Model-based optimal auto-transition and control synthesis for tail-sitter UAV KH-Lion

This paper presents a systematic control synthesis method in order to achieve auto-transition for KH-Lion, a tail-sitter hybrid UAV. Although there are huge potentials in various applications of the hybrid tail-sitter UAVs, the transition between vertical take-off and landing mode and cruise mode is still a challenge now. Due to the complex behaviour that the transition can generate, it is very difficult to implement the auto-transition as the reference transition trajectory is hard to obtain. In this paper, we propose to use the model validated from the experiments to generate an optimal reference trajectory for transition. A constrained dynamic programming technique is applied to the model with the consideration of all necessary constraints. A feedback control algorithm is also designed to track the desired transition trajectory. Simulation result and successful flight experiments have demonstrated the effectiveness of the proposed synthesis method.