Feasibility of spherical wheels.

[sganesh88]

We're trying to fit spherical wheels to move a prototype vehicle
rather than the circular one for our project. The
advantages we see are greater acceleration due to smaller M.I (for the
same mass of the wheels) and easy parking.
I suggested the conventional electric motor principle for giving drive to the
wheels. For steering, i think, by changing the orientation of the
field, we could bring about a change in the rotational axis.
Is this idea feasible? I am actually not sure about the steering part.

 

[Mech_Engineer]

I don't think that your perceived advantages of spherical wheels are entirely accurate, and they certainly don't outweigh the numerous disadvantages.

Perhaps you could explain in more detail how you plan to drive the wheels, it's not making much sense right now...

 

[sganesh88]

I don't think that your perceived advantages of spherical wheels are entirely accurate, and they certainly don't outweigh the numerous disadvantages.

QUOTE]

I don't know which advantage that i mentioned, you are referring to. If ou come with a point against it, i'd appreciate. Regarding the method of giving drive, i think of making the wheel just like the rotor of an electromagnetic motor.

 

[russ_watters]

The first advantage you mentioned, better acceleration, doesn't make sense to me. A spherical wheel would have more mass than a regular one and therefore be tougher to accelerate, would it not?

And it does also seem to me that driving such a wheel (mouse ball style?) would be very problematic. If you do it mouse ball style, you vastly increase the rolling resistance of the wheel because your driving rollers have to dig into the wheel, creating friction.

Regarding the method of giving drive, i think of making the wheel just like the rotor of an electromagnetic motor.

That doesn't help us very much. You mentioned multi-axis motion, but a motor has only one axis. And it also has an axle! Would your wheels have axles or be magnetically suspended, or what?

If your wheel has an axle and a single axis of rotating, then making it spherical just adds a lot of rubber and steel to the wheel that never gets used.

 

[sganesh88]

"The first advantage you mentioned, better acceleration, doesn't make sense to me. A spherical wheel would have more mass than a regular one and therefore be tougher to accelerate, would it not?"
M.I of a spherical wheel is lesser than that of a circular wheel of the same mass. Even with a decent increase in the mass in case of the spherical wheels, the M.I will turn out to be less.
http://en.wikipedia.org/wiki/List_of_moments_of_inertia (In the list, torus could serve as a close approximation for circular wheels i guess)
And yeah. I'm confused about the fitting of the wheels. One model i saw in the net has a small cylindrical wheel driving the spherical one through friction. But that was for some vacuum cleaner. That wouldn't do here.

 

[Mech_Engineer]

I don't think you should compare wheels of similar mass, because a sphere of the same mass as a cylindrical wheel will have a smaller diameter. Comparing wheels of the same diameter will give you a better comparison IMO.

You still haven't explained how you plan to drive the spherical wheel in the first place. Like Russ said, if it's driven about one axis (akin to having an axle through it), then there's no reason to use a sphere at all, since a cylinder of the same diameter will accomplish the same task with less weight.

 

[russ_watters]

"The first advantage you mentioned, better acceleration, doesn't make sense to me. A spherical wheel would have more mass than a regular one and therefore be tougher to accelerate, would it not?"
M.I of a spherical wheel is lesser than that of a circular wheel of the same mass. Even with a decent increase in the mass in case of the spherical wheels, the M.I will turn out to be less.
http://en.wikipedia.org/wiki/List_of_moments_of_inertia (In the list, torus could serve as a close approximation for circular wheels i guess)

I don't think you can really say either of those things. Wheels aren't easily reduceable to simple structures like that. You'll need to actually design one and calculate the mass of the wheel, tire, supporting spokes, etc. And what about contact area? How do you ensure you have enough tire touching the ground? And how do you support an inflated spherical tire?

Regardless, I still don't see how you would think that a sphere the same diameter as a torus or cylinder would have the same mass. I'm reasonably certain it would not.

 

[MIC]

I would like to see something like this, but you will have to develop a great way to manipulate the sphere. A sphere has many degrees of motion, you don't want it rolling in the wrong direction on mistake. I would like to see how you plan to make the various magnetic fields. The single rotor and stator design ( windings, teeth, disk shape ) won't be adequate, because you don't have the fixed axis in relation to the windings. Do you have some drawings of your "wheel", and a description of how the motion will be accomplished/controlled?

