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Two axis self-balancing Electric Unicycle?


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I've been casually following the progress made at Lit Motors, and if you are not familiar with them, they are the company that is trying to develop a commercial version of a self-balancing motorcycle.

https://www.youtube.com/watch?v=Z0m-cUxMcJw

The tech is basically based on those gyroscope toys you played with as a kid.  Once spinning, they tend to resist a change in orientation perpendicular to the axis allowing them to stay upright.  The Lit motorcycle uses an enclosed duo gyroscope I believe to counter act a tendency to fall from side to side.  If you watch how they kick and push the motorcycle, it's pretty neat to see it resist falling over.

What I was thinking about was whether it would be possible to incorporate a small spinning gyroscope into an electric unicycle so it would balance upright by itself.  The forward and backwards balancing is taken care of by the hub motor, but if one were to incorporate a small gyroscope on top say, then one could hop on and roll around without fear of falling over sideways.  In theory that sounds pretty good, but then I wonder how it would affect turns as it would resist sideways leans and weight shifting?  Would it just want to go forwards and backwards only?  Would the additional weight and power requirement to spin a mechanical gyroscope just be a hindrance to the battery's range?  It would be neat to see though a totally self-balancing EUC.

Edited by HunkaHunkaBurningLove
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@HunkaHunkaBurningLove Fascinating concept!  I believe that EUCs & EVs are in their infancy and that we will see tremendous advances in personal transport technology within the next few years. Your gyroscopically stabilized EUC that is totally self-balancing will eventually come to pass. Sure there will be technical obstacles, but what we can conceive, we can (eventually) achieve.  After all, if someone told you 30 years ago that today you would be carrying around more computer power in your back pocket than was on the Apollo 11 that landed on the moon, you'd think they had lost their mind. 

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@HunkaHunkaBurningLove, Honda are working on a self balancing in both axis EUC see at 5:00 minutes in this video:

However this uses a sort of caterpillar track come wheel design that, to me, looks a too complex to be a reliable concept, I certainly cannot envisage it working well after a few dips in mud.

If a mechanical gyro could be made to work as well as it appears to in the Lit motorcycle it would make EUC's very easy to ride and I doubt it would consume much additional energy.

I can't quite get my head around what the interaction with turning, etc would be though? It looks like it requires two flywheels spinning in opposite directions in which case the net impact of the system on handling should be almost zero except for the increased weight - unless, of course it actually resists all attempts to lean the wheel to turn, which I am fairly sure it would -  I wonder if that is why the Lit video does not show the motorcycle doing a turn at speed? 

If that is the case, slow speed turning on a stabilised EUC would have to be by body twisting (which lots of riders do already at slow speeds) as speed increases the spinning EUC wheel needs to take over balancing and the gyros slow down so they stop preventing leaning. A more complex, but surely quite possible, control mechanism. Hmmm, could certainly be the future ;-)

 

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Ah yes, I remember seeing that Honda self-balancing transport before.  It's cool in its own right, but probably not that practical in outdoor situations.  In the Lit motorcycle, it looks like the gyro orientation is pivoted to compensate for forces that try to tip it over.  In a turn I wonder if they pivot to alter the lean of the vehicle to work in the direction of the turn with varying lean dependent on angle of turn?  It's quite a neat way of using mechanical gyroscopes to affect the orientation of an object.  I've always been fascinated by gyroscopes and those science experiments where someone spins a bicycle wheel.  I had one of these as a kid and had hours of fun with it:

https://www.youtube.com/watch?v=p9zhP9Bnx-k

And I think we've all seen this video which boggles the mind:

https://www.youtube.com/watch?v=GeyDf4ooPdo

 

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If you look at the size of the gyroscopes in the Lit motorcycle in relation to the size of the vehicle itself, I wonder if a smaller version could be used on a EUC.  The EUC housing and weight is pretty minimal so maybe a hand-sized gyroscope would be enough if mounted just above the wheel where most handles are placed.  It also probably doesn't need to pivot a whole 360 degrees so I'm guessing maybe 30 degrees in either direction would be enough so the size of the housing wouldn't need to be large.  It would add some complexity to the balance system as a gyroscope controller would be needed to manage the orientation.  One problem might be that weight shifting turns would tend to be counteracted by the gyroscope as it naturally wants to stay level. 

