Robot and servo jitter suppression method thereof

Abstract

The invention provides a robot and a servo jitter suppression method thereof. The method comprises the following steps: obtaining an initial given speed according to a motor position instruction, motor position feedback information and a position loop gain; subtracting the reference speed from the initial given speed to obtain a first speed difference value; inputting the first speed difference value into a PI controller to enable the PI controller to output a current instruction before compensation; and the compensated current instruction is input into a current controller of the robot, so that the current controller outputs driving current to a motor in the robot based on the compensated current instruction, robot motion control is completed under driving of a transmission structure between the motor and a load, and jitter is restrained. Advanced compensation is introduced into a position loop, the phase margin of a low-modal system is improved in a targeted mode, the stability and jitter suppression effect of the control method for connecting a PI controller and an internal model controller in parallel on a low-modal frequency controlled system are improved, the jitter problem of the low-modal system is solved, and the stability and control precision of a robot system are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more specifically, to a robot and a method for suppressing servo jitter therebetween. Background Technology

[0002] Jitter suppression is a core requirement for ensuring operational accuracy in industrial robots, especially low-modal frequency systems (such as lightweight collaborative robots and long-arm, heavy-duty robots). Due to the flexibility of their joints, these systems are prone to instability and jitter caused by phase lag. While most industrial robots are designed to be very robust, exhibiting minimal vibration during low- to medium-speed operation, high-speed, high-acceleration motion places significant inertial forces on the transmission system between the robot's motors and links. In such cases, the flexibility of the transmission system leads to relatively large elastic deformation. When the robot stops, the recovery of this elastic deformation results in noticeable jitter on the link side. Commonly used three-loop control methods for robot servo motors can only achieve precise control of motor position, speed, and current, and cannot effectively control this link-side jitter. Summary of the Invention

[0003] The purpose of this invention is to provide a robot and a method for suppressing servo jitter therein, so as to improve the above-mentioned problems.

[0004] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows: In a first aspect, embodiments of the present invention provide a robot servo jitter suppression method, applied to a robot, the method comprising: Based on the motor position command, motor position feedback information, and position loop gain, advance phase compensation and gain conversion are performed to obtain the initial given speed; Subtract the reference speed corresponding to the actual speed of the load from the initial given speed to obtain the first speed difference; The first speed difference is input into the PI controller so that it outputs a current command before compensation. The compensated current command is input into the robot's current controller, so that the current controller outputs drive current to the motor in the robot based on the compensated current command. Under the drive of the transmission structure between the motor and the load, the robot's motion control is completed and jitter is suppressed. The compensated current command is obtained by subtracting the compensated current command output by the internal model controller from the pre-compensation current command.

[0005] Optionally, the step of performing advance phase compensation and gain conversion based on the motor position command, motor position feedback information, and position loop gain to obtain the initial given speed includes: The initial position difference is input into the advance compensator to obtain the position difference after its output phase is advanced. The initial position difference is the motor target position in the motor position command minus the actual motor position in the motor position feedback information. The position difference after phase advance is multiplied by the position loop gain to obtain the initial given velocity.

[0006] Optionally, the transfer function of the lead compensator is:

[0007] in, This represents the transfer function of the lead compensator. Represents the time constant. To represent the complex variable in the Laplace transform, Describes the leading factor and satisfies . Optionally, the method further includes: Based on the original cutoff frequency Determine the phase margin Among them, the original cutoff frequency The cutoff frequency is determined based on the amplitude-frequency characteristics of the open-loop transfer function of the original robot control system without a lead compensator. The maximum phase lead angle is determined based on the phase margin, the expected increase in phase margin, and the safety margin of the phase margin. The lead factor is determined based on the maximum phase lead angle; The time constant is determined based on the lead factor.

[0008] Optionally, the maximum phase lead angle The formula is:

[0009] in, Indicates the maximum phase lead angle. Indicates phase margin, This represents the expected increase in phase margin. , This represents the safety margin for phase margin.

[0010] Optionally, leading factor The formula is:

[0011] in, This indicates the maximum phase lead angle.

[0012] Optionally, the step based on the lead factor Determine the time constant ,include: The reference frequency is determined based on the gain crossover frequency of the robot's original control system. Among them, reference frequency The deviation from the gain crossover frequency is less than a preset frequency threshold; According to the reference frequency With leading factors Determine the time constant .

