Regulators are continually increasing the performance standards required of automobile manufacturers. An example is FMVSS 105 and 121 which define the performance of braking systems and are intended to ensure safe braking performance under normal and emergency conditions for heavy trucks and trailers. A typical change in these regulations is to reduce the distance required to stop the truck under emergency conditions. This can be achieved by designing bigger, heavier, more expensive brakes. Ragnar Ledesma, Principal Engineer for Meritor, took a different approach by addressing the algorithms used to control anti-lock braking systems used in nearly all mediumand heavy-duty trucks.
The simulation showed the proposed control system brings the vehicle to a complete stop in less than 4 seconds in a stopping distance of 177 feet (54 meters), demonstrating a way to meet the requirements of a tougher regulation without major changes to braking hardware. The results show a nearly constant deceleration response at the driver seat as opposed to the cyclical response with conventional ABS braking. The explanation for the improved performance is explained by the simulation results. The wheel angular velocities and tire slip ratios do not fluctuate from their desired values; hence the new ABS control system can sustain maximum braking forces almost over the entire braking cycle.