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On 4/2/2016 at 9:32 AM, HunkaHunkaBurningLove said:

If you look at the size of the gyroscopes in the Lit motorcycle in relation to the size of the vehicle itself, I wonder if a smaller version could be used on a EUC.  The EUC housing and weight is pretty minimal so maybe a hand-sized gyroscope would be enough if mounted just above the wheel where most handles are placed.  It also probably doesn't need to pivot a whole 360 degrees so I'm guessing maybe 30 degrees in either direction would be enough so the size of the housing wouldn't need to be large.  It would add some complexity to the balance system as a gyroscope controller would be needed to manage the orientation.  One problem might be that weight shifting turns would tend to be counteracted by the gyroscope as it naturally wants to stay level. 

I wanted to try it but I can't find an easy way to buy balanced flywheels.

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@HunkaHunkaBurningLove, I've looked at all of the footage I can find of the Lit Motorcycle; nowhere can I find footage of it banking into a turn, if anyone else manages to find some I would love to see it.

Your second video above shows the same twin counter-rotating gyros that it looks like Lit use, as all the videos show, the arrangement is excellent at keeping the vehicle upright - so well that I cannot get my head around how the thing can possibly lean over into a turn? My gut feeling is that the Lit Motorcycle will handle like a trike or motorcycle with sidecar. As such, of course a gyro stabilised EUC would be impossible to turn except by twisting. 

I'm sure that stabilisation and the ability to lean must be achievable, but I'm not at all sure Lit have solved it yet - the fact the vehicle has hemispherical tread I.e. Motorcycle type tires instead of flat car type ones does suggest I'm wrong (or at least Lit don't want people to know it can't be banked?) Offhand I can think of only two ways of achieving banking, neither even close to ideal: power down the gyros once the wheel is moving fast enough to balance itself or have physical servo rams driving the gyro subframe that, effectively, bank the vehicle whilst leaving the gyros horizontal.

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5 hours ago, Keith said:

@HunkaHunkaBurningLove, I've looked at all of the footage I can find of the Lit Motorcycle; nowhere can I find footage of it banking into a turn, if anyone else manages to find some I would love to see it.

Your second video above shows the same twin counter-rotating gyros that it looks like Lit use, as all the videos show, the arrangement is excellent at keeping the vehicle upright - so well that I cannot get my head around how the thing can possibly lean over into a turn? My gut feeling is that the Lit Motorcycle will handle like a trike or motorcycle with sidecar. As such, of course a gyro stabilised EUC would be impossible to turn except by twisting. 

I'm sure that stabilisation and the ability to lean must be achievable, but I'm not at all sure Lit have solved it yet - the fact the vehicle has hemispherical tread I.e. Motorcycle type tires instead of flat car type ones does suggest I'm wrong (or at least Lit don't want people to know it can't be banked?) Offhand I can think of only two ways of achieving banking, neither even close to ideal: power down the gyros once the wheel is moving fast enough to balance itself or have physical servo rams driving the gyro subframe that, effectively, bank the vehicle whilst leaving the gyros horizontal.

If you read the info on this page:

http://litmotors.com/c1/

It mentions that it uses the gyros to create lean to assist in steering just like a motorcycle.  I'm no gyroscope expert, but I think the tilting of the gyros that allow it to keep upright can be orientated while in motion to impact a change in the vehicle's camber position so it's tilted.  If the gyros are able to maintain an upright position they must be able to hold the vehicle at almost any angle I'm thinking even while it is stationary.

