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Hyundai and Kia's New 'Uni Wheel' Drive System Could Revolutionize EV Design (electrek.co) 195

Posted by BeauHD from the game-changer dept.
"Two articles from Electrek and InsideEVs describe Hyundai and Kia's new 'Uni Wheel' drive system that could revolutionize EV design," writes longtime Slashdot reader Uncle_Meataxe. From a report: Described by its makers as a "paradigm-shifting vehicle drive system," the Uni Wheel moves the main drive system components to the vacant space within an EVs wheel hubs. The approach utilizes a planetary gear configuration consisting of a sun gear in the center, four pinion gears on each side, and a ring gear surrounding everything. Traditional ICE vehicles utilize CV joints, but by moving them closer to the wheels requires a short drive train length and as a result, a decrease in efficiency and durability -- especially over bumpy terrain. Hyundai and Kia's Uni Wheel system on the other hand, can transmit power with almost zero changes to efficiency, regardless of wheel movement. "Advantages include more platform space and more room within an EV's interior," adds Uncle_Meataxe. "When this system may be integrated into an actual EV remains unclear, but Kia and Hyundai have already registered eight patents related to the technology." You can learn more about the new drive system via an instructional video on YouTube.
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Hyundai and Kia's New 'Uni Wheel' Drive System Could Revolutionize EV Design More

Hyundai and Kia's New 'Uni Wheel' Drive System Could Revolutionize EV Design

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  • Pretty sure my RWD Model 3 doesn't have CV joints anyway.

    As Rei already pointed out, in-hub motors increase unsprung weight is is bad for handling. The initial reason to make car wheels out of aluminium was unsprung weight (now it's largely cosmetic).

    • Re: (Score:3)

      by ukoda ( 537183 )
      I have the Model 3 performance but it still has diffs. This approach with four motor has advantages. BTW, it is not a hub motor, watch the video. Not sure I would want to buy the first gen version but give it a few years of real world use and this has potential to be better than the way Tesla does things.

      • I have the Model 3 performance but it still has diffs.

        Diffs are not CV joints. CV joints are only required on wheels that are used for steering.

        Eliminating the diff has some advantages, but there are already some EVs that have one motor per wheel on some axles.

        This new system still looks like it would increase unsprung weight.

        • It gets even more complicated, actually. But yes, there are reasons why the first cars were generally RWD, front wheel steer.

          Researching, SOME RWD vehicles, those with "independent suspension", will have CV axles on the rear wheels. But something like a pickup with a solid axle won't. You can support the motion they need for suspension purposes with regular u joints.

          So yeah, I'd rate it as "not required, sometimes used anyways for various reasons usually related to suspension"

          If you're just steering with

          • You need CV joints on a RWD vehicle in order to have independent suspension. Otherwise, the axle must be solid and the suspension is not independent (force against one wheel will transfer to the other, but inversely)
            This is very far from ideal, as one can imagine- if one wheel hits a bump or a pothole, the only motion the rear assembly is capable of is pivoting around the drive shaft- i.e., not following the road.

            I don't think I've seen a solid axle on a car since the pre-2015 S197 mustangs- pretty sure

            • I mentioned the CV joints on RWD for independent suspension in the 2nd paragraph.

              But you're right on flipping the preponderance of them. I fell for my logical/programming thought pattern - it isn't REQUIRED for RWD, so therefore it is optional. I was right that you use them for suspension purposes. Where I fell down was not mentioning that like 99% of vehicles with drive power in the rear (RWD,AWD,4WD) use them.

              • I mentioned the CV joints on RWD for independent suspension in the 2nd paragraph.

                You did, indeed. Your explanation of the difference was just fine as well. The only part you got wrong was the "some", and I figured if I recapped, it'd be immediately obvious to you and anyone reading why CV's are now the norm (because solid axles suck, minus the fact that they're obviously stronger lacking the joint)

        • Diffs are not CV joints. CV joints are only required on wheels that are used for steering.

          No. Some kind of articulating joint is required for any wheel that has any kind of independent suspension.
          That includes non-steering wheels that still go up and down.
          Since u-joints suck ass while articulating (non-constant velocity), it's going to be a CV joint.
          You are otherwise correct that differentials are not CV joints. Your CV joints are on the drive axles that connect from your wheel to your differential.

