Research On Frequency Domain Modeling And Anti-disturbance Control Of Servo System

With the development of power electronics technology,sensors technology,computer technology and modern motor control theory,permanent magnet synchronous motor AC speed control system has been widely used,especially in the field of high precision and high performance.In the practical application of high-performance servo system,belt pulley,ball screw,linkage rod,gears are used to drive the control objects.Compared with the system in which ball screw or linkage rod,belt pulley servo system has the characteristics of less rigidity,which makes its model more complicated and the control performance is hard to be satisfactory.Although a two-mass system model can be used to describe the belt pulley servo system,it has some limitations because the pulley-side parameters of the two-mass system model cannot be derived in practice.Therefore,the research based on the experimental data has important engineering significance in modeling the pulley servo system.In this paper,an iterative weighted least squares(IWLS)algorithm is designed to identify the frequency domain model of the belt pulley servo system.The proposed algorithm can minimize the amplitude-frequency and phase-frequency response errors of the identified model and the real system through iterative process,making the identified model as close as possible to the real system.In addition,in the practical application of belt pulley servo system there are time-varying load disturbance,nonlinear friction and other time-varying interferences,making the traditional control algorithm difficult to achieve satisfactory performances.Considering that these disturbances are often not limited to constant or slowly varying disturbances,a GPI observer is introduced to estimate a faster set of lumped disturbances.Then,based on the frequency domain model of the belt pulley servo system identified above,a composite control strategy based on PDD feedback and GPI feedforward is designed.The simulation results show that the composite controller improves not only the dynamic response speed of the belt pulley servo system,but also the anti-disturbance performance.Considering the existence of various periodic disturbances in the actual operation of PMSM and the frequencies of these periodic disturbances is usually unknown.In this paper,an adaptive internal model(AIM)based anti-jamming control scheme is proposed.An adaptive internal model is embedded into the velocity loop to identify the frequencies of periodic disturbances and to suppress the steady-state fluctuation of the servo system.Also,the scheme can be extended to simultaneously identify and suppress periodic disturbances of multiple unknown frequencies.For multiple periodic disturbances,the corresponding number of AIMs can be designed to identify the frequencies of multiple disturbances and to suppress the steady-state fluctuations of multiple disturbances.Simulation results show that the algorithm can accurately identify the frequencies of periodic disturbances and can effectively suppress the steady-state fluctuation of PMSM speed.