The UW EcoCAR2 Vehicle Development Process and Vehicle Level Torque Control Strategy Documentation
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The transportation sector accounts for 28% of total US energy consumption, and 93% of this energy comes from petroleum resources (Energy Information Administration, 2014). If the effect of energy use for the transportation industry go unchecked, the associated emissions represent one of the biggest threats to our global environment. To reduce energy consumption used by transportation simply by traveling less or shipping less goods would hinder commerce and slow economic growth. It becomes important then to find an engineering solution to the environmental impacts of personal transportation in order to allow commerce and economic growth to continue uninhibited. The EcoCAR2 competition is a three year long collegiate level automotive engineering competition in which fifteen universities across North America to reduce the environmental impact of personal automobiles without sacrificing the consumer acceptability of the vehicle (Argonne National Labratories, 2014). It is the first competition of its kind designed to create automotive technology that can penetrate the mass market and have significant and lasting environmental impact reductions. The technical goals allow for modifications to the power train of the vehicle and control strategy innovations to reduce greenhouse gas emissions, criteria emissions, petroleum energy consumption, and total energy consumption. The phrase "electrified vehicle" includes mild Hybrid Electric Vehicle (HEV), strong HEV, Plug-in Hybrid Electric Vehicle (PHEV), and fully electric vehicles (EV). These types of vehicle powertrains are one technology that can potentially improve upon all of the technical goals of EcoCAR2. The stronger the electrification of a vehicle, the better the improvement upon the competition's four main technical goals. However, with stronger electrification typically comes higher cost and increased emissions, both mostly due to the high voltage battery pack that is typically a NiMh (small capacity) or lithium chemistry. There are very few additional technologies that universally improve upon all of these criteria without causing detrimental effects on consumer acceptability. Hybrid vehicles consist of two or more torque producing components, typically an electric motor and a petroleum internal combustion engine. The driver interface for hybrid vehicles, however, still only has a single accelerator pedal. There is a need for a supervisory control strategy that controls the torque output of each component. This supervisory control strategy is responsible for commanding the vehicle drivetrain as a system to match the driver's intended torque demand, while optimizing to minimize emissions and energy consumption. This thesis outlines the vehicle development process utilized by the University of Washington EcoCAR2 team over all three years of the EcoCAR2 competition. The UWEC2 team came up with a Parallel Through the Road (PTTR) PHEV that can operate as an EV for the first 50 miles after being charged off of the grid. This very heavy reliance on grid electricity for propulsion addresses all four of the primary technical goals of the competition. Once the battery pack is depleted, the vehicle will turn on a 1.7L turbo diesel engine operating on B20 to drive the vehicle as a HEV for the following 350 miles in a charge-sustaining fashion. Biodiesel will reduce the criteria emissions and petroleum energy consumption of the charge-sustaining mode. These modes of operation combined with several other advantages of the PTTR architecture provide a very good baseline for the UWEC2 team to compete at year three competition of EcoCAR2.
- Mechanical engineering