    • It has 4, one on each end of the half-shafts between the hub and the combined motor-gearbox-diff unit.

      That's how the back wheels can move up and down without snapping off.

    • Pretty sure my RWD Model 3 doesn't have CV joints anyway.

      Um, what?
      How does one get independent suspension on such a wheel, then?
      I'm 99% certain its rear axles have CV joints.

    • Unsprung weight, but the inertial mass moment is lower. Having to spin up all the wheels does take energy, and on an rpm basis lowering the mass moment increases efficiency and thus power transmitted to the road.
  • Way to "invent" something at A. Exists B. Sucks for reasons state below (sprung mass, inertia namely)
    • Derp for not clicking link. Having an eccentric input planetary gear isn't super exciting, still.

    • Also, wouldn't those parts corrode much faster, because they would be partially submerged in snow and salt combination in winter?

  • I think hub motors are the future, but unless they can drastically reduce their weight consumers are going to hate the handling characteristics.

    • Re: (Score:2)

      by ukoda ( 537183 )
      It is not a hub motor, but has some of the ideas seen in hub motors. Watch the video, the idea has great potential.

    • but unless they can drastically reduce their weight consumers are going to hate the handling characteristics.

      Most consumers prefer big trucks and SUVs because of how they look. They handle like shit compared to cars, so I'm not convinced consumers care about handling. Though I did rent a mustang once (yay commercial rentals you get whatever they want to move to the airport!). That handled like a blob of jelly on top of a powerboat.

  • watch the video, don't be a dumbass (Score:4, Insightful)

    by dfghjk ( 711126 ) on Thursday November 30, 2023 @09:27PM (#64045455)

    This design allegedly improves packaging greatly, improves efficiency and does not increase unsprung weight. It also makes independent left and right side motors inherent with all its inherent benefits. It also makes room for more battery or reasonable batteries in smaller vehicles.

    • Re: (Score:2)

      by caseih ( 160668 )

      Yeah. It keeps the heavy weight of the motor on the frame, while tucking the reducer into the hub, but doing it in a way that eliminates the need for a CV joint. Definitely a neat idea. Still trying to wrap my head around the torque flow through those arms. Will torque on the input shaft cause movement of the arms? It appears not. And obviously it needs to be lubricated somehow, which they don't show. I'm sure there is secret sauce left out of the video, but may show up in the patents. Maybe there's a

      • Re: (Score:3)

        by Pascoea ( 968200 )
        Given that you still have to make the wheel turn left and right, unless they are only proposing this for the back wheels, there's definitely some aspects left out of this "educational video" from the manufacturer's advertising department. And yeah, that gearset just looks like it shouldn't work. At best, you're torque limited by the tensile strength of that little bar holding the gears in place.

        • Re: (Score:2)

          by AmiMoJo ( 196126 )

          Planetary gear systems are tried and tested technology. The Prius is probably the most famous example, using one to blend electric and fossil fuel power.

          • Planetary gear systems are pegged to rotating disks, everything rotates on bearings. These are under-constrained as a multi bar linkage. They will want to twist and suffer backlash and want to center the wheel in its vertical travel under torque.
        • They are shown as driving the front wheels in the video. So clearly this was a marketing video and not any actual revolutionary engineering.

      • I can't wait to have a gearbox full of oil bolted to a brake disc.

    • Re: (Score:2)

      by PPH ( 736903 )

      improves efficiency

      There is a friction loss at each gear to gear interface. Also a power loss associated with the churning of the lubricant. That's why many transmissions use a 1:1 (straight through) power path for their high gear. There is still a lubricant churning loss, but no friction at the gear interfaces.

      Planetary gears in the hubs is an old idea. Used on heavy equipment to get lower torque, higher RPM drive lines and axles. And on monster trucks. But they don't really care about fuel economy.

      • Re: (Score:2)

        by caseih ( 160668 )

        Indeed while watching the video a 2nd time, there are many problems with this design that aren't addressed in the video. There's no explanation of how the wheel would steer. Given that wheels have camber to them and actually tilt when turning, I don't see how this arrangement could possibly work without a CV joint in there still, only this time it would be spinning at 10,000 rpm. It's funny that they show a diagram of the car going around a curve but don't show the wheels turned. Even non-steering wheels

        • . It's funny that they show a diagram of the car going around a curve but don't show the wheels turned

          Maybe tank style handling is making a comeback. You could ditch the steering wheel for two levers, best part is you can zero radius turn for infinite doughnuts.

