Skidding at the wheel/rail interface under certain adherence conditions offsets the gains obtained in reducing braking distances through increased braking power. Thus, an Wheel Slide Protection system (WSP) needed to be developed to contain braking distances while preventing damage to wheel surfaces caused by locking.
The proposed WSP does not require the fitting of new sensors and detects skidding via the new “marginal locking time” (estimated time to the wheel locking) indicator obtained from speed data (Fig 1). This new indicator was applied in conjunction with an existing wheel slip prevention system and a new wheel skid control method was proposed which acts by releasing Brake Cylinder (BC) pressure. In tests where the system was applied to only 3 coaches out of a total 7 in a train consist, results showed that deceleration was increased by approximately 7% (Fig 2).
The new indicator can be combined with the majority of existing skid control systems. Furthermore, wheel lock prevention performance under this new method remains at the same level as with existing systems even when slipping frequency grows and skidding occurs on all wheelsets.