Abstract: ObjectiveTo solve the problem of partial failure of the actuator of underwater salvage robot caused by the decrease of shipborne power supply voltage or the corrosion of control system circuit. MethodsConsidering the influence of complex ocean conditions in deep-sea torpedo, cargo shipwreck and other engineering salvage operations, the terminal sliding mode observer is used to observe the uncertain disturbance of the system, and the fault-tolerant control method and finite-time control method are used to estimate the fault coefficient of actuator on-line, a finite-time trajectory tracking fault-tolerant control scheme with terminal sliding mode observer is designed. ResultThe 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 control system is reduced (the lateral displacement is reduced by 10s and the longitudinal displacement is reduced by 15s). ConclusionThis study can provide theoretical reference for trajectory tracking of underwater construction machinery, and has practical engineering significance.