Structural Analysis And Controller Design Of Fast Steering Mirror

Fast Steering Mirror(FSM)is a small precision optical instrument which is used to regulate the beam propagation direction.Due to its compact structure,easy adjustment,high positioning accuracy,and fast response,it is widely used in aerial cameras,laser communications,adaptive optics and other fields.Based on a certain dual-band aerial camera R&D project,the structure and controller design of the fast mirror are studied in this paper.Details are as follows:The main performance indicators and components of the fast mirror were analyzed,and the connection between the both was established.Based on the connection between the both,the mirror,flexible support,drive motor,and sensor of the mirror were analyzed and selected,and a mathematical model of the system was established through force analysis.The material selection,structure size and mechanical properties of the flexible support as a key component of the mirror are emphatically analyzed.The stiffness,accuracy and natural frequency of the flexible hinge are studied,and the finite element simulation is performed by MSC.Patron and MSC.Nastran.The analysis verifies the performance of various aspects of flexible hinges.Aiming at the shortcomings of closed-loop control strategy of PID used in fast steering mirror engineering,a two-closed-loop and two-degree-of-freedom control strategy was proposed.Firstly,a Model-based Expansion State Observer(MESO)based on model information was designed by integrating the modeling information into the traditional Expanded State Observer(ESO),and its stability was proved.And then,the MESO was applied to offset external disturbances and modeling error in fast steering mirror.At the same time,MESO was used to track the speed signal of fast steering mirror to design the inner loop of the speed feedback,the damping ratio of the system is increased,and the mechanical resonance of the system is suppressed.Then,the MEMO,speed inner loop,and position loop are combined to form a double closed-loop two-degree-of-freedom controller.Finally,simulation analysis is performed by Simulink.The results show that the controller designed in this paper has better bandwidth,anti-jamming capability and robustness compared to the traditional PID position closed-loop controller.The controller parameters setting designed in this paper is studied.Firstly,from the perspective of bandwidth,an improvement was made on the basis of the predecessor "3w" method,a "2w" parameter configuration method was proposed to increase the bandwidth of the MESO;then from the perspective of steady-state error,a design was made based on the genetic algorithm(GA).It can further improve the accuracy of the MESO.Finally,the availability of the parameter setting scheme is verified through simulation analysis.