Research On Backlash Compensation And Resonance Suppression Of Servo System

The servo system is an important branch in the field of motion control,and is widely used in high-tech fields such as modern industry and agriculture,national defense,and medical treatment.The typical mechanical structure of the servo system is that the high-speed servomotor drives the deceleration transmission mechanism,and then the transmission mechanism drives the load to complete the energy conversion.On one hand,non-linear factors such as backlash exist in the mechanical transmission structure inevitably,backlash nonlinearity is indispensable in the transmission process,at the same time seriously affects the performance of the servo system.On the other hand,the rigidity of the transmission mechanism is not ideally infinity,so the effect of mechanical resonance owing to the elasticity can not be ignored.Firstly,the article introduces the causes and research status of backlash nonlinearity as well as mechanical resonance.Then taking the permanent magnet synchronous motor(PMSM)servo system as the research object,the working principle and control scheme of PMSM are analyzed.In addition,several common mathematical models and applicable occasions of backlash nonlinearity are introduced,and the mechanism of mechanical resonance is analyzed based on the double inertia elastic system.The backlash nonlinearity and mechanical resonance of the servo system are studied respectively:On regard to the backlash nonlinearity,this paper adopts the least squares method and nonlinear least square method to identify the parameters of the backlash dead zone model and the approximate dead zone model respectively.The gear backlash torque is estimated based on the identified model and the feedback control scheme is designed based on gear backlash torque compensation.The proposed identification method and the proposed control scheme are verified through simulation and experiment.In addition,considering the lumped disturbances such as friction torque,current loop dynamics,and backlash modeling deviations,a high-order sliding mode observer(HOSMO)is designed to estimate the lumped disturbances existing in the servo system.The composite controller based on HOSMO and non-singular terminal sliding mode controller(NTSMC)is designed.The stability of the proposed disturbance rejection composite control scheme is proved.The proposed composite control method is verified through simulation and experiment.For the mechanical resonance,this paper introduces the frequency-domain identification method and the mechanical resonance suppression algorithm based on the notch filter.Then chirp signal is used as an excitation signal,and offline FFT transformation is used to analyze the resonance characteristics of servo system.Notch filter algorithm is designed to suppress mechanical resonance based on frequency-domain identification results.The proposed method is verified through experiment,and the experimental platforms include robotic arm,screw and pulley.