Low, and now ultra-low, emission zones are becoming common place in Europe, with many major cities implementing measures to help tackle air quality. While new diesel and petrol vehicles do not face penalties, electrification will have a huge role to play, and the technology is now readily available in the passenger and light commercial vehicle markets. This is only the tip of the iceberg.
Global demand for road freight continues to grow and 98% are still powered by diesel. However, British driveline engineering specialist, Drive System Design (DSD), believe they have developed a new approach to the design of electrified powertrains that aims to accelerate their adoption in the commercial vehicle market.
“Optimising the cost and range of a complete powertrain, rather than focusing on individual elements, will enable the development of vehicles that are fine-tuned for nuanced characteristics of different markets,” he continued. “For example, average duty cycle speeds in Europe are far lower than the US, but considerably higher than demanding conditions in India. By matching the powertrain requirements with each market, significant cost savings could be possible without compromising the required operating range.”“Concerns over high initial costs and vehicle range anxiety are the greatest hurdles to adoption of electric vehicle technology,” said Mike Savage, DSD chief engineer. “For example, a suitable battery pack to provide a 200km+ range for a medium duty truck would currently cost around £45,000 and weigh 1.25 tonnes.
DSD has developed optimisation techniques, processes and tools to quantify the impact of various subsystems on the overall powertrain performance using a systems approach. This provides a glimpse of the powertrain’s subsystem relationships and enables analysis of the most influential design considerations. As part of a recent project, the company simulated over 4000 different powertrain permutations to optimise the configuration of a 13-tonne commercial vehicle.
“Using the vehicle’s dynamic requirements and expected operating conditions, hypothetical targets provide a basis from which to calculate necessary power and torque, and vehicle range is determined by calculating the energy consumption during the drive cycle,” explained Savage. “Representative duty cycle and load cases are crucial for true cost optimisation of the powertrain: in this case, inclusion of the effect of gradient changes during a specific drive cycle resulted in a 15% peak power increase requirement.”
Savage suggests that an added benefit of a systems approach is that unexpected or counter-intuitive solutions are often uncovered. The company’s 13-tonne project is a compelling example: “We found that changing to a more expensive, more efficient motor permitted a significant reduction in battery pack size while maintaining desired range,” he said. “The more efficient motor drew less energy from the battery pack, which allowed the use of a reduced capacity unit. Introducing a multi-speed transmission can have a similar result, which can lead to motor downsizing. In each example, the benefit is a lower total cost of the powertrain alongside a weight reduction, which enables a greater payload. Ultimately, this leads to greater fleet operator profitability.”