Comparison of two robust predictive control strategies for trajectory tracking of flexible-joint robots

Two control design approaches are proposed for robust and accurate trajectory tracking of flexible-joint robot manipulators using motor-side measurements only. Within a two-degrees-of-freedom linear controller structure with reference anticipation, the design methods are based either on the Generalized Predictive Control (GPC) or the H_∞ frameworks. In the first case, the approach considers the Youla parametrization of an initial GPC controller, while in the second case, a two-degree-of-freedom H_∞ controller with anticipated reference is synthesized. Experimental evaluation of both methods is performed using the CEA lightweight ASSIST robot arm under rigid model-based compensation, which is modeled as an uncertain system and preliminary identified experimentally. Benefits and drawbacks of both methods are discussed.