Nonlinear PD Fault-Tolerant Control for Dynamic Positioning of Ships With Actuator Constraints

This paper addresses the asymptotic dynamic positioning of ships in the presence of actuator constraints and partial loss of actuator effectiveness faults. A simple saturated proportional-derivative controller is proposed. Lyapunov direct method is employed to prove asymptotic stability. Explicit conditions on control gains for ensuring asymptotic stability are presented. Advantages of the proposed controller include simple and intuitive structure, high computation efficiency, and absence of modeling parameter and fault detection and isolation mechanism in the control law formulation, and thus it is ready to implement. An additive appealing feature is that the proposed controller has the abilities to protect the actuator from control effort saturation and compensate the partial loss of actuator effectiveness faults. An illustrative example is presented to demonstrate the effectiveness of the proposed approach.