Second order sliding mode observers for Fault Detection of robot manipulators

The problem of detecting actuator and sensor faults of a robot manipulator using a model-based Fault Detection (FD) technique is addressed. With the proposed FD scheme it is possible to detect a single fault, which can occur on a specific actuator or on a specific sensor. The proposed scheme is composed by an Unknown Input Observer (UIO) and a modified Generalized Observer Scheme (GOS) to make analytical redundancy. The first enables the actuators FD, while the second enables the FD on the sensors. The Sub-Optimal Second Order Sliding Mode Control (SOSMC) approach is exploited to determine the input laws of the observers. The proposed approach is verified in simulation and experimentally on a COMAU SMART3-S2 robot manipulator.