Design of electrical powertrain for Chalmers Formula Student with focus on 4WD versus RWD and regenerative braking

Sammanfattning: This thesis describes the design of an electric powertrain for a Formula Student race car. The main focus isthe comparison of RWD versus 4WD and to investigate the possibilities to use regenerative braking and torquevectoring. 2014 will be the first time that Chalmers Formula Student team will compete with an electriclypowered vehicle; this thesis gives guidelines for the design.Models of the vehicle dynamics are set up to investigate the differences between RWD and 4WD. From thelongitudinal dynamics model the maximum possible acceleration is calcualted which is of great importance for arace car. This model also sets the requirements for the motors and gearings. The lateral dynamics investigatesthe performance of the car in cornering. The advantages in using a torque vectoring system are studied. Thevertical dynamics models give data about the affect of having higher unsprung mass, which in-wheel motorswill cause.From these models it is evident that major advantages can be gained by using 4WD. More traction, andthus better acceleration, is gained when the tire grip of all four wheels is used. It is also possible to implementa more powerful torque vectoring system when the driving force of all four wheels can be controlled. A torquevectoring algorithm were implemented on a RC-car to be able to evaluate the concept and control algorithms.Calculations on the regenerative braking show how much energy efficiency that can be gained. Thecalculations also show the large benefit of combining 4WD and regenerative braking. The most importantpowertrain components such as batteries, motors, gears and motor controller are investigated. Recommendationsof components types and important design parameters are presented.