| With the progress of science and technology,the applications of optics in military and civil fields have made important breakthroughs.Especially with the emergence of laser,optics has attracted more and more attentions.In order to meet the application requirements of multipurpose and multi-working conditions,optical systems are extending from a single laboratory environment to more complex application platforms,such as land,sea,air and space.However,the environmental disturbance of different platforms will have an important impact on the optical system,and becomes the key restrictive factor of application and development.Vibration is one of the most prominent environmental factors,which will cause beam jitter and optical axis offset.The propagation distance of the beam is usually long and it is very sensitive to vibration.Therefore,the effective way to improve the engineering application ability of the optical systems is to analyze the influence of environmental vibration on the transmission characteristics and study the optimal design method for improving the dynamic performance of optical mechanical structures based on high precision dynamic model.Optical reflector is an important element in optical system,which can change the direction of beam transmission,reduce the length of optical path and save design space.It is also the carrier of beam transmission,and its dynamic response directly affects the imaging quality and pointing accuracy of the optical system.Based on this background,this paper takes the precision optical reflector as the research object,and carries out some research on the key issues of dynamic analysis and optimization.The main research contents can be summarized as follows:The structural dynamic modeling method of the optical reflector is studied by combing the structural characteristics under different application backgrounds.Aiming at the periodic structural characteristics of optical reflector based on lightweight design,the equivalent model based on homogenization theory is studied.The efficiency of dynamic modeling and analysis is improved by the simplification of complex geometric details.The validation results show that the equivalent model is consistent with the experimental results,and the calculation error is less than 6% compared with the actual model.Aiming at the difficulty of structural dynamic modeling due to the existence of mechanical joints,an equivalent model including clamping joint of mirror and fixed joint of frame is established.At the same time,to overcome the disadvantage that the model parameters of the mechanical joints are difficult to be calculated theoretically,the model updating method of the high power laser mirror is studied to identify the joint parameters based on hierarchical model and step-by-step updating strategy.And the method is validated.An analytical method for beam transmission by considering the elastic deformation of mirror in reflected light path is proposed.Evaluation of optical transmission characteristics is the purpose of structural dynamic analysis in optical systems.As the traditional beam transmission analysis methods mostly adopt the idea of rigid body simplification,the calculation accuracy is poor in the case of severe vibration environment or low stiffness mirror.A method of describing elastic deformation of mirror based on dynamic subsurface partition and low-order Zernike polynomials is proposed.By comparing with the widely used global fitting method,the results show that the proposed method has obvious advantages and high precision surface characterization results can be achieved based on 5 to 10 order Zernike polynomials,which will reduce the dimension of the surface equation and the difficulty of solving.And then the complete beam transmission method is developed.Finally,taking the simple reflected light path and vehicle-mounted laser system as examples,the influence of elastic deformation and structural vibration reduction measures on the transmission accuracy of the optical system is analyzed.In order to improve the dynamic performance of the optical reflector,a topology optimization method considering both the optimization efficiency and the clarity of the topology structure is proposed.Using the idea of fast filtering of inefficient elements and model scale reduction,traditional topology optimization method is improved by a two-step strategy.And the solution of the two-step optimization problem is given.The comparison and validation results through a classic example show that the proposed optimization method has the advantages of traditional topology optimization method and also overcomes the shortcoming that the traditional methods can not take account of both iteration efficiency and topological clarity.A two-dimensional adjustable reflector in a chemical oxyen iodine laser resonator is used as an application example,a spherical restraint mechanism is proposed to improve the connection stiffness of the two-dimensional adjustable structure.Then the two-step topology optimization process for the reflector is studied,and the proposed method is further validated.The structural parametric optimization method of the optical reflector based on surrogate model is studied.The method of constructing dynamic surrogate model based on radial basis function is investigated and the process of parametric optimization is given through specific optimization examples.Firstly,in order to ensure the integrity of the optimal design process as the detailed design parameters of the two-dimensional adjustable resonator reflector can not be obtained by topology optimization,a comprehensive evaluation function is proposed,and the multi-objective parametric optimization method of the adjustable reflector in a chemical oxyen iodine laser resonator is further studied based on topology optimization.The optimization results show that the parametric optimization can not only obtain the structural optimal parameters,but also significantly improves the optimization objectives compared with the results of the topology optimization.Then,for the structure of space mirror,based on homogenization equivalent model,the surrogate based optimization method with structural weight,fundamental frequency and surface error as objecitves is studied.By reducing the calculation scale of the analysis model,the construction speed of the dynamic surrogate model is improved,and the optimal parameters of the honeycomb structure can be obtained more efficiently. |
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