Adaptive mollified prescribed performance controller for waverider vehicle subjected to mismatched disturbances

Abstract

Considering gliding waverider vehicle is often subjected to mismatched and matched disturbances, designing a strongly robust controller to accurately limit transient performance and ensure high-precision convergence of tracking error is of great significance for flight safety. Therefore, this paper investigates an adaptive mollified prescribed performance controller for waverider vehicle, including an adaptive anti-saturation prescribed performance function, and a mollified fixed-time sliding mode surface. Firstly, a novel adaptive anti-saturation prescribed performance function is designed for waverider vehicle to exactly restrict transient and steady-state performance of attitude, and reduce saturated duration of actuator without anti-saturation compensator. Meanwhile, compared with traditional function, the performance function can adaptively adjust boundary to ensure that tracking error is always enveloped within the performance function, thus avoiding severe singularity caused by error exceeding boundary. Then, a mollified fixed-time sliding mode surface is proposed to effectively suppress mismatched disturbances acting on gliding waverider vehicle, by introducing a novel designed mollified function. The mollified function can smooth sign function, making sliding mode surface continuously differentiable to reduce chattering. Based on the novel performance function, sliding mode surface, and mollified reaching law, the adaptive mollified prescribed performance controller can accurately restrict transient and steady-state performance of waverider vehicle, reduce saturation duration of actuator, and exhibit strong robustness against mismatched and matched disturbances. Finally, numerical simulations demonstrate the effectiveness of the proposed method.