Go to Post Just a note, there are 2,534 teams registered and competing in FRC this year. That means that there are 2,533 teams being run in a manner entirely different than your own. - Jay Trzaskos [more]
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Unread 10-06-2011, 09:10
Unsung FIRST Hero
JVN JVN is offline
@JohnVNeun
AKA: John Vielkind-Neun
FRC #0148 (Robowranglers)
Team Role: Engineer
 
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Re: Getting the bot to go straight?

The past two seasons, team 148 has utilized an articulating drivetrain. The robot shifts from one set of wheels to another via pneumatics. One of these sets of wheels consists of (4) high-traction wheels, spread to the outer 4 corners of the robot in "narrow/long body" configuration. This configuration of wheels makes it VERY difficult for the robot to turn due to the scrub forces of these wheels -- in addition... it makes it hard for the robot to BE turned. This "traction mode" keeps the robot driving straight as an arrow.

If we are ever in a situation where we need to push forward in a straight line (like autonomous this year), we run in this traction mode. For normal moving around the field, we use our other drivetrain mode.

For more information on drivetrain turning, and scrub forces... check out the math in Chris Hibner's whitepaper:
http://www.chiefdelphi.com/media/papers/1443

Note... articulating drivetrains aren't for everyone. There is some added complexity over a "standard" style drive. However, we on 148 like the benefits that come with such a drive.

Whatever solution you decide to go with for driving straight, be it a software or mechanical solution, I strongly urge you to work to develop / test it during the off-season. What else were you going to do this summer anyways? Sleep?

-John
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In the interest of full disclosure: I work for VEX Robotics a subsidiary of Innovation First International (IFI) Crown Supplier & Proud Supporter of FIRST
 


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