A fault-tolerant approach to the control of multibody mechanisms with flexible links

In this article a fault-tolerant control technique for flexible-link multibody mechanisms is proposed, and described in detail for the case of a planar four-bar mechanism, lying on a horizontal plane. When no fault occurs, the feedback control law is an adaptive PD controller, which makes use of the crank angle measure provided by an encoder and of the link curvatures provided by two strain gauges. When a fault occurs in one or both strain gauges, a fault detection and identification algorithm allows detecting the faulty device. The faulty signal is then replaced either with a previously stored waveform or with an estimate of the link curvature. The resulting controlled system simple stability is formally proved by means of a model-independent energy-based approach. The controller performances are tested in simulation