The Rejection Of Spatially Periodic Disturbance Based On Improved Repetitive Control

There are a variety of disturbances that are periodically related to the angular position in the rate turntable servo system.These disturbances will affect the speed stability and position tracking accuracy of the system.In this paper,the pitch axis of the dual-axis rate turntable is taken as the research object,and the rejection of spatially periodic disturbance based on improved repetitive control is studied.Aiming at the frequency offset in the repeated control method,this problem is solved from the two methods of adding frequency correction link and introducing fractional FIR filter.The dynamic repetitive control of spatially periodic disturbance rejection using time sampling is demonstrated.The effectiveness of these methods are proved based on the simulation results.This article focuses on the following aspects:Firstly,the dual-axis rate turntable system is modeled.The source and spatially periodic characteristics of the motor moment fluctuation are studied and analyzed.The position-domain frequency of the main component of the spatially periodic disturbance signal is determined,and the specific form of the interference model is given.Secondly,The stability condition and the capability of disturbance rejection of the repetitive control system are analyzed.First-order or second-order LPF is introduced into the controller to improve the stability of the system.The cause of the frequency offset in the repetitive control and the influence on the capability of disturbance rejection of system are studied.The frequency correction link is designed to improve the repetitive controller,and the effectiveness of the frequency amendment unit to compensate the frequency offset is proved according to the simulation results..Then,the phase-frequency characteristics of the LPF in the repeat controller are analyzed,and the FIR filter with linear phase-frequency characteristics is designed.Aiming at the realization of non-integer order delay in digital repeat controller,a design method of fractional FIR filter based on Lagrange interpolation and a new fractional FIR filter design based on window function method are given.The fractional-order FIR filter is effective for ensuring the stability of the repeated control system and improving the capability of disturbance rejection.Finally,in order to achieve the rejection of spatially periodic disturbance,a method of designing the position domain repeat controller is proposed based on the internal model principle.Due to the complexity of the position sampling method,the controller can be converted from the location domain controller to the time domain according to the domain conversion.,a dynamic repetitive controller is obtained,and dynamic frequency amendment unit and dynamic fractional FIR filter for dynamic repetitive controller design are also given.The improved repetitive control method is applied to the rate servo system.According to the simulation results,the effectiveness of the improved repetitive control method to reject the spatially periodic disturbance is proved after the frequency correction link or fractional FIR filter is introduced in the controller.