Sensorless Speed Tracking Control for Fault-tolerant Permanent Magnet Motor With Uncertainties in the Ship Shaftless Rim-driven Thruster System

The shaftless rim-driven thruster (RDT) has many attractive features and it would improve the fault-tolerance of RDT to select the fault-tolerant permanent magnet motor (FTPMM) as the propulsion motor. The FTPMM works under severe marine environment and subjects to uncertainty and sensorless conditions. To overcome this problem, a sensorless speed tracking control is proposed for the FTPMM with general uncertainties, e.g. perturbing or time-varying parameters, unknown nonlinearities and bounded disturbances. Based on adaptive nonlinear damping, a robust adaptive observer is constructed to estimate the FTPMM speed. The proposed scheme ensures that all the dynamic signals of the closed system are bounded and it is not needed to estimate the uncertain parameters and disturbances of the system. Furthermore, the estimation errors and the tracking errors can converge to arbitrarily small values by adjusting design parameters. The effectiveness of the proposed scheme is verified by the simulation and experiment results. Furthermore, the stability of the control system and the robustness for the parameter uncertainty and load torque disturbance can be guaranteed.