INNER-LOOP DESIGN AND ANALYSIS FOR HYDRAULIC ACTUATORS, WITH AN APPLICATION TO IMPEDANCE CONTROL

The behaviour of manipulators equipped with hydraulic actuators is dom inated by the dynamics of the hydraulics. The aim of an inner/outer-lo op control structure is to mask these hydraulic dynamics with an inner -loop. Constructing the inner-loop by using the inverse of the actuato r dynamics, or by placing the poles of the actuator system, is fundame ntally different. An analysis of these two options concludes that a po le placement is the best choice. First results of an actual implementa tion of a proposed method on an industrial hydraulic drive system show s the practical relevance of this controller.