      • Re: (Score:2)

        by dfghjk ( 711126 )

        The video claims improved efficiency, it was not my claim. Also, the different solutions have to be considered as a whole, not merely at "each gear to gear interface", and it needs to be considered for its range of usage in the vehicle.

        • Re: (Score:2)

          by Pascoea ( 968200 )

          The video claims improved efficiency

          The ad in my email claims that there are hot singles in my area that will do impure things to me. You seem pretty fired up about this article for some reason.

    • Re: (Score:2)

      by ukoda ( 537183 )
      They did play up the space side of things a bit much. The Tesla solution doesn't take up that much more space, their graphic of the existing BEV was the design you when the manufacturer half-asses it because they just reworked an ICEV and called it an EV. The control from a motor per wheel is the real benefit I see.

    • Re:watch the video, don't be a dumbass (Score:4, Insightful)

      by MacMann ( 7518492 ) on Thursday November 30, 2023 @10:40PM (#64045557)

      There's an inherent cost of independent left and right motors, the motors.

      I remember reading about some then new EV a long time ago about how there was a "last minute" change to the design from two motors to a single motor. I wondered why they'd do that. After some thinking I concluded that a likely reason is that is that two motors cost more than one, but it's not just the motors that need to be there but the motor controllers and such to get them spinning. Another thing that came to mind is that if there were some kind of motor failure then one wheel could have power while the other does not, or possibly each motor could be trying to spin in different directions. I suspect such failures would be rare, and could be mitigated against in a number of ways, but if there's a traditional differential on a single motor then they won't have to answer a bunch of questions on such things from safety regulators.

      This uni-wheel concept makes sense only if each driven wheel has it's own motor, and it rarely makes sense to have a motor for each driven wheel.

    • Well, I could have easily invented this years ago, but people always kept telling : "don't try to reinvent the wheel!"

  • Efficiency (Score:3)

    by ishmaelflood ( 643277 ) on Thursday November 30, 2023 @10:03PM (#64045509)

    WAG 94% efficient due to friction in each gear pair. Could easily be worse. That space is usually brakes. You fell for clickbait.

  • What is the anticipated survival rate after a season of winter driving?

    This looks a lot more delicate than a traditional drive system, and the abrasive grit that sprays everywhere along with water and road de-icer does a number on 'delicate', and that only gets worse once the vehicle gets car cancer.

    • It's not exactly far away from where the differential is on cars. Certainly on lorries those are very exposed to the elements. I suspect that keeping it well sealed is a pretty solve problem.

  • The only thing that would be revolutionary is a way to prevent 40,000 people just in the USA (1 million worldwide) dying of traffic accidents every year. That's more than double the amount of homicides. We spend $130 billion on law enforcement. Why can't we spend the same amount on ADAS or self-driving R&D to reduce the number of traffic deaths by 1000? Every time the ADAS does a life saving or serious injury prevention maneuver it should ban that driver from going near a motor vehicle again. If vehicle

    • Re: (Score:2)

      by Entrope ( 68843 )

      Most law enforcement doesn't deal with homicides. Compared to homicide investigations and prosecutions, a lot more is spent on -- drum roll -- traffic law enforcement. How much of that are you willing to redirect to R&D that might, in a few decades, replace most of the cars on the road with a system that protects against a fraction of today's automobile-related deaths?

  • Is it?

  • It looks a bit complicated, lot of moving parts, needing lubrication and sealing from environment (that sliding part will be interesting to seal). Though it does replace 2 cvs joints and shafts.
    How is the wheel load transferred to the chassis?

