A variable gain vibration suppression control method for high-speed SCARA robots

Abstract

The present invention discloses a variable-gain vibration suppression control method for a high-speed SCARA robot. The method involves testing the robot's task trajectory, collecting the angular acceleration of the drive joint motor, the Z-axis coordinate, and the vibration amplitude of the acceleration sensor, and taking the maximum or minimum absolute value of these data. The robot then officially executes the task trajectory, collecting these data in real time, and adjusting the controller's proportional gain, differential gain, and vibration suppression setting coefficient based on the trajectory's execution direction and vibration amplitude. The method repeats these steps until the residual vibration amplitude at the end effector falls within a minimum threshold. This method automatically adjusts the controller's proportional and differential gains by simply measuring the angular acceleration of the drive joint servo motor, the Z-axis coordinate, and the vibration amplitude of the acceleration sensor mounted on the end effector, thereby improving vibration suppression effectiveness and automating gain adjustment.

Description

Technical Field

[0001] The present invention relates to the field of robotics and automation, and in particular to a variable gain vibration suppression control method for a high-speed SCARA robot. Background Art

[0002] SCARA is the abbreviation of Selective Compliance Assembly Robot Arm, which means a robot arm used for assembly operations. It has three rotary joints and is most suitable for plane positioning. The joint control systems of high-speed SCARA robots generally adopt a fixed-gain PID control structure to ensure the stability and rapid response capabilities of the system. Among them, variable-gain PID (proportional-integral-differential) control means that in the PID control system, the gain values ​​(or coefficients) of the three control parameters of proportional (P), integral (I) and differential (D) are not fixed, but are dynamically adjusted according to the real-time operating status of the system or preset conditions. Compared with fixed-gain PID control, this control strategy has higher flexibility and adaptability, and can better cope with uncertainties such as changes in system parameters and external interference.

[0003] In practical applications, when a robot executes a high-speed, high-acceleration / deceleration pick-and-release motion trajectory, the nonlinear kinematics of the system cause the motors in each driving joint to perform high-acceleration / deceleration motion throughout the entire process. This in turn generates residual vibration at the robot's end-point, which in turn reduces end-point positioning accuracy. Furthermore, residual vibration at the end-point occurs at the end of the pick-and-release trajectory, and real-time feedback control based on vibration sensor signals cannot address this residual vibration problem after the robot stops moving. Therefore, in the field of high-speed SCARA robots, better vibration suppression control methods are needed. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a variable gain vibration suppression control method for a high-speed SCARA robot.

[0005] To solve the above problems, the present invention provides a variable gain vibration suppression control method for a high-speed SCARA robot. To achieve the above objectives, the technical solution adopted by the present invention to solve the technical problems is:

[0006] A variable gain vibration suppression control method for a high-speed SCARA robot comprises: step S1: trajectory trial operation; step S2: data analysis; utilizing the data collected in step S1; step S3: trajectory formal operation and determination of variable values; step S4: controller gain adjustment during the trajectory formal operation; step S5: vibration suppression setting coefficient adjustment; based on a PID feedback control strategy, the controller proportional gain and differential gain are automatically adjusted using the angular acceleration of a driving joint servo motor, the Z-axis coordinate, and the vibration amplitude of an acceleration sensor installed on an end effector.

[0007] As a further improvement of the present invention, step S1 includes: the robot executes the task trajectory, the number of executions is recorded as i, and the sampling period is set as T s The default Z-axis direction of the robot reference coordinate system is vertically upward. The actual rotation angle, angular velocity, and angular acceleration of the robot driving joint motor 2 encoder at the jth sampling moment are collected as θ(jT s ), (j=1,2,…,n), n is the total number of sampling cycles; the robot position forward solution algorithm is called to calculate the Z-axis coordinate of the end point at the jth sampling moment as z(jT s )(j=1,2,…,n); The acceleration voltage amplitude along the X, Y and Z axes at the kth sampling moment after the robot 1 stops moving is V X (kT s ), V Y (kT s ), V Z (kT s )(k=1,2,…,m).

[0008] As a further improvement of the present invention, step S2 includes: taking The maximum absolute value of Take z(jT s The maximum absolute value of )(j=1,2,…,n) is recorded as z max ; Take z(jT s The minimum absolute value of )(j=1,2,…,n) is denoted as z min ; Take V X (kT s The maximum absolute value of )(k=1,2,…,m) is recorded as V Xmax ; Take V Y (kT s The maximum absolute value of )(k=1,2,…,m) is recorded as V Ymax ; Take V Z (kT s The maximum absolute value of )(k=1,2,…,m) is recorded as V Zmax ; Using the above data, we can calculate

[0009] As a further improvement of the present invention, step S3 includes: when the trajectory is officially running, the actual angular acceleration of the robot driving joint motor encoder at the jth (j=1, 2, ..., n) sampling moment is collected in real time. The Z-axis coordinate of the end point is z w (jT s); Let λ represent the variable for determining the direction of motion of the robot's terminal trajectory, and its value is as follows:

[0010]

[0011] Let ξ represent the robot end amplitude judgment variable, and its value is shown in the following formula:

[0012]

[0013] Where [V] represents the minimum amplitude threshold, which is set according to work requirements.