[0013] Optionally, before subtracting the reference speed corresponding to the actual speed of the load from the initial given speed to obtain the first speed difference, the method further includes: The reference speed is obtained by multiplying the actual load speed in the load speed feedback information by a preset reduction ratio, wherein the reduction ratio is the ratio between the motor speed and the load speed.

[0014] Optionally, before inputting the compensated current command into the robot's current controller, the method further includes: Add the speed adjustment range in the load speed command to the actual load speed in the load speed feedback information, and then subtract the reverse analysis speed output by the reverse controller corresponding to the internal model controller to obtain the second speed difference. The second speed difference is input into the internal model controller to obtain the compensation current command output by the internal model controller.

[0015] Secondly, embodiments of the present invention provide a robot, the robot comprising: a lead compensator, a PI controller, an internal model controller, a current controller, and an inverse controller corresponding to the internal model controller; The robot is used to perform the robot servo jitter suppression method described above.

[0016] Compared to existing technologies, the robot and its servo jitter suppression method provided in this invention perform advance phase compensation and gain conversion based on motor position commands, motor position feedback information, and position loop gain to obtain an initial given speed. The initial given speed is subtracted from a reference speed corresponding to the actual load speed to obtain a first speed difference. This first speed difference is input to a PI controller to output a pre-compensation current command. The post-compensation current command is input to the robot's current controller, causing the current controller to output drive current to the motors in the robot based on the post-compensation current command. Driven by the transmission structure between the motors and the load, the robot's motion control is completed, and jitter is suppressed. By introducing advance compensation in the position loop, the phase margin of the low-modal system is specifically improved, enhancing the stability and jitter suppression effect of the parallel PI controller and internal mode controller control method for low-modal frequency controlled systems. This solves the jitter problem of low-modal systems and ensures the stability and control accuracy of the robot system.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is one of the flowcharts illustrating the robot servo jitter suppression method provided in this embodiment of the invention.

[0020] Figure 2 This is the second flowchart illustrating the robot servo jitter suppression method provided in this embodiment of the invention.

[0021] Figure 3 This is the third flowchart illustrating the robot servo jitter suppression method provided in this embodiment of the invention.

[0022] Figure 4 A schematic diagram of the architecture of the robot control system provided in this embodiment of the invention.

[0023] Figure 5 The link position of System 1 without a lead compensator provided in the embodiment of the present invention Response diagram.

[0024] Figure 6 The link position in System 2 provided in this embodiment of the invention without the addition of a lead compensator Response diagram.

[0025] Figure 7 The linkage position of the advance compensator added to system 2 provided in the embodiment of the present invention Response diagram.

[0026] Figure 8 The system 2 provided in this embodiment of the invention has a linkage position with or without a lead compensator. Response comparison chart. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0033] In this embodiment of the invention, the controlled system is a robot joint system, including a motor, a flexible transmission mechanism, and a load, wherein the load can be a link arm. The control objective is to ensure that the position and velocity of the motor are matched with the position and velocity of the link arm through a reduction ratio during motion. Therefore, the flexibility of the flexible transmission mechanism connecting the motor and the link arm often makes this control objective difficult to achieve, and this difficulty is even greater for joint systems with low modal frequencies. Here, the flexible part of the robot joint is simplified to a two-mass system for indirect substitution, and the relationship between the motor position and the link position can be derived as follows:

[0034] In the formula, R is the reduction ratio, and K is the stiffness of the flexible joint, in units of... B represents the flexible joint damping, in units of... . Let be the link inertia, and s be a complex variable under Laplace transform. Assume the control objective can be achieved, i.e., satisfy the following conditions during motion. However, actual robot joints are flexible, especially on the link side. The response is not ideal, exhibiting fluctuations and lag. To address this, a speed loop PI controller and an internal mold controller can typically be connected in parallel to adjust the position of the connecting rod. The response is close to ideal, but for systems with low modal frequencies (below 5Hz), the position of the link side... The response lag is greater, therefore a new lead compensator has been introduced into the motor position loop to improve the motor-side position. Phase advance, followed by joint flexibility, improves the link-side position of the low-modal system. The control effect.

