Experimental EV has four independently-actuated wheels
By Ben Coxworth
January 24, 2013
As any fan of electric cars will tell you, one of the keys to improving their range is getting their weight down. With that in mind, a team of researchers from Ohio State University are currently developing an EV that they claim weighs half as much as a conventional car. Because it’s so light, handling is definitely an issue – that’s why each of its wheels is independently controlled, and contains its own motor and battery pack.
The four-wheel independently actuated (FWIA) car weighs in at just 800 kilograms (1,764 lbs). It was built on the chassis of an existing Big Muddy utility vehicle, with the engine, transmission and differential removed.
Instead, each wheel contains its own 7.5-kW electric motor and 15-kW lithium-ion battery pack. One electrical cable connects all four motors to a central computer. That computer samples data from the steering wheel, gas pedal and brake 100 times a second, then actuates each wheel accordingly for optimum traction and motion control.
As a result, fishtailing is reportedly eliminated via independent control of the left and right sides of the vehicle. Traction is also said to be greatly enhanced, as one or more wheels can brake while others are accelerating. According to lead scientist Junmin Wang, it offers “better control than commercial four-wheel drive.” The computer is essential, however, as the car is “very hard to drive” without it.
When tested on good road conditions, the FWIA car followed within four inches (10 cm) of its driver’s intended path. On a snow-covered parking lot, that figure went up to eight inches (20 cm). Wang states that this is better than what could be managed by a conventional vehicle.
The team is now concentrating on improving the car’s energy efficiency and making it more fault-tolerant, so that it can compensate if one motor, wheel or brake malfunctions. They also plan on optimizing its weight distribution, and creating new algorithms to improve its control system.
Wang estimates that it will be another five to ten years before we see FWIA-enabled cars on the roads.
A paper on the research was recently published in the journal Control Engineering Practice.
Source: Ohio State University