New Transporter in the works

[KSagal]

Originally Posted by GadgetmanKen

How would having a third wheel help in stability in faster speed if you lean forward to go faster, which would lift up the rear wheel off the ground. Then it would serve no purpose. The HT, I2, X2 has great stability in slow speeds. Therefore the third wheel would have to be used in front for stability in faster speeds. If they are wanting to go after T3's share of the Police or Security market they would need the Segway to go faster than it does. So thats why I'm thinking it has to be a drop down wheel in the front, perhaps gravity feed, pendilum style. It would also have to be a castor type wheel that turns beacaus the turning as it is is controlled by increasing or decreasing the speed of one wheel. It will most likely fall forward at a certain rate of speed with a horizontal stabilizer that would lock in down. Probably with a curvature in it. Thats my thinking on it. I also think it will be called an I3.

Anyone who has seen a T3 take a hard turn at speed will realize that momentum will often cause the inside rear wheel to lift. This makes for an unstable situation.

Most single front wheel trikes of any sort have stability problems in high speed hard turns.

There are some that have vertical movement and active suspension for all the wheels, to compensate for this. But that would require a totally different machine to what we call a segway.

I do wonder. There are lots of possibilities.

Originally Posted by rickb

Stability in my opinion relates to the Seg in shut down mode or stopped position allowing for solid 3 point parking, safety in an emergency shutdown mode, and a stabile machine when mounting or dismounting. Ideal for equipment laden patrol officers and wannabe Segway owners with balance issues.

This is the concept that I presented with the PUMA. It has many wheels, but all but two are not used for motivation, and are used for crash avoidance (only come in contact if leaning too far, and out of operating envelope) or for parking, and mounting.

You could add this to a segway without a total and complete redesign. I do not believe you can add some of the other concepts and still have a segway or something we would recognize as one.

[rickb]

I wouldn't suggest or even imply changing the Segway as we know it unless Segway Inc. and purists feel minor design or engineering changes make it better from a performance perspective and ultimately enhancing the glide. I would 'speculate' a machine to compete with the T3 to be a totally different class of Segway.

[JohnM]

Originally Posted by rickb

I would 'speculate' a machine to compete with the T3 to be a totally different class of Segway.

Agree. Segway has shown with their robotic platforms that they are not completely married to the idea that all their offerings have to use dynamic stabilization. 2, 3 (with castors) and 4 wheel RMP configurations are available.
If the public safety market wants T3-like transporters, Segway is probably capable of offering something similar but better.

[Bob.Kerns]

Originally Posted by GadgetmanKen

How would having a third wheel help in stability in faster speed if you lean forward to go faster, which would lift up the rear wheel off the ground. Then it would serve no purpose. The HT, I2, X2 has great stability in slow speeds. Therefore the third wheel would have to be used in front for stability in faster speeds. If they are wanting to go after T3's share of the Police or Security market they would need the Segway to go faster than it does. So thats why I'm thinking it has to be a drop down wheel in the front, perhaps gravity feed, pendilum style. It would also have to be a castor type wheel that turns beacaus the turning as it is is controlled by increasing or decreasing the speed of one wheel. It will most likely fall forward at a certain rate of speed with a horizontal stabilizer that would lock in down. Probably with a curvature in it. Thats my thinking on it. I also think it will be called an I3.

Sigh. I can't think of a really good way to explain this without animations, and even then it might seem like magic. But here goes anyway...

You're thinking of things as if the platform and the three wheels were rigidly connected.

But that does not have to be the case. They can be linked so that the load is always shared between front and back wheels, with the center of gravity always "above" (relative to net acceleration) a point between front and back wheels. This is really no different from what the Segway does now, except (a) instead of balancing over the axle, it would involve balancing over an arbitrary point between axles, and (b) instead of rigidly connecting to the axles, at least one of front or back would need to be a non-rigid connection. (This non-rigid connection could be active or passive).

Remember, there's a computer on board. There is no need to rely on castoring to align the third wheel in the proper direction. You can compute the correct position based on the turn rate, and force the third wheel into that position with a servomoter.

Have you ever driven a shopping cart with a wheel that didn't quite make full contact, but kept wobbling back and forth?

You really do NOT want that.

[SegwayDan]

The point that seems to be being disregarded in this thread is the significant benefit and importance of the current Segway PT dynamic balancing system. Its benefits are:

1. Zero turning radius when needed
2. Combined acceleration/braking/steering control
3. Dynamic balancing over two side-by-side wheels
4. Smallest possible footprint

The T3, for example, has NONE of these attributes which results in its being significantly more awkward to handle:

1. >0 turning radius
2. Separate controls for acceleration/braking/steering
3. NO dynamic balancing which results in a MUCH less stable machine, especially when climbing and descending hills. I really wouldn't want to make a hard turn coming down a steep hill at speed, for example.
4. Larger footprint than a Segway PT

If Segway scraps any of the PT's attributes for the sake of a third wheel, they'd be throwing the baby out with the bath water.

Soooo, why and how would they add a third wheel sensibly?

I'm guessing a third wheel would serve to provide stability for when the machine is operating very slowly or when it is stopped or parked.

Why else would it be needed?

