Turning problems, we need suggestions PLZ

[spears312]

Orignally posted by: mechanicalbrain
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.

Actually, we had a 4 wheel drive train with two wheels on each side, both pairs attached to a AM gear box, and we never had any problems with our turning.

Anyway, Oumonkey, hopefully you will be able to work it out through code. You mentioned something about already lifting up the robot and trying to turn it and the wheels seemed to move in the turning fashion (one side forward, the other backward for tank drive like motion), did they not? If so, and it still doesn't seem to work, try and see if you can measure the speed of the wheels on each side of the robot. Make sure they are going at the speeds you want them to. If not, that may be your problem, possibly caused by a lack of power to the slower motors, a chain problem, a motor problem, or even still be a programing problem.
But, thats just my $.02

[sanddrag]

Originally Posted by spears312

Actually, we had a 4 wheel drive train with two wheels on each side, both pairs attached to a AM gear box, and we never had any problems with our turning.

Just because you bought an AM gearbox doesn't mean you can turn well and just because someone uses a kit gearbox doesn't mean it can't turn well. I guarantee you I can build a robot with an AM gearbox that will not turn at all and I guarantee you that I can build a robot with a kit geabrox that turns like a dream. There is a lot more to it than just the gearbox and number of wheels (final gearing, battery charge, current consumption, voltage drop, wheelbase, track width, ground pressure, tread material, coefficient of friction, interaction between tread and carpet, tread and surface deformation under pressure, etc etc etc.) Such general comments should not be made and no one should rush right out and buy an AM gearbox (or any other gearbox) because they think it will make their robot fast, or because it will make their robot powerful, or it will make their robot turn better. That is simply not the case.

A photograph (top view preferable) would give us the pretty much the whole story on mechanically related problems. Once we get that, we might be able to rush right out and say "yep, that's why you can't turn." Also, if there is anyway you can get a video of the attempt at turning, that would be awesome. Picture is good but sound and picture is much better.

[Oumonkey]

I might not be able to get a pic soon. But the more I think/talk about it I think we are getting to much traction. and if all fails we should be able to put it back to 2 wheel drive pretty simply right? Well I talk with Brian, the electronics guy on our team and he said he will get on here as soon as he can to answer the question I can't. Hehe I brained my hurt

[sanddrag]

Originally Posted by Oumonkey

I might not be able to get a pic soon. But the more I think/talk about it I think we are getting to much traction. and if all fails we should be able to put it back to 2 wheel drive pretty simply right?

Again, there is a heck of a lot more behind the way a robot turns than the number of wheels or the number of wheels driving etc. I cannot say "putting it back to 2 wheel drive" will fix your problem without seeing your setup . It is even probable that it will hurt performance even more, who knows?

Let's start with this:
1. How many wheels does the robot have?
2. Where are the wheels positioned?
3. What kind of wheels are they, and what exactly is the tread surface material?
4. How many of the wheels are being driven and which ones?
5. How many motors (and which ones) are driving the wheels?
6. What top speed (in feet per second) is the robot geared for? - if you don't know this, what gearbox is it using and what size sprockets are you using and what diameter wheels are you using?
7. Are you sure the battery was charged and if you are sure, how/why are you sure?

I know you probably answered some of these things before but let's get all the facts down in one place and then we can start to analyze this. Trying to help you we are kind of in a tough place here because we can't diagnose the problem with something if we don't really know what exactly that "something" is.

Also, I would recommend getting a few pictures of your robot to keep for yourself. You built it, you should be proud of it, you should have some pictures of it. (If there's anything I've learned in FIRST, it is do not put your eggs (in this case pictures) all in one basket). Robot pcitures are good for hanging on walls, setting as background images, browsing through when bored, taking up unused hard drive space, and posting on CD!

[spears312]

Orignally posted by sanddrag
Just because you bought an AM gearbox doesn't mean you can turn well and just because someone uses a kit gearbox doesn't mean it can't turn well. I guarantee you I can build a robot with an AM gearbox that will not turn at all and I guarantee you that I can build a robot with a kit geabrox that turns like a dream.

No no, I wasn't implying that the AM is any better than the standard gear box or that someone should go out and buy it just to get their robot to work (trust me, I was doing strategy this year and I saw plenty of awesome robots running standard transmissions, even one of my favorite teams, 1251, used them). I just was giving the basic set up for our robot and said that we had no problems turning. I know that there are so many more factors that could cause the issue at hand, and that wasn't even intended to be a suggestion to solve it. I'm sorry if my statement caused any confusion or implied something else.

