Technology Study Of Unmanned Aircraft Control For Geomagnetic Navigation Tasks

Recent years, due to the continuous improvement of geomagnetic theory, sensor and microprocessor and the increasingly sophisticated navigation algorithm, the geomagnetic navigation technology gained a rapid development,and it has become a hot in the navigation field because of its concealment, low cost, and moderate precision, etc. But there are still three major factors restricting the development and applications of the geomagnetic navigation technology fundamentally, the description precision of geomagnetic field, the detection performance and the navigation algorithms. In terms of the detection performance,there are a variety of sensors with high precision and weak magnetic have been developed,but there is no effective treatment technology for magnetic interference cancellation and error compensation terms. Aeromagnetic compensation technology is a technique to eliminate the magnetic interference. The direction and movement of aircraft flight status will affect the magnetic interference generated by the magnetic material on the aircraft directly. In order to ensure the detection performance of the aircraft, the attitude angle of the aircraft needs to be controlled. Therefore, the study of aircraft attitude control plays an important role in the geomagnetic navigation tasks.The controller design of aircraft control system is very complex because of its serious coupling between channels, its time-varying attitude angle and its uncertain external disturbances. Sliding Mode Variable Structure Control is very suitable for aircraft control system design for its unique advantages, such as the simple algorithm, the non-essential for the precise mathematical model of the controlled object, and the invariance when the system parameter perturbation and external disturbances complied the matching condition completely.However, the existence of "chattering" phenomenon in classic mode variable structure control system resulted great difficulties in the application of spacecraft attitude control system. In order to eliminate the "chattering" phenomenon in classic mode variable structure control system and retain its strong robustness, some scholars have proposed the thinking of high order sliding mode variable structure control (HOSMC). This paper mainly studied the HOSMC and applied it to the spacecraft attitude control system. Main works of the paper are as follows:1. According to the magnetic materials for the aircraft, the magnetic interference model and the causes have been analyzed, the solver for aircraft attitude angle have been studied to make the magnetic interference minimal, and the advantages and disadvantages of the solver methods have been analyzed.2. Aiming at the limitations of existing HOSMC algorithm, such as the algorithms are complex and the controlled object must satisfy some strict conditions, a new reaching condition of second order sliding mode variable structure control system is proposed. And a new design method of second order sliding mode variable structure control algorithm based on the reaching condition is proposed. Under the reaching conditions, the robustness of the control system and the system phase trajectory could asymptotic converge at the sliding mode is proved by constructing Lyapunov function. Combined with the theory of ordinary differential equations, the system phase trajectory is proved converge at the sliding mode in finite time. Then the simulation results demonstrate the correctness and effectiveness of the proposed control algorithm.3. Due to the aircraft motion equations, the aircraft motion is decomposed into three simple subsystem, including the pitching channel subsystem, the yaw channel subsystem and the roll channel subsystem. And The coupling items among three channels is equivalently viewed as external disturbance. When the coupling items among the three channels is bounded, the controllers the three subsystem based on the proposed reaching condition is given separately. Simulation results show that the proposed method is correct and effective,and can eliminate the chattering effectively of the aircraft control system.