Fault Tolerant Control Scheme for Robotic Manipulators Affected by Torque Faults

A Fault Tolerant Control (FTC) scheme for robotic manipulators affected by actuator faults is proposed in this paper. The actuator fault consists in an unknown partial joint torque reduction, which causes a loss of the desired end-effector motion. The FTC scheme includes a Fault Detection and Diagnosis (FDD) system based on a first-order sliding mode observer, in order to detect and estimate the joint torque fault. The estimated fault is mapped into a kinematic deviation of the motion of the end effector from the desired one, and compensated at the level of the kinematic controller. Simulation results demonstrate the effectiveness of the proposed scheme for a planar manipulator affected by two types of actuator faults, namely bias fault and partial torque fault.