| The aluminum mirrors with complex surface have the advantages of high degree of freedom,light weight,good optical performance,and integrated design of the optical machine.In recent years,it has been widely used in optical systems such as earth observation and high energy laser.However,the mirror surface obtained by the singlepoint diamond cutting technology can only meet the requirements of the infrared optical system,and the traditional polishing method is difficult to fit the polished surface and the unremovable material removal when processing the complex curved surface,resulting in a complex curved aluminum mirror.High-precision machining has become a problem that restricts the development and application of some advanced optical systems.As a deterministic soft body polishing technology,magnetorheological has the advantages of strong adaptability and high processing precision,which can realize the processing of complex curved aluminum mirrors.However,during the magnetorheological polishing process,the oxide film,fine scratches,etc.,may adversely affect the surface quality of the mirror,and this effect increases as the magnetorheological processing time increases.Therefore,in order to obtain high-precision surface shape while reducing the adverse effects on surface quality and subsequent processing,it is the key to explore the technical method of magnetic rheology high-efficiency and high-precision machining of free-form aluminum alloy mirror.Based on the application requirements of high-precision and complex curved aluminum alloy mirrors,this thesis aims to solve the key problems affecting the magnetic rheology and high-precision polishing of complex curved aluminum mirrors,and form a process route based on magnetorheological processing.Technical support for the processing of complex curved aluminum alloy mirrors.The main research work of the thesis includes the following aspects:(1)The influence of the curvature change of complex surface on the magnetorheological removal function is analyzed.The dynamic removal function modeling method from the plane removal function to the spherical removal function to the local removal function of the complex surface is proposed.The mapping relationship between the spherical removal function and the plane removal function under the same processing parameters was established and verified by experiments.Considering the removal of the function size and the local closest spherical fit accuracy,the selection of the projected area size of the fitted area is optimized.Finally,based on the linear equations model,the algorithm for solving the dynamic removal function dwell time is given.(2)Based on the principle of minimum curvature change,the magnetic rheological polishing path of complex curved aluminum mirror is optimized.The criteria and constraints of path optimization are determined.The algorithm principle and calculation steps of path optimization are given in detail.For the problem of slow calculation speed,an optimization strategy is proposed.(3)The causes of the nonlinear distortion of the surface shape error caused by the complex surface aluminum mirror wavefront interferometry are analyzed,and the distortion of the obtained surface shape error is corrected by the tracing method.The process of polishing the aluminum alloy mirror of complex curved surface was summarized and applied on two free-form aluminum alloy mirrors.Finally,the two freeform aluminum mirrors have reached the processing index of the surface error PV value better than 1/3λ,and the rms value is better than 1/20λ,which provides effective support for the conclusion of this paper. |
