This paper seeks to solve the problem of the partial failure of the actuator of an underwater salvage robot caused by a decrease in the shipborne power supply voltage or corrosion of the control system circuit.

Considering the influence of complex ocean conditions on deep-sea torpedoes, cargo shipwrecks, and other engineering salvage operations, the terminal sliding mode observer is used to observe the uncertain disturbance of the system, while the fault-tolerant control method and finite-time control method are used to estimate the fault coefficient of the actuator on-line, and a finite-time trajectory tracking fault-tolerant control scheme with a terminal sliding mode observer is designed.

The system output of this scheme is smooth, stable, and can reach the desired trajectory quickly. At the same time, compared with the traditional fault-tolerant control scheme, the steady-state time of the underwater salvage robot's control system is reduced (the lateral displacement is reduced by 10 s and the longitudinal displacement by 15 s).

This study has practical engineering significance and can provide theoretical references for the trajectory tracking of underwater construction machinery.