Kinematic Fault Tolerant Control of a Dual-Arm Robotic System under Torque Faults

A kinematic Fault Tolerant Control (FTC) scheme for a dual-arm system 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 kinematic controller is designed according to the Relative Jacobian method, while a hierarchic prioritized tasks architecture is exploited in order to perform secondary tasks. The FTC scheme includes a Fault Detection and Diagnosis (FDD) system based on first-order sliding mode observers, in order to detect and estimate the joint torque faults on the system. The estimated fault is mapped into a perturbation of the motion of the end effector from the desired one, and compensated at the kinematic controller level. Simulation results demonstrate that the proposed technique allows to reduce the tracking error (both for the absolute and the relative motion) generated by the fault for a dual-arm system composed of two planar manipulators.