THERE are many innovations turning up in the latest experimental and production electric cars, affecting everything from batteries to motors to control systems. The need to make them all work together is prompting a complete rethink about the way cars should be designed and manufactured, and it is unclear which technologies will dominate as the constraints imposed by internal combustion engines give way to the new limits and possibilities associated with electric propulsion. But one group of engineers have stuck their necks out and declared that a particular technology, the electric hub motor, is likely to become the most widely used drive system.
A hub motor, as its name suggests, is built into the hub of a wheel and drives it directly, rather than having a single motor driving the wheels via a mechanical transmission. It is an idea pioneered by Ferdinand Porsche, the founder of the carmaker of the same name, more than 100 years ago. Mr Porsche got his first job in the automotive business with Jacob Lohner in Vienna, and put electric motors into the hubs of the wheels of the Lohner-Porsche, a vehicle which made its debut at the 1900 World’s Fair in Paris. It was a hybrid car that relied on both batteries and a generator to produce electricity for its motors. Capable of more than 56kph (35mph), it also set a number of speed records.
At this week’s Deutsche Messe technology show in Hanover, researchers at the Fraunhofer Institute displayed an electric vehicle which they are using as a test platform to investigate new vehicle systems. It includes electric hub motors, which they have developed to be markedly more powerful than any such motors currently available. The motors have all the necessary power and control systems integrated into the wheel hub, greatly reducing the number of connections between the hub motors and the rest of the vehicle.
Because hub motors can deliver power independently to each wheel, tricks like four-wheel-drive are possible. With software monitoring each wheel, stability and traction control can also be built-in. Besides dispensing with the traditional engine bay on a car, hub motors save space and weight because there is no need for a mechanical transmission, with its driveshafts and differential units.
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