 

[analogic89]

The person wants to develop something new, despite the misconceived advantages, so instead of correcting him (or her), I present a solution.

I, too, have been doing the same research for a while. More specifically, since I, Robot came out with the Audi RSQ (drool). Beautiful car, but not much explanation of how it works. So, I tried to come up with something of my own.

I also thought that if I could electromagnetize the wheel, it would respond to changes in the field that could be directed by a computer that interprets signals from the driver. After while, I gave up on this concept and tried a mechanical solution.

I came up with something similar to what the berkeley came up with as described here:


http://bleex.me.berkeley.edu/ME102/proj_archive/S05/9-Spherical_Wheel/how_works.htm

though, I expect that they would haev problems with ground clearance and human interface.

I had a design that could be controlled with simple circuits and mechanics, but no working omdel yet...

 

[russ_watters]

Welcome to PF.

Neat project. Just to clarify, though, no one said it wouldn't work, we just questioned whether it would be better than regular wheels.

 

[calceus]

consider a single spherical "wheel" as the entire vehicle:

39 sec video:

 

[mf123]

I do not believe you have thought out the acceleration, with a sperical wheel there is less surface area in contact with the ground so there will be less grip so the acceleration will be poor. As for the handling you will need a multiple axes axle, one idea would be multiple rotating 'balls' that are in cotact with the wheel and these would be easier to control directly I suggest having 'balls' going round the ball as opposed to being on one side perhaps coming from the wheel arches and as for braking I do not know how you are going to work this out it is the same problem as the acceleration there is less surface area I'm contact with the ground so if you were to brak harshly the wheels would probably skid over the ground

I would personally like to see spehical wheel in the future, once these tweeks have been figured out I believe that the advantages of a spherical wheel would be far greater then conventional circular wheels even for one example of parking

 

[xxChrisxx]

A spherical wheel wouldn't necessarily be any better or worse than a standard wheel in terms of grip. As contact patch size has nothing to do with availalbe levels of grip (this isn't fully true but its close).

A non rectangular contact patch will make for funny handling however.

 

[Integral]

One of the features of a modern tire is that it deforms giving a larger foot print on the ground. The reason it can deform as much as it does is because it is pneumatic. How do you propose to achieve similar behavior in a spherical wheel? If you use material soft enough to deform without a pneumatic core your wear rate will be large. It would be very interesting if you could come up with a spherical pneumatic wheel!

 

[Emreth]

Pneumatic wheel then generates problems though when you try to drive it with the rollers, you'll lose traction there when its too soft. That berkeley thing is just a mouse. And i think its the only way you can drive a spherical wheel. There are so many disadvantages about spherical wheels. Inertia is high compared to normal wheels at same diameter, less traction due to small contact area-terrible grip, additional friction losses from the driving rollers. And what do you get in exchange?Better parallel parking?You can do that with normal wheels too. What else is the advantage?I don't see one advantage, that's why they are not used.

 

[tenacity2986]

It is highly expensive as well as highly possible to create a system that runs off of electromagnetics where the spherical wheel "floats" under the vehicle but is magnetically controlled by numerous sources that position the wheel to spin around the axis of magnetization. This way you wouldn't need any PHYSical connection between the sphere wheel and to turn the wheel in a certain direction, the magnetic force would have to alter to redirect...

 

[eye_mo99]

we're also doing a similar project on spherical wheels. we figured a way to control the sphere by using propellers to restrict it's movement. we consulted a professor here in our place and he said it was possible. do you have any ideas?

 

[eye_mo99]

Welcome to PF.

Neat project. Just to clarify, though, no one said it wouldn't work, we just questioned whether it would be better than regular wheels.

it COULD be better. if you could fine a way to control the sphere then why not? you could move up to the six degrees of movement.

 

[Emreth]

You don't have 6 degrees of freedom on the road (in a plane), just three..unless the car is going to fly as well.
The best way to increase mobility is to get normal wheels on axles that can make full rotations. It requires complicated transmission,etc but it can be done..and has been done.
Exercises on spherical wheels are encouraged to see why not to use them.

 

[xxChrisxx]

And if it'll fly, why have wheels at all :P

+1 for Emreths post.

 

[grimm110]

LEANING motions could be used to steer the spherical wheels