Ashwoods Automotive (United Kingdom)

One of the most promising methods to reduce vehicle fuel consumption and CO2 emissions is by using an electric motor in the vehicle powertrain system to assist the internal combustion engine, or propel vehicle by itself. This paper discusses a new potential method to improve axial flux motor performance and efficiency, by dynamically changing the air gap between the rotor and the stator. A series of experiments have provided insight into how certain key characteristics of the variable air gap (VAG) across a wide range of air gap settings. The results show that, on increasing the air gap from the normal 1.2mm to as much as 18mm, the peak torque reduces from 72Nm to 16Nm while the maximum speed of the motor increases from 5500rev/min to over 7000rev/min. It was seen that the high efficiency region moves towards the higher speed region as the air gap increases. Also, on increasing the air gap, the motor had a higher torque output at high speed. This behaviour is of limited benefit in a fixed geometry design, but the implementation of a software controlled air gap design allows the motor characteristics to be varied to suit the prevailing operating conditions. To demonstrate this benefit, the experimental data were used to build a model of the motor with a dynamically variable air gap concept incorporated into it. This model was then used with a fixed ratio powertrain, combined with a simple vehicle model and exercised over the NEDC drive cycle to predict the savings it would achieve when compared to a standard electric motor of similar technical specifications. The model predicts the overall battery energy usage reduced by 0.72% when using a VAG design. In addition, the VAG concept has the potential to reduce gearbox complexity and provide better drivability at higher speeds over the standard motor.

Driver behaviour can strongly affect fuel consumption, and driver training in eco-driving techniques has been shown to reduce fuel consumption by 10% on average. However the effects of this training can be short-lived, so there is an apparent need for continuous monitoring of driver behaviour. This study presents a driver advisory tool which encourages eco-driving, and its evaluation in the field. The system, developed by Ashwoods Automotive Ltd (UK) and the University of Bath (UK), is aimed at fleet operators of light commercial vehicles, where the driver is typically a company employee. A significant strength of the system is that it has been designed for easy integration with the vehicle CAN-bus, reducing complexity and cost. By considering the Inertial Power Surrogate (speed times acceleration) the core algorithm is able to identify behaviour which is likely to increase fuel consumption. The algorithm also enforces the advice of the Gear Shift Indicator to encourage earlier upshifting. Fuel saving is therefore encouraged both by reducing the power demand of the drive cycle and by operating the engine in a more efficient region. Instantaneous visual feedback to the driver is augmented by audible warnings, which avoids the need for the driver to concentrate on the display, reducing cognitive loading. Reports on driver performance are made available to the fleet manager so that fuel efficient and safe driving can be encouraged. Trials of the system ran for four weeks and included 15 vehicles from 7 companies; a total of 39 300 km of trip data were collected during more than 1 100 hours of real world driving. Results show an average fleet reduction in fuel consumption of 7.6%, with some vans showing savings up to 12%. Furthermore, reductions of over 10% in both average engine speed and throttle activation were observed. It was also noted that the system shows strong potential for synergetic use with a hybrid electric powertrain, where modifying driver behaviour may facilitate energy harvesting from regenerative braking.