Recuperation Efficiency and Stability Techniques for Battery Electric Vehicles Janet Maria, B.P. Harish Department of Electrical Engineering, University Visvesvaraya College of Engineering, Bangalore University, Bengaluru. Puneet Jain ESP-AS12, Robert Bosch Engineering and Business Solution, Bengaluru. Abstract— The conventional methodology of hydraulic braking in automobiles results in wastage of energy and exacerbated thermal profile due to the production of unwanted heat during braking. With the advent of electric vehicles, energy efficiency has assumed increased importance due to the constraints of battery capacity and the range of vehicle per charge. Hence, regenerative braking technique is widely used to achieve high energy efficiency. In regenerative mode, the motor acts as a generator and transforms the kinetic energy of the vehicle, upon braking, to electrical energy to restore the batteries or capacitors. To enhance the efficiency of regenerative braking in Battery Electric Vehicles (BEV) and achieve better stability of the vehicle, this work proposes 3 different techniques: Cooperative Regenerative Braking (CRB), Brake Force distribution (BFD) and Electronic Stability Program (ESP). This work details about improving the efficiency of Recuperation or Regenerative braking in BEV with the help of two electric-motors, mounted one on each axle, so that most of the kinetic energy generated while braking is gainfully utilized. It has been demonstrated that the braking efficiency is improved from 62.5% in existing methodologies to 84.66%. The successful implementation of these functional enhancements contribute to a new generation of electric vehicles on the road. Keywords—Recuperation or Regenerative braking, Battery Electric Vehicle (BEV), E-motor, Cooperative Regenerative Braking (CRB), Brake Force distribution (BFD), Electronic Stability Program (ESP), Advanced Simulation and Control Engineering Tool (ASCET) I. INTRODUCTION In conventional vehicles, large part of the kinetic energy is converted, during friction braking, into heat and is emitted into the environment. The regenerative braking system uses an electric motor as a generator and converts much of the kinetic energy lost during braking and this energy is stored in the battery to be used during vehicle acceleration. But all the kinetic energy generated during deceleration cannot be converted using regenerative or recuperation braking [1]. The battery operated electric vehicles with rechargeable batteries have no gasoline engine. Battery electric vehicles store electricity on board with high-capacity battery packs, their battery power is used to run the electric motor and all on board electronics. The BEVs do not emit any harmful emissions and hence hazardous pollution caused by traditional gasoline- powered vehicles can be avoided [2]. A fully electrified regenerative braking system increases the driving range of the vehicle, reduces risk and benefits optimum use of a battery. The regenerative braking system has been improved by the advanced power electronic components such as ultra- capacitor, DC-DC converter (Buck-Boost) and flywheel [3, 4]. In the proposed work, two electric motors or e-motors are used on either axle and performed Brake Force Distribution (BFD) and Cooperative Regenerative Braking (CRB) to improve the regenerative braking efficiency. Further, Electronic stability Program (ESP) technique is deployed to improve the stability of the vehicle. All the three functionalities of Brake Force Distribution (BFD), Cooperative Regenerative Braking (CRB) and Electronic stability Program (ESP) are implemented as a software solution using Advanced Simulation and Control Engineering Tool (ASCET). The rest of the paper is organized as follows: While Section II introduces brake force distribution, Section III presents cooperative regenerative braking. Section IV proposes electronic stability program. Section V presents results and discussion. Section VI concludes with directions to future work. II. BRAKE FORCE DISTRIBUTION When a driver applies the brake, the tyres carrying the least weight or load have more chance to skid and this can happen either by braking in the straight line or braking on cornering. To effectively brake an unevenly weighted car, braking power must be evenly distributed between the front and the rear wheels and is referred to as Brake Force Distribution. Brake force distribution plays a key role in a battery electric vehicle with two e-motors on each axle to improve the efficiency of regenerative braking. In the proposed work, while for brake circuit 1 regeneration process executes on the rear axle and hydraulic process executes on the front axle, for brake circuit 2 regeneration process executes on the front axle and hydraulic process executes on the rear axle. To find Regeneration force at front and rear axle, F FA = Regen FA * Total Regen + Fric FA -------------(1) where, F FA = Force at Front axle, Regen FA = Regeneration force at Front axle, Total Regen = Total regeneration, Fric FA = Friction at Front axle, The total force is given by, F Total = Total Regen + Fric FA + Fric RA -------------(2) where, Fric RA = Friction at Rear axle F FA = BFD FA * F Total -------------(3) where, BFD FA is the part of total brake force which acts at the front axle for any brake force distribution function. Substituting Eq. (1) and Eq. (2) in Eq. (3), Regen FA * Total Regen + Fric FA = BFD FA (Total Regen + Fric FA + Fric RA ) Regen FA = [BFD FA (Total Regen + Fric FA + Fric RA ) - Fric FA ] / Total Regen International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 http://www.ijert.org IJERTV9IS120065 (This work is licensed under a Creative Commons Attribution 4.0 International License.) Published by : www.ijert.org Vol. 9 Issue 12, December-2020 147