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Unread 07-15-2005, 01:47 PM
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Turning problems, we need suggestions PLZ

Hi, My robot is having turning problems now. Our programming seems to doing what it is to but our robot won't turn. We lifted it up and made sure it was working right and the motors are going in the right direction, but when we put it on the ground the motors will work forward or backwoods but when we try and turn it it just stands still and the motors struggle to move. I think it is the extra traction we put on the wheels to move smother, so if someone can give us ideas to check it would really help us a lot. If you need some more specific details I might not be able to check them for a few days.
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Unread 07-15-2005, 02:03 PM
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Re: Turning problems, we need suggestions PLZ

YOU AGIAN okay this i can help. its one of several problems one STOP TESTING if its making noises and not moving you have alot of power and you dont know what its doing it should be okay but still.... okay so check you speed controllers and tell me if you are using a gear box and your wheal layout in relation to how their being powered (chains, which wheals are powered, ect...) chances are its an electrical or mechanical problem.
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Last edited by mechanicalbrain : 07-15-2005 at 02:06 PM.
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Unread 07-15-2005, 02:06 PM
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Re: Turning problems, we need suggestions PLZ

First thing u should check is gear boxes, if it works when you lift it up then maybe there is something lose that is bending once you apply pressure to it (put it on the ground)

If thats not what the problem is then check for too much friction on the ground, you said you wouldnt be able to get more specs but can you tell us what type of drive it is.

2wd? 4wd? 6wd? are you using kit gear boxes?

Dave
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Unread 07-15-2005, 02:14 PM
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Re: Turning problems, we need suggestions PLZ

if you have two wheels powered by chain with one gearbox as i suspect you do (we had similar problems) make sure that one your motors turn the right way when you turn or you will break your gear box. and move your robot off any carpet try on a smooth floor. FIRST's double wheel design is really bad for turning.
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Unread 07-15-2005, 02:14 PM
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Re: Turning problems, we need suggestions PLZ

A picture of the robot would do wonders in helping us diagnose the problem. I can think of a few things off the top of my head. It is possible that if you are using two motors per side that one of them is not running or perhaps even running in the wrong direction (fighting). Take the breakers out and try them one at a time to make sure all the motors are spinning and in the direction you want them too. Make sure the program is giving full pwm value to the speed cotnrols when the joysticks are full travel. It is even possible that the Victors are way out of calibration, try calibrating them. Also, make sure you are using the correct amperage breakers for your motors (40 amp for Chiaphuas) Last, this may be obvious but make sure the battery is charged.

Some of the more likely problems are physical. What kind of tires are you using? If you are using pneumatic (air filled) tires or other high traction material and/or the robot is longer than it is wide, you may have difficulty turning. Also, make sur the robot is geared down enough. It is possible you don't have enough torque to overcome the friction in turning.

You can try putting duct tape (not legal for FRC btw) on one set of wheels (either front or back) or something like pool hose to make it turn better. (with ductape it will turn like a dream but it may lack traction and it is not legal) Or you can put a caser wheel lowered by a pneumatic cylinder or something like that or use omniwheels.
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Unread 07-15-2005, 02:19 PM
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Re: Turning problems, we need suggestions PLZ

i concur with sanddrag your problem is to vague take a couple picks of your drive train and electrical system. IM NOW DOING 1.6 POSTS A DAY!!! (everything should be a celebration )
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Unread 07-15-2005, 03:01 PM
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Re: Turning problems, we need suggestions PLZ

Hey, I knew I forgot something but I was rushed. Lets see we have 4 wheels that came with the starter kit thing, they are NOT air filled, we have 4 wheel drive as for the gear boxs I am going to say they are the things from the kit we got because I don't think we are rich enough to get anything else . As for the pics there is nothing I can do know until at the earliest Sunday But most of the stuff I don't know much about so I will email my electronics man and tell him to come here
But to something sanddrag said our robot is longer than it is wide and we added something for higher traction, which is what I think it is, But I'll try to get those questions about my question answered.
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Unread 07-15-2005, 03:06 PM
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Re: Turning problems, we need suggestions PLZ

Quote:
Originally Posted by Oumonkey
Hey, I knew I forgot something but I was rushed. Lets see we have 4 wheels that came with the starter kit thing, they are NOT air filled, we have 4 wheel drive. As for the pics there is nothing I can do know until at the earliest Sunday But most of the stuff I don't know much about so I will email my electronics man and tell him to come here
But to something sanddrag said our robot is longer than it is wide and we added something for higher traction, which is what I think it is, But I'll try to get those questions about my question answered.
also note your problem has an equal chance of being the drivetrain or the electronics. note however that it might also be your joystick programming which i believe follows under you. check your programming since you just had a bunch of changes to it made. we had our robot non responsive for a day and a half before our programming person thought to check his main method. funny thing was one day of that was him insisting it was an electrical problem
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Unread 07-15-2005, 03:07 PM
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Re: Turning problems, we need suggestions PLZ

Quote:
Originally Posted by mechanicalbrain
FIRST's double wheel design is really bad for turning.
Aaaaaactually...
It turns fine, when used correctly. I'm curious what exactly you're talking about? Perhaps you could give us some clarification or justification?

