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

Wouldn’t that be an advantage in this competition?

Teams have toyed with the concept before. 812 (2003) and 1135 have tried. It didn’t work too well in one of those cases.

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.

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.

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!)

squirrel,

Will your team be competing in Las Vegas Too?

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.

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…

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

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.

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.

What do you mean drive like a car?

Like Frontwheel Drive/Backwheel steering?
Vice versa?
I dont get it. I know many robots have done that.

Perhaps the reason is that teams that have the capability of designing a car-like steering mechanism also have the ability to go to an even more agile design - swerve or crab drive.

Here are a few images of previous robots with steering mechanisms similar to what have been discussed in this thread:

http://www.firstroboticscanada.org/site/node/410
http://www.firstroboticscanada.org/site/node/367
http://www.firstroboticscanada.org/site/node/325

http://www.firstroboticscanada.org/site/node/323

because the turning radius is to large and would put you out of position

p.s sorry if this was already posted didnt read through all of them

Like the others have said, it would be hard for you to turn around and go backwards in a quadrant. Other than that, this years game would promote it I think. If you decided not to hurdle the trackball or pick the trackball up off the ground, then you could build a really nice drive train that turns easy and could push the trackball around the track. I don’t how easy it would be to build a CAR like drive train,( I’m not that technically inclined in this area ).

The reason why I think most teams don’t use it is, like Kevin Sevcik said, you have to do a Y turn to turn around and its so much easier to have a drive train that can spin in a tight radius. Another reason is that it might be harder to build a CAR steering mechanism rather than lining up 6 wheels and running chain to all the wheels from a gearbox.

Car like steering was not really advantageous in the past because the games were more of maneuverability. This year however, since you will be running around the track, I would think if your strategy is to just run around to get points then it would work well. If you are herding it may cause some problems if you lose control and try to get the ball back.

This year, for the first time since I’ve been involved with FIRST (12 years) we discussed car type steering briefly. For this game it might have an advantage in that you would have better precision when driving through holes in traffic than with tank type drives. The down side, as others have mentioned, is that you can’t “turn in place” as with tank drive. Because of it’s simplicity, I’m sure most teams will use tank drive this year, but will be practicing some different driving skills than for most previous FIRST games.

Team 1504 is making this kind of steering.

Isn’t overdrive NASCAR for robots with a huge ball?

R3P0