A Study On Key Measurement & Control Problems Of Electro-Optical Stabilization Servo Mechanism

Developing with the modern equipments of high technology, Opto-Electronic (O-E) equipments play a more and more important role in reconnaissance, surveillance, orientation, navigation, communication systems. As an essential part of these weapons, the O-E stabilization and tracking systems should gradually been improved accuracy. The dissertation mainly focuses on the following content on O-E stabilization servo system with three-axis gimbal: kinematics, dynamics, signal process of MEMS gyro, fast design technique of servo loop, friction compensation and angular rate estimating.The main work is organized as follows:1. Using the relational methods of spatial mechanism, the author first illuminated the isolating principium of O-E stabilization and tracking platform of three-axis gimbal against the base disturbance, and derived the angular rate and acceleration equations. Based on those equations, the stabilization of direct and strapdown stabilization were analyzed respectively. And then the image characteristic change caused by the motion was derived. From the viewpoint of kinematics, the relationships between the O-E stabilization accuracy and the error of both the rate gyro's installation and the control error were analyzed.2. Based on Newton mechanics, the inertia coupling and dynamic equations of the O-E stabilization and tracking mechanism were analyzed. Then, the single axis servo loop control equation was derived. Following that, the different performances of the direct and strapdown stabilization system were compared from the impact of noise and disturbance. The analysis results showed that the strapdown approach will be faced to more error sources with sensor noise and motion disturbance. The simulation results verified this and indicated that the performance of the strapdown approach would not be as efficient as that of the direct approach.3. Analyzing the principle and error model of MEMS QRS gyro for the purpose of practical applications, the paper presented an autoregressive (AR) model for the gyro signal by means of time series theory. Then,the following conclusions were obtained the noise of rate gyro would cause not only the angular rate dithering which almost having equal quantitative rank to the noise, but also the long time angular drift. Aiming at the limitation of ordinary digital filter methods, Kalman filter based on AR model and the threshold filter according to wavelet were proposed and compared to process and compensate the gyro's signal. The denoising results showed that Kalman filter had the relatively small lag time to the ordinary filters, but( had) the bigger residuary error than wavelet filter.4. The basic problems of angular rate stabilization and position tracking loop of O-E stabilization system were primarily summarized. And the paper concluded that special frequency characteristic between the stabilization and tracking loop, which using rate gyro and angular position sensor respectively as feedback component, namely Low Frequency Position Tracking and High Frequency Rate Stabilizing, which was proved by the following theoretical and HIL (Hardware in the Loop) simulation. Using the tool of dSPACE, a normal method of fast design to the O-E stabilization control system was introduced and realized.5. The friction torque and its impact on the O-E stabilization accuracy were researched in the following part. The results showed that the friction torque existence of dead-zone in the movement caused by friction torque would be a main origin for the high precision O-E system, and in this situation, the servo algorithm generally used would not be so valid. Therefore, the third-harmonic test method was proposed to identify the dead-zone parameter in order to improve the O-E stabilization precision. And an adaptive slide mode controller is presented to compensate the nonlinear friction torque. The simulation results showed that the accuracy was improved. To the problem of the angular rate observing, a combined low acceleration estimation method was proposed so as to further improve the accuracy.6. The hardware configurations of a certain airborne O-E stabilization and tracking servo mechanism were illustrated in the last part. The controllers were designed and tested, and the experiment results showed the validity of the research work.