This work deals with utilisation of active steering and propulsion on individual wheels in order to improve a vehicle's energy efficiency during a double lane change manoeuvre at moderate speeds. Through numerical optimisation, solutions have been found for how wheel steering angles and propulsion torques should be used in order to minimise the energy consumed by the vehicle travelling through the manoeuvre. The results show that, for the studied vehicle, the energy consumption due to cornering resistance can be reduced by approximately 10% compared to a standard vehicle configuration. Based on the optimisation study, simplified algorithms to control wheel steering angles and propulsion torques that results in more energy efficient cornering are proposed. These algorithms are evaluated in a simulation study that includes a path tracking driver model. Based on a combined rear axle steering and torque vectoring control an improvement of 6–8% of the energy consumption due to cornering was found. The results indicate that in order to improve energy efficiency for a vehicle driving in a non-safety-critical cornering situation the force distribution should be shifted towards the front wheels.

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.

This paper describes a semi-physical tyre model that enables studies of rolling loss in combination with vehicle dynamic simulations. The proposed model, named extended brush tyre model (EBM), takes the effects of driving conditions, wheel alignment, and tyre materials into account. Compared to the basic brush tyre model, EBM includes multiple numbers of lines and bristles as well as integrated rubber elements into the bristles. The force and moment characteristics of the model are shown to have a good correlation with the Magic Formula tyre model and experimental data. The numerically estimated rolling resistance coefficients under different conditions are compared to findings in the literature, FE-simulations and experiments. The model can capture some aspects that are not covered by the available literature and experimental observations such as camber effect on rolling loss. EBM can be used as a platform for future studies of rolling loss optimisation using active chassis control.

This paper presents a test procedure developed to gather good quality data from objective and subjective testing on winter conditions. As the final goal of this test is to analyse the correlation between objective metrics and subjective assessments on winter for steering and handling, this procedure has to ensure a minimum change of the surface properties, which has a major influence on vehicle performance, during the whole test campaign. Therefore, the method presented keeps the total test time very low and allows similar vehicle configurations to be test- ed, objectively and subjectively, very close in time. Moreover, continuous maintenance work on the ice is performed. Reference vehicles are also used to monitor the changes on vehicle per- formance caused by weather conditions, which are inevitable. The method showed to be very effective. Initial results on objective metrics and subjective assessments are also presented. 

Achieving customer satisfaction concerning steering feel and vehicle handling requires subjective assessments and tuning of vehicle components by expert test drivers and engineers. Extensive subjective testing is expensive, time consuming and requires physical vehicles, which is in conflict with reduction of development time and cost. Objective testing and model-based development are constantly increasing but translating subjective requirements into objective ones is non-trivial. This paper summarises, discusses and classifies the methods, strategies and findings in previously published research regarding correlations of subjective assessments and objective metrics for vehicle handling and steering. The aim is twofold: (i) to identify key parameters of steering, handling and their preferred values and (ii) to compile and discuss the fundamental issues to deal with in the continued search for correlations between objective metrics and subjective assessments. The paper gives a comprehensive overview and insight of different aspects to take into account when conducting research in this field.

In this paper we assess the order of model complexity needed to capture a vehicle behaviour during a transient crosswind event, regarding the interaction of the aerodynamic loads and the vehicle dynamic response. The necessity to perform a full dynamic coupling, including feedback in real-time, instead of a static coupling to capture the vehicle performance both with respect to aerodynamics and the vehicle dynamics is evaluated. The computations are performed for a simplified bus model that is exposed to a transient crosswind. The aerodynamic loads are obtained using Detached Eddy Simulation (DES) with the overset mesh technique coupled to a single-track model for the vehicle dynamics including a driver model with three sets of controller parameters to obtain a realistic scenario. Two degrees of freedom are handled by the vehicle dynamics model; lateral translation and yaw motion. The results show that the full dynamic coupling is needed for large yaw angles of the vehicle, where the static coupling over-predicts the aerodynamic loads and in turn the vehicle motion. © 2016 Elsevier Ltd

This paper presents a fault handling strategy for electric vehicles with four individual-wheel drives, which are based on wheel hub motors. The control strategy to handle the faults is based on the principle of control allocation and is implemented in an experimental vehicle. Experimental tests has been performed with the experimental vehicle and with simulation. The results show that the directional stability of such a vehicle can be improved for the analysed manoeuvre and failure mode, and the tendencies of the experimental results correspond with the simulation results. It has been found that the lateral and yaw motion could be strongly improved. 

An experimental field study investigating the impact of single wheel hub motor failures on the dynamic behavior of a vehicle and the corresponding driver reaction is presented in this work. The experiment is performed at urban speeds on a closed off test track. The single wheel hub motor failure is emulated with an auxiliary brake system in a modified electric vehicle. Driver reaction times are derived from the measured data and discussed in their experimental context. The failure is rated and evaluated objectively based on the dynamic behavior of the vehicle. Findings indicate that driver reactions are more apparent for the accelerator pedal compared to the steering wheel response. The controllability evaluation of the vehicle behavior shows that no critical traffic situation occurs for the tested failure conditions. However, even small deviations of the vehicle can impair traffic safety, specifically for other traffic participants like bicyclist and pedestrians.

This paper focuses on increasing the available knowledge about correlations between objective metrics and subjective assessments in steering feel and vehicle handling. Linear and non-linear correlations have been searched for by means of linear regression and neural network training, complemented by different statistical tools. For example, descriptive statistics, the t-distribution and the normal distribution have been used to define the 95% confidence interval for expected subjective assessments and their mean, which makes it possible to predict the subjective rating related to a given objective metric and its area of confidence. Single- and multi-driver correlations have been investigated, as well as how the use of different databases and different vehicle classes affects the results. A method for automatizing the search for correlations when using the driver-by-driver strategy is also explained and evaluated. Ranges of preferred objective metrics for vehicle dynamics have been defined. Vehicles with characteristics within these ranges of values are expected to receive a higher subjective rating when evaluated. Finally, linear correlations between objective metrics have been studied, linear dependency between objective metrics has been identified and its consequences have been presented.