You know what sucks?
 

When the wheels on the left and right side of your robot rotate at the exact same rate... (using encoders and PID velocity control, AND we counted rotations to verify they spun at the same speed)


And your robot STILL doesn't go straight...


:p


The best part is: It goes as straight as a bullet in REVERSE, but not forward.

8 days to get this one sorted out!

I blame the mechanical guys :D, because one could guess that this is the difference between shifting your weight over nice fat grippy wheels (reverse) vs shifting your weight over slippery omnis (forward), combined with robots having no suspension to keep power down on all your wheels nicely, and a frame which is probably not perfectly flat at all corners.

So why is this in the programming forum?

Because during 5th week, EVERYTHING becomes a programming problem... hahah.

"Just make it go straight"

:ahh:

-SlimBoJones...

Re: You know what sucks?
 

So true. Motor swings arm around too fast with no load? Gear it down some? Have a transmission? No. Mount a gyroscope and use a PD loop to keep it at a reasonable rate of rotation.

Re: You know what sucks?
 

Slimbo quit whining and fix the programming. All this wasted time is why we are having problems. We build the perfect robot and what do you do but make in go in circles.

Re: You know what sucks?
 

Hey!

I'll do my best, but I'm this --><-- close to telling our drivers they're NASCAR styling it this season...

"Sorry boys and girls, left turns only!"

:D

-SlimBoJones...

Re: You know what sucks?
 

Your job as the programmer is to compensate for all of the SLOP, BACKLASH, FRICTION and CG miscalculations the mechanical team has built into the robot. And by the way, you only get one week to fix their five weeks screw-ups. :)

Happy programming

Re: You know what sucks?
 

it never mattered to me how straight it goes when you apply full forwars on both sides. it has always been more of a driver thing to fix. they just hafta drive it enough to be able to drive it in a straight line with their eyes closed. which really isnt too hard once you learn what your robot feels like doing at different times. and anyways, ive found i havent had to drive long distances completely straight anyways. things/robots get in the way way to often

Re: You know what sucks?
 

You should feel lucky, SlimBo. A lot of us have yet to dig into the programming.

Re: You know what sucks?
 

I happened to be a programmer, and ttedrow is right.
Last year we had to compensate for the differenced between the motors on the left and the right, but it is probably easier to fix by programming it, compared to rebuilding it.

Re: You know what sucks?
 

Yeah, at least your robot is in some shape to have software problems.

Re: You know what sucks?
 

Ah, but in the first few seconds of the match, the only driver is the code crafted by your team's programmer(s). If the robot has a turning bias that's not easily characterized, the programming job becomes a lot more difficult.

Re: You know what sucks?
 

Vacuum's suck... regardless, our 2004 robot did that; it horribly drifted towards one side (I think it was left), but when thrown into reverse, it went straight. I've always thought this to be a mechanical problem, so I took our gearboxes apart and saw that the coupling between the motor and gearbox was grinding against the housing. I got rid of all the friction (and these were off the shelf gearboxes) and it still had that horrible drift... Anyways, lots of driver practice fixed the problem -- so stop pointing fingers at the mechanics and programmers!!! =D

Re: You know what sucks?
 

You forget that with Steve even in the first week, it is a programming problem.

Re: You know what sucks?
 

ur right! i completely forgot about that lol. so maybe you do need a robot that can go straight. ive got a lot to learn...

Re: You know what sucks?
 

do u have the pwm cables hooked up right, in the code, there seems to be diffrent settings set for each one, maybe check that out, lol, i guess i better get back to working on everything, last day, and no one else has really showed up....

Re: You know what sucks?
 

guys you are forgetting a cardinal rule about motors, they have full power when applied to the positive, and when you apply full power negative, they spin slower...it was painfully obvious w/ the old drills.

You also might have a wheel out of alignment, aided with the tracking of your motors, may be why you are doing arc's