Dynamic Transition Corridors and Control Strategy of a Rotor-Blown-Wing Tail-Sitter

Abstract

Transition maneuvers are inherent challenges for tail-sitters because of the widely varying flight speed and pitch attitude. This paper investigates the dynamic model, the transition corridors, and the control strategy of a rotor-blown-wing (RBW) tail-sitter. Because the existing equilibrium transition corridor (ETC) cannot reflect system evolution trends of transition flights, a novel dynamic front transition corridor (DFTC) and a novel dynamic back transition corridor (DBTC) are developed. Compared with the ETC, the DFTC and DBTC are governed by dynamic nonequilibrium rules, thus covering transition trajectories more completely. Because excessive large altitude climb should be avoided in transition flights, the developed corridors are then enhanced by a climb velocity constraint. The effects of model mismatches on the enhanced DFTC and DBTC are analyzed. Based on the enhanced DFTC and DBTC, the transition strategy and controller are constructed by extracting typical features of the optimal transition trajectories. The transition robustness is increased by keeping the transition trajectory in the middle of the enhanced DFTC/DBTC. Numerical results indicate that the derived small altitude climb transition is more robust and natural than the constant altitude transition and the large altitude climb transition. Flight test results demonstrate the design principles of the RBW tail-sitter, the transition strategy, and the controller.