Sequence-Constrained Trajectory Planning and Execution for a Quadrotor UAV with Suspended Payload

The paper presents the design of a trajectory planner and feedback control system to autonomously navigate a quadrotor UAV with a suspended payload through a confined environment consisting of horizontal and vertical tunnels. The trajectory planning task is formulated as an optimal control problem and solved by applying an A⁎ search algorithm. A novel sequence-constrained action space is implemented to encourage the use of input shaping actions, which is an open-loop control technique for reducing vibrations in a response. To execute the planned trajectory, a trajectory regulator is designed to work in conjunction with the trajectory planner. The trajectory regulator uses feedback control to provide disturbance rejection and robustness to parameter uncertainty. The planning and execution is verified in simulation, using a system that is constrained to two dimensions. The trajectory planner successfully plans a collision-free path for the quadrotor with suspended payload through an environment with obstacles, tunnels and vertical chimneys. The regulator successfully controls the quadrotor with suspended payload to follow the planned trajectory through the environment, in the presence of external wind disturbances.