Fault-tolerant control of uncertain Stewart platform under loss of actuator effectiveness

A novel fault-tolerant control scheme is proposed for the uncertain Stewart platform under loss of actuator effectiveness. The uncertain friction, parameter estimated errors, unmodeled dynamics, and even the unknown actuator faults are analyzed in the controller design, which are open problems in the uncertain nonlinear system control theory and have not been well treated yet. The control torque is computed by the model-based control theory, and subsequently be renewed by compensating the influences of the uncertainties and disturbances based on time delay control scheme. Finally, the novel fault-tolerant controller is derived to extremely reduce the conservativeness and enhance the tracking accuracy. Numerical simulations in the fault-free and faulty conditions are both analyzed to verify the advantages of the proposed control scheme comparing with the model-based controller. Moreover, the proposed control theory can be employed in other parallel robots with a few modifications.