Gearless Wheel Motor Debuts At Medical Trade Show

An in-wheel motor system designed for use in battery-powered wheelchairs will be unveiled at Medtrade, November 18-21, 1998, in Atlanta. The PML FlightLink in-wheel motor system reportedly increases the range per battery charge by approximately 65%.

The system is brushless and completely eliminates oil and grease filled gearboxes, while providing silent and smooth operation that is essentially maintenance free. For the demonstration, the system will be fitted on a wheelchair from Sunrise Medical U.K.

The inner stator contains the winding and the outer rotor consists of the magnets mounted on the inside of a wheel rim. Once a standard tire is fitted around the motor casing, the motor virtually becomes the wheel. This gearless arrangement allows more of the motor's energy to be used to provide traction, while none is wasted overcoming gear friction or transmission drag.

Included in the system are two microprocessor controlled, 400-W wheel motors that provide smooth fast acceleration and regenerative braking. Steering is entirely electronic by differential speed control of the two motors. With the system, users can travel 31 miles per battery charge compared to 18 miles using conventional dc motor drives.

PML FlightLink has applied for a number of patents covering key mechanical, electronic, and software innovations used in the system. The prototype wheel motor system is not yet for sale in the United States.