Impact of regenerative braking torque blend-out characteristics on electrified heavy road vehicle braking performance.

Electric and hybrid vehicles use a co-operative brake system that consists of regenerative brake and friction brake with different dynamic characteristics to obtain adequate deceleration during braking. Hence, the mechanism of braking blend-out (that is the mechanism of switching off regenerative braking) may affect the vehicle braking performance. This work focusses on the development of various co-operative braking strategies (series and parallel) for electrified heavy road vehicles by considering instantaneous braking blend-out and ramp down braking blend-out characteristics. The developed co-operative braking strategies were evaluated in a Hardware-in-Loop experimental setup equipped with TruckMaker® software. The results showed that instantaneous braking blend-out has more impact on vehicle braking performance in terms of momentary magnitude change in the longitudinal deceleration, pitch angle and suspension deflection for a laden vehicle compared with an unladen vehicle on both dry and icy road surfaces. Ramp down braking blend-out reduced these momentary magnitude changes and thereby improved vehicle's braking performance in terms of stopping distance and ride comfort. The results of this study indicate that ramp down braking blend-out is expected to improve the vehicle dynamic performance during active braking control due to the smooth transition between friction braking torque and regenerative braking torque. [ABSTRACT FROM AUTHOR]