High-Security Path Tracking Control for Skid-Equipped Aircraft via Stability Augmentation Skid and Reachability Analysis

Skid landing gear is a particular type of landing device that can effectively satisfy unique aircraft design requirements. However, the mechanical properties of skid are vastly different from those of tire, resulting in poor yaw stability for aircraft equipped with nose wheel and rear skids. The severe issue undermines the practicality of skid landing gear in broader applications. To address this problem, the paper proposes a stability augmentation skid (SAS) and develops a high-security path tracking control. Firstly, the skid with adjustable friction coefficient is designed, and its control model is established through relevant experiments. Subsequently, the boundary protection control of the critical dynamic states of the aircraft is constructed based on reachability analysis, taking into account the limited control inputs and bounded disturbances of the dynamic system. Then, the directional control necessary for the aircraft is established using guidance law and integral sliding mode control. Finally, the path tracking control of excellent security is formed by combining the above two control methods based on a reasonable safety threshold. Simulation results indicate that the proposed skid is an effective actuator for aircraft directional control. Moreover, compared with traditional path tracking control, the developed method can enable the aircraft to safely track the runway centerline under severe initial conditions.