Advanced electric vehicle components for long-distance daily trips

This paper introduces a holistic engineering approach for the design of an electric sport utility vehicle focused on the reliable capability of long-distance daily trips. This approach is targeting integration of advanced powertrain and chassis components to achieve energy-efficient driving dynamics through manifold contribution of their improved functions. The powertrain layout of the electric vehicle under discussion is designed for an e-traction axle system including in-wheel motors and the dual inverter. The main elements of the chassis layout are the electro-magnetic suspension and the hybrid brake-by-wire system with electro-hydraulic actuators on the front axle and the electro-mechanical actuators on the rear axle. All the listed powertrain and chassis components are united under an integrated vehicle dynamics and energy management control strategy that is also outlined in the paper. The study is illustrated with the experimental results confirming the achieved high performance on the electric vehicle systems level

Optimal handling characteristics for electric vehicles with torque vectoring.

Torque vectoring by virtue of independent electric motors is the focus of an increasing number of studies as electric vehicles gain prominence as the chosen direction for the automotive industry. Building on active yaw control systems developed over the past decades, torque vectoring benefits from the high-responsiveness and controllability of the electric motor actuator. Furthermore, and especially in the case of vehicles equipped with one independent motor per wheel, the overall performance envelope of the vehicle is significantly improved, as well as the ability to actively shape the vehicle handling. Much attention has been focussed on controller development and control allocation aspects of torque vectoring controllers, but little on the appropriate yaw rate reference. Optimal control studies have been successfully used to mimic the expert driver in both minimum-time circuit racing and high-sideslip rally driving, and can offer insight into how to optimally tune active chassis control systems, such as torque vectoring yaw control. The main aim of this thesis was to investigate the optimal handling characteristics of an electric vehicle with four independent electric motors at the limits of performance. A TV controller was first developed for a prototype sportscar with 4 independent motors, employing a model-based design process that encompassed real-time software in the loop testing. Real-world track testing demonstrated the controller was able to successfully modify the handling characteristic of the vehicle in both understeer and oversteer directions, achieving good controller performance in steady-state and transient manoeuvres. The limit performance of the TV-controlled vehicle was subsequently investigated in the simulation domain. Numerical techniques were used to solve optimal control problems for a single-track vehicle model with linear tyres and an external yaw moment term representing the overall yaw moment arising from the difference in torques at each wheel. For a U-turn manoeuvre, it was shown that torque vectoring significantly lowers manoeuvre time in comparison with the vehicle without TV active, and that modifying the passive understeer gradient does not affect manoeuvre time. The system dynamics were reformulated to include a feedback torque vectoring controller. The target yaw rate reference was varied and it was found that the manoeuvre time was highly sensitive to the yaw rate reference. For minimising laptime, the target understeer gradient should be set to the passive understeer gradient value. The methodology was repeated for a higher fidelity model including nonlinear tyres and lateral load transfer, and found that when the torque vectoring controller was included in the system dynamics, the manoeuvre time showed little sensitivity to the target understeer gradient. Following the contradictory results of the optimal control problems, the vehicle models were investigated next. Time optimal yaw rate gain surfaces were generated from further minimum-time optimal control problems. Open-loop manoeuvres investigating effects of tyre model, lateral load transfer and torque vectoring generation mechanism found that tyre modelling was the dominant differentiator and tyre nonlinearity is an essential modelling consideration. Optimal control techniques have been used for high sideslip manoeuvring for conventional vehicles but no studies have explored the effects of torque vectoring on agility. In the final chapter, an aggressive turn-around manoeuvre was simulated and it was found that torque vectoring can significantly increase agility and reduce the space taken for an aggressive turn-around manoeuvre. Reducing yaw inertia increased agility, as well as increasing longitudinal slips limits. A critique of agility metrics in this context was given.PhD in Transport System

Traction motors for electric vehicles: Maximization of mechanical efficiency – A review

With the accelerating electrification revolution, new challenges and opportunities are yet emerging, despite range anxiety is still one of the biggest obstacles. Battery has been in the spotlight for resolving this problem, but other critical vehicle components such as traction motors are the key to efficient propulsion. Traction motor design involves a multidisciplinary approach, with still significant room for improvement in terms of efficiency. Therefore, this paper provides a comprehensive review of scientific literature looking at various aspects of traction motors to maximize mechanical efficiency for the application to high-performance Battery Electric Vehicles. At first, and overview on the mechanical design of electric motors is presented, focusing on topology selection, efficiency, transmission systems, and vehicle layouts; Special attention is then paid to the thermal management, as it is one of the main aspects that affects the global efficiency of such machines; thirdly, the paper presents a discussion on possible future trends to tackle ongoing challenges and to further enhance the performance of traction motors

