Robust position control design for an electromechanical actuator with time delay

This paper addresses the experimental identification, uncertainty modelling, and robust control design of a real EMA harmonic drive system with time delay. Two approaches were used in the robust controllers design, the first is a novel method based on complex Kharitonov theorem which not only robustly stabilizes the uncertain EMA system with time delay, but also maintains the pre-specified margins and bandwidth constraints. The second controller design is based on H∞ theory. Discrepancies between the linear model and the actual system, due to nonlinearities, were estimated as unstructured multiplicative uncertainty. Simulation and test results prove the superiority of the performance of the designed robust EMA with H∞ controller over the original EMA and robust EMA with Kharitonov´s controller; this preference is pertaining to its robustness to parametric uncertainties and high performance.