Benchmarking of regenerative braking for a fully electric car

Abstract

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