Tucked In: Protean’s in-wheel electric motors would be more powerful than others and save space under the hood.Illustration: Protean Electric
An innovative in-wheel motor for electric vehicles may get its first tryout in the smoggy, traffic-choked streets of Beijing—and could lead to a wave of powerful and radically redesigned electric cars. Protean Electric, an automotive start-up headquartered in Auburn Hills, Mich., is currently scouting sites for a manufacturing center in China and says the assembly line will be operational before the end of the year. The company expects its first customers to be Chinese automakers, who will use the motor in their plug-in hybrids or pure electric cars.
Andrew Whitehead, Protean’s director of strategic alliances, says China is becoming a test bed for electric vehicle technology, thanks to strong government support. “The way we see it, the key driver for electric and hybrid technology at the moment are government standards on emissions,” says Whitehead. “The regulations in China are certainly as strict as in Europe and North America, but there appears to be more political will to assist the industry in reaching those standards in China than in the rest of the world.” Air pollution in China’s capital city has reached a crisis point, and both manufacturers and car buyers in China can now benefit from government incentives designed to replace polluting cars with cleaner electric vehicles, Whitehead says.
While a typical EV has a central motor under the hood that sends power down the driveshaft to the axles, the Protean system generates power directly in small motors tucked inside the wheels. With no energy lost in transmission, Protean says its motors can provide significant efficiency gains. In addition, these gearless, direct-drive motors can each generate an impressive 1000 newton meters (738 foot-pounds) of torque each. By comparison, the all-electric Chevy Volt’s motor generates about 370 Nm (273 foot-pounds). Protean says that providing that much torque to individual wheels gives vehicles superior handling and performance. The power and control electronics, including the inverters that change DC battery power to AC power that drives the motor, are all tucked into the wheel space.
Whitehead says the 34-kilogram motor is suited for plug-in hybrids like the Chevy Volt and for all-electric vehicles; standard hybrids such as the Prius don’t rely on their electric motors for enough of their propulsion to make in-wheel motors cost-effective. A typical passenger car would have two such motors, while a heavy-duty or high-performance vehicle could have a motor in each of its wheels.
The in-wheel motor concept is hardly new; in fact, Ferdinand Porsche unveiled a car using such motors in 1900. However, early versions couldn’t provide much power or torque in the confined space of the wheel and also couldn’t withstand the vibrations, heat, dust, and water encountered as a car drives down the road. Whitehead says each component of the Protean Electric’s system was designed with that harsh environment in mind, and that the system “meets the mass-market requirements of the industry.”
Not everyone is convinced. While the efficiency and torque benefits of in-wheel motors are significant, so are the costs, says Sheldon Williamson, an associate professor of electrical engineering at Concordia University, in Montreal, who studies electric motor drives. “From aresearch perspective, we’re very optimistic,” he says, “but economically, it doesn’t make sense for commercial vehicles right now.” Williamson says that coordinating the in-wheel motors requires complex control systems, and he predicts it will take five to 10 years for the technology to be competitive.
Whitehead acknowledges that vehicles using the Protean motors would need new control software but says that in some ways the in-wheel system makes control simpler. In a conventional car, a driver presses the accelerator and sends a command via an electronic control unit (ECU) to the engine, telling it to produce torque that is distributed to the wheels through mechanical systems. In a Protean-powered car, the ECU “can deliver the torque to where you want it in the vehicle without those complex mechanical systems,” Whitehead says. This control could facilitate the individualized distribution of power to each wheel, a technology called torque vectoring, which was pioneered in race cars and has recently made its way into all-wheel-drive vehicles.
The manufacturer, FAW-Volkswagen Automotive Company (a joint venture between a Chinese car company and Volkswagen), apparently isn’t scared off by the challenges and is partnering with Protean Electric on a demonstration vehicle. Moving the motors to the wheels also opens up space in the car and allows for a great deal of design flexibility, which could lead to novel concept cars.
The Chinese government has established a goal of getting 500 000 “new energy vehicles” on the road by 2015, and 5 million by 2020, according to a report by the nonprofit Center for Automotive Research (CAR). Several cities, including Beijing, offer electric-vehicle subsidies and also allow EV buyers to skip the lotteries for license plates, which the cities use to keep the booming auto market in check. But Qiang Hong, a senior research scientist with CAR and coauthor of the report, says these incentives haven’t been enough to create a flourishing EV market. “In Beijing, if you want to buy an electric vehicle, you can get a license plate immediately,” he says. “But even with that, the consumers are not choosing to do so.” Hong says the lack of EV charging infrastructure poses an obstacle to consumer acceptance.
Still, Protean Electric’s leadership believes that Chinese automakers are willing to make the necessary R&D investments to create this EV market. China’s domestic car brands are struggling to compete with foreign brands, and Whitehead says that innovative EV technology can give them an edge. “In internal combustion technology, they have a century of industrial development to catch up on,” Whitehead says. “With electric vehicles, they can catch up and overtake.”
Eliza Strickland is a senior editor at IEEE Spectrum, where she covers AI, biomedical engineering, and other topics. She holds a master’s degree in journalism from Columbia University.