An Adaptive Compensation Method for Robot Friction Disturbance Considering Inertia Variation

Abstract

This invention discloses an adaptive compensation method for robot friction disturbances that considers changes in inertia. It includes applying a friction disturbance adaptive compensator, which considers the characteristics of changes in the equivalent load inertia of the drive joints, based on a position PID feedback control strategy. This suppresses errors caused by friction disturbances resulting from changes in robot configuration or end-effector load. The friction disturbance adaptive algorithm is stored in a separate arithmetic register, and its operation cycle is synchronized with the servo update cycle. The friction disturbance adaptive compensator of this invention is independent of the position PID feedback control structure and does not require online calculation of the robot's dynamic model. It is easily modified and implemented on existing robot control systems, and can eliminate abrupt changes in following accuracy that occur during start-up and commutation of the drive joint motors, thereby improving the robot's control accuracy.

Description

Technical Field

[0001] This invention relates to the fields of robotics and automation, and specifically to an adaptive compensation method for robot friction disturbances that takes into account changes in inertia. Background Technology

[0002] SCARA is an abbreviation for Selective Compliance Assembly Robot Arm, meaning a robotic arm used for assembly operations. It has three rotary joints and is best suited for planar positioning.

[0003] The joint control systems of high-speed SCARA robots generally adopt a composite control structure of "position PID feedback control + velocity feedforward control". This structure is simple, robust and reliable, which not only ensures system stability and fast response capability, but also improves dynamic positioning accuracy.

[0004] However, the tracking error of the robot's drive joint motors can be abruptly affected by friction when starting or changing direction, and crawling can occur when running at low speed, thus affecting the control accuracy of the system.

[0005] In addition, high-speed SCARA robots belong to a type of nonlinear time-varying system. The equivalent load inertia of their first and second drive joints changes with the robot configuration and end-effector load, which in turn causes changes in static friction disturbance. This makes it impossible for existing compensation techniques based on constant friction coefficient to accurately compensate for time-varying friction disturbance, thereby reducing control quality.

[0006] Therefore, the industry urgently needs a compensation method applicable to high-speed SCARA robots to improve the motion control accuracy of the robots. Summary of the Invention

[0007] The problem this invention aims to solve is to provide an adaptive compensation method for robot friction disturbance that considers changes in inertia. The adaptive compensation device for friction disturbance is independent of the position PID feedback control structure and does not require online calculation of the robot's dynamic model. It is easy to modify and implement on existing robot control systems and can eliminate the sudden change in following accuracy of each drive joint motor during start-up and commutation, thereby improving the robot's control accuracy.

[0008] To address the aforementioned problems, this invention provides an adaptive compensation method for robot friction disturbances that considers changes in inertia. The technical solution adopted by this invention to solve its technical problems and achieve the above objectives is as follows:

[0009] An adaptive compensation method for robot friction disturbance considering inertia variation includes: applying a friction disturbance adaptive compensator that considers the inertia variation characteristics of the equivalent load of the driven joint, based on a position PID feedback control strategy, to suppress errors caused by friction disturbance due to changes in robot configuration or end-effector load; step S1: offline selection of sample configuration coordinate points; step S2: offline calculation of sample configuration distance function; step S3: offline calculation of inertia variation weight vector; step S4: online calculation of current configuration distance function; step S5: online calculation of equivalent load inertia corresponding to the current position vector; step S6: online calculation of friction disturbance compensation value; step S7: implementation of compensation.

[0010] As a further improvement of the present invention, step S1 includes: selecting N on the trajectory of the robot's end effector motion. S There are 1 sample configuration coordinate points, and the position vector of each sample configuration coordinate point in the robot reference coordinate system is denoted as r. p,j (j = 1, 2, ..., N) S The equivalent load inertia of the i-th driven joint of the robot at each sample point is calculated using a dynamic model and denoted as . N R This indicates the number of drive joints in the robot.

[0011] As a further improvement of the present invention, step S2 includes: using the position vector r obtained in step S1 p,j Calculate the position vector r of the k-th sample. p,k Relative to the position vector r of the j-th sample p,j Distance function:

[0012]

[0013] In the formula, ζ represents the function width.

