Satisfactory Control Strategy For Photoelectric Stabilized Tracking Systems With Target Areas

Photoelectric measuring instruments are the great tools for gaining information in modern warfare. Various kinds of photoelectric devices mounted on mobile vehicles have to take account of the isolation for line-of-sight (LOS) from vehicles'motion, so as to accomplish the precision target tracking, laser aiming, or beam orienting in particular cases. Equipments integrated the above functions are known as the stabilized tracking systems. In this dissertation, a brand-new concept of "target area" was introduced, and the stabilized tracking process was thus divided into two events:target tracking and target losing. Based on this principal, the relevant theoretical and practical issues were deeply analyzed, and the primary work was organized as follows:1. Using rigid body kinematics, the isolating principium of LOS against base turbulence was illuminated from the aspects of angular velocity compensation and angle position compensation respectively, and the auto tracking principle as well as the general considerations of two-axis gimbals was also given. Based on inertia coupling factors, the mathematics models of electro-mechanical system which performs the stabilization and tracking tasks were discussed in detail. The errors and their main origins in photoelectric stabilized tracking systems were outlined, and the structure chart together with transfer function manner were used to analyze the mechanism of these error sources. Following this, the theoretical framework of stabilized tracking control problems with multiple indices constraints was constructed by aid of noise whitening filter.2. The relevant concepts of target area, residence state, exceeding tolerance state, and random passage period frequency were clarified, and on this basis the stabilization and tracking error analysis were extended from conventional spatial domain to time-space domain. The passage characteristics on a certain target area were provided by taken mean value, mean-square deviation and natural frequency as basic elements, and then the tracking interruption probability, a key index of the system was put forward, which was further transformed to a set of probability distribution characteristic indices combined by residence time, exceeding tolerance time, and random passage period time.3. The desired performance indices of stabilized tracking systems were concludes as rapidity index symbolized by regional poles, accuracy index symbolized by dynamic error coefficients or quality factors, precision index symbolized by steady error covariance, robust index symbolized by disturbances rejection H-infinite norm, and the stochastic passage indices symbolized by probability distribution and statistics characteristics. Based on state feedback control and PID control strategy, the stochastic passage characteristic (SPC) indices on zonal target area were deduced respectively, and the consistency between different performance indices was analyzed. When the above indices are consistent, a modified differential evolution (DE) algorithm was utilized together with linear matrix inequality (LMI) method to find out a set of satisfactory optimal parameters for the certain control strategy.4. In light of the actual situation of a photoelectric observation/aiming subsystem in a distributed fire control system, a method for estimating the attitude of aerostat was proposed. A monocular vision system was established by four coplanar reference points on the ground and a double-focus CCD camera in the carrier, and the feasibility and shortage of an analytical algorithm were analyzed. Then a second-order time-correlation model was applied to obtain the state equations of the system, and the fading memory factor was introduced to reform the square-root unscented Kalman Filter (SR-UKF), which was able to restrain the estimating accuracy decline caused by system modeling error.5. Experimental equipments were set up for the photoelectric observation/aiming subsystem based on embedded microprocessor unit, and the hardware modules as well as the software flow chart of the controller design was briefly described. According to the different task requirements, a piecewise control strategy with multi-performance indices constraints was devised. The final physical simulation and field tracking test have validated the chief theoretical achievements of this dissertation.