Why don't I ever see robots that steer like a car

[abeD]

It's definitely been done in the past, but it would probably be under 1% of all robots in the last 8 or so years. I know my team did it in 2003 and had some success.

[Kevin Sevcik]

Ackermen steering is a definite advantage for smooth turns and probably has speed advantages. It's also nicer on the wheels and carpet. However, it's not terribly useful for precise positioning. Imagine if there was a trackball right beside your car. If you wanted to grab it, you'd have to pull a reasonably complicated two-point turn. Or pull all the way around, etc. A tank drive robot merely has to turn 90 degrees in place.

[MrForbes]

This is a discussion we've been having for a week now! no resolution in sight, either.

We're working on a car steering type chassis design, as well as playing with the control algorithm for last year's 6wd. It'll be interesting to see how this showdown comes out, we are sort of planning to build the Ackermann design and drive both around and see how they compare.

For those who had trouble with car type robots in the past, what specifically were the problems? Your help would be appreciated!

(and Kevin, it might even be better to make another quick lap and make another attempt at the ball!)

[Capt. Quirk]

Originally Posted by squirrel

This is a discussion we've been having for a week now! no resolution in sight, either.

squirrel,

Will your team be competing in Las Vegas Too?

[MrForbes]

We signed up for Phoenix and Los Angeles FRC regionals....no Vegas...although the FTC team wants to go to the Vegas FTC regional. We haven't figured out yet if they are, school might interfere with their fun.

[popo308]

The only plus i see to having the front wheels spin like a car is you keep your motors running at top speed while you turn you never slow down as you turn.

As with a tank steer you have to cut power to half of your drive train in order to turn so potentially you are losing speed. Not much but you are....

[MrForbes]

Yup, and if you design the robot with the CG about 6" off the floor like we are, you should be able to just zip around corners like nobody's business.

[popo308]

Originally Posted by squirrel

Yup, and if you design the robot with the CG about 6" off the floor like we are, you should be able to just zip around corners like nobody's business.

Very true if you gear it right nobody will be able to catch you as well

[Racer26]

1075 did a very "out there" drive as far as FIRST goes in 2003, our rookie year.

Anyone that was at the Canadian Regional that year (now Greater Toronto Regional, as there are now TWO Canadian Regionals!) would have seen it. I think Delphi E.L.I.T.E (FRC#48) gave us an award for most unique drivetrain.

It functioned a bit like a tricycle, we had two undriven wheels at the back of the robot, and an 8" wide track driven by the two CIMs and two Bosch drill motors they used to give us. Then we swung the whole track unit about a point at the front of it. We used a potentiometer on the pivot to track its location, and our autonomous mode was able to climb the ramp very quickly.

I remember that we had a match against one team whose autonomous mode never left the starting box, but instead extended an arm up and over the plexiglass border to reach the pyramid of boxes. Our drivetrain allowing us to turn at full speed got our whole robot to the boxes before they could get their arm there.

This particular unit was plagued by a problem with our inexperience at building drivetrains. It used a miter gear, but we didnt support it closely enough, and under load they were skipping teeth and shredding the gear. We finished 2nd in the competition, mainly because the gear was so shredded we couldn't even climb the ramp.

[Capt. Quirk]

Originally Posted by squirrel

We signed up for Phoenix and Los Angeles FRC regionals....no Vegas...although the FTC team wants to go to the Vegas FTC regional. We haven't figured out yet if they are, school might interfere with their fun.

I'll come and check out your bot in LA. We recieved our funding too late to be able to compete close to home. So were going to Vegas instead.