Servo motor nonlinear friction disturbance suppression method and system

Abstract

The invention discloses a nonlinear friction disturbance suppression method and system for a servo motor, relates to the technical field of high-precision servo control systems, and overcomes the defects of an existing friction torque compensation method for the servo motor. Comprising the following steps that S1, after a servo motor is driven to rotate, the angular speed of the servo motor at the current moment and the current value of the servo motor at the current moment are monitored; s2, the improved Luenberger observer calculates a current compensation value of the servo motor at the current moment by using the angular velocity of the servo motor at the current moment, the current value of the servo motor at the current moment and a dynamic model of the system; and S3, superposing the current compensation value of the servo motor at the current moment and the initial current control instruction, and re-inputting the superposed current compensation value and initial current control instruction into the current controller to form closed-loop negative feedback control.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-precision servo control system, and particularly relates to a servo motor nonlinear friction disturbance suppression method and system. BACKGROUND

[0002] As the core actuator of high-precision motion control system, the dynamic performance and control accuracy of servo motor directly determine the overall performance limit of high-end equipment. However, in actual engineering practice, due to factors such as machining tolerance, nonlinear and time-varying characteristics of bearing friction characteristics, deviation of mass center and rotation center, etc., the servo motor system generally has inherent friction torque imbalance. Such disturbance presents strong nonlinear, dynamic time-varying and other complex characteristics, making it difficult to achieve accurate and stable control by traditional linear compensation strategies based on fixed parameter model. On the one hand, the fixed parameter method cannot adapt to the changes of friction with temperature, speed and running posture, resulting in continuous fluctuation of motor control torque, aggravating energy loss and system heating; on the other hand, at low speed and torque reversal stage, friction disturbance easily induces significant speed chattering and position tracking error, seriously restricting the performance of the system in precise alignment, superfinishing and other scenarios.

[0003] Current methods mostly rely on high-precision friction modeling or complex observer design, which are highly sensitive to system parameters. Especially when facing unknown disturbance and model uncertainty coupling, the traditional control architecture lacks online self-tuning and dynamic anti-interference ability. Therefore, there is an urgent need for an adaptive compensation technology that can identify friction changes in real time, without the need for accurate mechanism model, and has strong robustness, to improve the dynamic control quality and stability of the servo system in a wide operating range. SUMMARY

[0004] The present application overcomes the deficiencies of existing servo motor friction torque compensation methods.

[0005] The servo motor nonlinear friction disturbance suppression method of the present application, after the target speed is given, the command is transmitted to the speed controller to generate the initial current control command; the initial current control command enters the current controller to output the corresponding current signal to the servo motor to drive the servo motor to generate accurate torque, and then drive the servo motor to rotate, including the following steps: Step S1, after driving the servo motor to rotate, the angular velocity of the servo motor at the current time and the current value of the servo motor at the current time are monitored respectively; Step S2, the improved Luenberger observer uses the angular velocity of the servo motor at the current time, the current value of the servo motor at the current time and the dynamic model of the system to calculate the current compensation value of the servo motor at the current time; Step S3, the current compensation value of the servo motor at the current time and the initial current control instruction are superimposed and re-input into the current controller to form a closed-loop negative feedback control.

[0006] Further, in one embodiment of the present application, in the step S2, the improved Luenberger observer calculates the current compensation value of the servo motor at the current time by using the angular velocity of the servo motor at the current time, the current value of the servo motor at the current time and the dynamic model of the system, including the following steps: Step S201, the angular velocity of the servo motor at the current time and the current value of the servo motor at the current time are monitored respectively; Step S202, the linear friction coefficient of the servo motor and the moment of inertia of the servo motor are obtained respectively by the dynamic model of the system and based on the angular velocity of the servo motor at the current time and the current value of the servo motor at the current time; Step S203, the estimated angular velocity of the servo motor at the current time and the estimated nonlinear friction torque of the servo motor at the current time are iteratively calculated respectively by the improved Luenberger observer and based on the linear friction coefficient of the servo motor, the moment of inertia of the servo motor, the monitored angular velocity of the servo motor at the current time and the current value of the servo motor at the current time; Step S204, the current compensation value of the servo motor at the current time is calculated based on the estimated nonlinear friction torque of the servo motor at the current time.

