Research on digital valve-controlled hydraulic system for active radial control of wheelsets

This paper addresses the issue of excessive heat generation in active radial hydraulic servo control systems by proposing an active radial digital valve-controlled hydraulic system for wheelsets based on the pulse-code modulation (PCM) technique. This approach mitigates heat generation at its source by replacing the servo valve control with high-speed on/off valve-based PCM control, with a focus on the main contributing elements. A mathematical model of the PCM-based digital valve-controlled hydraulic system was derived from an analysis of PCM-based digital valve control principles, and a closed-loop controller design method was developed, which incorporates speed feedforward terms for both position and pressure control. Following simulations on position trajectory tracking control performance, a test stand was built for the PCM-based digital valve-controlled hydraulic system. This experimental setup was then utilized to conduct experiments assessing position trajectory tracking performance and fault conditions for wheelsets on trains negotiating a track section with a curve radius of 250 meters. The results indicate that the proposed system not only achieves precise position trajectory tracking control, but also demonstrate satisfactory fault tolerance performance. The proposed system offers a solution to the system overheating associated with the application of the active radial hydraulic servo control technique on trains.