[0014] As a further improvement of the present invention, step S4 includes: step S401: when λ=-1, it means that the trajectory is in an ascending or horizontal motion direction, and at the jth moment, the proportional gain K in the PID controller in the robot driving joint control system is P (jT s ) and differential gain K D (jT s ) is adjusted using the following formula:

[0015]

[0016]

[0017] Where K P0 With K D0 They represent the initial values ​​of the proportional gain and differential gain set by the robot at the factory; α i and β i They represent the proportional gain and differential gain vibration suppression tuning coefficients after the i-th trial run, and their initial values ​​are determined based on experience.

[0018] As a further improvement of the present invention, step S4 includes: step S402: when λ=1, it means that the trajectory is in the descending direction, and at the jth moment, the proportional gain K in the PID controller in the robot driving joint control system is P (jT s ) and differential gain K D (jT s ) is adjusted using the following formula:

[0019]

[0020]

[0021] As a further improvement of the present invention, step S5 includes: when ξ=1, it means that the residual vibration amplitude is within the minimum threshold range, α i and β iunchanged; when ξ=-1, it means that the residual vibration amplitude is outside the minimum threshold range, and the vibration suppression tuning coefficient for the (i+1)th trial run is updated using the following formula:

[0022]

[0023] Where η represents the training speed coefficient, which can be adjusted according to the actual debugging situation.

[0024] As a further improvement of the present invention, step S6 is included; step S6: after the update of step S5 is completed, steps S1 to S5 are re-executed until ξ=1 is satisfied.

[0025] The beneficial effect of the variable-gain vibration suppression control method for a high-speed SCARA robot using this application is that it uses residual vibration signals to adjust the PID gain, thereby reducing residual vibration after the robot stops moving and improving motion control accuracy. By simply measuring the angular acceleration of the driving joint servo motor, the Z-axis coordinate, and the vibration amplitude of the accelerometer mounted on the end effector, the controller's proportional and differential gains can be automatically adjusted, which helps improve vibration suppression and the automation of gain adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0027] Figure 1 This is a block diagram of a variable gain vibration suppression control structure according to an embodiment of the present invention;

[0028] Figure 2 This is a flow chart of a variable gain vibration suppression control method according to an embodiment of the present invention.

[0029] 1-SCARA robot; 2-motor; 3-servo drive; 4-PID controller. DETAILED DESCRIPTION

[0030] The present invention will be described in further detail below with reference to specific embodiments:

[0031] To achieve the objectives of the present invention, a variable-gain vibration suppression control method for a high-speed SCARA robot is proposed. The core of the method is to iteratively update the controller proportional gain and differential gain using the angular acceleration of the drive joint motor, the Z-axis coordinate, and the vibration amplitude of the accelerometer installed on the end effector, collected during the i-th trial run trajectory, to ensure that the residual vibration amplitude of the end effector falls within a minimum threshold range. The method includes the following steps:

[0032] Since the control systems of each driving joint of the robot all adopt PID controller 4 and the variable gain vibration suppression control method is the same, the following takes one of the driving joints as an example to illustrate its execution process. Figure 2 shown.

[0033] Step S1: Trajectory test run

[0034] Let SCARA robot 1 execute the task trajectory, the number of executions is recorded as i, and the sampling period is set to T s , the default Z-axis direction of the reference coordinate system of SCARA robot 1 is vertically upward, and the actual rotation angle, angular velocity, and angular acceleration of the encoder of SCARA robot 1 driving joint motor 2 at the jth sampling moment are collected respectively as θ(jT s ), (j=1,2,…,n), n is the total number of sampling cycles. Call the SCARA robot 1 position forward solution algorithm to calculate the Z-axis coordinate of the end point at the jth sampling moment as z(jT s )(j=1,2,…,n). The acceleration voltage amplitude along the X, Y and Z axes at the kth sampling moment after the SCARA robot 1 stops moving is collected using the three-dimensional acceleration sensor installed on the end effector. X (kT s ), V Y (kT s ), V Z (kT s )(k=1,2,…,m).

[0035] Step S2: Data analysis

[0036] Using the data collected in step S1:

[0037] Pick The maximum absolute value of (j=1,2,…,n) is recorded as

[0038] Take z(jT s The maximum absolute value of )(j=1,2,…,n) is recorded as z max ;

[0039] Take z(jT s The minimum absolute value of )(j=1,2,…,n) is denoted as zmin ;

[0040] Take V X (kT s The maximum absolute value of )(k=1,2,…,m) is recorded as V Xmax ;

[0041] Take V Y (kT s The maximum absolute value of )(k=1,2,…,m) is recorded as V Ymax ;

[0042] Take V Z (kT s The maximum absolute value of )(k=1,2,…,m) is recorded as V Zmax ;

[0043] Using the above data, we can calculate

[0044] Step S3: The trajectory is formally run and the variable value is judged

[0045] When the trajectory is officially running, the actual angular acceleration of the encoder of the SCARA robot 1 driving the joint motor 2 at the jth sampling moment (j = 1, 2, ..., n) is collected in real time: The Z-axis coordinate of the end point is z w (jT s ).

