Research On Feedforward Control For Optical-Electro Tracking System On Moving Platform

With the continuous development of optical-electro tracking equipment,more and more optical-electro tracking systems are applied to the moving platform.In addition,the types and characteristics of tracking targets are also changing,which puts forward higher requirements for the optical-electro tracking system.The two main tasks of target tracking on moving platform are line of sight?LOS?stabilization and target tracking.LOS stabilization need additional inertial sensor,the main engineering in the actual application and based on the classical control theory,divided into based on feedback control method?such as multiple closed-loop technology,etc.?,and a series of feedforward control based on disturbance measure and estimate method?disturbance observer,etc.?,is a key point in the research of the current,is also the precondition of target tracking.Under the condition of LOS stabilization,the performance of target tracking decided the tracking precision of the system.And the performance of the target detector is the main factor affecting the system tracking performance.The traditional feedback control improves the tracking performance mainly by increasing the open loop gain and improve the system type.However,these methods will affect the stability and dynamic performance of the system.Theoretically,the feedforward control is a very effective method to improve the tracking accuracy.However,the target detector of the optical-electro tracking system can only obtain the LOS error between the target position and the LOS,and cannot achieve feedforward control directly in most cases.For optical-electro tracking system installed on the ground,achieving equivalent feedforward through the sensor data fusion and predictive filtering technology acquired more and more application and development.For tracking system on the moving platform,Due to the influence of the additional carrier motion,some method that can be applied on ground tracking is not entirely applicable to moving platform and the related research is not that much,in addition,the validity of the equivalent feedforward method relies on acquisition of the low noise,high SNR of signal.It depends on the accuracy of target information synthesis which is affected by the accuracy of time delay estimation,identification precision of the controlled object model and etc.Therefore,it is of great significance to explore new control methods to improve the target tracking performance of the moving platform photoelectric tracking system.This text applied a feedforward control method which was based on Youla parameterization to the optical-electro tracking system on the moving platform.It combined the LOS error and the output of the controller to generate a feedforward channel which is linked to the original feedback loop.Its sensitive function is the product of sensitive function of traditional feedback loop and 1-Q?s?e^-T₁s,which means that this method turns the problem of designing controller to the problem of optimizing Q filters.A low-pass characteristic of Q?s?can restrain model accuracy which have impact on the system stability.Since this method is efficient for both error suppression and disturbance suppression and it does not rely on the additional sensor characteristics,only uses the LOS error provided by the image sensor,it is also applicable to the optical-electro tracking system on the moving platform.Since the design of feedforward filter Q?s?is very important,this paper optimizes the filter Q?s?to a Q31 low-pass filter.Matlab simulation analysis and experimental verification based on fast mirror system all show that the feedforward control method based on Youla parameterization can effectively improve the tracking performance of the system in the low frequency.When the target motion frequency is below 1Hz,compared with the traditional feedback control,the tracking performance of this method can be improved3-4 times.