Design and Motion Characteristics Analysis on a Dynamically Reconfigurable Rotorcraft

A dynamically reconfigurable rotorcraft is proposed to solve the problem that the rotorcraft can't pass continuously a narrow space along its path due to its body structure limits. The motion response to the space change is achieved by changing the body structure, and the continuous mobile operation performance of the rotorcraft in a complex environment is improved. The system with a chained modular structure can change its 2D configuration by rotating joints. The kinematic model of the airframe is established according to the structural characteristics and motion control mode, the spatial transformation matrix is derived based on the D-H (Denavit-Hartenberg) rule, and the changed center of gravity is also obtained. A solution method of configuration transformation based on geometric, dynamic and control response constraints is proposed, and the corresponding boundary conditions are derived. The experiments demonstrating flight stability, maneuverability and critical configuration are conducted. The results show that the attitude of the rotorcraft is stable without obvious mutation, and the maximum variations of different axes are all within 4° during the whole configuration transformation. The flight control remains smooth and the tracking control response can be completed in 0.1 s when approaching the critical configuration. The angle set of the critical configuration with controllable attitudes is 180°, 180°, 113° in the experiments. Geometric evaluations show that the passing radius can be reduced by 21.89% in the fixed heading mode, and the maximum passing radius can be reduced by 67% when combining with heading control. The rotorcraft can complete dynamic reconfiguration when passing through a narrow gap.