A direct yaw moment control (DYC) for energy-efficiency and a DYC for stability of electric vehicles (EVs) are proposed. The DYC for energy-efficiency is active during non-safety-critical cornering manoeuvres to improve the energy-efficiency of EVs. The DYC for stability is active during safety-critical manoeuvres to keep the vehicle stable. A combination of the DYC for energy-efficiency and the DYC for stability is studied. A stability judgement based on the yaw rate and slip angle is designed for evaluating the criticality of the vehicle's working state. A switching principle for alternating between the DYC for energy-efficiency and the DYC for stability is designed. During non-safety-critical cornering manoeuvres, it is shown that the DYC for energy efficiency can save considerable percentage of energy compared to both equal torque driving and the DYC for stability. During cornering manoeuvres containing both non-safety-critical parts and safety-critical parts, the simulation results in this work show that the combination of the DYC for energy-efficiency and the DYC for stability can give 12% to 18% energy savings compared to the DYC for stability only for the vehicle and manoeuvres studied.

An active energy-efficient direct yaw moment control (DYC) for in-wheel motor electric vehicles taking motor efficiency maps into consideration is proposed in this paper. The potential contribution of DYC to energy saving during quasi-steady-state cornering is analysed. The study in this paper has produced promising results which show that DYC can be used to reduce the power consumption while satisfying the same cornering demand. A controller structure that includes a driver model and an offline torque distribution law during continuous driving and cornering is developed. For comparison, the power consumption of stability DYC is also analysed. Simulations for double lane change manoeuvres are performed and driving conditions either with a constant velocity or with longitudinal acceleration are designed to verify the effectiveness of the proposed controller in different driving situations. Under constant velocity cornering, since the total torque demand is not high, two rear wheels are engaged and during cornering it is beneficial to distribute more torque to one wheel to improve energy efficiency. In the simulated driving manoeuvres, up to 10% energy can be saved compared to other control methods. During acceleration in cornering, since the total torque demand is high, it is energy-efficient to use all the four in-wheel motors during cornering.

For sustainability reasons it is important to reduce energy consumption during driving. One contribution to energy savings is by using proper wheel torque distributions during manoeuvring. An active energy-efficient direct yaw moment control (DYC) for electric vehicles has previously been proposed by the authors, taking the motor efficiency map into consideration. The results show a potential for reduced energy losses during driving, but it might result in stability problems during safety-critical maneuvres. In this work, consequences on stability due to this proposed energy efficient DYC is explored. Also an approach combining DYC both energy-efficiency and stability is proposed. The simulation results show that for the studied case the combination of DYC for energy-efficiency and stability can have an potential to both keep the vehicle safe and save considerable percentage of energy during both non safety-critical and safety-critical driving manoeuvres.

As the concerns regarding environmental pollution, climate change and the fossilfuel crisis have grown, electric vehicles (EVs) have attracted a great deal of attention. However, for EVs to be more competitive compared with internal combustion engine vehicles (ICEVs), their driving range needs to be increased. Therefore,energy-efficient control of EVs is considered to be a very important research field.

Electrification of actuators for EVs makes decentralized driving systems possible,such as systems providing individual wheel torque, individual wheel steering andindividual wheel camber control. Electrified vehicle actuators can provide morecontrol possibilities than the normal control of motion in the longitudinal and thelateral direction. EVs equipped with these kinds of actuators are thereby overactuated and more advanced motion controls focusing on energy-efficiency andvehicle directional stability can be realised.

The research objective of the work presented in this doctoral thesis was the exploration of energy-efficient control methods for over-actuated EVs. In order toevaluate the contribution of different control strategies to energy saving, modelsfor energy loss during driving, especially during cornering, were developed. Both alinear tyre model with a camber effect and a non-linear tyre model with a cambereffect were studied. The powertrain efficiency based on a motor efficiency map ofin-wheel motors, was considered.

On the basis of vehicle dynamics with a linear tyre model, camber’s contributionto tyre slip loss reduction during cornering and the corresponding contributionof direct yaw moment control (DYC) when neglecting the powertrain losses werestudied and compared. The results show that camber control can reduce the tyreslip loss significantly and DYC in this case has a small contribution to tyre slip lossreduction. Using a non-linear tyre model, a camber controller based on the lateralacceleration was developed, the effectiveness of this controller was evaluated andthe results show a promising energy saving.

In addition, to investigate the influence of the powertrain losses, a DYC for energyefficiency considering a motor efficiency map was proposed. While satisfying thesame cornering demand, by actively distributing the wheel torques using DYC forenergy-efficiency, the overall energy-efficiency during non-safety-critical manoeuvres could be improved.

Since there might be a higher risk of accidents when applying DYC for energyefficiency in safety-critical manoeuvres, a DYC for safety was developed based ona stability judgement considering the yaw rate and slip angle. To handle this compromise, a switching principle for alternating between DYC for energy-efficiencyand DYC for stability was then proposed. Furthermore, a method for designing arule-based DYC for energy-efficiency was developed to reduce the calculation task and thereby enable real-time implementation.

This research has resulted in an increased understanding of how to improve energyefficiency using different actuators in an over-actuated EV. Different ways in whichover-actuation of EVs can improve the energy-efficiency are presented and analysed in this thesis. Altogether, potential energy loss reductions (up to 22% usingcamber control) for the studied vehicles and manoeuvres have been found usingthe developed methods. Even though the actual improvement will depend on theconsidered vehicle, actuators and driving conditions, the methodology presented inthis thesis can be applied to other vehicles and driving situations.

For sustainability reasons it is important to reduce energyconsumption during driving. One contributionto energysavings is by AQ1using proper wheel torque distributions during manoeuvring. An activeenergy-efficient direct yaw moment control (DYC) for electric vehicleshas previously been proposed by the authors, taking the motor efficiencymap into consideration. The results show a potential for reduced energylosses during driving, but it might result in stabilityproblems duringsafety-critical maneuvres. In this work, consequences on stability dueto this proposed energy efficient DYC is explored. Also an approachcombining DYC both energy-efficiency and stability is proposed. Thesimulation results show that for the studied case the combination ofDYC for energy-efficiency and stability can have an potential to bothkeep the vehicle safe and save considerable percentage of energy duringboth non safety-critical and safety-critical driving manoeuvres.

This paper focuses on the use of camber control and torque vectoring in order to make future vehicles more energy efficient and thereby more environmentally friendly. The energy loss during steady state cornering including rolling resistance loss, aerodynamic loss, longitudinal slip loss and lateral slip loss, is formulated and studied. Camber control, torque vectoring control and a combination of both are compared. From the simulation results, it can be concluded that during steady state cornering, torque vectoring has a very small contribution to energy reduction while camber control can make a significant contribution to energy saving. By combining torque vectoring and camber control during steady state cornering, in theory up to 14% energy saving are found for certain cases.

Actively controlling the camber angle to improve energy efficiency has recently gained interest due to the importance of reducing energy consumption and the driveline electrification trend that makes cost-efficient implementation of actuators possible. To analyse how much energy that can be saved with camber control, the effect of changing the camber angles on the forces and moments of the tyre under different driving conditions should be considered. In this paper, Magic Formula tyre models for combined slip and camber are used for simulation of energy analysis. The components of power loss during cornering are formulated and used to explain the influence that camber angles have on the power loss. For the studied driving paths and the assumed driver model, the simulation results show that active camber control can have considerable influence on power loss during cornering. Different combinations of camber angles are simulated, and a camber control algorithm is proposed and verified in simulation. The results show that the camber controller has very promising application prospects for energy-efficient cornering.