[0035] This invention provides a robot servo jitter suppression method, which is applied to robots. Due to the inherent characteristics of low-modal industrial robot systems, their phase lag is significant. The targeted phase compensation mechanism effectively improves the phase margin of the system at low modal frequencies, thereby improving stability and jitter suppression effect, and ensuring the positioning accuracy and operational reliability of the robot.

[0036] Please refer to Figure 1 , Figure 1 This is one of the flowcharts illustrating a robot servo jitter suppression method provided in an embodiment of the present invention. The robot servo jitter suppression method includes steps S11, S13, S14, and S15, which are described in detail below.

[0037] S11, based on the motor position command, motor position feedback information and position loop gain, performs advance phase compensation and gain conversion to obtain the initial given speed.

[0038] By performing advance phase compensation to advance the phase of the motor position, the response of the position loop is accelerated, the overshoot of the position loop is reduced, and thus the stability of the system is increased.

[0039] S13, subtract the reference speed corresponding to the actual speed of the load from the initial given speed to obtain the first speed difference.

[0040] S14, input the first speed difference value into the PI controller so that it outputs the current command before compensation.

[0041] Because the advanced phase compensation has been completed, the current command output by the PI controller enables the speed of the linkage side of the controlled system to respond in a timely manner and match the speed of the motor side through the reduction ratio, thereby suppressing the jitter amplitude.

[0042] S15, input the compensated current command into the robot's current controller, so that the current controller outputs drive current to the motor in the robot based on the compensated current command. Driven by the transmission structure between the motor and the load, the robot motion control is completed and jitter is suppressed.

[0043] The compensated current command is obtained by subtracting the compensated current command output by the internal model controller from the pre-compensation current command. Ultimately, the current controller controls the robot's movement. Throughout the process, the PI controller tracks and controls the velocity of the links, while the internal model controller suppresses link-side jitter.

[0044] In the robot servo jitter suppression method provided in this embodiment of the invention, advance compensation is introduced into the position loop to specifically improve the phase margin of the low-modal system, thereby enhancing the stability and jitter suppression effect of the control method of the parallel PI controller and internal mode controller for the low-modal frequency controlled system, solving the jitter problem of the low-modal system, and ensuring the stability and control accuracy of the robot system.

[0045] Based on the preceding text, regarding the content of S11, this embodiment of the invention also provides an optional implementation method, please refer to the following. S11, based on the motor position command, motor position feedback information, and position loop gain, performs advance phase compensation and gain conversion to obtain the initial given speed, including: S111 and S112, as detailed below.

[0046] S111, input the initial position difference value into the advance compensator to obtain the position difference value after its output phase advances. The initial position difference value is the motor target position in the motor position command minus the actual motor position in the motor position feedback information.

[0047] S112, multiply the position difference after phase advance by the position loop gain to obtain the initial given speed.

[0048] The transfer function of the lead compensator is:

[0049] in, This represents the transfer function of the lead compensator. Represents the time constant. To represent the complex variable in the Laplace transform, Describes the leading factor and satisfies . Building upon the preceding text, this invention also provides an optional implementation method regarding the meaning of each symbol in the transfer function of the lead compensator, as detailed below. The robot servo jitter suppression method further includes steps S31 to S34, which are described in detail below.

[0050] S31, based on the original cutoff frequency Determine the phase margin .

[0051] Among them, the original cutoff frequency The cutoff frequency is determined based on the amplitude-frequency characteristics of the open-loop transfer function of the original robot control system without a lead compensator.

[0052] S32, determine the maximum phase lead angle based on the phase margin, the expected increase in phase margin, and the safety margin of the phase margin.

[0053] Optionally, maximum phase lead angle The formula is:

[0054] in, Indicates the maximum phase lead angle. Indicates phase margin, This represents the expected increase in phase margin. , This represents the safety margin for phase margin.

[0055] S33, determine the lead factor based on the maximum phase lead angle.

[0056] Optionally, leading factor The formula is:

[0057] in, This indicates the maximum phase lead angle.

[0058] S34, determine the time constant based on the lead factor.

[0059] S34, based on the leading factor Determine the time constant This includes S341 and S342, which are described in detail below.

[0060] S341, Determine the reference frequency based on the gain crossover frequency of the robot's original control system. Among them, reference frequency The deviation from the gain crossover frequency is less than the preset frequency threshold.

[0061] S342, according to the reference frequency With leading factors Determine the time constant .