[0007] Further, in one embodiment of the present application, in the step S201, the dynamic model of the system is specifically: ; Wherein, is the moment of inertia of the servo motor, is the angular velocity of the servo motor at the current time, is the current value of the servo motor at the current time, is the linear friction coefficient of the servo motor, is the torque coefficient of the servo motor, is the nonlinear friction torque of the servo motor, is the current time.

[0008] Further, in one embodiment of the present application, in the step S203, the improved Luenberger observer is specifically: ; Wherein, is the moment of inertia of the servo motor, is the linear friction coefficient of the servo motor, is the angular velocity of the servo motor at the current time, is the current value of the servo motor at the current time, is the estimated angular velocity of the servo motor at the current time, is the estimated nonlinear friction torque of the servo motor at the current time, is the torque coefficient of the servo motor, and are different parameters of the improved Luenberger observer, respectively.

[0009] Further, in an embodiment of the present application, the influence of the different parameters of the improved Luenberger observer on the estimated nonlinear friction torque of the servo motor at the current time is as follows: ; wherein, and are different parameters of the improved Luenberger observer, is the moment of inertia of the servo motor, is the linear friction coefficient of the servo motor, is the Laplace transform operator, is the estimated nonlinear friction torque of the servo motor at the current time, is the nonlinear friction torque of the servo motor, is the Laplace transform of , and is the Laplace transform of .

[0010] Further, in an embodiment of the present application, in the step S203, the estimated angular velocity of the servo motor at the current time and the estimated nonlinear friction torque of the servo motor at the current time are respectively iteratively calculated, and the calculation is as follows: ; ; wherein, is the estimated angular velocity of the servo motor at the current time, is the current value of the servo motor at the current time, is the estimated angular velocity of the servo motor at the previous time, is the sampling period, is the linear friction coefficient of the servo motor, is the moment of inertia of the servo motor, is the torque coefficient of the servo motor, and are different parameters of the improved Luenberger observer, respectively, is the estimated nonlinear friction torque of the servo motor at the previous time, Estimating the nonlinear friction torque of the servo motor at the current time.

[0011] The servo motor nonlinear friction disturbance suppression system described in the application is realized by any of the above-mentioned servo motor nonlinear friction disturbance suppression methods. Module S1, after driving the servo motor to rotate, the angular velocity of the servo motor at the current time and the current value of the servo motor at the current time are monitored respectively. Module S2, the improved Luenberger observer calculates the current compensation value of the servo motor at the current time by using the angular velocity of the servo motor at the current time, the current value of the servo motor at the current time and the dynamic model of the system. Module S3, the current compensation value of the servo motor at the current time and the initial current control instruction are superimposed and re-input into the current controller to form a closed-loop negative feedback control.

[0012] The application overcomes the shortcomings of the existing servo motor friction torque compensation method. 1. The servo motor nonlinear friction disturbance suppression method described in the application calculates the current compensation value of the servo motor at the current time according to the angular velocity of the servo motor at the current time and the current value of the servo motor at the current time, and based on the combination of the improved Luenberger observer and the dynamic model of the system, which adapts to the time-varying characteristics of the friction torque. 2. The servo motor nonlinear friction disturbance suppression method described in the application reduces the dependence on the mechanism model by using the improved Luenberger observer to observe the friction torque. 3. The servo motor nonlinear friction disturbance suppression method described in the application effectively suppresses speed fluctuations and tracking errors, and enhances the robustness and control accuracy of the system under complex working conditions. The servo motor nonlinear friction disturbance suppression method described in the application combines the dynamic model of the system with the improved Luenberger observer, aiming to solve the problem of nonlinear friction disturbance caused by machining errors, bearing friction asymmetry, load eccentricity and assembly inconsistency. It is suitable for application scenarios with high requirements for motion stability, trajectory accuracy and anti-interference ability, including but not limited to aerospace optical stabilization and aiming systems, precision manufacturing equipment, industrial robot joint control and high-precision measurement turntables, etc. BRIEF DESCRIPTION OF DRAWINGS

