Turning Trouble!

[KyleGilbert45]

Please search...

http://www.chiefdelphi.com/forums/sh...ighlight=turns

[Cadetdan]

I did search for the pre=posted thread, but I didnt think it was an over-grip problem. We have been running on a shop floor made of concrete, and our tire actualy lay rubber when we put the hammer down. So you guys are all thinking this is to much grip, and that we are tripping the 40 Amp breakers? Thanks for the help

[ngreen]

If you are burning rubber going straight and tripping breakers that way it most likely is the wrong gearing. What motors were you using? If it was the drill motors are you using the transmission in high or low gear? What kind of reduction do you have either from the the CIMs or from the drill motors? What size of wheels are you using?

From the information you have posted I see it as overgearing the motors. You'll have to provide more information before I could tell you.

[Cadetdan]

Were running the Cim's with a 27:1 reduction and using the Innova tires from the KOP. And were not tripping the breakers on forward or reverse, but we can lay some nice rubber.

[ngreen]

That doesn't seem too high..Ok, I took it as tripping the breaker going forward and backwards too. It shouldn't be the gear ratio, It doesn't seem like it would be friction in the system if it work normal forwards and backward (unless the drive shifts in someway that makes it bind when you turn). I would still stick with too much traction then. Usually it is better on concrete but if it is only while you are turning and your are using AWD tank steering traction and sliding always are a huge factor.

[the_short1]

jerkyness can also be caused be a WEAK batery!! ! ! !

push the 'select button' on the Operator interface until it shows the batery voltage.. *using a multimeter at this time is not the solution, it may read 12V, but while driving is a different story..

while driving and making turns, abserve how the voltage meter changes..(should fluctuate) if your voltage drops below about 7 (even momentarily) thats a sign your batery is getting low, you will start having those problems turning!... this is partially due to the friction on your wheels as well, as that will increase the amp draw on all the motors, hence making your batery pay the price..

hope that helps.

[scali]

We've noticed the same problem, but it only happens when the battery is starting to die. In fact, that's how we know to change the battery in the middle of practice =P

[slickguy2007]

We had the same problem with turning as you have and we found a way to fix it. We decided to scrap the 4WD system and just ended up going with 2WD. This fixed the problem with the jerky turning and now it has even gotten faster at turning.


GO 1403!!!

[Warren Boudreau]

A low battery can cause this problem. Also, check to see if your backup battery is fully charged. And is plugged in.

It might be a software glitch since you say it doesn't occur until after 30 seconds or so.

Do you have any sensors on the robot? Hall effect sensors? Encoders? These could be causing problems.

Also, check which PWMs you are using to drive the speed controllers. Avoid PWM 13 through PWM 16 if you can. They are handled differently than the lower 12.

[Ken Patton]

Make sure your battery connections and high current connections are all really good.

Make sure you don't have misalignment or binding in the drivetrain when the wheels are side-loaded (which is exactly what happens when you are turning). If you can pull the motor only out of the drive system, and feel the friction as you just rotate the wheel, and then feel the friction as you sideload (dont be gentle) and rotate the wheel, you might identify a misalignment or binding problem.

If you still have the problem, consider moving weight around on the robot to take weight off the wheels you want to slip the most (take care to not do anything that makes you super-tippy of course). Or, as suggested earlier in the thread, make the wheel slip more by reducing its traction.

Ken

[Mark Pettit]

The Dukes (991) had the same problem. We found that there are a number of fixes that work for this. The aforementioned cable ties or else vacuum hose cable-tied onto the wheels work but they don't look very attractive.
If you have the option to gear down, then that will help.
Those were our 2004 solutions.
This year, we were having the problem with bouncing through turns, but when we started testing auto mode the robot was turning as smoothly as silk. This points to a software problem.
In RC mode, we're tank drive, so it's hard to get the same exact power output to each side while turning. To remedy that, we programmed a button on each joystick to turn the robot in place by sending equal (but opposite for each side) power to the motors. That worked for us!
BTW- we're using the 8" Skyway wheels.