Fault-tolerant formation control of nonholonomic robots using fast adaptive gain nonsingular terminal sliding mode control

This paper addresses the problem of robust relative motion control in a multirobotic system using the artificial potential field (APF) method for path planning and fast adaptive gain nonsingular terminal sliding mode control (NTSMC) technique for designing a robust controller. A fast adaptive reaching law is also proposed to further improve the speed of convergence. The proposed sliding surface as well as the novel formation error utilizes only the relative position measurements of the follower with respect to the leader. The novel adaptive tuning algorithms are designed for tuning the controller parameters, in such a way that finite-time stability property of the NTSMC is retained. This will help to cope with uncertainties and varying operating conditions. An adaptive fuzzy-based fast reaching law is also proposed as an alternative to reduce the chattering. In the event of any critical system fault, to isolate the faulty robots and to facilitate the formation reconfiguration avoiding the collision between the healthy robots and the faulty ones, we have proposed a fault-tolerant APF module employing the fault parameters. The fault parameters are estimated using a residual-based synchronous fault-detection scheme. The efficacy of the proposed strategy has been validated through rigorous real-time experimentations.