New wheels / floor and encoders for position.

[Daniel_LaFleur]

Originally Posted by martin417

It is great that First included encoders and the ability to mount them to the gearbox. It's too bad that combination will be effectively useless this year. With the limited traction, there will be so much wheel spinning, as well as lateral sliding, that gearbox encoders will not give any useful information about where the bot is, and what it's doing.

<R06> talks a great deal about what wheels can be used for traction, and that no devices may be used to increase traction. What about a high traction wheel that touches the ground, but does not affect traction? Say, a wheel with an encoder attached? The way I interpret the rule, this would be acceptable.


Any disagreement?

Not quite correct
<R06>
ROBOTs must use ROVER WHEELS (as supplied in the 2009 Kit Of Parts and/or their equivalent as provided by the supplying vendor) to provide traction between the ROBOT and the ARENA. Any number of ROVER WHEELS may be used. The ROVER WHEELS must be used in a “normal” orientation (i.e. with the tread of the wheel in contact with the ground, with the axis of rotation parallel to the ground and penetrating the wheel hub). No other forms of traction devices (wheels, tracks, legs, or other devices intended to provide traction) are permitted. The surface tread of the ROVER WHEELS may not be modified except through normal wear-and-tear. Specifically, the addition of cleats, studs, carved treads, alterations to the wheel profile, high-traction surface treatments, adhesive coatings, abrasive materials, and/or other attachments are prohibited. The intent of this rule is that the ROVER WHEELS be used in as close to their “out of the box” condition as possible, to provide the intended low-friction dynamic performance during the game.

R06 does not stop you from increasing traction, it just prevents you from using anything else to provide traction

Originally Posted by martin417

Actually, a caster was what I had in mind. I believe that any resistance from the caster will be at least an order of magnitude less than wheel friction, so in engineering terms is "negligible", therefore can be ignored.

Negligible traction is still traction.

Originally Posted by Russ Beavis

Why couldn't you use encoders with slipping wheels? The sensors will certainly tell you actually how fast the wheel is spinning. Maybe you can use that information with an expected PWM signal vs. speed curve for traction control?

For example, if you observe that the wheels suddenly start spinning from a low speed to a higher speed, assume that slippage is occurring and reduce the drive signal.

Cars are really starting to take advantage of traction control. Maybe FIRST robots can learn from them?

Russ

Traction control and accelleration control will be key this year to winning alliances. IMHO