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The Uni Wheel Is How the South Koreans Reinvented the Drive Systems for EVs

When most of us are buying a car, the first thing we look at are the vehicle's design and the capabilities provided by its powertrain. Very few of us give any thought to other systems, like what kind of drive helps turn the powertrain's power into wheel motion. Because if we did, we'd soon come to the conclusion that there's a lot that could surprise us, especially when it comes to electric vehicles.
Hyundai Kia Universal Wheel Drive System 12 photos
Photo: Hyundai/Kia
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Before going into what brought us here today, a very short recap of what is a wheel drive system might be needed. In a nutshell, it's the system that drives two or four wheels by sending the engine or electric motor's power to them.

In conventional, internal combustion cars, that is done with the help of drive shafts and devices called constant velocity joints (CVs). For electric cars, the same effect is achieved with the help of a motor and reduction gear.

Automakers have been advancing these systems for ages now, and there are several high-profile such technologies in use already, driving the front, rear, or all wheels in some of the world's most impressive cars, SUVs, and pickups. People are very pleased with all of them, meaning no one was really expecting a new such system to be presented.

Yet that's exactly what the South Koreans from Hyundai and Kia did this week at a special event held in Seoul. There, the two partners introduced to the world something called the Universal Wheel Drive System, or the Uni Wheel, as they like to call it.

The tech is described as a "paradigm-shifting vehicle drive system" that “will revolutionize the design of future mobility devices." Yes, devices, because this thing is not meant solely for vehicles but might just as well power wheelchairs, bicycles, and delivery robots. A one-solution-fits-all kind of deal, if you will.

Hyundai Kia Universal Wheel Drive System
Photo: Hyundai/Kia
But what is this Uni Wheel? According to the two carmakers, it's a piece of tech that integrates existing drive components but in a way meant to increase passenger space inside an electric vehicle, give electric cars more range, and allow for the development of purpose-built vehicles.

Hyundai and Kia say the development of the tech started from the idea that cars are slowly transforming from being means of transportation to being more like living spaces thanks to the rise of EV and autonomous technologies. That's why the main issue Uni Wheel tries to solve is the one that has to do with interior space.

That is achieved by moving the technology's EV reduction gear inside the wheel hub. That is further enhanced by installing an individual electric motor close to each of the four wheels, and reducing the length of the drive shafts.

This approach allows for a flat-floor configuration, which in turn makes available to users "space within a vehicle that was previously unavailable." This extra space can be used, obviously, either to transport additional cargo or people, but it could also open up new design ideas for the vehicles' trunks and frunks.

As far as what the Uni Wheel can do for an electric vehicle's performance, Hyundai and Kia say the extra space coming from its deployment could also be used to include larger-capacity batteries, thus increasing range.

Hyundai Kia Universal Wheel Drive System
Photo: Hyundai/Kia
Then, despite being more compact than traditional electric motors, torque output could increase, because the reduction gear is now inside the wheel hub. It also allows for independent control of up to four drive units, and comes with "high levels of steering and driving stability."

How does the Uni Wheel work? Well, the system comes with an innovative planetary gear configuration. It has a sun gear in the center, four pinion gears on each side, and a ring gear going around the entire thing.

The power from the electric motor is sent to the sun wheel, and that moves the pinion gears. Their movement is transmitted to the ring gear, which in turn spins the car's wheel itself. Compared to conventional drive systems, whose efficiency tends to be affected by the angle of the drive shaft deflection, especially over uneven terrain, this one could "transmit power with almost no change to efficiency regardless of wheel movement."

As far as the suspension system goes, the Uni Wheel is said to support a wide range of suspension articulations, but also air-based systems. When used with such a tech, the Uni WHeel could boost the car's performance based on the different needs of driving off- or on-road.

The two South Korean carmakers say the Uni Wheel can be adapted to be used on all types of vehicles, from bland city cars to high-performance vehicles, not in small part because it can use the same powertrain and reduction gear functions as in conventional designs.

Hyundai Kia Universal Wheel Drive System
Photo: Hyundai/Kia
The system is also scalable and can work with wheels ranging in size from four to 25 inches (and possibly even larger). In certain conditions it could also power robots that can climb stairs.

Hyundai and Kia don't say exactly when we are to expect the first commercial application of the Uni Wheel. The companies are at the moment testing it for stability, efficiency, and durability, and are trying to iron out some issues with reduction gear ratio, lubrication, and cooling.

The thing is as serious as they get, though, with eight patents registered in South Korea, Europe, and the U.S.

You can get a visual sense of what the Uni Wheel is all about in the video attached below.

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About the author: Daniel Patrascu
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Daniel loves writing (or so he claims), and he uses this skill to offer readers a "behind the scenes" look at the automotive industry. He also enjoys talking about space exploration and robots, because in his view the only way forward for humanity is away from this planet, in metal bodies.
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