Composite Nonlinear Feedback Sliding Mode Control Strategy For Electrostatic Driven MEMS Torsional Micromirror

Micro-Electro-Mechanical System(MEMS)is a kind of micro-mechanical device which involves many disciplines,and its magnitude is usually below millimeter level.Electrostatic driven MEMS torsional micromirror has the characteristics of simple structure,low power consumption and high scanning frequency.It is widely used in optical communication,medical scanning imaging,projection display and other fields.How to use the control strategy to ensure the good transient performance and accurate positioning of the electrostatic driven MEMS torsional micromirror is a hot issue in the field of MEMS control.On the other hand,under the electrostatic driving mechanism,when the driving voltage is too high,the electrostatic pull-in phenomenon will be triggered,resulting in device damage.At the same time,the influence of external disturbance on system performance needs to be considered.Therefore,this paper considers the control problem of electrostatic driven torsional MEMS micromirror with limited input and disturbance,and mainly completes the following work:(1)An optimal composite nonlinear feedback sliding mode control strategy based on hybrid optimization algorithm is proposed.The algorithm is composed of composite nonlinear feedback control and sliding mode control.The composite nonlinear feedback control has good transient performance by adjusting the damping ratio of the closed-loop system.The sliding mode control is used to eliminate the influence of disturbance on the system.On this basis,the parameter selection problem of the composite nonlinear feedback control law is transformed into a minimum problem,and the parameter setting problem of the composite nonlinear feedback control is solved by using the hybrid optimization algorithm based on tabu search algorithm and particle swarm optimization algorithm.The simulation results show that the hybrid optimization algorithm can effectively solve the problem of controller parameter selection,and the controller has good transient performance and robustness under the condition of limited system input.(2)An optimal composite nonlinear feedback second order sliding mode control method is proposed for the problems of input constraint and buffeting.The composite nonlinear feedback control system has good transient performance and the second order sliding mode control ensures the system robustness and reduces chattering.The Lyapunov function is designed to prove the system stability under input constraint.The simulation results demonstrate the effectiveness of the controller.Compared with theoptimal composite nonlinear feedback sliding mode control,the controller can guarantee the transient performance and robustness of the micromirror system,at the same time it can reduce chattering when the input is limited.(3)An optimal composite nonlinear feedback fast sliding mode control method based on improved approach law is proposed.The composite nonlinear feedback control is used to guarantee the control accuracy and improve the transient performance of the system;the sliding mode control based on improved approach law has the advantage of reaching the sliding mode surface quickly,improving the quality of sliding mode control and enhancing the robustness of the system.Simulation results show that the controller can realize precise positioning control and good transient response with limited input,and enhance the robustness.