Controller Design And Study Of Performance Limiting Factors For Fast Steering Mirror

Fast steering mirror system is widely used in many fields because of its fast response and wide frequency bandwidth,such as aerospace,telescope and photoelectric tracking.The performance of FMS needs further improvement at present.FSM is a research hotspot.In this paper,the FSM of practical engineering project is taken as the research object.There are three objectives.First,the control system is designed to meet the expected performance indicators;Second,the performance limit of the system is further studied.At the same time,the factors restricting the performance of the system and their relationship with the system performance are analyzed.Third,we can give some suggestions in order to further improve the system performance.Firstly,the essential non-linear model of the system with noise is established,which is noise model + linear model + non-linear model.The linear partial model of the system is obtained by means of three methods: theoretical analysis,frequency domain tool and artificial identification.For the nonlinear model,the nonlinear model can be simplified to the physical upper and lower limits in order to facilitate analysis and reflect the actual system.The value of the upper and lower limits of the nonlinear parameters are obtained through experimental tests and theoretical calculations.For the noise model,the actual test noise sequence is packaged into a signal source form.The sensitivity of model parameters is analyzed.Aiming at the primary resonance of the system must be wrapped in the closed loop bandwidth and the phase margin is small,an integral notch advanced controller is designed to achieve the desired performance index.The control is not the limiting factor of the system performance.A feedforward controller is designed for tracking the phase lag of 500 Hz sinusoidal signal.The addition of feedforward controller makes the system easy to enter the nonlinear saturation limit,and the nonlinearity is the key factor limiting the performance of the system.Then the ultimate performance of the system is studied.Through theoretical analysis and simulation,it is concluded that the relationship between the bandwidth and the acceleration saturation limit is quadratic function under a certain range of motion.When the saturation limit is fixed,the relationship between bandwidth and motion range is hyperbolic.At the same time,the steady-state accuracy,dynamic index and tracking accuracy of the system in the limit state are analyzed under different motion ranges.It is concluded that the voltage saturation limit is the most important factor limiting the improvement of the system performance.Finally,the robustness of the control system is analyzed.In order to further analyze the factors that limit the performance of the system,the coupling problem is analyzed.Three decoupling control methods are studied.the forms of feedforward compensated decoupling controller and feedback compensated decoupling controller are simplified.the limit capability analysis and time-domain robustness analysis of disturbance observer decoupling controller are carried out.and three decoupling methods are simulated and verified.finally,several decoupling controllers are compared and analyzed.The integral notch advance controller is simulated and digitally realized.The closed-loop experiment verifies the correctness of the design.Finally,the factors that limit the performance of the system and the accuracy index of the system in the limit state are summarized.The method are given for further improvement.