Watch the video on this page, and you can see some slight banked turns:

http://www.dailymail.co.uk/sciencetech/article-3083109/When-bike-car-MERGE-Futuristic-C-1-reach-100mph-NEVER-fall-thanks-self-balancing-technology.html

@MetricUSA. I can see why the gyro stabilized bicycle wasn't a big seller as slapping on a pair of training wheels would do pretty much the same thing for a lot cheaper.  But with the EUC balancing side to side is much trickier than on a bicycle so maybe there is some reason why a totally self-balancing system would be a benefit.  For robotics a robot EUC that is side to side stable that can pivot on the wheel might open up whole new possibilities for a small foot print device. Now imagine BB-8 having something like that and imagine the places it could roll around to...

Edited by HunkaHunkaBurningLove
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Having gyroscopes on a euc doesn't make sense.  The C1 uses a steer by wire system which means that every aspect of a turn is controlled by the electronics.  So it uses the gyroscopes to lean or the front wheel counter steer based on speed and input from the driver via the steering wheel.

Euc's are simple and use a simple mechanism which relies on the riders own sense of balance to handle all sorts of speeds and riding conditions.  To achieve what they are trying to do with the C1 on a euc would require a special seat and steering mechanism.  Essentially you would end up with something that would be entirely different to what we know as a euc and at that point you would end up with a transportation device so large that might as well add an extra wheel.

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On April 4, 2016 at 1:15 AM, lizardmech said:

I wanted to try it but I can't find an easy way to buy balanced flywheels.

Make your own?

Regarding oolong's post, I was not thinking of making a Lit EUC, but maybe just having a small secondary system that can be shut off or turned on depending on the need.  Like making it easier for learners or for long treks where you just want to lean and go or for bumpy pathways where a little gyro action can help keep you on track, for autonomous robots to defuse bombs that can get to places faster and easier or for busy places where you don't want to have an accident.  Oh well it's probably just a future thought...

I wonder if one could take a powerball and attach it to a EUC whether it would be big enough.... I was watching some cool powerball 12000 rpm videos...

Edited by HunkaHunkaBurningLove
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Can someone point me to some useful equations for gyroscope?  There are many web sites about gyro but all of them just show very complicated math which is difficult to understand without digging further into physics.  I just want to relate angular velocity, angular mass, to stabilization, in simple formula.  What I am getting at is to be able to calculate how big a flywheel is required and how fast it has to rotate for it to be able to stabilize a person at a certain weight.

Edited by hyiu00
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  • 1 year later...

I don't care about side-to-side balancing, we can all do that already, but what about using a gyroscope as a secondary system for balancing in the front to back plane as protection against catastrophic failures like MOSFETs burning up, mainboard problems, wiring issues, etc? The gyro would not propel you forward, but it could keep you from faceplanting. Seems like you could do that with a fairly small gyroscope package.

Now, feel free to poke holes in that idea while I sit back and watch. :popcorn:

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That's a neat self-balancing stick.

Just a theoretical question after watching this video again, what would happen if another rotating weight spinning in the same direction were to be placed on the other end.  Would that increase the rate of the gyroscopic precession?  Would the "bar bell" feel lighter allowing it to be picked up easier in the middle of the bar?  It still boggles my mind to see him able to pick up the bar by the end and over his head if the weight remains constant since he could barely lift the weight near the wheel.  :blink:

Regarding dbfrese's idea, that would be a neat safety feature to be able to dampen a faceplant or stop it entirely, but I think it would counteract the rider's ability to control the speed and braking as the forward and backward forces would be dampened by the safety gyro?

Edited by Hunka Hunka Burning Love
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5 hours ago, Hunka Hunka Burning Love said:

but I think it would counteract the rider's ability to control the speed and braking as the forward and backward forces would be dampened by the safety gyro?

I had that thought too, but how about if the gyro's gimbel wasn't "locked" in place while the EUCs motor was functioning normally? In the event of failure, the gyro would instantly lock into place, stabilizing the wheel in the front-back plane. In that case, a "failure detector" would be needed to trigger the lock within a few milliseconds. 

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