Joint is the key to ensure the safe and stable operation of space manipulator as one of the critical components.For the characteristic of a high failure probability of the drive motor

the fault-tolerant joint is designed against a single motor failure and the detail dynamic model is established for this joint.The nonlinear factors such as clearance and meshing error are taken into account in the model.Base on this model

the anti-torque saturation nonlinear PD control is designed and the closed-loop system is solved by the Precise Integration Algorithm.The simulation results show that the joint can run steadily when the power failure or locked-rotor of either motor and the output torques of both the motor and the joint are kept within the allowable range.