Research Of Three Axis Tracking-pointing Platform Servo Control System

Airborne electro-optical tracking and pointing platform is an airborne target detection equipment that use the photoelectric sensor to search、identify and locate for targets whether on the ground or in the air. Photoelectric tracking &pointing platform as a key part of the inertial navigation and guidance system, its stability and control precision has a great influence on the precision of the whole system. On the one hand, photoelectric tracking and pointing system requires accurate stable institutions; On the other hand, it also requires the tracking system with high precision, so the research on photoelectric tracking-pointing platform has important practical significance and theoretical guidance. Because the complex working environment, serious interference and strong coupling relationship exists among the ring frame, moreover, photoelectric sensor and the delay caused by video tracker can cause a lot of dynamic error and reduce the stability of the system. So several aspects need to be studied in order to improve the performance of photoelectric tracking-pointing control platform, such as enhance robustness of the stability control, anti-interference capability and tracking precision and so on.This paper analyzes the structure of photoelectric tracking &pointing platform of three-axis gimbals, working principle and the dynamic relationship between the rings. Firstly considering coupling and much closer to the actual object situation, derive and write the dynamic equations, set up the precise mathematical model of three-axis gimbals, and then simplify and deform the complex nonlinear term, finally get a suitable mathematical model for controller design. Secondly, don’t consider the coupling and derive the mathematical model of various modules. Lastly,write the corresponding state space equations and get mathematical model of the ring frame.Design a state feedback H?stabilization controller based on linear matrix inequality(LMI) and multiple input system pole assignment controller for stabilization loop, respectively build tracking-pointing platform stability control system based on the designed two different kinds of controller and then do comparative study about the control effect. The simulation results showed that both controllers can realize stable control of the photoelectric tracking-pointing platform and had a certain robust performance. Compared with the complexity of multiple input pole assignment, the design of H? state feedback controller is more simple, the simulation overshoot is more smaller, the time of reaching stability state is also short, have the higher steady precision and response speed, control performance is obviously improved.Design variable universe fuzzy PID controller for tracking loop and choose reasonable scale factors ?and ?, design variable universe fuzzy PID tracking controller under the following two different situations: considering coupling and without considering the coupling of three ring frame, and then compared with general fuzzy PID. Simulation results showed that after joining variable region thoughts the control effect get better compared to fuzzy PID tracking controller. Such as the antiinterference ability of the system is enhanced, steady time get shorter, overshoot volume is decreased and so on. Of course, control performance got improved.In conclusion, the stabilization loop used state feedback H? stability control, tracking loop used the improved method: variable universe fuzzy PID controller with feed-forward added, then the two circuits form closed-loop control system, finally, do simulation and study for the closed loop performance of photoelectric tracking and pointing platform, satisfactory control results have been achieved.