011] Where M represents the inertia matrix and B represents the damping matrix. and Let these represent the first and second derivatives of the error between the expected trajectory and the actual trajectory, respectively. Represents the variable velocity curvature of a surface in an uncertain environment. ΔF represents the variable acceleration curvature of an uncertain environment surface, and ΔF represents the force tracking error.

[0012] Introducing adaptive adjustment term ΔB dynamic compensation The adjusted admittance model is expressed as follows:

[0013]

[0014] The adaptive update law expression for the adaptive adjustment term ΔB is:

[0015]

[0016] Where λ represents the sampling period of the controller, α represents the update rate, α > 0, and σ is a very small positive number to prevent the denominator from being 0;

[0017] The update rate α can also be updated adaptively, and its adaptive update law expression is:

[0018]

[0019] Where γ1 and γ2 are coefficients, both of which are positive constants, and α max This represents the maximum value of the update law. The first derivative of the force tracking error is represented.

[0020] Furthermore, the active disturbance rejection control includes a tracking differentiator, an extended state observer, and a nonlinear state error feedback controller, wherein the expression for the second-order fastest discrete tracking differentiator is:

[0021]

[0022]

[0023] Where k represents the order, x represents the state variable, v0 represents the input signal, v1 represents the output signal, v2 represents the derivative of v1, h represents the sampling period, r represents the speed factor, h0 represents the filter factor, and sign(·) represents the sign function.

[0024] The expression for the extended state observer is:

[0025]

[0026] Where z1, z2, z3 represent the observations of the extended state observer, β 01 ,β 02 ,β 03 The gain coefficient of the extended state observer is 0 < α < 1, and the interval [-δ, δ] is a linear segment set to avoid high-frequency jitter.

[0027] The expression for the nonlinear state error feedback controller is:

[0028]

[0029] Where r1 represents the input error, η1 and η2 represent the controller gain, and b0 represents the control gain.

[0030] Furthermore, determining whether to operate the admittance controller specifically includes:

[0031] The actual external force F ez With preset threshold F th1 Compare, if F ez <F th1 If F ez ≥F th1 Then, the position of the robot in the Z-axis direction is controlled by the admittance controller, while the position in other orthogonal directions is still controlled by the main robot.

[0032] Furthermore, the expected force F d The threshold is set to F th2 And the threshold F th2 Condition F is satisfied. th2 <F th1 In the expectation force F d Linear change to threshold F th2 During the process, at a certain moment, F begins to be satisfied. ez <F th1 If this happens, the admittance controller will stop controlling the slave robot, thereby restoring the master-slave robot motion mapping in all directions.

[0033] Beneficial effects:

[0034] This invention solves the problem of the difficulty for the slave robot to interact stably with the environment or objects under the control structure of the traditional force-position type master-slave teleoperation system by introducing an admittance controller into the robot control system.

[0035] The dual adaptive admittance control algorithm based on active disturbance rejection control designed in this invention adjusts the admittance model parameters in real time by constructing a dual adaptive update law, and further improves the force tracking accuracy and robustness of the robot by introducing active disturbance rejection control.

[0036] The teleoperation compliant control strategy designed in this invention can easily combine admittance control with master-slave teleoperation, enabling the slave robot to have good master-slave position tracking performance when moving freely, and good force tracking performance when interacting with the robot. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the improved force-position type master-slave teleoperation system control structure of the present invention;

[0038] Figure 2 This is a flowchart of the dual adaptive admittance control algorithm based on active disturbance rejection control of the present invention;

[0039] Figure 3 This is a schematic diagram illustrating the verification results of constant force tracking using the dual adaptive admittance control algorithm based on active disturbance rejection control of the present invention.

[0040] Figure 4 This is a schematic diagram illustrating the verification results of the variable force tracking using the dual adaptive admittance control algorithm based on active disturbance rejection control of the present invention.