[fervent]

Ya I'm the electronics guy, Brian, that monkeyman was talking about. Lately we've been having trouble with pwm cables being broken but now we have all victors working. But I concur that it is too much traction although I have noticed that when we try to turn, unless the joystick is pushed entireley over only one side of the robot is moving and the other side is not going in the opposite direction it is at a standstill. This could possibly be a problem I dont know. Also we are using the standard single wheel drive drain with a double sprocket for 4wd and anything else that could possibly needed to know you can ask me.

[Oumonkey]

Hey, Well from what brian says I should be able to program it to once it reaches a certain point in the 0-255 scale thingy to just be 255 right? The guy who help us with the programings earlier did something like that to make the controls become neutral if near 127.

[sanddrag]

Originally Posted by fervent

I have noticed that when we try to turn, unless the joystick is pushed entireley over only one side of the robot is moving and the other side is not going in the opposite direction it is at a standstill.

Are you driving with one joystick? If so, try two joysticks with default code and tell us if that works.

[Oumonkey]

Yes one joystick. I would answer your question above but I don't know some of then but I'll try
1. How many wheels does the robot have? 4
2. Where are the wheels positioned? 4 on each side...Not sure if you need more specific info on this
3. What kind of wheels are they, and what exactly is the tread surface material? The wheels are the ones from the kit As for the material I don't know
4. How many of the wheels are being driven and which ones? All 4wd
5. How many motors (and which ones) are driving the wheels? 4..But There was something with our arm its a pneumatic thingy so not sure if that counts or not. They are the ones from the kit.
6. What top speed (in feet per second) is the robot geared for? - if you don't know this, what gearbox is it using and what size sprockets are you using and what diameter wheels are you using? .....Thats a question Brian needs to answer...BRIAN WHERE ARE YOU!!
7. Are you sure the battery was charged and if you are sure, how/why are you sure? This was something brought up cause the arm was moving slower then normal. We need to try that as well.

[fervent]

as for the gearbox and sprockets they are all the same as the ones from the kit and the wheels have had teh rubber milled off and we have a material thats used on conveyour belts covering the tire

[JBotAlan]

All of these posts are very hard to read! Here are the things (I think) other people are thinking:

1: The battery is dead.
2: The code is bad.
3: The transmissions are bad.

More detail:

1: Pretty self-explainatory. Less power in the battery, less power in the motors. Charge it overnight, try again.

2: If this is the default code, this shouldn't be the case. If the code HAS been changed, make sure that the PWM value is near either one of the limits while testing. That is, the PWM value is being set to near 255 or 0. The pwm_XX variables are the variables that control the speed of the motors. Replace the XX with any number, corresponding to the PWM output you are trying to change, 01 for PWM 1, 10 for PWM 10, and so on. Tell me if you need more description than this. I can probably help on the programming.

3: Grinding noises usually indicate mechanical failiure, but buzzing noises are normal because of the way Victor speed controllers work. Make sure you put the transmissions together right. I'm not a mechanic by any means, so I probably am not any help in that field.

Hope this helps...
Jake
Team 1140

[663.keith]

if the wheels turn fine when they are off the ground, and the arm was moving slower than normal, I would definitely agree with a couple other people and say it is the battery, change it out with a fresh one and see if it fixes it.

[Oumonkey]

OK, thanks. I was going to try a new battery and I should be able to get pics tomorrow.
But I don't remember the pwm getting up to max speed 0 or 255, I could be wrong though. I think the lowest i saw was in the 60s but I don't remember the highest but I don't recall then going above 200. But to that grinding noises thing posted by JbotAlan I haven't heard the noise in a few days so I might be wrong but If I recall correctly there were grinding noises when we tried to turn, but I think that was just because the traction caused it not to be able to turn.

[Ryan M.]

Originally Posted by Oumonkey

But I don't remember the pwm getting up to max speed 0 or 255, I could be wrong though. I think the lowest i saw was in the 60s but I don't remember the highest but I don't recall then going above 200.

Just see what happens if you give it full power. I know that our robot (at least a few iterations) couldn't turn without a fair about of power.

[EricH]

Originally Posted by fervent

Ya I'm the electronics guy, Brian, that monkeyman was talking about. Lately we've been having trouble with pwm cables being broken but now we have all victors working. But I concur that it is too much traction although I have noticed that when we try to turn, unless the joystick is pushed entireley over only one side of the robot is moving and the other side is not going in the opposite direction it is at a standstill. This could possibly be a problem I dont know. Also we are using the standard single wheel drive drain with a double sprocket for 4wd and anything else that could possibly needed to know you can ask me.

That (the bolded section) could explain a bit. Maybe you need to recalibrate your joystick using the small side wheels (on the right side and bottom). In this case, I'd try the bottom one. After checking the calibration, tape the wheel down as solidly as you can to hold the calibration. If that doesn't work, I don't know what to do.