Study On Nonlinear LTR Control Medthod Based On DLUKF

Ball-plate system is a classical non-linear motion control system.Because of its strong non-linearity and strong coupling,it requires high control difficulties in regulating speed and overshoot.It is widely used in the verification of the effectiveness of control methods and in the teaching of universities.Continuous stirred tank reactor(CSTR)is an important chemical process control system.In addition to the non-linear problem of the system,there are also some control problems that can not be directly measured,as well as serious noise and interference.Therefore,the research of the two systems has always been the hotspot and difficulty in the field of nonlinear control.Loop transfer recovery(LTR)is a simple,clear and good control method based on linear quadratic regulator(LQR)and Kalman filter.The research of LTR method in domestic and foreign literature mainly focuses on the application of motion control system such as aircraft,,which has certain limitations.In this paper,based on the extensive literature of nonlinear control methods,the linear LTR method is extended to the field of nonlinear control,and a nonlinear DLUKF-LTR method with simple design and good robustness is proposed,which solves the control problems in Ball-plate system(nonlinear motion control)and CSTR system(nonlinear process control)to a certain extent,and achieves good control effect.The main work of this paper is as follows:Firstly,the theoretical basis of control research is given,the concept of sensitivity function is introduced,the basic principle of Kalman filter algorithm and LTR method and the derivation process of loop transfer function recovery are described.Secondly,the mathematical models of Ball-plate system and CSTR system are established and deduced respectively,and the two systems are analyzed briefly with the knowledge of control theory.Thirdly,taking the Ball-plate system as an example,based on the ordinary Kalman filter,extended Kalman filter(EKF),unscented Kalman filter(UKF),double layers unscented Kalman filter(DLUKF)designed the LTR controller,and through the simulation experiment,analyzed the influence of the choice of the weighting matrix parameters on the control effect.At the same time,compared the control effect of the classical double closed-loop PID method with the linear LTR method and the nonlinear LTR method,it was proved that the nonlinear LTR control effect based on DLUKF was the best.Finally,a state estimator based on EKF,UKF and DLUKF is designed for propylene glycol production process,and the estimation results are compared.Then a nonlinear LTR controller based on DLUKF is designed.Compared with classical PID controller and terminal sliding mode controller,it is proved that the method proposed in this paper has better control effect and good robustness when the input conditions are close.