Future generations of green vehicles will depend on in-wheel motors. The technology involves a combination to wheels, tires, motors, brakes, steering, suspension and cooling systems. It eliminates the need for traditional components such as engines, transmissions, differentials and transmission shafts, which can result in a 10 percent to 25 percent weight reduction and a 20 percent to 30 percent fuel savings.

In-wheel motors are also referred to as electric corner modules. They require a high-voltage system (above 42 volts) for energy and power transfer to and from an electric motor and battery. Alternative powertrain vehicles, such as hybrid, electric and fuel cell vehicles, have higher voltage ranges and are most likely to be equipped with in-wheel motors in the future.

Several Japanese automakers, such as Honda, Mitsubishi and Toyota, have showcased in-wheel motor technology in their electric- and fuel cell-powered prototypes. “The market will be driven by tire and motor suppliers rather than OEMs,” says Vijayendra Rao, powertrain industry manager at Frost & Sullivan Inc. (San Antonio).

Suppliers such as AISIN, Bridgestone, Continental and Michelin, have already unveiled prototype systems. “However, some of the concepts still face challenges in terms of unsprung mass, higher temperatures of motors at high speed, and operations on dusty roads,” Rao points out.

At the Paris Motor Show last October, Michelin displayed its Active Wheel. Engineers integrated all essential components, such as engine, brake disk, clutch, gearbox, suspension and transmission, into the wheel itself. The integrated motor is powered by electricity that’s generated by a battery or a fuel cell.

With the Michelin Active Wheel, vehicle suspension is no longer mechanical. The electrical system features extremely fast response time, while all pitching and rolling motions are automatically corrected.

Michelin claims that its in-wheel motor will simplify the vehicle design and assembly process by making traditional mechanical components unnecessary. For instance, simplifying vehicle architectures will allow engineers to eliminate traditional engine compartments and create a flat floor that adds more interior space.