[0041] Figure 5 This is a schematic diagram of the remote operation compliant control strategy of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] The present invention provides a compliant control method for a master-slave teleoperated robot, employing, as follows: Figure 1 The improved force-position type master-slave teleoperation system control structure shown, based on the realization of master-slave motion and force feedback, follows... Figure 5 The teleoperation compliant control strategy shown achieves compliant control of the robot. This strategy is based on a designed active disturbance rejection control dual adaptive admittance control algorithm, with a desired force F as the input. d The algorithm outputs the robot's position adjustment amount, thereby achieving accurate interactive force control.

[0044] In this embodiment, the desired force F d The settings are divided into two types: F under constant force. d =25N, F when the force is variable d =25 + 12.5sin(0.2π·t)N, as Figure 3 and Figure 4 The verification results are shown in the figure.

[0045] The compliant control method for this master-slave teleoperated robot specifically includes:

[0046] Introduce an admittance controller into the system control structure of a force-position type master-slave teleoperated robot. For details, refer to... Figure 1 In order to achieve force-position hybrid control of the robot, an admittance controller C5 is introduced from the robot control system as another position controller, that is, force control is performed in one direction and position control is performed in other directions.

[0047] Design a dual adaptive admittance control algorithm based on active disturbance rejection control, and apply it to the admittance controller, such as... Figure 2 As shown. Specifically, the admittance model without steady-state error, which includes uncertainties in environmental position information, is derived from the traditional second-order admittance model:

[0048]

[0049] Where M represents the inertia matrix and B represents the damping matrix. and Let these represent the first and second derivatives of the error between the expected trajectory and the actual trajectory, respectively. Represents the variable velocity curvature of a surface in an uncertain environment. ΔF represents the variable acceleration curvature of an uncertain environment surface, and ΔF represents the force tracking error.

[0050] In this embodiment, M=1, B=200.

[0051] Introducing adaptive adjustment term ΔB dynamic compensation The adjusted admittance model is expressed as follows:

[0052]

[0053] The adaptive update law expression for the adaptive adjustment term ΔB is:

[0054]

[0055] Where λ represents the sampling period of the controller, α represents the update rate, satisfying α > 0, and σ is a very small positive number to prevent the denominator from being 0. m This indicates the actual contact force.

[0056] The update rate α can also be updated adaptively, and its adaptive update law expression is:

[0057]

[0058] Where γ1 and γ2 are coefficients, both of which are positive constants, and α max ΔF represents the maximum value of the update law, and ΔF represents the first derivative of the force tracking error ΔF.

[0059] In this embodiment, σ = 0.01, α max =0.2, γ1=0.055, γ2=0.01.

[0060] The active disturbance rejection control includes a tracking differentiator, an extended state observer, and a nonlinear state error feedback controller. The expression for the second-order fastest discrete tracking differentiator is:

[0061]

[0062] Where v0 represents the input signal, v1 represents the output signal, v2 represents the derivative of v1, h represents the sampling period, r represents the speed factor, h0 represents the filter factor, and sign(·) represents the sign function;

[0063] In this embodiment, r = 2000, h = 0.005, and h0 = 0.01.

[0064] The expression for the extended state observer is:

[0065]

[0066] Where z1, z2, z3 represent the observations of the extended state observer, β 01 ,β 02 ,β 03 The gain coefficient of the extended state observer is 0 < α < 1, and the interval [-δ, δ] is a linear segment set to avoid high-frequency jitter.

[0067] In this embodiment, β 01 =75, β 02 =208, β 03 =1736, b0=1.8, α1=0.5, α2=0.25, δ=0.05.

[0068] The expression for the nonlinear state error feedback controller is:

[0069]

[0070] Where η1 and η2 represent controller gains, and b0 represents control gain;

[0071] In this embodiment, η1 = 1.2, η2 = 0.2, α3 = 0.5, and α4 = 0.75.

