A Simple Improvement to Driving

[generalbrando]

It's true that you're going to have half the turning speed and that you'd end up arching when pushing one stick.

That code mentioned above is correct I believe - my version is a bit more cluttered but hopefully either gets the idea across.

Anyway, in defense of the argument that it'll turn too slow, you're going to have to agree that we can't generalize. Slower turning on 246's 2004 bot is better because of the balance of the weight to the non-drive side means that it has a heavy tail - it's tough to control at times. And yet, it still allows for quick enough maneuvering in this case. Different robots will benefit from different programming.

This isn't something for every 'bot, but if a team wanted this effect but didn't want to lose their turning speed, you could include another piece of code downstream of this. It would check to see (for example) if the sticks were each pushed in opposite directions past the 3/4 (or half...you'd have to tweak it probably) point. For those familiar with code, you'd check if one stick was under 64 while the other was above 192 or vise versa. If it is, then you'd tell it to send the values of the ports directly to the pwm outs (as usual).

But yes, it's valid to say that it would be a bad idea for some skilled drivers who are used to that absolute non-interpretive control, not to mention the turning being potentially a problem.

[Matt Attallah]

Team 5 use to used tank drive for the 1998, 99, 00, and 01 years. Rember - when you take the motors and flip them opposite of eachother (So when moving foward - one motor thinks it's running in reverse) these motors seem to have a (?)Reverse bias? It's in the way the brushes think.

We just took care of that in programming. Just take away from the more powerful side that kept pushing the robot to be crooked...

[krhs_programmer]

My teams first robot used tank drive but with two drive wheels and two spining casters which made it very unstable at times and like you guys have said, it doesn't like to go in straight lines. Although this could be do inpart to the fact that one of the motors was slightly weaker that the other, but still that idea should work for us. After read the thread and seeing the drawbacks to it i came up with this idea:
If you were to designate one of the buttons on your joystick as a toggle switch and used it to toggle that function on and off depending on whether you want to be accurate or quick when driving.

first set up code so when you push the button it switches a variable between 2 values. (you'll have to do this on your own because i don't know how. sorry )
Then just use if statements:

if ( toggle == 1 ) /* toggle = var. controlled by button */
{
pwm01=(p1_y+((p1_y+p2_y)/2)/2);
pwm02=(p2_y+((p1_y+p2_y)/2)/2);
}

else
if ( toggle == 0 )
{
pwm01 = /* what ever your normal code is */ ;
pwm02 = /* what ever your normal code is */ ;
}

in theory that should work if you wanted to do that. thats what we did for our compressor last year to override the pressure sensor to build enough pressure to do the pull up on the bar.

[Jeff K.]

Originally Posted by Matt Attallah

Team 5 use to used tank drive for the 1998, 99, 00, and 01 years. Rember - when you take the motors and flip them opposite of eachother (So when moving foward - one motor thinks it's running in reverse) these motors seem to have a (?)Reverse bias? It's in the way the brushes think.

That's because they're drill motors. The drill motor gear box turns one way faster than the other. One way you can fix that is by not having one drive train mirror the other, but actually build it, so that it looks exactly like the other side. Example- Our drivetrain is in an L shape, what we have to do is make it into an upside down 'L' Shape, so that the motor is in a different position, not right next to the other one. It should sorta look lik a demented 'H' right next to each other. That should fix your problem, that is if you're using drill motors. If you're using another kind of motor, then I don't know.

[greencactus3]

Originally Posted by Stonefan5271138

That's because they're drill motors. The drill motor gear box turns one way faster than the other. One way you can fix that is by not having one drive train mirror the other, but actually build it, so that it looks exactly like the other side. Example- Our drivetrain is in an L shape, what we have to do is make it into an upside down 'L' Shape, so that the motor is in a different position, not right next to the other one. It should sorta look lik a demented 'H' right next to each other. That should fix your problem, that is if you're using drill motors. If you're using another kind of motor, then I don't know.

one thing. maybe you just phrased it confusingly, but the gearboxes do not turn anything faster in one direction than the other, it is as Matt Attallah says. the brushes are timed advanced in one direction. which means the brushes are not centered from the permanent magnets

[Jeff K.]

Oh, my bad, sorry, I thought it was in the gearboxes.