Straight-Line Tracking Control of Ships Based on Nonsingular Terminal Sliding Mode Control

The ship straight-line tracking system is restricted by unintegrable second order nonholonomic constraint, so it is underactuated and difficult to control. The control of the ship straight-line tracking was converted to the control of an actuated system by the output variable redefined method. The stabilization of tracking system, which can be ensured by the stabilization of the new system, was proved. A novel nonsingular terminal sliding mode control was presented for the new system. The control method can get finite time convergence and good performance by introducing the nonlinear item into the terminal sliding mode. The serious control chattering occurred because of the discontinuous at the origin. To solve the chattering problem, the saturant function was used to substitute the sign function, which can preserve the good performance of the control method. The simulation validates the control method.