NEW 'UNI WHEEL' DRIVE SYSTEM COULD SHAKE UP EV DESIGN
The latest breakthroughs in electrification, autonomous driving and connectivity technologies are revolutionizing mobility products like never before. Hyundai Motor Group (the Group) last year revealed a paradigm-shifting vehicle drive system that could significantly improve EV driving range and passenger space.
The “Universal Wheel Drive System,” also known as “Uni Wheel,” is meant to dramatically improve the interior space of an EV by moving the main drive system components to the vacant space within the wheel hub.
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 remains the same.
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, thus reducing the length of the drive shafts.
The system frees up far more interior space compared to conventional drive systems, enabling future mobility products optimized for various applications.
Stable Driving
Uni Wheel 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.
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.
Conventional drive systems employing regular CV joints experience reduced efficiency and durability as the angle of the draft shaft deflection increases when driving over uneven surfaces. However, Uni Wheel overcomes this issue by transmitting power with minimal impact on efficiency irrespective of wheel movement. This design ensures exceptional durability and ride comfort.
When coupled with electronic air suspension that can modify the ride height based on driving conditions, Uni Wheel technology can further enhance vehicle stability on rugged terrains by increasing the ride height, or optimize power and stability during high-speed driving by lowering the ride height. This integration allows for an adaptable and versatile driving experience on various types of roads.
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.
Space Efficiency
By relocating 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.
With Uni Wheel, it’s also possible to move away from conventional seating arrangements designed around the driver, creating new interior layouts. Most EV batteries are placed on the floor of the vehicle, which can impose limitations on design, such as the need for taller garages or potential reduction in passenger space if alternative arrangements are not feasible.
Uni Wheel, on the other hand, optimizes battery packaging, with the loss of passenger space minimized.
Clearing Hurdles
After a series of trailblazing efforts from the Group, Uni Wheel has successfully completed structural, strength and transmission efficiency tests that need to be verified for the wheel drive system.
The Group registered patents in both Korea and the United States, and detailed target tests for vehicle development are planned to be conducted this year.
The product currently being tested is a rear-wheel-based system, but based on its performance, the Group also plans to develop Uni Wheel for front-wheel application.