The Research Of Optical Axis Stabilization Of The Airborne Photoelectric Platform

High precision airborne photoelectric stabilized platform is mounted on the aircraft pods of photoelectric detection equipment, which has the mechanical structure of the precision and accurate computer control system. Currently it widely used in the field of national defense military for the capture of the air or ground military targets, tracking, and target tasks.However, the optical axis of photoelectric platform may shake even deviate from the goal because of external environment of various disturbances in the process of flight, which seriously affect the image quality of mission objectives.Therefore, how to improve the disturbance rejection capability of the photoelectric platform system is key to improving the accuracy of LOS stabilization and the focus of this study.This paper analyzes the structure and composition of the photoelectric stabilized platform,and then does an in-depth study of the disturbance factors which affecting LOS stabilization.By analyzing the causes and characteristics of electromagnetic torque disturbance in the process of Dc torque motor running,repetitive control strategy is introducted to the photoelectric stabilized platform control system, in order to solve the interference of electromagnetic torque disturbance.Combined with repetitive control strategy and the immunity control strategy, giving full play to the advantages of each control strategy, the photoelectric stabilized platform control system were designed and obtained the satisfactory visual axis stability precision.This article main research content is as follows:1. First analyzes in detail the two axis four frame structure of the stabilized platform and frame connection relationship.Compared to the two axis framework platform structure, the advantages of this structure is explained.And the torque transfer relationship between the frame and shaft coupling relationship is explained in detail. Then analyzes the principle and the method to eliminate noise of the gyro sensor,which is the most important measuring device in the stabilized platform.This paper briefly introduces the working principle of the control system of stabilized platform, this paper provides direction for improving the disturbance rejection capability and designing control system.2. By analyzing the working principle and mathematical model of the key component in the photoelectric stabilized platform,we simplify every frame model using current loop for constant torque output. According to the cause and the mechanism which effecting axis stabilization, the disturbances are devided into models, torque and motor disturbances and so on. The sum effect of these disturbances as an equivalent voltage function simplifies the system model and it also fits the perturbation analysis method in the auto-disturbance-rejection control method.3. When platform run steady speed working state, the electromagnetic wave characterized by periodic disturbance torque, torque by using the traditional controller is difficult to do good inhibitory effect to this kind of periodic disturbance.Repetitive control strategy is developed on the basis of the principle of membrane control method, its characteristic is the system in theory can be done to external periodic reference signals astatic tracking, or completely suppress periodic disturbance.In this paper, the modified repetitive control system, according to two axis four frame platform related the repetitive controller parameters design of low pass filter and dynamic compensator, and its application in the stability control of airborne photoelectric stabilized platform system, well restrain the influence of electromagnetic torque fluctuations.4. Traditional control methods have their limitations. Close analyzing the outcome based on extended state observer(ESO), a fluctuation phenomena arises. It turns out that electromagnetic torque of the motor has a influence on tracking system, furthermore it has an impact on Auto-disturbance- rejection control system’s work. The test in this article runs on the photoelectric stabilized platform control system. By using internal model control strategy the electromagnetic torque of the motor is suppressed.5. Based on ADRC and repetitive controller and combined with traditional controller, photoelectric stabilized platform control system is designed. The speed stability test and target tracking experiment was carried out on the vibration.Compare the designed photoelectric stabilized platform control system with Square hysteresis of traditional control method,which do a research on the disturbance control ability within 1°,3Hz.The experimental results showed that, as the change of disturbance frequency, disturbance isolation degree increased(6.28-16.9)Db with the designed control system which compared with the traditional control method.And the designed control system has strong robustness,which allows the control object parameters change in the range of 15%. Moreover, the designed control system shows superior performance in the reliability experiments such as: high-low-temperature, vibration impact,et..Therefore, the designed photoelectric stabilized platform control system has high practical value in improving visual axis stability precision with Aerial photoelectric stabilized platform control system.