Line-of-Sight Stabilization Of Opto-electronic Load For UAV

As the eye of unmanned aerial vehicle, line-of-sight stabilization system of opto-electronic load is significant in the task of aerial scouting. It has two main functions, one of them is line-of-sight stabilizing and the other is object tracking. Focus of the system is the control technology of line-of-sight stabilization. As the key device of the system, MEMS inertial device is used for the mini-type UAV because it has a lot of advantages such as tiny volume, low cost, large measurement range, better reliability and easy to be digitalized.Because of the complex aerial environment, it is very important that how efficiently to isolate the shaking and disturbing and realize high accuracy, high reliability, high stability control to the optoelectronic stabilized platform. The traditional control method is based on the hypothesis that all of the parameters are constant, but in fact some of the parameters of controlled object will change such as the gimbal's moment of inertia and the friction moment. It is very important to enhance the system's stabilizing precision and tracking performance by adopting efficient robust control.Firstly, Line-of-sight stabilization system of opto-electronic load for UAV is analyzed and the mathematic model is built. The main problem for system design is analyzed, which includes the hardware and software plan for the system controller, the choosing of stabilizing axis number and scheme, the movement analysis of stabilized axis, the necessity analysis of robust control and the denoising and temperature compensation for MEMS gyro. According the problem of environment temperature influencing on MEMS gyro, A whole temperature range demarcating and compensation method is brought up, the temperature error is compensated after the optimal subsection error compensation model analysis. The test indicates that this method can solve the MEMS gyro temperature compensation problem effectively.Basing on the analysis of uncertain parameters of system model, According to the parameters uncertainty of three-axis line-of-sight stabilization system of opto-electronic load, A Quantitative Feedback Theory method is brought forward to design the robust controller for line-of-sight stabilization system. The QFT model of line-of-sight stabilization system of opto-electronic load for UAV is analyzed, the performance of QFT controller and PID controller is compared. The simulation result indicates that performance of QFT controller is better than PID controller. QFT control method has good robustness, and it can solve the problem of performance decreasing which occurs under the situation of parameters changing in the control system.According the characteristic of multi-input and multi-output for the line-of-sight stabilization system of opto-electronic load, the MIMO Quantitative Feedback Theory control method is studied, A decoupling and simplifying design method is put forward for the QFT controller of MIMO system, which firstly converts the MIMO system control problem to a series of MISO sub-system. Secondly adopts basically noninteracting method to reduce the number of MISO sub-system. Thus the QFT design for MIMO system is simplified and has no effect on the system performance. The analysis result indicates that this method is effective for solving the problem of controller design for MIMO system.Basing on the QFT controller analysis and design, a combined method is put forward which integrate the Quantitative Feedback Method and H∞control method. The difference and relationship between these two methods is analyzed and the detail procedure of integrated controller design is given, The performance result is compared between the QFT controller and the integrated controller, the simulation indicates that this integrated method has more ideal performance than QFT method, it has shorter adjust time and less steady-state error. Not only it is more convenient, but also can it combine the advantages of two kinds of different control methods.Finally the closed-loop simulation for the system is done under the condition of variant parameters, the simulation result indicates that traditional controller has larger overshoot and steady-state error, QFT controller has better robustness performance under the condition of model parameters changing and load disturbing, the more important thing is that QFT controller has shorter adjust time and less overshoot, it can fit the performance request of system effectively.