Reconfigurable cooperative control of networked lagrangian systems under actuator saturation constraints

Abstract

In this study, a reconfigurable control strategy is proposed for state synchronisation and tracking control of networked (electro-) mechanical Euler–Lagrange (EL) systems that are subject to input saturation constraints that may arise as a result of actuator faults or failures. The reconfigurable controller consists of three main parts. The first part, denoted as the constrained ‘nominal’ controller, is a distributed controller that is employed to guarantee global stability of the multi-agent-networked EL system provided that certain mild connectivity conditions are satisfied in the absence or presence of actuator saturation constraints. The second part, denoted as the constrained ‘reconfigured’ controller, is a non-linear smooth distributed controller that has a different structure and gains from the constrained nominal controller. This controller can preserve the overall control objectives in the presence of actuator faults and actuator saturation constraints. The third part is a switching strategy between the constrained nominal and the constrained reconfigured controllers. Global stability as well as asymptotic convergence of the synchronisation and the tracking errors to origin for switchings under certain conditions between the constrained nominal and the constrained reconfigured controllers with non-vanishing dwell-times for a fixed network topology are shown to be guaranteed. Simulation results of a network of three robotic manipulators are reported to demonstrate and validate the merits of the proposed controllers.