A model reference observer for time-delay control and its application to robot trajectory control

This paper addresses the estimation problem of the states and their derivatives for time-delay control (TDC), a robust control technique for nonlinear systems. To this end, an observer design method is presented. In addition, the sufficient conditions are discussed and implementation issues are addressed. Finally, experiments were undertaken on a SCARA-type robot subject to substantial inertia variations and external disturbances. The results showed that the controller/observer performs quite robustly under inertia variations and disturbances and is much less sensitive to sensor noise than the controller using numerical differentiations