Most on-road vehicles today use only the front wheels to steer. Four-wheel steering is usually limited to heavy equipment, monster trucks, and off-road vehicles because they are extremely maneuverable. Really, vehicles that spend most of their time driving in a straight line don’t need to be that maneuverable anyways, but what about city cars? With great maneuverability comes great need for control, and with the advent of electric vehicles [EV], greater levels of control are available than have been ever before possible.
Modern conventional and hybrid vehicles have vehicle dynamics systems that help to keep your vehicle stable, even in poor road conditions, by controlling wheel speed and engine torque. Computer controls can even apply the brakes to a single wheel to keep the vehicle in the desired path.
Electric motors are even more responsive to computer control, and a team at Ohio State University recently demonstrated how this computer control can make even a four-wheel-steering vehicle just as easy to drive as a traditional vehicle.
The 4×4 EV prototype is an off-road utility vehicle, only about half the size of a typical sedan, with four-wheel steering. The conventional engine, transmission, and transfer case have been removed, and the four wheels are now powered independently by a 15kWh lithium-ion battery pack and a 7.5kW electric motor. The four motors and batteries are connected to a single control unit, which controls each motor’s speed and torque independently of the others to keep the vehicle stable.
In fact, the prototype vehicle can outmaneuver any other vehicle on the market, but “without the controller, it’s very hard to drive. With the controller, it’s quite nice—quiet, and better control than commercial four-wheel drive,” said Junmin Wang, assistant professor of mechanical engineering and Director of the Vehicle Systems and Control Laboratory at Ohio State. It might be a few years before such a 4×4 EV with four-wheel-steering and power might make it to production, but handling and safety will be a welcome addition to tight city streets, as well as being completely emissions-free.