Research On Anti-interference Control Technology Of Optoelectronic Tracking System Under Moving Platform

With the expansion of the application fields of the optoelectronic tracking system,it is expected that the optoelectronic tracking system has flexibility and maneuverability,so that stable tracking can be achieved no matter what kind of motion platform.The technical challenges faced by optoelectronic tracking systems under moving platforms are greater than traditional ground-based optoelectronic devices.Since the maneuvering of the moving carrier and the environmental vibration will seriously affect the stability of the line-of-sight(LOS)of the system,the anti-interference technology of the optoelectronic tracking system is vital.In this paper,aiming at the problems faced by the execution structure of the optoelectronic tracking system such as the gimbal and the precision stable platform in the realization of the LOS,the proposed design method of the disturbance observer based on the H? principle,the three closed-loop control based on virtual velocity,an improved Smith predictor,the compound stable platform and control method were analyzed respectively.Through experimental verification,the performance effects of the proposed method are analyzed.Firstly,the working principle of the optoelectronic tracking system is introduced,and the processing methods of stability and tracking are analyzed.By establishing the coordinate system of the optoelectronic tracking platform,the disturbance compensation equation for realizing the LOS stability is derived,and the two installation methods of the inertial gyro are explained based on the disturbance compensation equation.Secondly,the composite axis control structure of the optoelectronic tracking system is analyzed,and the mathematical model of the gimbal and the precision stable platform are respectively performed.Because the stability of the system's boresight depends on the system's ability to suppress disturbances.For any servo system,the disturbance suppression capability of system is composed of active suppression capability and passive suppression capability.The performance of the active suppression capability depends on the characteristics of the controlled object,the inertial sensor and the control algorithm.The passive suppression capability depends on the mechanical isolation characteristics of platform.This paper starts the research of stability control technology from two aspects of active suppression and passive suppression.A design method of disturbance observer based on H? principle is proposed.The disturbance observer is used to observe the external disturbance and feed forward compensation to improve the disturbance suppression ability of the gimbal system.However,the nonlinear characteristics of the controlled object in the gimbal will affect the stability of the disturbance observer.In this paper,H? control theory is used to analyze the optimization equation of the Q filter design of the disturbance observer to ensure the stability of the disturbance observer.Because this optimization equation is a non-standard H? optimization equation type,it is difficult to solve.Therefore,the calculation steps of converting non-standard optimization equations into optimization equations are further theoretically derived and analyzed.In order to verify the control performance of the algorithm,an experimental verification was performed on the pod experimental platform.The experiments show that the disturbance observer is stable and can increase the perturbation capability at 1Hz by-11.22 d B when the pod has obvious friction nonlinear characteristics.In order to meet the needs for lightweight and miniaturization of precision stable platforms,from the perspective of reducing the number of sensors and saving costs,the stability requirements of the system are taken into account.A three-closed-loop control method based on a virtual velocity loop is proposed.The MEMS linear accelerometer with low price,small size,light weight and wide measurement bandwidth is used to estimate the angular velocity signal of the platform.The basic principle of digital integration of signals was deduced,and a periodic virtual initial velocity correction method was designed to eliminate the effects of accumulated errors during the integration process.The experimental results show that the virtual velocity signal can replace the use of gyro in the low-frequency domain,and achieve the approximate characterization of the velocity information.And using the virtual velocity signal as the velocity feedback signal to achieve a three closed-loop control system,verifying the feasibility of the method.Considering the limitation of the delay to the closed-loop bandwidth,an improved Smith predictor compensation method is proposed.By comparing and analyzing the control structure and compensation principle of Smith predictor,internal model control and disturbance observer,the design ideas of disturbance observation and compensation are introduced into the traditional Smith predictor,and an improved Smith predictor is obtained.The theoretical analysis of the improved Smith predictor shows that this method can not only improve the influence of the gyro signal lag on the velocity loop,but also improve the disturbance rejection ratio of the system in the low-frequency domain.Finally,the effectiveness of the improved Smith predictor algorithm is verified in the stability control experiment based on the precision stable platform.Aiming at the problem of insufficient high-frequency vibration isolation capability of the precision stable platform,a compound stable platform structure was proposed.Starting from the analysis of the passive isolation characteristics of the single-stage precision stable platform and the dynamic equations in the closed-loop,it is pointed out that reducing the platform stiffness coefficient and improving the passive isolation capability have created limitations on the system's active stable bandwidth design.Therefore,the passive isolation characteristics of the composite platform,the dynamic equations of the primary stable platform and the dynamic equations of the secondary stable platform are modeled and analyzed.A model-based robust controller design method is proposed for the uncertain problem of the secondary stable platform in the closed-loop design process.Further,a corresponding composite stability experimental verification platform is set up.The final experimental results show that the compound stable platform can greatly improve the system's disturbance rejection ability in the whole frequency band.