[0062] Optionally, time constant The formula is:

[0063] in, Indicates the reference frequency. This represents the leading factor.

[0064] Please refer to Figure 2 Before subtracting the reference speed corresponding to the actual speed of the load from the initial given speed in S13 to obtain the first speed difference, the robot servo jitter suppression method also includes S12, which is described in detail below.

[0065] S12, multiply the actual load speed in the load speed feedback information by the preset deceleration ratio to obtain the reference speed.

[0066] The reduction ratio is the ratio between the motor speed and the load speed (connecting rod speed).

[0067] Please refer to Figure 3 Before inputting the compensated current command into the robot's current controller in S15, the robot servo jitter suppression method also includes S21 and S22, as follows.

[0068] S21, add the speed adjustment range in the load speed command to the actual load speed in the load speed feedback information, and then subtract the reverse analysis speed output by the reverse controller corresponding to the internal model controller to obtain the second speed difference.

[0069] The inverse controller performs inverse analysis based on the compensated current command from the previous cycle to obtain the inverse analysis speed.

[0070] S22, input the second speed difference to the internal model controller to obtain the compensation current command output by the internal model controller.

[0071] Please refer to Figure 4 , Figure 4This is a schematic diagram of the robot control system architecture provided in an embodiment of the present invention. In the diagram, KP represents the position loop gain, and R represents the reduction ratio. The current controller outputs drive current to the robot joint controlled system (motor). Under the drive of the transmission structure between the motor and the load, the robot motion control is completed, the load position is changed, and jitter is suppressed. It should be noted that the original robot control system without a lead compensator and... Figure 4 The only difference is that it does not have a lead compensator; all other structures are the same.

[0072] To better illustrate the technical effects of the robot servo jitter suppression method, this invention also provides a set of comparative experiments, which are performed using joint systems with two different modal frequencies. Please refer to the following text.

[0073] Here, we introduce two different 1-axis parameters for industrial robots to maximize the stimulation of the robot's link side position. The vibration, here the motor position The input uses a unit step signal to verify the effectiveness of the above method. Detailed parameters of the two joint systems are shown in Table 1 below. Given the motor's rotational inertia, the data shows that the modal frequency of system 1 is significantly higher than that of system 2. Under the same PI controller and internal model control parameters, the two systems are compared using simulation software. and Control effectiveness, especially tracking response and jitter suppression.

[0074] Table 1

[0075] For detailed simulation results, please refer to... Figure 5 , Figure 6 , Figure 7 as well as Figure 8 ,in, Figure 5 The link position of System 1 without a lead compensator provided in the embodiment of the present invention Response diagram, Figure 6 The link position in System 2 provided in this embodiment of the invention without the addition of a lead compensator Response diagram, Figure 7 The linkage position of the advance compensator added to system 2 provided in the embodiment of the present invention Response diagram, Figure 8 The system 2 provided in this embodiment of the invention has a linkage position with or without a lead compensator. Response comparison chart.

[0076] contrast Figure 5 and Figure 6 The control effect of system 1, which has a higher modal frequency, is more ideal, and the linkage position... The tracking response is timely, with almost no jitter period, fast convergence time, and good suppression effect. System 2, with higher modal frequencies, exhibits less than ideal control performance, particularly regarding link position... The jittering cycle is long, and the convergence time is also long. And... Figure 7 The control results after adding a lead compensator to low-modal system 2 Figure 8 The comparison diagram for low-modal system 2 with and without a lead compensator shows that, even for systems with low modal frequencies, Figure 7 Middle link position The jitter period is higher than Figure 6 With fewer components and a shorter convergence time, the performance of the lead compensator in controlling low-modal systems has been verified, and the linkage position has been improved. The convergence speed effectively suppresses jitter cycles. Figure 8 The thin solid line represents the link position response of System 2 without a lead compensator, while the thick solid line represents the link position response of System 2 with a lead compensator.

[0077] This invention also provides a robot, which includes: a lead compensator, a PI controller, an internal model controller, a current controller, and a reverse controller corresponding to the internal model controller.

[0078] The robot is used to perform the robot servo jitter suppression method described above.