[0013] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the following drawings of which: Figure 1 is a flow chart of the method for suppressing nonlinear friction disturbance of the servo motor according to the first embodiment; Figure 2 is a waveform diagram of the angular velocity before current compensation according to the first embodiment; Figure 3 is a waveform diagram of the angular velocity after current compensation according to the first embodiment; Figure 4 is a flow chart of the method for calculating the current compensation value of the servo motor at the current time according to the second embodiment. DETAILED DESCRIPTION

[0014] Various embodiments of the present application will be described herein below with reference to the accompanying drawings. The embodiments described by reference to the accompanying drawings are exemplary and are intended to explain the present application, and should not be construed as limiting the present application.

[0015] According to the method for suppressing nonlinear friction disturbance of the servo motor of the first embodiment, after a target speed is given, a command is transmitted to a speed controller to generate an initial current control command. The initial current control command enters a current controller to output a corresponding current signal to the servo motor to drive the servo motor to generate an accurate torque, and then drive the servo motor to rotate, including the following steps. Step S1, after driving the servo motor to rotate, the angular velocity of the servo motor at the current time and the current value of the servo motor at the current time are monitored respectively; Step S2, the improved Luenberger observer uses the angular velocity of the servo motor at the current time, the current value of the servo motor at the current time, and the dynamic model of the system to calculate the current compensation value of the servo motor at the current time; Step S3, the current compensation value of the servo motor at the current time and the initial current control command are superimposed and re-input into the current controller to form a closed-loop negative feedback control.

[0016] In order to solve the technical problems existing in the prior art, the purpose of the present embodiment is to overcome the shortcomings of the existing servo motor friction torque compensation method, and to provide a dynamic adaptive compensation strategy based on the measured target speed and current output. Without relying on an accurate friction model, high-efficiency compensation can be achieved, and the speed control quality and disturbance rejection ability of the servo motor are significantly improved. As shown in Figure 1 the method includes the following steps: Once the target speed is given, the command is transmitted to the speed controller, generating an initial current control command. This command enters the current controller, which outputs a corresponding current signal to the servo motor, driving the motor to generate precise torque, which in turn drives the servo motor to rotate. Sensors monitor the servo motor's current angular velocity and current value in real time. The improved Luenberger observer uses the servo motor's current angular velocity, current value, and the system's dynamic model to calculate the servo motor's current compensation value to offset the effects of friction. This compensation current is superimposed on the initial current control command and re-input into the current controller, forming a closed-loop negative feedback control.

[0017] The angular velocity and current value of the servo motor at the current moment are obtained by a high-bandwidth speed sensor and a high-bandwidth current sensor, respectively.

[0018] like Figures 2 to 3 As shown, by real-time monitoring of the servo motor's current angular velocity and current value, and combining this with the system's dynamic model, an improved Luenberger observer is used to generate the servo motor's current compensation value. Compensation using this current compensation value allows the real-time monitored servo motor angular velocity to more closely approximate the desired angular velocity.

[0019] Therefore, this embodiment fully utilizes the rapid response characteristics of the sensor to the angular velocity and current value of the servo motor at the current moment, and can perform millisecond-level dynamic compensation for changes in friction torque, which is especially suitable for ultra-low speed and high-precision application scenarios.

[0020] Implementation Method 2: This implementation method further defines the servo motor nonlinear friction disturbance suppression method described in Implementation Method 1. In step S2, the improved Luenberger observer calculates the current compensation value of the servo motor at the current moment using the angular velocity of the servo motor, the current current value of the servo motor, and the dynamic model of the system. This includes the following steps: Step S201: Monitor the angular velocity and current value of the servo motor at the current moment, respectively. Step S202: Using the system's dynamic model, and based on the angular velocity and current value of the servo motor at the current moment, obtain the linear friction coefficient and moment of inertia of the servo motor, respectively. Step S203: Using the improved Luenberger observer, and based on the linear friction coefficient of the servo motor, the moment of inertia of the servo motor, the current angular velocity of the servo motor, and the current value of the servo motor at the current moment, the estimated angular velocity of the servo motor at the current moment and the estimated nonlinear friction torque of the servo motor at the current moment are calculated iteratively. Step S204: Calculate the current compensation value of the servo motor at the current moment based on the estimated nonlinear friction torque of the servo motor at the current moment.

