Hydraulic servoactuator for adaptive force control of fast trains pantographs

Quality of current collection is a critical issue in high speed trains to reduce wear of the sliding surfaces, electrical arcs and electromagnetic interferences. Over the years, several studies were performed and different solutions proposed to improve the quality of current collection. These studies were primarily focused to pantograph kinematics, dynamics of the pantographcatenary system, and estimation of the contact force between pantograph and overhead catenary, while less attention was given to the actuation system developing the control force on the pantograph. A research activity was hence conducted to develop a control and actuation system providing optimum control of the contact force. This was done with specific reference to the pantographs of Alstom high speed tilting trains. The paper first presents an overview of the past work in this field, outlines the characteristics of the pantograph-catenary system and analyses the factors acting as error sources for the force control system: variations of catenary height, uncertainty of the force measurement, signals noise, aerodynamic forces. The paper then describes architecture and characteristics of the force control and actuation system that was eventually defined for attaining the optimum force control; the system uses a combination of adaptive control and hydraulic actuation to obtain an accurate, fast responding and long life system. A dedicated mathematical model was developed and validated for simulating the system performance. The results of the system behaviour over the whole expected range of operating, service and environmental conditions are presented together with a conclusive assessment of its accuracy and robustness