Trajectory Tracking of a Novel Underactuated AUV via Nonsingular Integral Terminal Sliding Mode Control

This paper addresses the 3D trajectory tracking problem of a novel underactuated underwater vehicle with 4 propellers. A 5-DOF kinematic and dynamic model of the quadrotor underwater vehicle (QUV) is established based on the underwater vehicle and quadrotor unmanned aerial vehicle movement mechanism. A double-loop control structure is then developed. By constructing a Lyapunov function for the outer-loop controller, a 5-DOF trajectory tracking error equation and a velocity virtual control law are obtained. The inner-loop controller is built based on nonsingular integral terminal sliding mode control (NITSMC). Finally, the effectiveness and robustness of our control algorithm are demonstrated through numerical simulations. In particular, given a smooth, second-order derivable 3D reference trajectory, the QUV can quickly track the trajectory and satisfactorily converges in the neighborhood of the expected value in a finite time via NTISMC, which verifies its superiority compared with the other popular backstepping control (BSC) method.