[0072] The admittance controller, employing a dual adaptive admittance control algorithm based on active disturbance rejection control, achieves compliant and stable control of the master-slave teleoperated robot. Specifically, this includes:

[0073] S1. Initialize the poses of the master and slave robots, start the master-slave robot motion mapping, and let the slave robot follow the master robot in the free motion space;

[0074] S2. Acquire force / torque data from a six-dimensional force / torque sensor, and perform filtering, gravity compensation, and other processing to calculate the actual external force F. ez The external force F obtained ez With threshold F th1 Compare, if F ez <F th1 If F ez ≥F th1 Then, the position of the robot in the Z-axis direction is controlled by the admittance controller, while the position in other orthogonal directions is still controlled by the main robot;

[0075] S3. After completing the interactive task, use an external switch to apply the desired force F. d Set to threshold F th2 Threshold F th2 Condition F is satisfied. th2 <F th1 ; in expectation force F d Linear transformation to F th2 During the process, from a certain moment onwards, F is satisfied. ez <F th1 At this point, the admittance controller will stop controlling the slave robot, thereby restoring the master-slave robot motion mapping in all directions.

[0076] In this embodiment, F th1 =2N,F th2 =1N.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compliant control method for a master-slave teleoperated robot, characterized in that: An admittance controller based on a dual adaptive admittance control algorithm using active disturbance rejection control is introduced into the robot control system. The admittance control algorithm is specifically as follows: Introducing adaptive adjustment term ΔB dynamic compensation The adjusted admittance model is expressed as follows: Where M represents the inertia matrix and B represents the damping matrix. and Let these represent the first and second derivatives of the error between the expected trajectory and the actual trajectory, respectively. Represents the variable velocity curvature of a surface in an uncertain environment. ΔF represents the variable acceleration curvature of an uncertain environment surface, and ΔF represents the force tracking error. The adaptive update law expression for the adaptive adjustment term ΔB is: Where λ represents the sampling period of the controller, α represents the update rate, satisfying α > 0, and σ is a positive number to prevent the denominator from being zero; F m F represents the actual contact force. d Indicates expectation; The update rate α is adaptively updated, and its adaptive update law expression is: Where γ1 and γ2 are coefficients, both of which are positive constants, and α max This represents the maximum value of the update law. The first derivative represents the force tracking error; The compliance control method includes the following steps: S1. Initialize the poses of the master and slave robots, start the master-slave robot motion mapping, and let the slave robot follow the master robot in the free motion space; S2. Acquire force / torque data from a six-dimensional force / torque sensor, perform filtering and gravity compensation processing, and calculate the actual external force F. ez The external force F obtained ez With threshold F th1 Compare, if F ez <F th1 If F ez ≥F th1 Then, the position of the robot in the Z-axis direction is controlled by the admittance controller, while the position in other orthogonal directions is still controlled by the main robot; S3. After completing the interactive task, use an external switch to apply the desired force F. d Set to threshold F th2 Threshold F th2 Condition F is satisfied. th2 <F th1 ; in expectation force F d Linear transformation to F th2 During the process, from a certain moment onwards, F is satisfied. ez <F th1 At this point, the admittance controller will stop controlling the slave robot, thereby restoring the master-slave robot motion mapping in all directions.

2. The compliant control method for a master-slave teleoperated robot as described in claim 1, characterized in that: The active disturbance rejection control includes a tracking differentiator, an extended state observer, and a nonlinear state error feedback controller, wherein the expression for the tracking differentiator is: Where k represents the order, x represents the state variable, v0 represents the input signal, v1 represents the output signal, v2 represents the derivative of v1, h represents the sampling period, r represents the speed factor, h0 represents the filter factor, and sign(·) represents the sign function. The expression for the extended state observer is: Where z1, z2, z3 represent the observations of the extended state observer, β 01 ,β 02 ,β 03 The gain coefficient of the extended state observer is 0 < α0 < 1, and the interval [-δ, δ] is a linear segment set to avoid high-frequency jitter. The expression for the nonlinear state error feedback controller is: Where r1 represents the input error, η1 and η2 represent the controller gain, and b0 represents the control gain.

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