Dynamics analysis and control of coaxial high-speed helicopter in transition flight

Abstract

Coaxial high-speed helicopters (CHHs) provide an interesting combination of the vertical takeoff and landing capabilities of helicopters and the efficient forward flight of airplanes. During the transition mode, the employed control laws must be able to handle the changing control authorities, which result from the special aerodynamic layout of coaxial rotors, propeller and aero-surfaces. In this paper, the dynamic characteristics of the CHH in transition mode are analyzed, and a unified Decoupled Allocation Transition Control (DATC) method is proposed to achieve a stable flight and improve the handling quality. The presented control architecture is designed by the explicit model following (EMF) and classical control techniques with a T-S fuzzy model-based parameter scheduling mechanism, in which the actuator saturation is considered. Furthermore, the developed multi-stage control allocations are capable of handling the changing control authorities of actuators, and efficiently distribute the required control actions between coaxial rotors, propeller and aero-surfaces. Thus, the required control authority transition is achieved smoothly. The numerical simulations demonstrate the feasibility and performance of the proposed transition flight control laws, and this method will be eligible for a potential practical implementation to CHH vehicles.