[0021] This embodiment further defines step S2 as described in embodiment one, such as... Figure 4 As shown, it includes the following steps: Step S201: Monitor the angular velocity and current value of the servo motor at the current moment using sensors. Step S202: Using the system's dynamic model, and based on the angular velocity and current value of the servo motor at the current moment, obtain the linear friction coefficient and moment of inertia of the servo motor, respectively. Step S203: Using an improved Luenberger observer, and based on the linear friction coefficient of the servo motor, the moment of inertia of the servo motor, the current angular velocity of the servo motor, and the current value of the servo motor at the current moment, the estimated angular velocity of the servo motor at the current moment and the estimated nonlinear friction torque of the servo motor at the current moment are calculated iteratively. Step S204: Using the estimated nonlinear friction torque of the servo motor obtained in step S203, calculate the current compensation value of the servo motor at the current moment. ,in, This is the estimated nonlinear friction torque of the servo motor at the current moment. This is the torque coefficient of the servo motor; Step S205: Send the initial current control command Current compensation value of the servo motor at the current moment After being superimposed, it serves as the input to the current loop controller; Step S206: Monitor the angular velocity and current value of the servo motor at the next moment using sensors, and repeat step S203.

[0022] The method described in this embodiment can effectively improve the speed control stability of servo motors under ultra-low speed conditions.

[0023] Implementation Method 3: This implementation method further defines the servo motor nonlinear friction disturbance suppression method described in Implementation Method 2. In step S201, the dynamic model of the system is specifically as follows: ; in, This refers to the rotational inertia of the servo motor. The angular velocity of the servo motor at the current moment. This represents the current value of the servo motor at the current moment. The linear friction coefficient of the servo motor is . This refers to the torque coefficient of the servo motor. For the nonlinear frictional torque of the servo motor, This refers to the current moment.

[0024] In this embodiment, the improved Luenberger observer in step S203 specifically refers to: ; in, This refers to the rotational inertia of the servo motor. The linear friction coefficient of the servo motor is . The angular velocity of the servo motor at the current moment. This represents the current value of the servo motor at the current moment. This is the estimated angular velocity of the servo motor at the current moment. This is the estimated nonlinear friction torque of the servo motor at the current moment. This refers to the torque coefficient of the servo motor. and These are different parameters for the improved Luenberger observer.

[0025] In this embodiment, the influence of different parameters of the improved Luenberger observer on the estimated nonlinear friction torque of the servo motor at the current moment is specifically as follows: ; in, and These are different parameters of the improved Luenberger observer. This refers to the rotational inertia of the servo motor. The linear friction coefficient of the servo motor is . This refers to the Laplace transform operator. This is the estimated nonlinear friction torque of the servo motor at the current moment. For the nonlinear frictional torque of the servo motor, for Laplace transform, for Laplace transform.

[0026] In this embodiment, the dynamic model of the servo motor system is considered, specifically as follows: ; in, The moment of inertia of the servo motor (unit: ), The angular velocity of the servo motor at the current moment (unit: ), The current value of the servo motor at the current moment (unit: ), The linear friction coefficient of the servo motor (unit: ), Torque coefficient of servo motor (unit: ), The nonlinear frictional torque of the servo motor (unit: ), This refers to the current moment.

[0027] The nonlinear frictional torque of the servo motor Treating it as an unknown disturbance, we can obtain: .

