Kia and Hyundai Motor have developed a drivetrain with integrated components that can improve efficiency, power and durability without impacting ride comfort. Known as the Uni Wheel – for Universal Wheel Drive System – it is said to be paradigm-shifting and can 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 by moving the main drive system components to the vacant space within the wheel hub. In doing so, there is a completely new structure for the drive system.
In internal combustion engine vehicles, power is transmitted from the engine through the transmission and to the wheels via driveshafts and constant velocity (CV) joints. In EVs, however, the engine and transmission are replaced by a motor and reduction gear, but the final method of transmission to the wheels is the same.
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 space efficiency
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 storage compartment or a ‘frunk’.
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. Utilising 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.
More interior space
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.
This will be a valuable feature for Purpose-Built Vehicles which need to maximise interior space by offering a low, flat-floor design. The flat-floor platform enabled by Uni Wheel allows for strong flexibility and scalability when it comes to PBVs, enabling the design of various body types depending on the intended use case.
For all types of EVs
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 100 mm and as large as 630 mm 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.
“We are pleased to showcase innovative ideas that could become game-changers in the future mobility market,” said Jongsool Park, Senior Fellow at the Institute of Advanced Technology Development of Hyundai Motor Group. “We will perfect the technology so that customers can experience mobility in a completely different and new way.”
Kia and Hyundai Motor have applied for and registered 8 patents related to Uni Wheel in South Korea as well as the United States and Europe.