Influences of drive torque distribution on road vehicle handling and efficiency

With recent developments in active vehicle drivelines and the trend towards the use of electric propulsion in road vehicles, the optimal way to distribute power in a vehicle has become an interesting area of research. Automobiles with Active Torque Distribution (ATD) capabilities demonstrate improved handling and stability, and there is the possibility that energy consumption could be reduced through better distribution of power. Motorcycles that can apply some of the drive torque at the front wheel exist, with the aim of increasing tractive force on low-friction surfaces. Research is required to investigate the effects of torque distribution on the handling and efficiency of motorcycles and automobiles. In this work, multibody models of both motorcycles and automobiles are created, and are verified with existing mathematical models. The vehicle models include the influences of suspension, aerodynamics and gyroscopic effects, and complex tyre models are used that account for combined lateral and longitudinal slip and the vertical loading situation. Simple driver models are used to control the speed and yaw rate of the vehicles while they undertake a series of on-road manoeuvres. Left–right torque vectoring is shown to be effective in the alteration of the steady-state handling characteristics of the automobile, and front–rear torque vectoring has a small effect at high speeds. A slight increase is possible in transient responsiveness at moderate speeds, but instabilities can be exacerbated at high speeds. In motorcycles, the torque distribution has only a small effect on handling in steady-state situations. During straight-running, the optimum efficiency of the both vehicles is shown to occur when the torque is distributed in proportion with the vertical load at the tyres. During cornering, a slight additional bias towards the front wheel(s) is beneficial. Despite the alteration in handling characteristics made available through ATD, the effects of weight distribution and tyre characteristics still dominate. At normal speeds, almost the same effect on automobile handling can be achieved through left–right torque vectoring in a front- or rear-wheel-drive vehicle, as in a four-wheel-drive vehicle. In these steady-state situations, the energy efficiency of the vehicles varies only by small amounts, with aerodynamic and lateral slip dissipations dominating. The models presented in this thesis, and the results and conclusions obtained from them, offer the designers of future vehicles useful information for the improvement of vehicle handling, efficiency and quality

Influences of drive torque distribution on road vehicle handling and efficiency

With recent developments in active vehicle drivelines and the trend towards the use of electric propulsion in road vehicles, the optimal way to distribute power in a vehicle has become an interesting area of research. Automobiles with Active Torque Distribution (ATD) capabilities demonstrate improved handling and stability, and there is the possibility that energy consumption could be reduced through better distribution of power. Motorcycles that can apply some of the drive torque at the front wheel exist, with the aim of increasing tractive force on low-friction surfaces. Research is required to investigate the effects of torque distribution on the handling and efficiency of motorcycles and automobiles. In this work, multibody models of both motorcycles and automobiles are created, and are verified with existing mathematical models. The vehicle models include the influences of suspension, aerodynamics and gyroscopic effects, and complex tyre models are used that account for combined lateral and longitudinal slip and the vertical loading situation. Simple driver models are used to control the speed and yaw rate of the vehicles while they undertake a series of on-road manoeuvres. Left–right torque vectoring is shown to be effective in the alteration of the steady-state handling characteristics of the automobile, and front–rear torque vectoring has a small effect at high speeds. A slight increase is possible in transient responsiveness at moderate speeds, but instabilities can be exacerbated at high speeds. In motorcycles, the torque distribution has only a small effect on handling in steady-state situations. During straight-running, the optimum efficiency of the both vehicles is shown to occur when the torque is distributed in proportion with the vertical load at the tyres. During cornering, a slight additional bias towards the front wheel(s) is beneficial. Despite the alteration in handling characteristics made available through ATD, the effects of weight distribution and tyre characteristics still dominate. At normal speeds, almost the same effect on automobile handling can be achieved through left–right torque vectoring in a front- or rear-wheel-drive vehicle, as in a four-wheel-drive vehicle. In these steady-state situations, the energy efficiency of the vehicles varies only by small amounts, with aerodynamic and lateral slip dissipations dominating. The models presented in this thesis, and the results and conclusions obtained from them, offer the designers of future vehicles useful information for the improvement of vehicle handling, efficiency and quality

Systematization of integrated motion control of ground vehicles

This paper gives an extended analysis of automotive control systems as components of the integrated motion control (IMC). The cooperation of various chassis and powertrain systems is discussed from a viewpoint of improvement of vehicle performance in relation to longitudinal, lateral, and vertical motion dynamics. The classification of IMC systems is proposed. Particular attention is placed on the architecture and methods of subsystems integration

