| The Photoelectric tracking stabilized platform taken as “eye of reconnaissance UAV”,is widely used in enemy reconnaissance,target location,forest fire prevention,rescue and other sectors.With the development of UVA,the requirement for detection range and resolution of the measurement equipment on the Photoelectric tracking stabilized platform is increased much further and higher,it puts forward higher requirements for the control stability of Photoelectric tracking stabilized platform.The tracking accuracy and stabilizing accuracy of the O-E stabilized platform directly affects the target image quality of the overall system,as matter of fact,the vibration sources of aircraft itself and external atmospheric turbulence in the process of flight also cause disturbance effects to the platform.So,in order to ensure the LOS of the imaging/tracking system in photoelectric stabilized platform remain stable relative to the inertial space,and isolate the jitter caused by various vibration,there must use anti-disturbance control on the Photoelectric tracking stabilized platform.Based on the project requirements of “Small day and night reconnaissance stabilization platform ”,according to the new requirements for tracking accuracy and resolution,this paper focused on studying the anti-disturbance control technology on two axis four framework based Photoelectric tracking stabilized platform.Firstly,this paper conducted an in-depth investigation and research on the development of control technology of the photoelectric stabilized platform at home and abroad,reviewed the development process of the photoelectric stabilized platform control technology,and then introduced the latest development and performance characteristics of the photoelectric stabilized platform control technology at home and abroad.The control strategy and the ideology of the main components of the system was also introduced.According to the requirement of working environment of the airborne Photoelectric tracking stabilized platform and the performance requirement of the platform photoelectric load,mechanical structure,servo control system,an in-depth analysis of the functional relationship between each payload gimbal moment of inertia and angle variables of each frame was conducted.The mathematic model for each payload gimbal moment of inertia and controlled quantity was established,and the controlled quantity of motor was operated real adjustment,thus provided theoretical support for the boresight of the Photoelectric tracking stabilized platform to maintain the best stabilization precision.Secondly,in order to reduce the influence of the LOS stability accuracy of the platform caused by gyro signal measurement error,Based on the IMU laser gyro signal model,the mathematical expectation,variance,power spectral density and other major statistical characteristics,analyzed the factors that affected the error of tracking measurement,performed predictive filter to the original signal of IMU laser gyro using fading Kalman filter.The simulation results showed that:1.According to the comparison to the gyro original signal curve and the Butterworth filtering curve,the fading Kalman filtering algorithm reach a better effect;2.Through statistical characteristics before and after filtering suggests that fading kalman filtering algorithm can't completely filter out the zero error,but decreased by more than 50% of variance of the signal,and filtering the high frequency noise signal effectively.Thirdly,in order to improve the tracking accuracy of the Photoelectric tracking stabilized platform,using the inertial navigation technology,took the azimuthal angle,pitch angle and laser ranging value of the photoelectric platform as raw information,established the Photoelectric tracking stabilized platform coordinate system,the airborne coordinate system,local geographic coordinate system,geocentric coordinate system and WGS-84 geodetic coordinate system.On the basis of the homogeneous transformation,analyzed and calculated the joint action between the inside corner precision pair and targeting system precision of each coordinate system,and then further worked out the longitude,latitude and altitude information of the objective,thus provided reliable data support for accurate control of angle and tracking precision of the Photoelectric tracking stabilized platform.Finally,in order to improve the LOS stabilization accuracy of the Photoelectric tracking stabilized platform,the paper established the mathematical model of velocity stabilized loop of photoelectric tracking platform,and simplified the model by introducing current loop.Introduced the ideology of general disturbance through the principle of equivalent disturbance action,and came up with an improved control method for boresight stabilization based on ADRC.Designed the ADRC containing reduced-order ESO,excised real-time observation and linear feedforward compensation to general disturbance.The simulation results show that,with the same designed bandwidth,the stabilization time of step response of the ADRC control system was reduced by 32.53% and the overshoot amplitude was reduced by 72.73% compared with the PI control system;when introduced a sinusoidal disturbance with an amplitude of 1° and a frequency of less than 2.5Hz,the disturbance isolation of the ADRC control system gained an increase of 54.67% compared with the PI control system.Then,run a detailed contrast experiment between the traditional PI control system and the ADRC control system designed in this paper.The results verify the theoretical analysis of the control algorithm proposed in this paper,and improves the system disturbance isolation performance effectively,and had great practical value in improving the accuracy of boresight stabilization. |
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