| A trend for the development of imaging target seeker is its miniaturization,light weight,and high precision.A mirror stabilization platform can adjust the direction of the line of sight(LOS)movement by controlling one or more mirrors in the imaging optical path,and it has several obvious advantages,such as flexible installation and small size,compared with conventional mass stabilization platforms.However,the flexible installation orientation for the mirrors in the imaging optical path makes the LOS movement complicated and variable,making a challenge to designing a high-precision mirror LOS control system.To solve this problem,the mirror LOS movement mechanism,the LOS kinematic and dynamic modeling method,the adaptive robust controller design,and macro-micro dual-stage controller design have been thoroughly studied in this paper.The main work of this paper includes the following parts.(1)The mirror LOS movement mechanism has been carefully analyzed.Firstly,combined with the optical reflection vector theory and the mass stabilization platform LOS movement mechanism,a virtual azimuth-elevation double-gimbaled mass stabilization platform is proposed for the equivalent mirror LOS movement.And a general method for deriving the LOS kinematic equation of the mirror platform is established.This proposed method could be applied to different types of mirror platforms.Secondly,considering the non-linear LOS movement characteristic of the bias axis mirror platform,a virtual three-gimbaled mass stabilization platform is proposed,which maintains a linear relationship between the virtual mass stabilization platform gimbal angle and the mirror platform gimbal angle,thus providing a solution to derive the LOS kinematic and dynamic equations for the bias axis mirror platform.Since,aiming at the non-linear LOS movement characteristic of the bias axis mirror platform,it is further proposed to follow the principle of linear relationship between the mass stabilization platform gimbal angle and the mirror platform gimbal angle,which provides a design guidance for the gimbal assembly selection of the virtual mass stabilization platform,and provides a foundation for the LOS dynamic modeling and control system design of the bias axis mirror platform.(2)In order to better obtain the dynamic characteristics of the mirror platform,it is necessary to identify system dynamic parameters.Firstly,considering the requirements in practical applications,this paper presents a method to identify the dynamic parameters such as the inertia moment and frictional moment under finite-stroke constraints and without torque sensors.Then,focusing on the control problems such as parameter uncertainty,nonlinear disturbance torque and motor saturation,an adaptive robust control strategy is integrated with command filter and extended state observer(ESO).The ESO is used in real-time to compensate for system modeling errors and nonlinear disturbance torque,reducing the conservativeness of the robust controller and improving the control precision.The command filter is used to effectively eliminate the motor saturation effect and ensure system control stability.Finally,the stability of the control system is proved by Lyapunov approach.The proposed control strategy provides an effective path to achieve high-precision LOS control for the bias axis mirror platform.(3)A macro-micro dual-stage control system is introduced into the mirror stabilization platform,adding a high-bandwidth,high-precision micro-control device in the imaging optical path.Since there are dynamic differences between the macro and micro stages,such as control loop bandwidth and working stroke,the stability of the dual-stage system should be considered in the process of controller design.Firstly,a robust H_? control method based on adaptive model compensation is proposed,where an adaptive model compensation method is introduced to online estimate and compensate nonlinear disturbance torques and system parameters to simplify the dual-stage system dynamic model.Then,with the simplified dynamic model,the design difficulty and conservativeness of the robust H_?controller is obviously reduced.The proposed controller can further improve the position tracking accuracy and attenuate the effect of model uncertainty.Finally,the stability of the control system is proved by Lyapunov approach and the H_?tracking performance is guaranteed.(4)The control algorithms proposed in this paper have been verified in experiments.For a practical mirror stabilization platform prototype,the design of software and hardware in the control system had been completed.Performance tests for the mirror stabilization platform prototype were carried out on a five-axis simulation flight turntable.The effectiveness of the designed controller and imaging guiding ability is verified by experimental results. |
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