State Estimation and Control of Active Systems for High Performance Vehicles

In recent days, mechatronic systems are getting integrated in vehicles ever more. While stability and safety systems such as ABS, ESP have pioneered the introduction of such systems in the modern day car, the lowered cost and increased computational power of electronics along with electrification of the various components has fuelled an increase in this trend. The availability of chassis control systems onboard vehicles has been widely studied and exploited for augmenting vehicle stability. At the same time, for the context of high performance and luxury vehicles, chassis control systems offer a vast and untapped potential to improve vehicle handling and the driveability experience. As performance objectives have not been studied very well in the literature, this thesis deals with the problem of control system design for various active chassis control systems with performance as the main objective. A precursor to the control system design is having complete knowledge of the vehicle states, including those such as the vehicle sideslip angle and the vehicle mass, that cannot be measured directly. The first half of the thesis is dedicated to the development of algorithms for the estimation of these variables in a robust manner. While several estimation methods do exist in the literature, there is still some scope of research in terms of the development of estimation algorithms that have been validated on a test track with extensive experimental testing without using research grade sensors. The advantage of the presented algorithms is that they work only with CAN-BUS data coming from the standard vehicle ESP sensor cluster. The algorithms are tested rigorously under all possible conditions to guarantee robustness. The second half of the thesis deals with the design of the control objectives and controllers for the control of an active rear wheel steering system for a high performance supercar and a torque vectoring algorithm for an electric racing vehicle. With the use of an active rear wheel steering, the driver’s confidence in the vehicle improves due a reduction in the lag between the lateral acceleration and the yaw rate, which allows drivers to push the vehicle harder on a racetrack without losing confidence in it. The torque vectoring algorithm controls the motor torques to improve the tire utilisation and increases the net lateral force, which allows professional drivers to set faster lap times

Stability Control of Electric Vehicles with In-wheel Motors

Recently, mostly due to global warming concerns and high oil prices, electric vehicles have attracted a great deal of interest as an elegant solution to environmental and energy problems. In addition to the fact that electric vehicles have no tailpipe emissions and are more efficient than internal combustion engine vehicles, they represent more versatile platforms on which to apply advanced motion control techniques, since motor torque and speed can be generated and controlled quickly and precisely. The chassis control systems developed today are distinguished by the way the individual subsystems work in order to provide vehicle stability and control. However, the optimum driving dynamics can only be achieved when the tire forces on all wheels and in all three directions can be influenced and controlled precisely. This level of control requires that the vehicle is equipped with various chassis control systems that are integrated and networked together. Drive-by-wire electric vehicles with in-wheel motors provide the ideal platform for developing the required control system in such a situation. The focus of this thesis is to develop effective control strategies to improve driving dynamics and safety based on the philosophy of individually monitoring and controlling the tire forces on each wheel. A two-passenger electric all-wheel-drive urban vehicle (AUTO21EV) with four direct-drive in-wheel motors and an active steering system is designed and developed in this work. Based on this platform, an advanced fuzzy slip control system, a genetic fuzzy yaw moment controller, an advanced torque vectoring controller, and a genetic fuzzy active steering controller are developed, and the performance and effectiveness of each is evaluated using some standard test maneuvers. Finally, these control systems are integrated with each other by taking advantage of the strengths of each chassis control system and by distributing the required control effort between the in-wheel motors and the active steering system. The performance and effectiveness of the integrated control approach is evaluated and compared to the individual stability control systems, again based on some predefined standard test maneuvers

Measurement and analysis of rally car dynamics at high attitude angles

This research aims to investigate the nature of high β-angle cornering as seen in rallying and in particular the World Rally Championship. This is achieved through a combination of sensor development, on-car measurement and vehicle dynamic simulation. Through the development of novel β-angle measurement technology it has become possible to measure and study vehicle attitude dynamics on loose gravel surfaces. Using this sensor, an understanding of how a rally driver uses the dynamics of the vehicle and surface to maximise performance has been obtained. By combining the new data stream with accepted vehicle dynamic theory, the tyres have been considered and general trends in gravel tyre performance unveiled. Through feedback, these trends have been implemented as a means of tuning a dynamic model to improve realism and permit an analysis of cornering trends in rally cars. Active control systems have been considered that could implement more sophisticated algorithms based on this understanding and potentially use the new sensor information as an input signal. A case study which explores such a possibility is included