Research On Fuzzy PD + Control Algorithm For Spacecraft Attitude

The attitude control system of spacecraft presents the characteristics of strongnonlinear and strong coupling. To meet the requirement of control accuracy and controlperformance for modern space mission, nonlinear PD+is investigated for spacecraftattitude maneuver. This paper modified commonly used constant PD+attitude controllerand three modified PD+controllers are developed by integrating fuzzy control, adaptivecontrol and sliding mode control with the constant PD+attitude controllerFirstly, fuzzy control is adopted to modify the constant PD+attitude controller and afuzzy PD+controller is proposed for the attitude maneuver of spacecraft. The fuzzy PD+controller adjusts the gains of PD+controller online according to the attitude errors andangular velocity errors during the maneuver procedure.Then, adaptive fuzzy control is adopted to modify the constant PD+attitude controllerand an adaptive fuzzy PD+controller is proposed for the attitude maneuver of spacecraft.With the adaptive fuzzy PD+controller, the avoidance of actuator saturation, quickresponse and robustness can be achieved simultaneously. The adaptation mechanism of theadaptive fuzzy PD+controller is designed based on Lyapunov theory to guarantee thestability of closed-loop system. To achieve good performance of the closed-loop systemunder the constraint of actuator saturation, controller parameters optimization is developedon the basis of genetic algorithm.Finally, model reference adaptive integral sliding mode control, which is based on theadaptive fuzzy control, is developed to strengthen the robustness of the attitude controlsystem. A constant controller is designed for the nominal attitude model to obtain goodtransient and steady performance. Then, model reference integral sliding mode controllerfor the practical system with parametric uncertainty and environmental disturbance isdeveloped to make the practical states track the states of nominal system precisely.Simulation results are presented to show the advantage of the modified PD+controllers.