Robust Sliding Mode Control for Release of Spacecraft from Maglev Launch Assist

Abstract

Robust flight and launch control laws based on vari able structure control (VSC) and Lyapunov direct method are designed for the transition of an aircraft from a magnetic levitation launcher to free flight. A new aircraft mount, the variable angle of attack (VAOA) mount, is proposed here. The VAOA utilizes the ability to change the aircraft’s angle of attack without changing the aircraft’s control surf aces to achieve lower drag during initial acceleration and smooth transition to free flight, with minimal loss of kinetic energy. A PID control law is developed for the high level magneti c levitation plant and a Sliding Mode Control (SMC) law is derived, for control of the ai rcraft and VAOA with plant uncertainties and input disturbances. A stable sliding mode and r obust asymptotic stability are investigated for both the aircraft and VAOA control laws. Measurable states and sliding surface are chosen for the VSC so that the zero-dyn amics of the system are stable. Simulation results are provided to show the effecti veness of the proposed control design and methods.