Benchmarking of regenerative braking for a fully electric car

Short range of electric vehicles is one of the stumbling blocks in the way of electric cars to gaining wide user acceptance and becoming a major market player. The possibility to recover vehicle energy otherwise lost as heat during braking is an inherent advantage of a hybrid electric or a fully electric vehicle. Regeneration has the potential to answer this problem by aiding in range extension with recuperation of vehicle energy during braking. The control and dynamics of braking undergoes a major change as compared to a conventional vehicle with friction braking, due to the addition of motor-generator. In this research two regenerative braking concepts namely serial and parallel have been studied and implemented on an electric vehicle. Also a point of interest is to find if any additional states are required from the TNO Vehicle state estimator (VSE) which would aid in regeneration. From the results obtained we try to draw a conclusion on the difference in energy recuperation level in the two strategies with consistent pedal feel in mind. The proposed brake torque distribution strategy has been tested through the simulation on the New European Driving Cycle (NEDC) drive cycle and straight line braking scenario. Care has been taken to observe and adjust brake torque such that wheel lock up is prevented and hence regeneration is un-interrupted. The research couldn’t come with any additional parameters to be added to VSE. However, it would be worthwhile to employ VSE to achieve a more accurate estimation of the braking force, which may aid in prolonging regeneration time and hence more energy recuperation. The results provide a good case to invest more time and money into developing serial regenerative braking as it clearly out-performs parallel regenerative braking strategy. The simulation tests conducted in this research are for a longitudinal braking scenario. Further investigation is required to study effects with lateral motion and cornering maneuvers