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.

A failure-sensitive driver model has been developed in the research study presented in this paper. The model is based on measurements of human responses to dierent failure conditions inuencing the vehicle directional stability in a moving-base driving simulator. The measurements were made in a previous experimental study where test subjects were exposed to three sudden failure conditions that required adequate corrective measures to maintain the vehicle control and regain the planned trajectory. A common driver model and a failure-sensitive driver model have been compared, and results for the latter agree well with the measured data. The proposed failure-sensitive driver model is capable of maintaining the vehicle control and regaining the planned trajectory similarly to the way in which humans achieved this during a wheel hub motor failure in one of the rear wheels.

This work deals with how to utilise active suspension on individual vehicle wheels in order to improve the vehicle performance during straight-line braking. Through numerical optimisation, solutions have been found as regards how active suspension should be controlled and coordinated with friction brakes to shorten the braking distance. The results show that, for the studied vehicle, the braking distance can be shortened by more than 1 m when braking from 100 km/h. The applicability of these results is studied by investigating the approach for different vehicle speeds and actuator stroke limitations. It is shown that substantial improvements in the braking distance can also be found for lower velocities, and that the actuator strokes are an important parameter. To investigate the potential of implementing these findings in a real vehicle, a validated detailed vehicle model equipped with active struts is analysed. Simplified control laws, appropriate for on-board implementation and based on knowledge of the optimised solution, are proposed and evaluated. The results show that substantial improvements of the braking ability, and thus safety, can be made using this simplified approach. Particle model simulations have been made to explain the underlying physical mechanisms and limitations of the approach. These results provide valuable guidance on how active suspension can be used to achieve significant improvements in vehicle performance with reasonable complexity and energy consumption.

The improvement in tire rolling efficiency is one of the key elements to optimize the fuel economy and thereby reduce the vehicle emissions. Earlier efforts to reduce the rolling resistance have mainly been focusing on new materials in the tire compounds. The overall research aim of this study is to present the potentials of implementing innovative chassis concepts with the focus on Wheel Corner Modules (WCM) by describing the possibilities in affecting rolling resistance and relating them to previous research findings. The core idea of the concept is to actively control and actuate all degrees of freedom in the wheel i.e. implementing steering, suspension and propulsion functions into a unique module which can be implemented in each corner of the vehicle. Using this concept the limitations of traditional wheel kinematics can be resolved extensively. This article presents the first step towards creating a vehicle simulation model that can show how the WCM functionality can influence the rolling resistance. A model of loss is chosen after analysing the behaviour of a three different rubber models and then implemented into a brush tire model. An effective way, but less complicated compared to current methods, to introduce the loss into tire model is presented. In conventional suspensions, the design is compromising between for example safety, comfort and rolling resistance, etc. at all driving conditions. However, using the WCM, the possibility of achieving a better compromise between those objectives is possible.Finally, based on WCM functionalities a plausible control architecture is proposed. 

The improvement in tire rolling efficiency is one of the key elements to optimize the fuel economy and thereby reduce the vehicle emissions. Earlier efforts to reduce the rolling resistance have mainly been focusing on new materials in the tire compounds. The overall research aim of this study is to present the potentials ofimplementing innovative chassis concepts with the focus on Wheel Corner Modules (WCM) by describing thepossibilities in affecting rolling resistance and relating them to previous research findings. The core idea of theconcept is to actively control and actuate all degrees of freedom in the wheel i.e. implementing steering,suspension and propulsion functions into a unique module which can be implemented in each corner of the vehicle. Using this concept the limitations of traditional wheel kinematics can be resolved extensively. This article presents the first step towards creating a vehicle simulation model that can show how the WCM functionality can influence the rolling resistance. A model of loss is chosen after analysing the behaviour of three different rubber models and then implemented into a brush tire model. An effective way, but less complicatedcompared to current methods, to introduce the loss into tire model is presented. In conventional suspensions, thedesign is compromising between for example safety, comfort and rolling resistance, etc. at all drivingconditions. However, using the WCM, the possibility of achieving a better compromise between those objectivesis possible. Finally, based on WCM functionalities a plausible control architecture is proposed.

This paper presents results on how to optimally negotiate two safety-critical vehicle manoeuvres depending on available actuators and road friction level. The motive for this research has been to provide viable knowledge of limitations of vehicle capability under the presence of environmental preview sensors, such as radar, camera and navigation. An optimal path is in this paper found by optimising the sequence of actuator requests during the two manoeuvres. Particular interest is paid on how the vehicle control strategy depends on friction. This work shows that actuation of forces and torques on and around the vehicle centre of gravity are all approximately scaled with the friction coefficient. However, this pattern is not valid at a wheel individual level, i.e. the optimal force allocation among the wheels differs under different friction conditions. One key is that lower friction level yields lower load transfer which substantially influences the wheel individual tyre force constraints.

The aim of this study is to evaluate optimal active camber strategies for improvement of vehicle performance and safety during limit handling. Numerical optimisation is used to find solutions on how the active camber should be controlled and coordinated in cooperation with individual braking and front axle steering. Based on the characteristics of a multi-line brush tyre model, a Simple Magic Formula description is developed where camber dependency, load sensitivity and first order speed dependent relaxation dynamics are included. The vehicle is analysed during an evasive manoeuvre when the vehicle is running at the limit. It is evident from the results that active camber control can improve safety and performance during an avoidance manoeuvre.

The implementation of wheel corner modules on vehicles creates new possibilities of controlling wheel forces through the utilisation of multiple actuators and wheel motors. Thereby new solutions for improved handling and safety can be developed. In this paper, the control architecture and the implementation of wheel slip and chassis controllers on a down-scaled prototype vehicle are presented and analysed. A simple, cost-effective force allocation algorithm is described, implemented and evaluated in simulations and experiments. Straight line braking tests were performed for the three different controller settings individual anti-lock brakes (ABS), yaw-torque-compensated ABS and force allocation using both wheel torque and steering angle control at each wheel. The results show that force allocation is possible to use in a real vehicle, and will enhance the performance and stability even at a very basic level, utilising very few sensors with only the actual braking forces as feedback to the chassis controller.

This paper presents a fault handling strategy for electric vehicles with in-wheel motors. The ap-plied control algorithm is based on tyre-force allocation. One complex tyre-force allocation meth-od, which requires non-linear optimization, as well as a simpler tyre force allocation method are developed and applied. A comparison between them is conducted and evaluated against a standard reference vehicle with an Electronic Stability Control (ESC) algorithm. The faults in consideration are electrical faults that can arise in in-wheel motors of permanent-magnet type. The results show for both tyre-force allocation methods an improved re-allocation after a severe fault and thus re-sults in an improved state trajectory recovery. Thereby the proposed fault handling strategy be-comes an important component to improve system dependability and secure vehicle safety.

This paper presents results on how to optimally utilise vertical loading on individual wheels in order to improve vehicle performance during limit handling. Numerical optimisation has been used to find solutions on how the active suspension should be controlled and coordinated together with friction brakes and electric power assisted steering (EPAS). Firstly, it is investigated whether the brake distance can be shortened. Secondly, the performance during an evasive manoeuvre is investigated. The result shows that brake distance can be improved by at least 0.5 m and the speed through the evasive manoeuvre by roughly 1 km/h for the studied vehicle. Quick actuators is shown to give even better performance. These results provide guidance on how active suspension can be used to give significant improvements in vehicle performance.