In internal combustion engine (ICE) vehicles power is transmitted from the engine through the transmission and to the wheels via drive shafts and constant velocity (CV) joints. In EVs, the engine and transmission are replaced by a motor and reduction gear, but the final method of transmission to the wheels is the same.

The Uni Wheel opens new possibilities and enables a flat-floor configuration by moving an EV’s reduction gear inside the wheel hub, locating a compact individual motor close to each wheel, reducing the length of the drive shafts.

It uses a special planetary gear configuration consisting of a sun gear in the center, four pinion gears on each side and a ring gear surrounding this arrangement. Power generated by the motor is transmitted to the sun gear, which in turn engages the pinion gears to rotate the ring gear. This is connected to the wheel to drive the vehicle.

The Uni Wheel’s pinion gears are connected to each other to form two linkages, and this multi-link mechanism enables the Uni Wheel’s multi-axis movement to allow a wide range of suspension articulation.

A conventional drive system using a regular CV joint suffers from a decrease in efficiency and durability as the angle of drive shaft deflection increases when travelling over bumpy, undulating surfaces. The Uni Wheel can transmit power with almost no change to efficiency regardless of wheel movement, ensuring high durability and ride comfort.

When combined with electronic air suspension that can adjust ride height according to the driving situation, this can be increased to stabilize the vehicle on rough roads, or decreased for high-speed driving to improve power and stability.

By moving the reduction gear to the wheel hub, the Uni Wheel’s high reduction ratio delivers a significant torque output and allows for a more compact electric motor. With independent control of up to four efficient electric drive units, Uni Wheel also allows for unprecedented levels of torque vectoring to boost dynamic ability and deliver high levels of steering and driving stability.

The Uni Wheel concept frees up space within a vehicle that was previously unavailable to users. By relocating many components of the drive system to the wheel hub and downsizing the electric motor with no impact on performance, the extra space made available within the vehicle body can be utilized as additional cargo room.

It’s also possible to move away from conventional seating arrangements designed around the driver, creating new interior layouts and designs for the era of fully autonomous driving. Utilizing this space to improve battery capacity can also improve driving range, meaning users can achieve the range of a large EV without the physical size of the vehicle growing.

In addition to vehicles of various sizes, the Uni Wheel can also be applied to other types of mobility devices, such as wheelchairs, bicycles and delivery robots. Depending on the requirements of these different forms of mobility, it can be scaled to work with wheel sizes as small as four inches and as large as 25 inches or more. In addition, Uni Wheel’s ability to move the rotation axis of the wheel makes it possible to create forms of personal mobility that can climb stairs as smoothly as an escalator.

Kia and Hyundai Motor are continuously verifying the stability, efficiency, and durability of the Uni Wheel through various tests to perfect its development and will continue efforts to improve its efficiency by adjusting the reduction gear ratio, and upgrading the lubrication and cooling system.