[FRC] [problem] Motor issues...

[robinspi]

I hate the ambiguous topic, but anyhow, here is the issue:

Motors spin one way, not easily the other. I looked through the program, and there doesn't seem to be any problems in there. (Though I will say that we are using a custom build PID system). We are using Talon motor controllers and using some VEX motors.
So, the motor will spin one direction perfectly fine, but when we switch the direction, the motors slowly move in that direction, slowly, but very choppily.

Any explanations? If none do arise, then I will probably go look in the PID loop of the program and look through that with the author. Also, if you need anything more cleared up, I would be happy to answer those questions.

Edit: Now the motors are not moving at all. We guessed that the joystick might not work, but the driver station is still reading the input from those buttons.

Edit: We are also using C++ as our language (with the latest from FRC, as we are a rookie team)

--robinspi

[TikiTech]

I would start off and load a simple code without PID loops to verify the error.

Have you tried to recalibrate the motor controller?

These are a few easy things to try.

I will talk to my programming cadre later today. We had some issues with twitching motors once we added more than one set of motor control.

Was an issue with LabVIEW code and was found by creating simple portions of code and adding more portions until the error was found.

Go simple and start added one element at a time.


Good luck!

Aloha

[robinspi]

Apologies for not mentioning earlier, but we are using C++. We have been in FTC for the past couple years, and we decided to move to the big league. Also, we have been practicing with PID for a while, and I think that it wouldn't be in there.

We'll try recalibrating the motors.

[Nathan Streeter]

Is the motor hooked up to a gearbox? to a mechanism?

[robinspi]

Yes, everything is hooked up correctly. As posted, it does like to run one direction, but not so smoothly in the other. Also, the x-box controller buttons are being read in the Control station, so it doesn't appear to be a problem with the joysticks. I will see about the calibrations tomorrow.

[Nathan Streeter]

Originally Posted by robinspi

Yes, everything is hooked up correctly. As posted, it does like to run one direction, but not so smoothly in the other. Also, the x-box controller buttons are being read in the Control station, so it doesn't appear to be a problem with the joysticks. I will see about the calibrations tomorrow.

When I asked if it was hooked up, to a gearbox (and mechanism), I was wondering if that could also be the source of the problem... what gearbox is it? What's hooked up to it? Perhaps post a picture of your setup.

Have you tried swapping the polarity on the motor wires (AFTER the speed controller!) to see if it follows the mechanical system or if it follows the code? Perhaps also try a similar version of this by swapping the polarity of the code. You could be sending conflicting values in separate lines of code.

[JesseK]

I'm with Nathan - this may be a case where you're in a mechanical stall condition due to binding, change in surface properties, over-tightening of bolts on a gearbox, or other such type of nuance that isn't obvious. It will become obvious once the motor catches on fire (I kid!), but until then could you post a picture or describe the mechanism?

[FrankJ]

Write the output to motor controllers to smart dashboard. Easy way of seeing if it is hardware or software. What I am saying? It is always software.

[JamesBrown]

Originally Posted by robinspi

Yes, everything is hooked up correctly. As posted, it does like to run one direction, but not so smoothly in the other. Also, the x-box controller buttons are being read in the Control station, so it doesn't appear to be a problem with the joysticks. I will see about the calibrations tomorrow.

A Simply process for tracking down the cause.

1.) Unhook the motor from the speed controller, and connect directly to a battery. Run the motor in both directions. If the problem occurs then the issue is mechanical, and you need to evaluate the mechanics of the system.

If the problem does not occur in 1.)

2.) Hook the motor up to the speed controller, and connect the controller to PWM 1, and run the default tank code. If the problem occurs then the issue is in the custom code, if it does not then the issue is your speed controller.

If the problem does not occur in 1 or 2 then the issue is in the code. start stripping functionality out until you can track it down.

[Addison4300]

Originally Posted by robinspi

Apologies for not mentioning earlier, but we are using C++. We have been in FTC for the past couple years, and we decided to move to the big league. Also, we have been practicing with PID for a while, and I think that it wouldn't be in there.

We'll try recalibrating the motors.

Even if you don't think it would be in there, it never hurts to make sure. Sometimes problems come from placing you think are flawless

[notmattlythgoe]

Also, check the status lights of the motor controllers, are both motor controllers attempting to drive and are they driving in the same direction.

[cgmv123]

Originally Posted by notmattlythgoe

are they driving in the same direction.

Most drive trains require motors on opposite sides to move in opposite directions. The OP didn't say what the motors were driving.

[notmattlythgoe]

Originally Posted by cgmv123

Most drive trains require motors on opposite sides to move in opposite directions. The OP didn't say what the motors were driving.

Correct, for some reason I was under the assumption that it was 2 motors mechanically hooked together.