| Swing scanning and push scanning are two widely used imaging methods of space remote sensing cameras.Swing scanning can expand the field of view without changing the optical lens.With the exploration of more and more space,the satellite payload has been developing towards the direction of miniaturization.The space real-time monitoring system based on small satellites is a hot research topic at home and abroad,and is widely used in agriculture,meteorology and military fields.The basic conditions of visible light of small satellite in space surveillance constellation are small size,light weight,wide monitoring range and fast maneuvering speed.Therefore,it is necessary to study the two-dimensional scanning mirror mechanism and stable imaging control algorithm suitable for small satellite platform with light weight,compact structure and high pointing accuracy in zero-gravity space environment.In this paper,the lightweight design of two-dimensional scanning mirror and stable imaging control algorithm will be studied:1)Design a two-dimensional scanning mirror that can be used for space imaging.In order to save space and reduce launch cost,a two-dimensional scanning mirror mechanism suitable for small satellite platform was designed,and the lightweight design of the scanning mirror was carried out,including the selection of materials and the initial design of the structure.Then the finite element model of the initial structure was established,with the thickness of the mirror body,the size of the cutting Angle,the thickness of the edge and the thickness of the lightweight reinforcement as the design variables.Multi-objective optimization was carried out with the boundary conditions of surface peak value less than 63 nm and mean root root less than 12 nm.The structural parameters of the scanning mirror were obtained by using the computer optimization algorithm,and the lightweight design of the scanning mirror was completed.The 120-degree circular beam is used as the flexible support,and the integrated design of mirror seat is adopted.After the lightweight design of the component is completed,the space environment of the component is checked.The finite element analysis method is used to verify that all indicators of the statics space environment meet the imaging requirements.Then the finite element dynamic simulation of the scanning mirror component is carried out,including modal analysis and harmonious response analysis,to verify that it can meet the domestic rocket launch frequency.It can resist the impact and vibration of the satellite launching process,and the supporting structure of the component will not occur plastic deformation and fracture damage.The pendulum module has the advantages of simple structure,small size and light weight,which can meet the requirements of optical imaging in space environment,effectively reduce the weight of satellite load,and reduce the moment of inertia of the pendulum module,and reduce the control difficulty of the servo system to a certain extent.After the lightweight design of the two-dimensional scanning mirror assembly is completed,the shafting calculation of the rotating table of the scanning mirror is carried out,the preliminary selection of the servo motor is carried out,and the mathematical modeling and analysis of the pointing error and positioning accuracy of the scanning mirror are carried out,proving that the mechanical error meets the requirements of the index.2)For the designed two-dimensional scanning mirror mechanism,the control algorithm that can be used for imaging is studied.The two dimensional scanning mirror servo control system for space needs not only good dynamic performance and static error,but also strong robustness and anti-interference ability.Therefore,the permanent magnet synchronous motor with good control performance is used to build the three closed-loop servo control system of current-velocity-position.The specific process is as follows:(1)Establish the mathematical model of permanent magnet synchronous motor,adopt vector control algorithm and zero D-axis control strategy.The classical PID control algorithm is used to analyze the time domain and correct the frequency domain of the current-velocity-position three-loop controller from inside out.(2)In view of the errors between the ideal model and the actual model,Stribeck friction torque,noise interference and sudden load torque are introduced to make the model more close to the actual control system,which is called a new hybrid PMSM control system,which provides convenience for later adjustment of controller parameters.(3)In view of the shortcomings of traditional PID control system,such as large overkill,slow response time,large following error,and insufficient robustness and anti-interference ability,nonlinear active disturbance rejection controller is introduced into the speed loop,while PI controller is still used in the current loop.We call it PMSM new hybrid control system based on active disturbance rejection control.It is found that the dynamic performance,steady-state error,robustness and anti-interference ability of the new active disturbance rejection control algorithm are superior to the traditional PID control.3)Designed the hardware circuit of the two-dimensional scanning mirror threeclosed-loop servo system,carried out software development on the built hardware circuit,adjusted parameters,and established the algorithm verification platform.The experimental results show that the dynamic performance,steady-state error,robustness and anti-interference ability of the new hybrid control system based on active disturbance rejection PMSM designed in this paper are superior to the traditional PID control,and meet the requirements of two-dimensional scanning mirror servo control of space remote sensing camera.The mirror component is small in size,light in weight and high in pointing accuracy,which can better meet the space imaging. |
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