[0014] As a further improvement of the present invention, step S2 includes: step S201: ζ is set according to the actual debugging effect, and the initial value is two.

[0015] As a further improvement of the present invention, step S3 includes: utilizing the equivalent load inertia of step S1. The sample configuration distance function obtained in step S2 Calculate the inertia change weight vector W of the i-th driving joint. i :

[0016]

[0017] In the formula

[0018]

[0019] The calculated inertia change weight vector W i It is stored in the data register of the robot control system and is called up during online calculations.

[0020] As a further improvement of the present invention, step S4 includes: using the position vector r obtained in step S1 p,j Calculate the robot's current position vector r P Relative to the position vector r of the j-th sample p,j Functions:

[0021]

[0022] Construct a vector using the function in the above formula

[0023] As a further improvement of the present invention, step S5 includes: using the inertia change weight vector W obtained in step S3. i The function vector obtained in step S4 The equivalent load inertia of the i-th drive joint corresponding to the current position vector is calculated using the following formula:

[0024]

[0025] As a further improvement of the present invention, step S6 includes: using the equivalent load inertia corresponding to the robot's current position vector obtained in step S5, calculating the friction disturbance compensation value using the following formula:

[0026]

[0027] In the formula

[0028]

[0029] Here, μ s and μ c These represent the maximum static friction factor and the Coulomb friction factor, respectively. The critical velocities are all obtained through friction identification experiments. and These represent the commanded angular acceleration and angular velocity of the i-th drive joint motor, respectively.

[0030] As a further improvement of the present invention, step S7 includes: adding the friction disturbance compensation value obtained in step S6 to the output value of the PID feedback controller, and sending it as a control command to the servo driver to realize friction compensation.

[0031] The beneficial effects of the adaptive compensation method for robot friction disturbance considering inertia changes proposed in this application are as follows: it can effectively address the impact of changes in the equivalent load inertia of each drive joint on friction disturbances, and thus design a compensation algorithm to suppress errors caused by friction disturbances. The friction disturbance compensator is independent of the feedback control structure, and its algorithm does not require calculation of the robot system's dynamic model, making it easy to modify and implement on existing robot control systems. It can eliminate the sudden changes in following accuracy that occur during start-up and commutation of each drive joint motor, thereby improving the robot's control accuracy. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a control structure block diagram of one embodiment of the present invention.

[0034] 1-SCARA robot; 2-Motor; 3-Servo driver; 4-PID feedback controller. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments:

[0036] To achieve the objectives of this invention, an adaptive compensation method for robot friction disturbance considering inertia changes is provided, comprising the following steps:

[0037] Step S1: Select sample configuration coordinate points offline

[0038] On the trajectory of the SCARA robot 1's end effector, select N. S There are 1 sample configuration coordinate points, and the position vector of each sample configuration coordinate point in the SCARA robot 1 reference coordinate system is denoted as r. p,j (j = 1, 2, ..., N) S The equivalent load inertia of the i-th drive joint of the SCARA robot at each sample point can be calculated using the dynamic model, denoted as . N R This indicates the number of drive joints in SCARA robot 1.

[0039] Step S2: Calculate the sample configuration distance function offline.

[0040] Using the position vector r obtained in step S1 p,j Calculate the position vector r of the k-th sample.p,k Relative to the position vector r of the j-th sample p,j Distance function:

[0041]

[0042] In the formula, ζ represents the function width, which can be set according to the actual debugging effect, with an initial value of 2.

[0043] Step S3: Calculate the inertia change weight vector offline.

[0044] Using the equivalent load inertia of step S1 The sample configuration distance function obtained in step S2 Calculate the inertia change weight vector W of the i-th driving joint. i :

[0045]

[0046] In the formula

[0047]

[0048] The calculated inertia change weight vector W i It is stored in the data register of the SCARA robot 1 control system for online calculation.

[0049] Step S4: Calculate the current configuration distance function online.

[0050] Using the position vector r obtained in step S1 p,j Calculate the current position vector r of SCARA robot 1 P Relative to the position vector r of the j-th sample p,j Functions:

[0051]

[0052] The above function can be used to construct a vector.