This is why I think it should be in back and be a caster so that it could simply caster to follow the two main wheels. It would be on an arm or hinge which would lift it up once the machine went above a certain slow speed so that Segway-style dynamic balancing could be actuated for the two main wheels.

One distinct advantage of the existing PTs is their stability fore and aft while ascending and descending hills. The driver remains vertical and the platform remains essentially level.

This is not the case for the T3. It would also tend to accelerate going down hill where the PT doesn't.

[Bob.Kerns]

Originally Posted by SegwayDan

The point that seems to be being disregarded in this thread is the significant benefit and importance of the current Segway PT dynamic balancing system. Its benefits are:

1. Zero turning radius when needed
2. Combined acceleration/braking/steering control
3. Dynamic balancing over two side-by-side wheels
4. Smallest possible footprint

The T3, for example, has NONE of these attributes which results in its being significantly more awkward to handle:

1. >0 turning radius
2. Separate controls for acceleration/braking/steering
3. NO dynamic balancing which results in a MUCH less stable machine, especially when climbing and descending hills. I really wouldn't want to make a hard turn coming down a steep hill at speed, for example.
4. Larger footprint than a Segway PT

If Segway scraps any of the PT's attributes for the sake of a third wheel, they'd be throwing the baby out with the bath water.

Soooo, why and how would they add a third wheel sensibly?

I'm guessing a third wheel would serve to provide stability for when the machine is operating very slowly or when it is stopped or parked.

Why else would it be needed?

This is why I think it should be in back and be a caster so that it could simply caster to follow the two main wheels. It would be on an arm or hinge which would lift it up once the machine went above a certain slow speed so that Segway-style dynamic balancing could be actuated for the two main wheels.

One distinct advantage of the existing PTs is their stability fore and aft while ascending and descending hills. The driver remains vertical and the platform remains essentially level.

This is not the case for the T3. It would also tend to accelerate going down hill where the PT doesn't.

The system I'm talking about would not give up any dynamic balancing. The platform would still dynamically balance. I quite agree with you about the benefits of a self-balancing system. I don't think you have to give up any of them.

And I can't tell, thanks to there being no clear terminology, if you've gotten my point about the third wheel and dynamic vs active castoring. IMO, it should NOT just "follow along", but should be electrically placed in the position it SHOULD be if castoring worked ideally. Which it doesn't.

My apologies if I'm getting redundant here. I can't tell if I'm making a muck of the explanation, or not.

Remember the SegTrax? That balances the platform, with an entire tank tread on each side. More dramatic a difference than a 3rd wheel.

Now consider a triangular frame connecting the three wheels.

Now attach two pivots to that frame, above the triangle, between front and back, at the level of the Segway's wheel axles.

Now, drive the wheels forward and back to keep the platform level. Now you *almost* have a Segway.

The one difference is that when you drive the wheels of a Segway forward to catch up with the platform, the torque you apply to the wheels also tends to tip the platform back. So we either have to be more aggressive about accelerating the platform, or apply a torque back to the platform. Springs would be one possibility, so would an active system with a servomotor.

Bottom line, Segway doesn't have to give up any "Segwayness" by adding a third wheel -- except the part about it falling over if you turn it off. Balancing a platform does not require exactly two wheels -- but two wheels requires balancing.

Anyway, I think I've run out of ways to explain it. I hope at least one makes sense to people.

One thing you probably DO lose with 3 wheels -- turning radius. You can turn around the midpoint of the two wheels. But if the third wheel is further away from that point than the current rear corner of the platform (which seems likely) you'll need a bit more room to turn than presently. It would sure beat the T3 though!

[JohnM]

Despite all the supposed advantages of the dynamically stabilized 2 wheeler and the supposed disadvantages of the non-dynamically stabilized 3 wheeler, the T3 fits the needs of a segment of the public safety market, drawing off sales from Segway Inc. If there are customers that want a 3 wheeler, its in Segway's best interest to offer one.

"Segway Director of Global Police and Government Business Chip MacDonald said the new vehicle is not a replacement for the company’s current line of two-wheel public safety patrollers, but a natural extension of it that’s designed to fulfill additional roles in a market the company created."

Segway might be better off giving the public safety market what they want rather than offering them only what current EPAMD enthusiasts want.

[Bob.Kerns]

Originally Posted by JohnM

Segway might be better off giving the public safety market what they want rather than offering them only what current EPAMD enthusiasts want.

I quite agree. My point is, they can, in theory at least, do it better and safer by including dynamic stability.

In practice, you come into questions of cost. I *think* self-balancing 3-wheeled could be done around their price point, but that's a lot harder to evaluate sitting here.

[jgbackes]

I think it would be cool if it stood up on two wheels when you started moving. Going down a curb would be much easier if you are balanced on two wheels.

Slow down and it rocks down on three wheels. It will be interesting.

[Lily Kerns]

I'm not an engineer and not qualified to do any technical speculation. But I've said from the first time I was on one that it needed retractable landing gear. The stand is fragile simply because if it was stiff it could/would catch when you start up and cause big trouble.

I am not a fan of 3-wheeled devices unless they can deal with the potential for tipping inherent with a front third wheel. I'd rather see it be the "landing gear" concept for stability when not moving. The fact that it is being designed for police/security work makes me suspect that whatever is included will allow an officer to step off and let the Seg wait for his return.

We shall see! Patience!