Theoretical and experimental determination of bandwidth for a two-axis fast steering mirror

Fast steering mirror (FSM) system is a precise beam steering mechanism which modulates the beam between a light source and a receiver using its reflecting surface. High bandwidth is an important property of FSM, which is associated with the response speed and stable precision. It is difficult to design the closed-loop bandwidth for FSM, which relies on the open-loop frequency response of the system and the design of the controller. A theoretical analysis, simulation, and testing method to determine an appropriate bandwidth designation for a two-axis FSM are developed in this paper. An ideal open-loop plant frequency response is compared to a final closed-loop bandwidth requirement, and then, stiffness of elastic support in each direction is researched and idea of stiffness design of elastic support is put forward. An integrated mechanical control simulation (IMCS) method is introduced to simulate the structural response and controller design synchronously to predict the final closed-loop control performance of the two-axis FSM system. Finally, the open-loop plant frequency response and closed-loop bandwidth of the assembled two-axis FSM system are tested with the results confirming the general validity of the analysis and simulation method presented in this paper.