Anti-disturbance control of a quadrotor manipulator with tiltable rotors based on integral sliding mode control

Unmanned aerial vehicle (UAV) manipulator is a promising platform for physical interaction with environments. However, wind disturbances introduce a great challenge to the control of the UAV manipulator and degrade the flight performance of the vehicle. In this paper, an over-actuated quadrotor manipulator with tiltable rotors is proposed to utilize its end-effector to follow a prescribed trajectory in the presence of wind disturbances while transporting objects. Wind forces generated by wind disturbances are imposed on the channel of input of the dynamic equations of the proposed quadrotor manipulator. In a practical case, the bound of wind forces is known. Since integral sliding mode control retains robustness from the initial state in the presence of bounded disturbances and unmodeled uncertainties, a model-based integral sliding mode is designed to assure asymptotical convergence based on the Lyapunov stability analysis. In the process of transporting an object, it is a common task for the end-effector of the quadrotor manipulator system to follow a prescribed 6-DOF trajectory, which may come from a customer's demand or result obtained from path planning with surrounding environment constraints taken into consideration. A simulation with the Dryden model to represent wind disturbances verifies that the proposed integral sliding mode controller can suppress wind disturbances and enhance the flight performance of the quadrotor manipulator.