Kia and Hyundai have announced an innovative new ‘Uni Wheel’ drive system that aims to revolutionise the design and packaging of future electric vehicles.
Uni Wheel (which stands for Universal Wheel Drive System) is described as a functionally integrated wheel drive system that moves the main drive system components to the vacant space within the wheel hub.
This allows for a more space efficient vehicle design that maximises occupant and luggage space.
In conventional internal combustion engined vehicles power is transmitted from the engine through the transmission and to the wheels via drive shafts and 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.
But the Uni Wheel changes all that, enabling a flat-floor configuration by moving the EV’s reduction gear inside the wheel hub, locating a compact individual motor close to each wheel and reducing the length of the drive shafts.
This not only results in a bigger interior but also allows the platform to be optimised for various applications, such as Purpose Built Vehicles.
It also makes it 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.
“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.”
How it works
The Uni Wheel design makes use of 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.
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.
Check how it works in the video below: