Steering control for path tracking in autonomous vehicles is well documented in the literature. Also, continuous direct yaw moment control, i.e., torque-vectoring, applied to human-driven electric vehicles with multiple motors is extensively researched. However, the combination of both controllers is not yet well understood. This paper analyzes the benefits of torquevectoring in an autonomous electric vehicle, either by integrating the torque-vectoring system in the path tracking controller, or through its separate implementation alongside the steering controller for path tracking. A selection of path tracking controllers is compared in obstacle avoidance tests simulated with an experimentally validated vehicle dynamics model. A genetic optimization is used to select the controller parameters. Simulation results confirm that torque-vectoring is beneficial to autonomous vehicle response. The integrated controllers achieve the best performance if they are tuned for the specific tire-road friction condition. However, they can also cause unstable behavior when they operate in lower friction conditions without any retuning. On the other hand, separate torque-vectoring implementations provide consistently stable cornering response for a wide range of friction conditions. Controllers with preview formulations, or based on appropriate reference paths with respect to the middle line of the available lane, are beneficial to the path tracking performance.

Electric vehicles (EVs) are characterized by a significant variety of possible powertrain configurations, ranging from one to four electric machines, which can have an on-board or in-wheel layout. Multiple models of production EVs have recently been introduced on the market, with 4-wheel-drive (4WD) architectures based on a central motor within each axle, connected to the wheels through a gearbox, a differential, and half-shafts. In parallel, an important body of research and industrial demonstrations have covered the topic of 2-speed transmission systems for EVs, with the target of enhancing longitudinal acceleration and gradeability performance, while increasing the operating efficiency of the electric powertrain. Although several recent studies compare different electric powertrain architectures, to the best of the authors’ knowledge the literature misses a comparison between 2-wheel-drive (2WD) and 4WD configurations for the same EV, from the viewpoint of drivability and energy consumption. This paper targets this gap, by assessing 2WD and 4WD powertrain layouts with central motors, for a case study light passenger car for urban mobility, including consideration of the effect of single- and 2-speed transmission systems. An optimization routine is used to calculate the energy-efficient gear state and/or torque distribution for each considered configuration. For the specific EV, the results highlight the favourable trade-off of the single-speed 4WD layout, capable of reducing the energy consumption during driving cycles by approximately 9% with respect to the conventional 2WD layout with single-speed transmission, while providing satisfactory drivability and good gradeability, especially in low tire–road friction conditions.

No abstract

Purpose The scope of this paper is to present the results of the Project HyTech, which aimed, amongst other objectives, to quantify the environmental and economic effects of generalized introduction and use of electric vehicles in Greece. Method The expected energy consumption and life cycle economic and environmental cost of electric vehicles for the present and immediate future is estimated after a relevant literature review. The future evolution of the Greek vehicle fleet relative to the Gross Domestic Product per capita is approximated by use of a Gompertz curve. The number of new vehicles registered every year, the age composition of the vehicle fleet, the resulting Green House Gas (GHG) emissions and energy use costs are calculated depending on a set of parameters. Choosing different sets of assumptions and calculating the resulting vehicle fleet statistics through year 2030, we investigated a number of scenarios. Results The effect of market penetration by electric and hybrid vehicles and the resulting benefit on energy use cost and GHG emissions, compared to conventional vehicles is presented for each scenario. Fuel consumption and mileage of the vehicle fleet is a major factor that determines energy use cost and GHG emissions, regardless of fleet composition. In the case of an optimistic scenario that assumes a high renewal rate for the vehicle fleet, significant EV and HEV market penetration and use of renewable energy sources for battery recharging, a reduction of 668 kT CO2 in GHG emissions and 362 million € in energy costs per year in 2030 could be achieved.

An extensive literature discusses traction control system designs for electric vehicles. In general, the proposed control structures do not include consideration of the actuation dynamics, which are especially important for vehicles with onboard drivetrains, usually characterized by significant torsional dynamics of the half-shafts. This paper compares the performance of a selection of traction controllers from the literature, with that of PID and ∞ control structures specifically designed for on-board electric drivetrains. The analysis in the frequency domain and the simulation results in the time domain show the significant performance improvement provided by the control system designs considering the actuation dynamics.