Hyundai Motor Company and Kia Corporation have unveiled the Universal Wheel Drive System – called ‘Uni Wheel’. This paradigm-shifting vehicle drive system will revolutionise the design of future mobility devices.
Uni Wheel is a functionally integrated wheel drive system that dramatically improves available space inside an electric vehicle (EV) by moving the main drive system components to the vacant space within the wheel hub. In doing so, Hyundai Motor and Kia have designed a completely new structure for the drive system.
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.
Advancing future mobility through new technology
Uni Wheel uses a special planetary gear configuration consisting of a sun gear in the centre, 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.
Uni Wheel’s pinion gears are connected to each other to form two linkages, and this multi-link mechanism enables 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. 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 stabilise 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, 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.
More efficiency, more interior space
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 utilised as additional cargo room, such as a larger trunk or a ‘frunk’.
The developments Uni Wheel allows will also significantly increase passenger space. EV batteries are conventionally located low down in a vehicle’s body, which requires a raised ride height, often reducing passenger space by the volume of the battery. However, Uni Wheel optimises battery packaging, with the loss of passenger space minimised.
Uni Wheel is highly flexible and easily adaptable to all types of EVs, including regular passenger and high-performance EVs, as the system can implement the same powertrain and reduction gear functions required for conventional EVs.
In addition to vehicles of various sizes, 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, Uni Wheel can be scaled to work with wheel sizes as small as 4 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.
Hyundai Motor and Kia are continuously verifying the stability, efficiency, and durability of 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.
Hyundai Motor and Kia have applied for and registered eight patents related to Uni Wheel in South Korea as well as the United States and Europe.
More information and detailed visual representations of the innovative Uni Wheel drive system can be found here:
www.youtube.com/watch?v=Nd6C0y8xc20.
