Advanced Powertrain Design Using Model-Based Design
The use of alternative fuels and advanced powertrain technologies has been increasing over the past few years as vehicle emissions and fuel economy have become prominent in both manufacturer needs and consumer demands. With more hybrids emerging from all automotive manufacturers, the use of computer modeling has quickly taken a lead in the testing of these innovative powertrain designs. Although on-vehicle testing remains an important part of the design process, modeling and simulation is proven to be an invaluable tool that can be applied anywhere from preliminary powertrain design to controller software validation.
The Hybrid Electric Vehicle Team (HEVT) of Virginia Tech is applying for participation in the next Advanced Vehicle Technology Competition. EcoCAR 3 is a new four year competition sponsored by the Department of Energy and General Motors with the intention of promoting sustainable energy in the automotive sector. The goal of the competition is to guide students from universities in North America to create new and innovative technologies to reduce the environmental impact of modern day transportation. EcoCAR 3, like its predecessors, will give students hands-on experience in designing and implementing advanced technologies in a setting similar to that of current production vehicles. The primary goals of the competition are to improve upon a provided conventional, internal combustion engine production vehicle by designing and constructing a powertrain that accomplishes the following:
• Reduce Energy Consumption • Reduce Well-to-Wheel (WTW) Greenhouse Gas (GHG) Emissions • Reduce Criteria Tailpipe Emissions • Maintain Consumer Acceptability in the area of Performance, Utility, and Safety • Meet Energy and Environmental Goals, while considering Cost and Innovation
This paper presents a systematic approach in selecting a powertrain for HEVT to develop in the upcoming competition using model-based design. Using a base set of powertrain component models, several powertrain configurations are modeled and tested to show the progression from a basic conventional vehicle to several advanced hybrid vehicles. Each model is designed to generate energy consumption data, efficiency, emissions, as well as many other parameters that can be used to compare each of the powertrain configurations.
A powertrain design is selected to meet the goals of the competition after exploring many powertrain configurations and energy sources. Three parallel powertrains are discussed to find a combination capable of meeting the target energy consumption and WTW GHG emissions while also meeting all of the performance goals. The first of these powertrains is sized to model a typical belted alternator starter (BAS) system and shows small improvements over a conventional vehicle. The next design is a parallel through the road hybrid that is sized to meet most power needs with an electric motor and a smaller IC engine. This case comes closer to the design goals, but still falls short on total energy consumption. Lastly, the battery and motor size are increased to allow a charge depleting mode, adding stored grid electricity to the energy sources. This electric energy only mode is able to displace a large amount of the fuel energy consumption based on the SAE J1711 method for determining utility factor weighted energy consumption of a plug-in hybrid vehicle. The final design is a Parallel Plug-In Hybrid Electric Vehicle using E85 fuel and a 7 kWh battery to provide an all-electric charge depleting range of 34 km (21 mi).