An LPV pole-placement approach to friction compensation as an FTC problem

The concept of combining robust fault estimation within a controller system to achieve active Fault Tolerant Control (FTC) has been the subject of considerable interest in the recent literature. The current study is motivated by the need to develop model-based FTC schemes for systems that have no unique equilbria and are therefore difficult to linearise. Linear Parameter Varying (LPV) strategies are well suited to model-based control and fault estimation for such systems. This contribution involves pole-placement within suitable LMI regions, guaranteeing both stability and performance of a multi-fault LPV estimator employed within an FTC structure. The proposed design strategy is illustrated using a non-linear two-link manipulator system with friction forces acting simultaneously at each joint. The friction forces, considered as a special case of actuator faults, are estimated and their effect compensated within a polytope controller system, yielding a robust form of active FTC that is easy to apply to real robot systems.