Development of an electrorheological active buffer for railway vehicles - Estimation of the capacity from prototype performance

This paper is a study on the development of an active buffer for railway vehicles using electrorheological (ER) fluid as a functional material. The coupler force is controlled by adjusting the electric field applied to the ER fluid. A prototype buffer, which consists of a hydraulic cylinder, an ER bypass slit valve and a PID feedback controller, is fabricated. The damping force is developed in the ER valve both through the bypass slit and at the piston-cylinder gap. In the theoretical analysis, it is assumed that the flow of the ER fluid through the bypass slit is the Bingham plastic flow-mode flow while it is in the Newtonian mixed-mode flow in the piston-cylinder gap. The force opposed by the buffer is obtained as a function of the shaft velocity and the electric field applied to the ER fluid. The theoretical results are compared with the experimental results. Further, an active control test using the PID feedback controller is carried out for the problem where the shaft reaction force is retained at a constant prescribed strength while the shaft is translating at a constant velocity. Both results show that the coupler force of the railway vehicle can be controlled effectively by using the proposed electrorheological bypass damper.