Hyundai and Kia have unveiled their new “paradigm-shifting vehicle drive system” called the Uni Wheel — short for Universal Wheel Drive System — which will allow the electric vehicles (EV) of the future to be much more versatile.
“Uni Wheel is a functionally integrated wheel drive system that dramatically improves available space inside an EV by moving the main drive system components to the vacant space within the wheel hub,” said the Korean automakers.
“In doing so, Hyundai Motor and Kia have designed a completely new structure for the drive system.”
From a mode of transport to a living space
Hyundai believes that cars are currently in a transformational era, evolving from their original use as people haulers into living spaces on the move, which necessitates innovative solutions to vehicle design and packaging.
One of the first examples of such an invention is the Uni Wheel.
Traditionally, an EV delivers power from the motor and reduction gear – which in a petrol car would be an engine and transmission – to the wheels via drive shafts and constant velocity (CV) joints.
While the Uni Wheel still has all these components, it has taken an all-new approach to how they are configured.
The concept wheel moves an EV’s reduction gear inside the wheel hub and positions a small e-motor closer to each wheel, thus reducing the length of the drive shafts.
In turn, it frees up significantly more interior space in comparison to conventional drive systems, enabling future cars and other mobility products to be optimized for various applications beyond just transporting people.
The inside of the Uni Wheel incorporates a special planetary gear configuration consisting of a sun gear in the centre and four pinion gears on each side, which are surrounded by a ring gear.
Power is then transmitted from the e-motor to the sun gear, which subsequently engages the pinion gears that rotate the ring gear that is connected to the wheel.
The multi-link mechanism of the Uni Wheel’s pinion gears enables multi-axis movement for a wider range of suspension articulation compared to the rigid traditional setup, which when combined with electronic air suspension, results in a wider spectrum of ride adjustment without sacrificing driving quality.
In addition, the ability to move the rotational axis of the wheel makes it possible to create forms of vehicles that can climb stairs as smoothly as an escalator, the automakers claim.
“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,” said Hyundai.
“Uni Wheel can transmit power with almost no change to efficiency regardless of wheel movement, ensuring high durability and ride comfort.”
By moving the reduction gear to the wheel hub, the Uni Wheel’s high reduction ratio also delivers a higher torque output from a more compact e-motor.
Independent control of up to all four wheels further permits “unprecedented levels” of torque vectoring that improve handling and power delivery.
Not only does it boost performance, but the Uni Wheel’s biggest claim to fame is that it enhances interior space and design possibilities.
By relocating drive components to the wheel hub and downsizing the e-motor it frees up space that was previously occupied by mechanical hardware, which can be utilized to completely change the look and versatility of the vehicle inside and out.
The newfound room can be dedicated to extra cargo room such as a larger boot or frunk, or the fitment of a larger battery that can increase driving range without impacting the car’s size.
It also opens up the possibility of having new interior and seating layouts that improve passenger space or are designed for a specific use case.
Left: Traditional EV platform. Right: Uni Wheel platform.
Moreover, the Uni Wheel can be scaled to work with wheel sizes as small as 10cm up to 63cm or more, and it is therefore not only viable for passenger and high-performance EVs, but also for wheelchairs, bicycles, and delivery robots.
There has been no word on when the Uni Wheel will make it into a production vehicle from either Hyundai or Kia, but the automakers have stated that they are continuously verifying the stability, efficiency, and durability of the innovation and enhancing its performance in preparation for potential mass adoption.
You can watch a detailed visual representation of the Uni Wheel in action below.
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