  • Interesting (Score:3)

    by burtosis ( 1124179 ) on Thursday November 30, 2023 @10:42PM (#64045561)
    The pros listed seem to be correct, except there really isn’t much if any efficiency gain from motor to wheel. It adds a separate gearbox with increased part count at each wheel, so it’s not clear if it’s price competitive. Looks like the sprung weight would be slightly more than a standard hub with cv joint. All the pinions on the outside are going to be under very high torque and thus tooth forces, unlike the pinion in a traditional layout which is at reduced torque due to the gear reduction. Though it’s load sharing between two arms, it’s still greater than traditional setups and assuming helical gears to maintain better load sharing on a tooth by tooth interface means the side loading is going to be high putting quite a bit of torsional stress on the linkage. Further, the torque applied to the wheel is going to want to twist the linkage which will apply unnatural forces to the vertical deflection at the wheels, looks like they will want to center between the ends of travel with applied torque. Also it will need to be sealed at a large diameter which reduces efficiency and would be a failure point, I doubt it’s still 92% with that large diameter seal. The seal for the input shaft also isn’t shown, it’s going to need a massive boot to seal it though at least it’s not constantly flexing like a CV joint. It’s not clear how the outer gear is constrained, it looks like it’s riding on the two driven and two free pinions which brings up questions of how durable it’s going to be given the impact loading under its own mass and vibrations.

    I’m all for design optimization given new input constraints, but we will likely see a long process of teething to really see which innovations make the cut.

  • It seems that the the gears inside the wheel are exposed to the environment. Not sure if you can fully cover that to retain the flexibility but prevent sand from entering the planet gearsâ¦

  • I know manual is basically redundant on an EV or Hybrid however part of the massive resistance to switching is having to switch to automatic style transmission.

    Many love the muscle memory. As a Brit I'm well used by the vast majority of cars on the road being manual. Automatics are pretty rare, more expensive and the only option if you want to move to EV/hybrid.

    Having a manual license I can legally drive any automatic, those that passed the test in an automatic are unable to legally drive manual without a

    • Re: (Score:3)

      by merde ( 464783 )

      There is no particular reason why an EV cannot be programmed to behave just like a manual car. The controlling CPU would need to be connected to a clutch pedal and a gear stick, with force feedback - game controller on steroids - and some thought would have to put in to generating the right sound effects... getting the grinding noise and vibration that result from a careless gear change just right might be a challenge. I think the hardest part would be generating the evil smell that results from abusing the

    • Something very much like what you want is already being done with Continuously Variable Transmissions (CVTs). They're a different kind of automatic transmission that doesn't have the traditional gear shifts. Those were missed (yes, even by drivers of automatics), and so they have been artificially added back in. Drivers believe they are feeling a shift take place...even when they aren't doing it themselves.

      I also drive standard, but currently have an automatic. It's a great car, but I detest not having

    • > I know manual is basically redundant on an EV or Hybrid however part of the massive resistance to switching is having to switch to automatic style transmission.

      The vast majority of EVs don't have a "transmission" at all, but a single ratio gearbox. There's not even the "soft" shifting of an automatic.

      There are some manufacturers playing with the idea of faking shift points though. IIRC Dodge featured a Charger EV with fake engine noise and shifting...
      =Smidge=

    • Fake shifting is stupid and you only need the clutch because of the pathetic low RPM torque output of an ICE. Electric motors make peak torque at 0 RPM, so you are getting absolutely nothing out of fake shifting or a clutch except fooling yourself.

      "I recall one of the hurdles was the fact an automatic style transmission was much simpler to implement in an EV and the only issue was they hadnt figured out to implement manual yet."

      Almost no EVs have a transmission, just a couple. And they are only two speed. M

  • The basic mechanics are sound. The system does have less unsprung weight than wheel motors, and likely weighs less than all other EV drive options. But the devil is in the details.

    1. How will the system be sealed from the elements and road dirt? The input shaft likely needs more than a boot around it.

    2. How will steering be done? Will the inboard motor also have to pivot with the wheel? Or will a CV joint still be needed?

    3. The planetary gears don't have much bite on the outer wheel ring gear. How long will

  • Steve Jackson Games predicted this, postulating individual electric motors for each wheel in their (excellent) tabletop auto battle game Car Wars in 1980.

    https://en.m.wikipedia.org/wik... [wikipedia.org]

  • Way too many gears. Contrary to common sense gears are less efficient than chains or belts. Also, I know it's only a promotional video but all those gears looked like they have the same tooth count, which means that the the same teeth will continually mesh together. For maximum longevity, gear ratios are always picked so that over a number of revolutions, the meshing teeth always change. How will the gears be mounted? bearings? bushes? Be interesting to see how that lot would be kept lubricated. I just can'

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