Vibration Characteristic Analysis And Suppression Of AC Servo System

Permanent Magnet Synchronous Machine(PMSM)as the control object of AC servo system has been widely used in industry,in some high-demand occasions,such as CNC engraving and milling Machine and high-speed drilling and attacking center,etc.,The fast response performance and process precision of permanent magnet synchronous servo system are required.The speed control of servo system usually adopts the double closed-loop structure of the outer loop of speed and the inner loop of current.Because the bandwidth of the inner loop of current is much larger than that of the outer loop of speed,the bandwidth of the outer loop of speed becomes the key factor affecting the dynamic performance of the servo system.When the speed controller is designed,the servo motor,transmission device and load are often regarded as a rigid body.Generally,the inertia of the transmission device is relatively small,which is directly equivalent to the motor side.In the actual servo system,because the transmission device is not ideal rigidity,it is easy to cause the mechanical oscillation of the system,so it is necessary to design reasonable speed controller to avoid the vibration of the system.According to the speed control principle of servo system,the mathematical model of permanent magnet synchronous motor is established,and the vector control strategy of permanent magnet synchronous motor is expounded.When the speed controller is designed,the transmission device in the servo system is equivalent to a torsional spring,so the servo system can be simplified as servo motor-spring-double moment of inertia load system.According to the simplified mathematical model of double inertia system,the cause of vibration is explained in principle,and then the influence of elastic coefficient and inertia ratio between motor side and load side on resonant frequency is analyzed.Finally,the influence of vibration on system performance is further explained from two aspects of system stability and dynamic performance.After simplifying the system,it is discussed that increasing the gain of the speed loop can improve the speed response of the system,but at the same time it will bring unexpected vibration.According to the closed-loop transfer function of the control model,the relationship between the vibration frequency and the model parameters of the control object is studied,and the shortcomings of the load torque observer method based on the adjustable inertia ratio are analyzed.An improved method,which is based on the feedback compensation method of velocity error signal,is proposed to suppress the vibration.Through the analysis of transfer function,this paper expounds the improved method in this paper,the working principle and design of the internal model control of observer and filter parameters,finally using simulation platform to verify the feasibility and effectiveness of the improved method.Servo system in the transmission of elastic coefficient is changed,the vibration frequency of the system is also changed,easy cause the traditional filtering method suppresses the failure,so in order to meet the demand of the online system vibration suppression,the vibration suppression method of adaptive IIR filter,through Fourier analysis method(FFT)real-time analysis speed error signal,the vibration parameter identification and extraction,and the identification results as online adaptive IIR filter parameters setting of the object.Finally,a simulation model is established to verify the effectiveness of the adaptive IIR filter method.The FFT algorithm and notch filtering algorithm are verified on CCS3.3 software,and the effectiveness of the filter method is verified by using the established experimental platform.