Research On Mechanical Resonance Suppression Of Servo Drive System Based On Model Predictive Control

In recent years,servo drive system is widely used in many industrial fields such as CNC machine tools,robots,auto parts testing equipment and national defense industry.The elasticity of the transmission mechanism of the servo drive system makes the system itself have resonance frequency,and the existence of resonance frequency will bring mechanical resonance to the system.The existence of mechanical resonance will lead to the oscillation of the system when the torque and speed of the servo drive system are controlled.When the servo drive system is operated under mechanical resonance for a long time,it will not only affect the control performance and precision of the system,but also damage the transmission mechanism,burn down the driving motor,and even cause industrial accidents.Therefore,the suppression of mechanical resonance is of great significance for improving the control quality of the servo drive system,it is beneficial to improve the stability,safety and production efficiency of industrial application equipment,and provides theoretical and practical exploration for the research and development of high-performance servo drive products.In order to further study the vibration mechanism of the servo drive system and improve the control performance of the servo drive system,a two-inertia servo drive system model was firstly established in this paper,and analyzed the causes and influencing factors of the mechanical resonance of the two-inertia servo drive system.Secondly,the influence of time-varying meshing stiffness on system mechanical resonance in the process of gear transmission was considered,a four-inertia servo drive system model was established on the basis of the traditional two-inertia servo drive system model,and the mechanism and influencing factors of mechanical resonance of the four-inertia servo drive system were analyzed.Then,aiming at the problem of suppressing the mechanical resonance of the multi-inertia servo drive system,a model predictive control method was proposed to suppress the mechanical resonance of the four-inertia servo drive system including time-varying meshing stiffness,the model predictive controller based on the system state space expression was designed and verified by simulation tests compared with conventional PID control method.Finally,a bench built in the laboratory was used to verify the effectiveness of the model predictive control method for the two-inertia servo drive system.In view of the problems that the research of servo drive system’s mechanical resonance suppression,the main work of this paper is as follows:(1)The composition,classification and characteristics of the servo drive system were analyzed,the typical servo drive system structure was simplified,and a two-inertia servo drive system model including motor and load was established.In-depth analysis of the reasons for the mechanical resonance of the two-inertia servo drive system,and the influence of the inertia ratio,the stiffness coefficient of the drive shaft and the damping coefficient of the drive shaft on the mechanical resonance of the two-inertia servo drive system were discussed separately.From the analysis results,compared with the system drive shaft damping coefficient,inertia ratio and drive shaft stiffness coefficient had more significant effects on the mechanical resonance of the two-inertia servo drive system.(2)In order to suppress the mechanical resonance of servo drive system more accurately,based on the modeling of two-inertia servo drive system and the analysis of mechanical resonance,considering the influence of time-varying meshing stiffness of gear pair on mechanical resonance,a four-inertia servo drive system model including motor,active and passive gear and load was established.Then this paper analyzed the cause of mechanical resonance of four-inertia servo drive model,and analyzed the influence of different inertia ratio,meshing stiffness and meshing damping of gear pair on the mechanical resonance of the system.The results showed that the change of meshing stiffness had a great influence on the mechanical resonance of four-inertia servo drive system,especially in the high frequency region.Therefore,it was necessary to consider time-varying meshing stiffness as variable stiffness when establishing the servo drive system model.The time-varying meshing stiffness model was established,and the meshing stiffness value of gear pair was approximately expressed by time-varying waveform.The mechanical resonance performance characteristics of servo drive system model with or without time-varying meshing stiffness were compared.The results showed that the mechanical resonance of the servo drive system with time-varying gear meshing stiffness was more obvious.(3)The model predictive control method is used to solve the control problem of mechanical resonance suppression of servo drive system.The basic principle of model predictive control was introduced.The method of suppressing mechanical resonance of four-inertia servo drive system with time-varying meshing stiffness was studied.A model predictive controller based on four-inertia servo drive system was designed to suppress mechanical resonance.The controller consisted of four parts: prediction model establishment,objective function design,constraint condition design and optimization solution.The simulation model was built in Matlab/Simulink to verify the performance of the model predictive control method in suppressing the mechanical resonance,and compared with the PID control method.The simulation results showed that the designed model predictive controller can effectively suppress the mechanical resonance of the four-inertia servo drive system,and the suppression effect was better than the PID method.(4)In order to further verify the effectiveness of the model predictive control method to suppress the mechanical resonance of the servo drive system,the model predictive control method was tested and verified for the two-inertia servo drive system based on the existing laboratory conditions.This paper introduced the structure of mechanical resonance suppression test bench for servo drive system,described the main hardware parts and parameters of the test bench,analyzed the basic requirements of the test bench software,and introduced the main program and main interrupt program in the motor driver.The experimental results showed that the model predictive control method could effectively suppress the mechanical resonance of the system.Compared with the PID control method,the control performance of the model predictive control method was better,and the system robustness and dynamic response performance were improved,which provided a reference for the suppression of mechanical resonance of the multi-inertia servo drive system.