Robot friction disturbance self-adaptive compensation method considering inertia change

Abstract

The invention discloses a robot friction disturbance self-adaptive compensation method considering inertia change, which comprises the following steps of: applying a friction disturbance self-adaptive compensator considering inertia change characteristics of an equivalent load of a driving joint on the basis of a position PID (Proportion Integration Differentiation) feedback control strategy; errors caused by friction disturbance due to the change of the configuration or the tail end load of the robot are inhibited. The friction disturbance self-adaptive algorithm is stored in an independent operation register, and the operation period of the friction disturbance self-adaptive algorithm is synchronous with the servo updating period. The friction disturbance self-adaptive compensator is independent of a position PID feedback control structure, a kinetic model of a robot does not need to be calculated on line, an existing robot control system is easily modified and achieved, the following precision sudden change phenomenon occurring when all driving joint motors start and reverse can be eliminated, and the reliability of the robot is improved. The control precision of the robot is improved.

Description

Technical Field

[0001] The invention relates to the field of robotics and automation, and in particular to a robot friction disturbance adaptive compensation method considering inertia changes. Background Art

[0002] SCARA is the abbreviation of Selective Compliance Assembly Robot Arm, which means a robot arm used for assembly work. It has three rotation joints and is best suited for flat positioning.

[0003] The control systems of various joints of high-speed SCARA robots generally adopt a composite control structure of "position PID feedback control + speed feedforward control", which has a simple structure, strong robustness and high reliability. It not only ensures system stability and rapid response capabilities, but also improves dynamic positioning accuracy.

[0004] However, the robot's driving joint motors will be affected by friction when starting or reversing, resulting in a sudden change in tracking error, and creeping when running at low speed, thus affecting the control accuracy of the system.

[0005] In addition, the high-speed SCARA robot belongs to a type of nonlinear time-varying system. The equivalent load inertia of the first and second driving joints changes with the robot's position and end load, which in turn causes the static friction disturbance to change. The existing compensation technology based on the constant friction factor cannot accurately compensate for the time-varying friction disturbance, thereby reducing the control quality.

[0006] Therefore, in terms of technical expectations of this industry, there is an urgent need for a compensation method that can be applied to high-speed SCARA robots to improve the robot's motion control accuracy. Summary of the invention

[0007] The problem to be solved by the present invention is to provide a robot friction disturbance adaptive compensation method taking into account inertia changes. The friction disturbance adaptive compensator 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 the existing robot control system. It can eliminate the sudden change in following accuracy of each driving joint motor during starting and reversing, thereby improving the control accuracy of the robot.

[0008] In order to solve the above problems, the present invention provides a robot friction disturbance adaptive compensation method considering inertia change. In order to achieve the above purpose, the technical solution adopted by the present invention to solve its technical problems is:

[0009] A robot friction disturbance adaptive compensation method considering inertia change comprises: on the basis of a position PID feedback control strategy, applying a friction disturbance adaptive compensator considering the inertia change characteristics of the equivalent load of a driving joint, so as to suppress the error caused by the friction disturbance caused by the robot configuration or end load change; step S1: selecting sample configuration coordinate points offline; step S2: calculating the sample configuration distance function offline; step S3: calculating the inertia change weight vector offline; step S4: calculating the current configuration distance function online; step S5: calculating the equivalent load inertia corresponding to the current position vector online; step S6: calculating the friction disturbance compensation value online; step S7: implementing compensation.

[0010] As a further improvement of the present invention, step S1 includes: selecting N on the trajectory of the robot end movement S The position vector of each sample configuration coordinate point in the robot reference coordinate system is denoted by r p,j (j=1,2,…,N S ), the equivalent load inertia of the robot’s i-th driving joint at each sample point is calculated by the dynamic model and recorded as N R Indicates the number of driven joints of 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 kth sample position vector r p,k Relative to the jth sample position vector r p,j The distance function is:

[0012]

[0013] Where 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: using the equivalent load inertia of step S1 The distance function of the sample configuration obtained in step S2 Calculate the inertia change weight vector W of the i-th driven joint i :

[0016]

[0017] In the formula

[0018]

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

[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 jth sample position vector r p,j Function:

[0021]

[0022] Use the above function to construct a function vector

[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 driven 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 current position vector of the robot obtained in step S5, the friction disturbance compensation value is calculated using the following formula:

[0026]

[0027] In the formula

[0028]

[0029] Here, μ s and μ c denote the maximum static friction factor and Coulomb friction factor respectively, represents the critical speed, both obtained through friction identification experiments; and They represent the command angular acceleration and angular velocity of the i-th driving 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 the result as a control instruction to the servo driver to achieve friction compensation.

[0031] The beneficial effect of the robot friction disturbance adaptive compensation method considering inertia change of the present application is that it can effectively deal with the influence of the change of equivalent load inertia of each driving joint on the friction disturbance, and then design a compensation algorithm to suppress the error caused by the friction disturbance. The friction disturbance compensator is independent of the feedback control structure, and its algorithm does not need to calculate the dynamic model of the robot system. It is easy to modify and implement on the existing robot control system, and can eliminate the sudden change of following accuracy of each driving joint motor during starting and reversing, thereby improving the control accuracy of the robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a control structure block diagram of an implementation mode of the present invention.