[0053] Step S5: Calculate the equivalent load inertia corresponding to the current position vector online.

[0054] The inertia change weight vector W obtained in step S3 i The function vector obtained in step S4 The equivalent load inertia of the i-th drive joint corresponding to the current position vector can be calculated using the following formula:

[0055]

[0056] Step S6: Calculate friction disturbance compensation value online

[0057] Using the equivalent load inertia corresponding to the current position vector of SCARA robot 1 obtained in step S5, the friction disturbance compensation value is calculated using the following formula:

[0058]

[0059] In the formula

[0060]

[0061] Here, μ s and μ c These represent the maximum static friction factor and the Coulomb friction factor, respectively. The critical velocity can be obtained through friction identification experiments. and

[0062] These represent the commanded angular acceleration and angular velocity of the i-th drive joint motor 2, respectively.

[0063] Step S7: Implement compensation

[0064] The friction disturbance compensation value obtained in step S6 is added to the output value of the PID feedback controller 4 and sent as a control command to the servo driver 3 to achieve friction compensation.

[0065] The advantages of this invention are: it can estimate the impact of changes in the load inertia of the drive joint on frictional disturbances in real time without the need for online calculation of complex machine dynamics models; the algorithm is simple and easy to implement; and it can further improve the control accuracy of each joint during high-speed operation.

[0066] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An adaptive compensation method for robot frictional disturbances considering changes in inertia, characterized in that, include: Based on the position PID feedback control strategy, a friction disturbance adaptive compensator that considers the change characteristics of the equivalent load inertia of the drive joint is applied to suppress the error caused by friction disturbance due to changes in robot configuration or end load. Step S1: Select sample configuration coordinate points offline; Step S1 includes: On the trajectory of the robot's end effector, select There are 1 sample configuration coordinate points, and the position vector of each sample configuration coordinate point in the robot reference coordinate system is denoted as . ( The robot's position at each sample point is calculated using a dynamic model. The equivalent load inertia of each driven joint is denoted as ( ); Indicates the number of driven joints in the robot; Step S2: Calculate the sample configuration distance function offline; Step S2 includes: Using the position vector obtained in step S1 Calculate the first Sample location vector Relative to the first Sample location vector Distance function: ， ， ， In the formula, Indicates the function width; Step S3: Calculate the inertia change weight vector offline; Step S3 includes: Using the equivalent load inertia of step S1 The sample configuration distance function obtained in step S2 Calculate the first Inertia change weight vector of each driving joint : ， ， In the formula ， ， The calculated inertia change weight vector It is stored in the robot control system's data register and retrieved during online calculations; Step S4: Calculate the current configuration distance function online; Step S4 includes: Using the position vector obtained in step S1 Calculate the robot's current position vector Relative to the first Sample location vector Functions: ， ， Construct a vector using the function in the above formula ; Step S5: Calculate the equivalent load inertia corresponding to the current position vector online; Step S5 includes: Using the inertia change weight vector obtained in step S3 The function vector obtained in step S4 The following formula is used to calculate the first position vector corresponding to the current position. Equivalent load inertia of each driven joint: ， ； Step S6: Calculate the friction disturbance compensation value online; Step S6 includes: Using the equivalent load inertia corresponding to the robot's current position vector obtained in step S5, the friction disturbance compensation value is calculated using the following formula: ， In the formula ， ， Here, and These represent the maximum static friction factor and the Coulomb friction factor, respectively. The critical velocities are all obtained through friction identification experiments. and They represent the first The commanded angular acceleration and angular velocity of each drive joint motor; Step S7: Implement compensation.

2. The adaptive compensation method for robot friction disturbance considering inertia variation according to claim 1, characterized in that: Step S2 includes: Step S201: The initial value is set to two based on the actual debugging results.

3. The adaptive compensation method for robot friction disturbance considering inertia variation according to claim 1, characterized in that: Step S7 includes: The friction disturbance compensation value obtained in step S6 is added to the output value of the PID feedback controller and sent as a control command to the servo driver to achieve friction compensation.

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