| Fast Steering Mirror(FSM)is an important component that can achieve precise adjustment and stabilization of the beam between the light source and the target by controlling the rapid and precise deflection movement of the mirror.The FSM system is small in size,high in accuracy,fast in response and strong in tracking signals.It is widely used in many important fields such as adaptive optics,astronomical telescopes,laser processing equipment and inter-satellite laser communications.FSM originated in the 1980 s.After years of research and development in Western developed countries,the FSM system has matured and entered commercialization.The development of my country’s FSM system is later than that of Western developed countries,but with the continuous increase in investment in recent years,my country’s FSM system has also made rapid progress,but there is still a gap with Western developed countries.Therefore,we need to conduct research on higher-performance FSM systems and provide highperformance FSM systems with completely independent intellectual property rights for related fields in my country.Based on the test platform of a laser communication laboratory,this research briefly introduced the characteristics and development status of inter-satellite laser communication in various countries,described in detail the development history and product technical characteristics of FSM systems at home and abroad,and analyzed the flexible hinge structure in FSM the key role in the flexure hinge and the research progress of flexible hinges.Through the selection and comparison,the research on the mechanical structure of the FSM system with the deep-cut flexure hinge as the deflection part is finally carried out.The research content includes the overall design of the mechanical structure of the FSM system,the derivation,simplification,simulation and experimental verification of the working stiffness of the deep-cut flexure hinge.The derivation of the calculation formula of the vibration shape direction stiffness of the degree of freedom flexible support system,the derivation and simulation verification of the first three-order natural frequency calculation formula of the FSM system,and the multi-objective optimization design of the natural frequency of the FSM system are described as follows:By analyzing the performance requirements of the verification platform of the laser communication laboratory,five main indicators of the FSM system’s reflector diameter,rotation angle range,rotation angle resolution,repeat positioning accuracy and control bandwidth are determined.The mechanical structure of the FSM system is composed of a flexible support system,a mirror,and an isolation plate,and the deflection of the system is realized through the elastic deformation of the flexible hinge.Through the analysis and comparison of commonly used materials,the material usage of the FSM system structure is determined.The whole system is small in size,frictionless and compact in structure.The configuration and performance characteristics of different flexure hinges are compared,the motion performance indicators are analyzed,and the motion performance of a flexure hinge is described by three indicators of motion range,motion accuracy and stress concentration of the flexure hinge.By comparing the performance of different configurations of flexure hinges and combining the performance requirements of the FSM system in this study,it is determined that a deep cut flexure hinge with small stroke and high motion accuracy is used as the deflection component of the FSM system in this study.Then,using the energy method and the second theorem of Karnofsky,the theoretical calculation formula of the working direction stiffness of the deep-cut flexure hinge is deduced,and it is simplified by the method of nonlinear fitting.Finally,the simplified theoretical calculation formula is verified by finite element simulation and experimental testing,which proves that the simplified stiffness calculation formula greatly reduces the complexity of the formula under the premise of ensuring accuracy.The control bandwidth of the FSM depends on the natural frequency of the system.This research adopts the method of reducing the low-order natural frequency in the working direction of the system and increasing the high-order natural frequency in the non-working direction of the system to increase the control bandwidth of the system.The natural frequency of the system is related to the stiffness and load of the system.Therefore,this paper first conducts a modal analysis of the system,obtains the mode direction of the first three-order natural frequencies of the FSM system,and derives the stiffness calculation formula of the first three-order mode direction and the system in the first three-order mode direction.The calculation formula of the moment of inertia finally combines the above two to obtain the calculation formula of the first three-order natural frequency.The theoretical calculation formula of the natural frequency is verified by finite element simulation.Then,the sensitivity analysis of the four structural parameters in the natural frequency is carried out,which proves the rationality and necessity of including the thickness of the mirror into the optimization calculation.Finally,using the NSGA-II algorithm,a multi-objective optimization calculation was performed to find the minimum first and second natural frequencies and the maximum third-order natural frequencies,and the Pareto frontier was obtained,and the research was selected from the Pareto frontier by the relative ranking method.The optimal solution required.Through finite element simulation analysis and comparison,it can be concluded that the optimized structure has decreased-7.8% and-7.11% compared with the first and second order natural frequencies before optimization,and the third order natural frequency has increased by 139.8%,which proves the effectiveness of the optimization calculation.The results of this study can effectively improve the control bandwidth of the FSM system,and provide a theoretical basis and design plan for the development of the FSM system and the research of the matching FSM control system. |