[0028] The nonlinear frictional torque of the servo motor was analyzed using an improved Luenberger observer. Real-time observation; the improved Luenberger observer expression is as follows: ; in, This is the estimated angular velocity of the servo motor at the current moment. This is the estimated nonlinear friction torque of the servo motor at the current moment. and These are different parameters of the improved Luenberger observer, which need to be adjusted. and Estimated nonlinear friction torque of the servo motor at the current moment The effect can be expressed as: ; in, For the Laplace transform operator, for Laplace transform, for Laplace transform.

[0029] By adjusting and This allows you to change the estimated nonlinear friction torque of the servo motor at the current moment. Nonlinear frictional torque of servo motor The accuracy of the estimate.

[0030] Based on the estimated nonlinear friction torque of the servo motor at the current moment The current compensation value of the servo motor at the current moment can be calculated. .

[0031] It should be noted that existing Luenberger observers, because they use the current controller input current as the observer input, fail to fully consider the saturation characteristics of the actual current controller. Directly using them in the method described in this embodiment will lead to control instability, meaning that the desired technical effect cannot be achieved. Therefore, this embodiment improves upon the existing Luenberger observer. Since the improved Luenberger observer uses the servo motor feedback current as the observer input, it can directly obtain the actual output current of the current controller, thus achieving the desired technical effect and solving the technical problems of this embodiment.

[0032] Implementation Method Four: This implementation method further defines the servo motor nonlinear friction disturbance suppression method described in Implementation Method Two. In step S203, the estimated angular velocity and estimated nonlinear friction torque of the servo motor at the current moment are iteratively calculated separately, specifically as follows: ; ; in, This is the estimated angular velocity of the servo motor at the current moment. This represents the current value of the servo motor at the current moment. This is the estimated angular velocity of the servo motor at the previous moment. The sampling period is The linear friction coefficient of the servo motor is . This refers to the rotational inertia of the servo motor. This refers to the torque coefficient of the servo motor. and These are different parameters of the improved Luenberger observer. This is the estimated nonlinear friction torque of the servo motor at the previous moment. This is the estimated nonlinear friction torque of the servo motor at the current moment.

[0033] Implementation Method 5: The servo motor nonlinear friction disturbance suppression system described in this implementation method is based on the servo motor nonlinear friction disturbance suppression method described in Implementation Method 1. After a target speed is given, the command is transmitted to the speed controller, generating an initial current control command. The initial current control command enters the current controller, which outputs a corresponding current signal to the servo motor, driving the servo motor to generate a precise torque, thereby driving the servo motor to rotate. The system includes the following modules: Module S1, after driving the servo motor to rotate, monitors the angular velocity and current value of the servo motor at the current moment. Module S2, the improved Luenberger observer, uses the angular velocity of the servo motor at the current moment, the current value of the servo motor at the current moment, and the dynamic model of the system to calculate the current compensation value of the servo motor at the current moment. In module S3, the current compensation value of the servo motor at the current moment is superimposed with the initial current control command and re-inputted into the current controller to form a closed-loop negative feedback control.

[0034] The above provides a detailed description of the servo motor nonlinear friction disturbance suppression method and system proposed in this invention. Specific examples have been used to illustrate the principle and implementation of this invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for suppressing nonlinear frictional disturbances in a servo motor, wherein after a target speed is given, the command is transmitted to the speed controller, generating an initial current control command; the initial current control command enters the current controller, which outputs a corresponding current signal to the servo motor, driving the servo motor to generate a precise torque, thereby driving the servo motor to rotate, characterized in that… Includes the following steps: Step S1: After driving the servo motor to rotate, monitor the angular velocity and current value of the servo motor at the current moment. Step S2: The improved Luenberger observer uses the angular velocity of the servo motor at the current moment, the current value of the servo motor at the current moment, and the dynamic model of the system to calculate the current compensation value of the servo motor at the current moment. Step S3: The current compensation value of the servo motor at the current moment is superimposed with the initial current control command and re-input into the current controller to form a closed-loop negative feedback control.

