Identification and robust controller design for an electromechanical actuator with time delay

Abstract

This paper addresses the experimental identification, structured and unstructured uncertainty modelling, and robust control design of a real electromechanical actuator (EMA) harmonic drive system with time delay. Two approaches were used in the design of the robust controllers; the first is a novel method based on the 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 H∞ theory-based approach was applied in the second controller design. Furthermore, the discrepancies between the linear model and the actual system, due to non-linearities, were estimated as a multiplicative uncertainty. Experimental results prove the superiority of the performance of the designed robust EMA with an H∞ controller over the original EMA and robust EMA with Kharitonov’s controller; this preference pertains to its robustness to parametric uncertainties and high performance.