Motion Control is Key to OSU's Futuristic Electric Car

It's half the size of your average passenger car, corners like it's on rails, and is capable of being folded to fit into a parking spot. Meet the future for the urban electric car, if Ohio State University (OSU) researchers have anything to say about it.

A team led by Junmin Wang, assistant professor of mechanical engineering and director of the Vehicle Systems and Control Laboratory at OSU, has been working on a new design for an electric vehicle -- created by repurposing a gasoline-engine utility vehicle -- since 2009, Wang told Design News.

The key to the vehicle's design is that each of its wheels turn independently, courtesy of dedicated, battery-operated motors that allow the car more capability and maneuverability than the electric cars on the market. Those vehicles depend on one motor to provide torque to all the wheels, he told us.

"They have more freedom in terms of control," Wang said of the wheels on OSU's experimental vehicle. "In a typical electrical vehicle, the torque transmitting from the wheels cannot be arbitrarily assigned. For this one, we can do this because they are not mechanically coupled."

This makes the car more nimble in terms of turning and performing lateral and yaw motions. It also makes the car safer when it turns sharp corners and stops suddenly, given its more stable and precise movements.

Researchers performed tests with the vehicle at the Transportation Research Center in East Liberty, Ohio, in which the car was able to follow a driver's desired path within four inches. They also tested its maneuverability on slippery road conditions in a university parking lot on a snowy day. In that test, the car's accuracy of movement was up to eight inches, and it did not fishtail on the slippery surface, thanks to independent control of each side of the car.

Wang said the vehicle -- which weighs 800 kilograms (about 1750 pounds), or about half the weight of the average passenger car -- could be the ideal electric car for urban environments because of its maneuverability, and another feature that makes it handy, especially in cities with limited parking spots: "It is architecturally flexible, so it could be folded to fit into a smaller parking space," he said. "Because it's small and compact, it's promising in urban areas to use for commuting and driving. I think it's a promising future platform."

The original project that spawned the car -- which called for OSU researchers to improve the motion control and stability of electric car designs -- stemmed from a grant from the Office of Naval Research. Last year, OSU received funding from the National Science Foundation to continue the work for another five years, Wang said.

Researchers will aim to improve the operational energy efficiency of the vehicle in the next phase of their work by studying how the vehicle carries loads. Data collected will then be incorporated into the vehicle's driving- and energy-management strategies.

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