Robust contact force control of an active pantograph via sliding mode controller and sliding mode observer

In this paper, a sliding mode controller together with a sliding mode observer is proposed in order to regulate the contact force robustly in the presence of variation with respect to the equivalent stiffness of the catenary system. The plant model used for the controller design includes flexibility of the actual pantograph. Furthermore, some physical interpretations of the closed-loop dynamics and pole-zero cancellations are given by analysis from a viewpoint of the output zeroing.