All electric utility vehicles such as the Columbia ParCar SUV-LN, shown in the figure, are used in a wide variety of industrial and commercial applications where tools, equipment, and personnel need to be transported efficiently with zero emissions. A large number of these vehicles on the market are powered by brush-type separately wound dc motors using 48 to 72 V lead acid batteries for energy storage. Under a program sponsored by the Defense Logistics Agency, DLA, the Center for Electromechanics researched possible performance improvements by upgrading the stock lead acid batteries to state of the art lithium-ion batteries or integrating a hydrogen fuel cell with supplemental energy storage.

Many modeling techniques use steady state efficiency maps and torque-speed curves to describe the performance of electric motors, which can overlook transient response dynamics, current limits, and thermal limits that may affect the end vehicle performance. The paper, “Electric Vehicle Modeling Utilizing DC Motor Equations,” coauthored by Clay Hearn, Damon Weeks, Richard Thompson, and Dongmei Chen, and presented at the 2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics in Montreal, Quebec, July 9-11, 2010, discusses using bond-graph techniques to develop a causal model of an electric vehicle powered by a separately wound dc motor and development of the appropriate feed-forward and feed-back controllers required for route following. The causal model performance is compared to a PSAT model of the same electric vehicle, which uses motor torque-speed curve and efficiency map.

For more information, please contact Clay Hearn