[0079] In summary, the robot and its servo jitter suppression method provided by this invention perform advance phase compensation and gain conversion based on motor position commands, motor position feedback information, and position loop gain to obtain an initial given speed. The initial given speed is subtracted from a reference speed corresponding to the actual load speed to obtain a first speed difference. This first speed difference is input to a PI controller to output a pre-compensation current command. The post-compensation current command is input to the robot's current controller, causing the current controller to output drive current to the motors in the robot based on the post-compensation current command. Driven by the transmission structure between the motors and the load, the robot's motion control is completed, and jitter is suppressed. By introducing advance compensation in the position loop, the phase margin of the low-modal system is specifically improved, enhancing the stability and jitter suppression effect of the parallel PI controller and internal mode controller control method for low-modal frequency controlled systems. This solves the jitter problem of low-modal systems and ensures the stability and control accuracy of the robot system.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0081] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for suppressing robot servo jitter, characterized in that, Applied to robots, the method includes: Based on the motor position command, motor position feedback information, and position loop gain, advance phase compensation and gain conversion are performed to obtain the initial given speed; Subtract the reference speed corresponding to the actual speed of the load from the initial given speed to obtain the first speed difference; The first speed difference is input into the PI controller so that it outputs a current command before compensation. The compensated current command is input into the robot's current controller, so that the current controller outputs drive current to the motor in the robot based on the compensated current command. Under the drive of the transmission structure between the motor and the load, the robot's motion control is completed and jitter is suppressed. The compensated current command is obtained by subtracting the compensated current command output by the internal model controller from the pre-compensation current command.

2. The robot servo jitter suppression method as described in claim 1, characterized in that, The step of performing advance phase compensation and gain conversion based on motor position commands, motor position feedback information, and position loop gain to obtain the initial given speed includes: The initial position difference is input into the advance compensator to obtain the position difference after its output phase is advanced. The initial position difference is the motor target position in the motor position command minus the actual motor position in the motor position feedback information. The position difference after phase advance is multiplied by the position loop gain to obtain the initial given velocity.

3. The robot servo jitter suppression method as described in claim 2, characterized in that, The transfer function of the lead compensator is: in, This represents the transfer function of the lead compensator. Represents the time constant. To represent the complex variable in the Laplace transform, Denotes the leading factor, and satisfies .

4. The robot servo jitter suppression method as described in claim 3, characterized in that, The method further includes: Based on the original cutoff frequency Determine the phase margin Among them, the original cutoff frequency The cutoff frequency is determined based on the amplitude-frequency characteristics of the open-loop transfer function of the original robot control system without a lead compensator. The maximum phase lead angle is determined based on the phase margin, the expected increase in phase margin, and the safety margin of the phase margin. The lead factor is determined based on the maximum phase lead angle; The time constant is determined based on the lead factor.

5. The robot servo jitter suppression method as described in claim 4, characterized in that, The maximum phase lead angle The formula is: in, Indicates the maximum phase lead angle. Indicates phase margin, This represents the expected increase in phase margin. This represents the safety margin for phase margin.

6. The robot servo jitter suppression method as described in claim 4, characterized in that, Advanced factors The formula is: in, This indicates the maximum phase lead angle.

7. The robot servo jitter suppression method as described in claim 4, characterized in that, According to the advance factor Determine the time constant ,include: The reference frequency is determined based on the gain crossover frequency of the robot's original control system. Among them, reference frequency The deviation from the gain crossover frequency is less than a preset frequency threshold; According to the reference frequency With leading factors Determine the time constant .

8. The robot servo jitter suppression method as described in claim 1, characterized in that, Before subtracting the reference speed corresponding to the actual speed of the load from the initial given speed to obtain the first speed difference, the method further includes: The reference speed is obtained by multiplying the actual load speed in the load speed feedback information by a preset reduction ratio, wherein the reduction ratio is the ratio between the motor speed and the load speed.

9. The robot servo jitter suppression method as described in claim 1, characterized in that, Before inputting the compensated current command into the robot's current controller, the method further includes: Add the speed adjustment range in the load speed command to the actual load speed in the load speed feedback information, and then subtract the reverse analysis speed output by the reverse controller corresponding to the internal model controller to obtain the second speed difference. The second speed difference is input into the internal model controller to obtain the compensation current command output by the internal model controller.

10. A robot, characterized in that, The robot includes: a lead compensator, a PI controller, an internal model controller, a current controller, and a reverse controller corresponding to the internal model controller. The robot is used to perform the robot servo jitter suppression method according to any one of claims 1-9.

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