Optimum Brake Control Via Multi-Mode Shifting of Slip Control Zone

During the railway train braking process, the effective braking takes place in the adhesion region and sliding occurs in the slip region of the adhesion-slip curve. The effectiveness of the braking changes as the friction condition at the wheel-rail interface and speed of the rail vehicle change. The conventional brake control systems do not differentiate these changes in conditions and consider a constant slip reference which limits the use of the maximum available adhesion, resulting in a longer braking distance and time. To overcome this issue, a new control algorithm for a wheel slide protection (WSP) device incorporated in the ECP brake system has been proposed. Unlike conventional controllers, the proposed controller algorithm is responsive to the change of operational and environmental parameters between wheel and rail. It is designed based on multiple modes shifting during operations as the friction conditions change which allows utilisation of the maximum adhesion available and prevents the occurrence of sliding. The control algorithm is developed in a modular approach, where the first module identifies the adhesion condition at the wheel-rail interface and the result from the first module is further implemented in the second module to search for the optimum slip range for that friction condition and vehicle speed. Two different simulations are performed to compare the proposed control algorithm and the conventional algorithm. The simulation result suggests that the proposed control algorithm is able to optimally utilise the available adhesion between wheel and rail to ensure the shortest possible braking distance while maintaining vehicle stability.