Exploiting over-actuation to reduce tyre energy losses in vehicle manoeuvres

Abstract: Due to environmental and economic challenges road vehicles need bettersolutions to reduce energy consumption. Improvement in tyre rolling e-ciency is one of the key enablers for lower energy consumption. The shifttowards electrication and intelligent driving creates new opportunities todevelop energy-ecient vehicles. For instant over-actuated vehicles whichenables dierent objectives such as safety, performance and energy e-ciency to be fullled during a manoeuvre. The objective of this thesis is todevelop a simulation environment to simulate the energy dissipated fromthe tyre in order to investigate the potential to controlling dierent chassisparameters to reduce rolling losses during driving.The rst part of the thesis is dedicated to develop a high-delity semi-physical non-linear tyre model called the Extended Brush Tyre Model(EBM) to be used for energy studies in vehicle dynamics simulations andlater answer whether it is reasonable to believe that there is any potentialto reduce the rolling loss, and thereby energy consumption, using over-actuation.In the second part of the thesis the benets of over-actuation are invest-igated to enable rolling loss reduction. A control strategy using camber-sideslip control (CSC) is proposed. The allocation problem is solved in the formof an optimisation problem using Dynamics Programming (DP) and ModelPredictive Control (MPC). Exploiting the function for a chosen vehicle ina simulation environment shows a signicant improvement of about 60% inrolling loss reduction while maintaining path tracking. Also by using thisfunction the tyre forces can be distributed more evenly while maintainingthe global force, which results in an increase in the available tyre forcesthat is especially benecial when driving at the limit. It is revealed thatoptimising the vehicle manoeuvre from an energy perspective is sometimesin con ict with the safety demand, thus the energy and safety criteria needto be considered simultaneously during optimisation.Finally, experimental studies using an over-actuated concept vehicleconrmed that the CSC function can reduce overall energy consumptionduring low velocity manoeuvres up to about 13%. By increasing the speed,the saving potential decreases but the contribution is nonetheless of signi-cance. The developed simulation environment, including the EBM, willenable future studies of dierent solutions using over-actuation to reducerolling losses in dierent types of vehicles and driving tasks.