2. The method for suppressing nonlinear frictional disturbances in a servo motor according to claim 1, characterized in that, In step S2, the improved Luenberger observer calculates the current compensation value of the servo motor at the current moment using the angular velocity of the servo motor, the current current value of the servo motor, and the dynamic model of the system. This includes the following steps: Step S201: Monitor the angular velocity and current value of the servo motor at the current moment, respectively. Step S202: Using the system's dynamic model, and based on the angular velocity and current value of the servo motor at the current moment, obtain the linear friction coefficient and moment of inertia of the servo motor, respectively. Step S203: Using the improved Luenberger observer, and based on the linear friction coefficient of the servo motor, the moment of inertia of the servo motor, the current angular velocity of the servo motor, and the current value of the servo motor at the current moment, the estimated angular velocity of the servo motor at the current moment and the estimated nonlinear friction torque of the servo motor at the current moment are calculated iteratively. Step S204: Calculate the current compensation value of the servo motor at the current moment based on the estimated nonlinear friction torque of the servo motor at the current moment.

3. The method for suppressing nonlinear frictional disturbances in a servo motor according to claim 2, characterized in that, In step S201, the dynamic model of the system is specifically as follows: ； in, This refers to the rotational inertia of the servo motor. The angular velocity of the servo motor at the current moment. This represents the current value of the servo motor at the current moment. The linear friction coefficient of the servo motor is . This refers to the torque coefficient of the servo motor. For the nonlinear frictional torque of the servo motor, This refers to the current moment.

4. The method for suppressing nonlinear frictional disturbances in a servo motor according to claim 2, characterized in that, In step S203, the improved Luenberger observer specifically refers to: ； in, This refers to the rotational inertia of the servo motor. The linear friction coefficient of the servo motor is . The angular velocity of the servo motor at the current moment. This represents the current value of the servo motor at the current moment. This is the estimated angular velocity of the servo motor at the current moment. This is the estimated nonlinear friction torque of the servo motor at the current moment. This refers to the torque coefficient of the servo motor. and These are different parameters for the improved Luenberger observer.

5. The method for suppressing nonlinear frictional disturbances in a servo motor according to claim 4, characterized in that, The effects of different parameters of the improved Luenberger observer on the estimated nonlinear friction torque of the servo motor at the current moment are as follows: ； in, and These are different parameters of the improved Luenberger observer. This refers to the rotational inertia of the servo motor. The linear friction coefficient of the servo motor is . For the Laplace transform operator, This is the estimated nonlinear friction torque of the servo motor at the current moment. For the nonlinear frictional torque of the servo motor, for Laplace transform, for Laplace transform.

6. The method for suppressing nonlinear frictional disturbances in a servo motor according to claim 2, characterized in that, In step S203, the estimated angular velocity and the estimated nonlinear friction torque of the servo motor at the current moment are calculated iteratively, specifically as follows: ； ； in, This is the estimated angular velocity of the servo motor at the current moment. This represents the current value of the servo motor at the current moment. This is the estimated angular velocity of the servo motor at the previous moment. The sampling period is The linear friction coefficient of the servo motor is . This refers to the rotational inertia of the servo motor. This refers to the torque coefficient of the servo motor. and These are different parameters of the improved Luenberger observer. This is the estimated nonlinear friction torque of the servo motor at the previous moment. This is the estimated nonlinear friction torque of the servo motor at the current moment.

7. A servo motor nonlinear friction disturbance suppression system, wherein the system is implemented based on the servo motor nonlinear friction disturbance suppression method according to any one of claims 1-6, wherein after a target speed is given, the command is transmitted to the speed controller to generate an initial current control command; the initial current control command enters the current controller and outputs a corresponding current signal to the servo motor to drive the servo motor to generate a precise torque, thereby driving the servo motor to rotate, characterized in that, Includes the following modules: Module S1, after driving the servo motor to rotate, monitors the angular velocity and current value of the servo motor at the current moment. Module S2, the improved Luenberger observer, uses the angular velocity of the servo motor at the current moment, the current value of the servo motor at the current moment, and the dynamic model of the system to calculate the current compensation value of the servo motor at the current moment. In module S3, the current compensation value of the servo motor at the current moment is superimposed with the initial current control command and re-inputted into the current controller to form a closed-loop negative feedback control.

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