H^∞Control for an Experimental System of the Pantograph with a Linear DC Motor

This paper is concerned with robust H^∞ control for an experimantal system of the pantograph with a Linear DC Motor. Recently higher train speeds have caused various problems such as power supply and aerodynamic noise. One of the approaches to solve these problems is to optimize the overhead wire-panotograph system. The low-noise pantograph is now being researched and developed, and needs active force control to stabilize the current. In this paper, we use a Linear DC Motor (LDM) as an actuator of the pantograph in order to control the contact force between the overhead wiring and the pantograph. An experimental machine has been designed and developed, and has an oscillatory characteristic. We designed the robust force controller for the system in order to improve step response and the frequency-domain performance. At first, the experimental machine and the digital controller of the active pantograph system are introduced. Next, its linearized model is formulated in a state-space form. Then, H^∞ control system using differential game theory in the time domain is designed. Finally, the several experiments are carried out so as to evaluate the control performance of the designs, where the proposed control scheme is compared with the H^∞ mixed sensitivity control.