[0046] Let λ represent the variable for determining the direction of motion of the end trajectory of SCARA robot 1, and its value is as follows:

[0047]

[0048] Let ξ represent the amplitude judgment variable of the end of SCARA robot 1, and its value is as follows:

[0049]

[0050] Where [V] represents the minimum amplitude threshold, which is set according to work requirements.

[0051] Step S4: Controller gain adjustment during trajectory formal operation

[0052] Step S401: When λ=-1, it indicates that the trajectory is in the ascending or horizontal motion direction. At the jth moment, the proportional gain K in the PID controller 4 in the SCARA robot 1 driving joint control system is P (jT s ) and differential gain K D (jT s ) is adjusted using the following formula:

[0053]

[0054]

[0055] Where K P0 With K D0 They represent the initial values ​​of the proportional gain and differential gain set by the robot at the factory. i and β i The motor 2 and the PID controller 4 are connected via a servo driver 3.

[0056] Step S402: When λ=1, it indicates that the trajectory is in the descending direction. At the jth moment, the proportional gain K in the PID controller 4 in the robot driving joint control system is P (jT s ) and differential gain K D (jT s ) is adjusted using the following formula:

[0057]

[0058]

[0059] Step S5: Adjust the vibration suppression coefficient

[0060] When ξ=1, it means that the residual vibration amplitude is within the minimum threshold range, α i and β i constant.

[0061] When ξ=-1, it means that the residual vibration amplitude is outside the minimum threshold range. The following formula is used to update the vibration suppression tuning coefficient during the (i+1)th trial run:

[0062]

[0063] Where η represents the training speed coefficient, which can be adjusted according to the actual debugging situation. After the update is completed, steps S1 to S5 are re-executed until ξ = 1 is satisfied.

[0064] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A variable gain vibration suppression control method for a high-speed SCARA robot, characterized in that: include: Step S1: trajectory trial run; Step S2: data analysis; Using the data collected in step S1; Step S3: The trajectory is formally run and the variable values ​​are judged; Step S4: controller gain adjustment during the trajectory formal operation; Step S5: adjusting the vibration suppression setting coefficient; The step S2 comprises: Pick 、 、 、 、 The maximum absolute value of 、 、 、 、 ,Pick The minimum absolute value of , For the The actual angular acceleration of the robot driving joint motor encoder at the sampling moment, For the The Z-axis coordinate of the end point at each sampling moment, , is the total number of sampling periods, 、 、 The first time after the robot stops moving The acceleration voltage amplitude along the X, Y, and Z axes at each sampling moment, ; The step S3 comprises: When the track is officially running, real-time collection of The actual angular acceleration of the robot driving joint motor encoder at the sampling moment is: , the Z-axis coordinate of the end point is ; make It represents the variable for judging the direction of the robot's end trajectory, and its value is shown in the following formula: ； make It represents the robot end amplitude judgment variable, and its value is shown in the following formula: ； Where, Indicates the minimum amplitude threshold, which is set according to work requirements. ； The step S4 comprises: Step S401: When When , it means the trajectory is in the ascending or horizontal direction. The proportional gain of the PID controller in the robot drive joint control system at the same time With differential gain Use the following formula to make adjustments: ； ； Where, and They represent the initial values ​​of the proportional gain and differential gain set by the robot at the factory; and Respectively represent The proportional gain and differential gain vibration suppression tuning coefficients after the first trial run are determined based on experience. Step S402: When When , it indicates that the trajectory is in the descending direction. The proportional gain of the PID controller in the robot drive joint control system at the same time With differential gain Use the following formula to make adjustments: ； ； The step S5 comprises: when When , it means that the residual vibration amplitude is within the minimum threshold range, and constant; when When , it means that the residual vibration amplitude is outside the minimum threshold range, and the following formula is used to update the Vibration suppression setting coefficient during the first trial run: ， ； Where, Indicates the training speed coefficient, which can be adjusted according to the actual debugging situation; Also includes step S6; Step S6: After the update in step S5 is completed, re-execute steps S1 to S5 until the until.

2. The variable gain vibration suppression control method for a high-speed SCARA robot according to claim 1, characterized in that: The step S1 comprises: The robot executes the task trajectory, and the number of executions is recorded as , set the sampling period to , the default Z-axis direction of the robot reference coordinate system is vertically upward, collect the At the sampling moment, the actual rotation angle, angular velocity, and angular acceleration of the robot driving joint motor encoder are 、 、 ; Call the robot position forward solution algorithm to calculate the The Z-axis coordinate of the end point at each sampling moment is ; Use the three-dimensional acceleration sensor installed on the end effector to collect the first The acceleration voltage amplitude along the X, Y, and Z axes at each sampling moment is 、 、 .

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