[0034] 1-SCARA robot; 2-motor; 3-servo drive; 4-PID feedback controller. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with specific embodiments:

[0036] In order to achieve the purpose of the present invention, a robot friction disturbance adaptive compensation method considering inertia change comprises the following steps:

[0037] Step S1: Offline selection of sample configuration coordinate points

[0038] On the trajectory of the end motion of SCARA robot 1, select N S The position vector of each sample configuration coordinate point in the reference coordinate system of SCARA robot 1 is denoted as r p,j (j=1,2,…,N S ), the equivalent load inertia of the i-th driving joint of SCARA robot 1 at each sample point can be calculated by the dynamic model and is denoted as N R Indicates the number of drive joints of SCARA robot 1.

[0039] Step S2: Offline calculation of sample configuration distance function

[0040] Using the position vector r obtained in step S1 p,j , calculate the kth sample position vector rp,k Relative to the jth sample position vector r p,j The distance function of :

[0041]

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

[0043] Step S3: Offline calculation of inertia change weight vector

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

[0045]

[0046] In the formula

[0047]

[0048] The calculated inertia change weight vector W i Stored in the SCARA robot 1 control system data register for use during online calculations.

[0049] Step S4: Online calculation of the current configuration distance function

[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 jth sample position vector r p,j Function:

[0051]

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

[0053] Step S5: Online calculation of the equivalent load inertia corresponding to the current position vector

[0054] 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 driven joint corresponding to the current position vector can be calculated using the following formula:

[0055]

[0056] Step S6: Online calculation of friction disturbance compensation value

[0057] Using the equivalent load inertia corresponding to the current position vector of the 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 denote the maximum static friction factor and Coulomb friction factor respectively, represents the critical speed, which can be obtained through friction identification experiments. and

[0062] They represent the command angular acceleration and angular velocity of the i-th driving 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 to the servo driver 3 as a control instruction to achieve friction compensation.

[0065] The advantages of the present invention are that the influence of the change of the load inertia of the driving joint on the friction disturbance can be estimated in real time without online calculation of a complex machine dynamics model. The algorithm is simple and easy to implement, and the control accuracy of each joint during high-speed operation can be further improved.

[0066] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A robot friction disturbance adaptive compensation method considering inertia change, characterized in that: include: On the basis of the position PID feedback control strategy, a friction disturbance adaptive compensator is applied that takes into account the change characteristics of the equivalent load inertia of the driving joint to suppress the error caused by the friction disturbance caused by the change of the robot's configuration or end load; Step S1: Select sample configuration coordinate points offline; Step S2: Offline calculation of sample configuration distance function; Step S3: Offline calculation of inertia change weight vector; Step S4: online calculation of the current configuration distance function; Step S5: online calculation of the equivalent load inertia corresponding to the current position vector; Step S6: online calculation of friction disturbance compensation value; Step S7: Implement compensation.

2. The robot friction disturbance adaptive compensation method considering inertia change according to claim 1 is characterized in that: The step S1 comprises: On the trajectory of the robot's end motion, select N S The position vector of each sample configuration coordinate point in the robot reference coordinate system is denoted by r p,j (j=1,2,…,N S ), the equivalent load inertia of the robot’s i-th driving joint at each sample point is calculated by the dynamic model and recorded as N R Indicates the number of driven joints of the robot.

3. The robot friction disturbance adaptive compensation method considering inertia change according to claim 2 is characterized in that: The step S2 comprises: Using the position vector r obtained in step S1 p,j , calculate the kth sample position vector r p,k Relative to the jth sample position vector r p,j The distance function of : Where ζ represents the function width.

4. The robot friction disturbance adaptive compensation method considering inertia change according to claim 3 is characterized in that: The step S2 comprises: Step S201: ζ is set according to the actual debugging effect, and the initial value is two.

5. The robot friction disturbance adaptive compensation method considering inertia change according to claim 4 is characterized in that: The step S3 comprises: Use the equivalent load inertia from step S1 The distance function of the sample configuration obtained in step S2 Calculate the inertia change weight vector W of the i-th driven joint i : In the formula The calculated inertia change weight vector W i It is stored in the robot control system data register and called during online operation.

6. The robot friction disturbance adaptive compensation method considering inertia change according to claim 5 is characterized in that: The step S4 comprises: Using the position vector r obtained in step S1 p,j , calculate the robot's current position vector r P Relative to the jth sample position vector r p,j Function: Use the above function to construct a function vector 7. The robot friction disturbance adaptive compensation method considering inertia change according to claim 6 is characterized in that: The step S5 comprises: 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 driven joint corresponding to the current position vector is calculated using the following formula:

8. The robot friction disturbance adaptive compensation method considering inertia change according to claim 7 is characterized in that: The step S6 comprises: Using the equivalent load inertia corresponding to the current position vector of the robot obtained in step S5, the friction disturbance compensation value is calculated using the following formula: In the formula Here, μ s and μ c denote the maximum static friction factor and Coulomb friction factor respectively, represents the critical speed, both obtained through friction identification experiments; and They represent the command angular acceleration and angular velocity of the i-th driving joint motor respectively.

9. The robot friction disturbance adaptive compensation method considering inertia change according to claim 8, characterized in that: The step S7 comprises: The friction disturbance compensation value obtained in step S6 is added to the output value of the PID feedback controller and sent to the servo driver as a control instruction to achieve friction compensation.

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