Back to the problem at hand...

You mention adding traction to the wheels; this leads me to hypothesize that the added scrub friction during turning has now overcome your turning moment.

The symptoms you describe, also make me believe that you may have a low battery. (Low battery = less motor torque = less turning moment). When was it last charged? (I'm just speculating here...)

If the battery is charged after all and the problem persists; cover the tread on 2 of the wheels (rear or front) with duct tape and see if that helps. If so, your problem is as I described above.

There are many solutions for this ranging from quick and dirty to elegant and expensive.

Good Luck,
John
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Unread 07-15-2005, 03:10 PM
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Re: Turning problems, we need suggestions PLZ

Quote:
Originally Posted by JVN
Aaaaaactually...
It turns fine, when used correctly. I'm curious what exactly you're talking about? Perhaps some clarification or justification?

Back to the problem at hand...

You mention adding traction to the wheels; this leads me to hypothesize that the added scrub friction during turning has now overcome your turning moment.

The symptoms you describe, also make me believe that you may have a low battery. (Low battery = less motor torque = less turning moment). When was it last charged? (I'm just speculating here...)

If the battery is charged after all and the problem persists; cover the tread on 2 of the wheels (rear or front) with duct tape and see if that helps. If so, your problem is as I described above.

There are many solutions for this ranging from quick and dirty to elegant and expensive.

Good Luck,
John
if you have two wheels on each side connected to a single gear box and your robot is rectangular the wheals will fight each other when turning. its part of the reason car wheels swivle when turning.
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Unread 07-15-2005, 03:14 PM
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Re: Turning problems, we need suggestions PLZ

I also am not sure of your problem, but I would check out this white paper....
http://www.chiefdelphi.com/forums/pa...le&paperid=222

It relates to turning in a "tank" style train, and depending on the setup of your wheels how hard it is for the robot to turn.
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Unread 07-15-2005, 03:17 PM
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Re: Turning problems, we need suggestions PLZ

Quote:
Originally Posted by Ben Lauer
I also am not sure of your problem, but I would check out this white paper....
http://www.chiefdelphi.com/forums/pa...le&paperid=222

It relates to turning in a "tank" style train, and depending on the setup of your wheels how hard it is for the robot to turn.
Yes... I was just about to reach for it... but Ben is quicker on the draw!

The "Hibner Turning Whitepaper" is a GREAT reference for all those who are trying to understand the physics behind skid-steer turning.

Once again, Chris Hibner we salute you.

-John
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Unread 07-15-2005, 03:20 PM
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Re: Turning problems, we need suggestions PLZ

or you could do what we do now and use omni wheels and turn on a quarter (yes a quarter becuase we didnt have a dime). you can also drive sideways or even diagionally. were still trying to get it rotating while moving in a straight line.
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Unread 07-15-2005, 05:50 PM
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Re: Turning problems, we need suggestions PLZ

Quote:
Originally Posted by Ben Lauer
...how hard it is for the robot to turn.
I'll just go off of this, because a lot of the other posts have been de-grammaritized, de-capitalized, and de-spellingatized to the point of unreadability.

I'd make sure that you're sending full power to the Victors in your code.

You can check if it's your code by setting up a quick pwmXX = 255 and comment out your normal speed code. If your robot can't move with that, it's definitely mechanical. On the other hand, if it does move, you know it's the code.

P.S. I'm not saying that your post was unreadable, Ben. I actually understood it.
P.P.S. It's bad to use made up words in posts which critique spelling.
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Unread 07-15-2005, 06:31 PM
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Re: Turning problems, we need suggestions PLZ

Ok, thanks for the link guys. I'll do that things to the code to make sure its not it
But to make sure what ryan M. is talking about you want pwmXX + pwmXX = Limit_Mix(2000 +p1_y - p1_x + 127) ,well I don't remeber if that limit mix line is exact but whatever, to pwmXX + pwmXX = 255? I just want to make sure my programmins skills aren't to good But the wheels fighting against each other was something brought up but I guess we will see.
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