Problem with old bot

[kinganu123]

Was fixing up an old bot and encountered a weird problem. All directions work but when going backward the robot just stops responding and requires a disable-reenable to start moving again. It's most probably an electrical problem and all other movements work fine so I have no clue what it could be. Anyone have any ideas?

[Alan Anderson]

Originally Posted by kinganu123

Was fixing up an old bot and encountered a weird problem. All directions work but when going backward the robot just stops responding and requires a disable-reenable to start moving again. It's most probably an electrical problem and all other movements work fine so I have no clue what it could be. Anyone have any ideas?

Check each wire between a speed controller and a drive motor. One of them is likely shorted to the frame, and there is probably another frame connection elsewhere. The big things to worry about are the cRIO case and the Axis camera.

Your drive motors aren't the biggest BaneBots, are they? Those are notorious for developing internal shorts between the case and one of the terminals, apparently due to debris left over from manufacturing.

[Al Skierkiewicz]

Originally Posted by kinganu123

Was fixing up an old bot

How old, please?

[kinganu123]

lol, sorry about that guys. Once again I had sent a freshman to do research, and I can almost guarantee you that they didn't search before posting (with my account).
But basically, we stripped the good 'ole 2010 robot and basically left the 4 CIM motors, the 4 mecanum wheels, the PD board, the cRIO, and the DS. It's all mounted on wood and the other parts (such as relays) are still mounted, just not connected to anything.
That being said, we can go forward, left, right, and spin properly, but once we go backward, the bot essentially stops working. I expected it to be motorsafety to be throwing it off, but alas, the freshman didn't do enough asking or researching and they assumed it to be electrical, because 224's programmers are never wrong XD. I'd also like to throw in that the joysticks and motorspeeds are programmatically correct, but i haven't had them check motorsafety yet.
However, I dare not eliminate electrical as the problem YET. I will make note to them to make sure that the robot is properly grounded.
Are there any other suggestions?
Thanks

[Ninja_Bait]

Originally Posted by kinganu123

224's programmers are never wrong XD.

Yeah, neither are ours.

I would go through the wires very carefully, looking for shorts and the like. However, since all the wheels work independently and the bot only crashes when they all drive backwards, I'd say it's safe to blame code. I can't think of any other reason that would cause the bot to act like that.

[Alan Anderson]

Originally Posted by kinganu123

I will make note to them to make sure that the robot is properly grounded.

What does "properly grounded" mean to you? Absolutely nothing should be electrically connected to the frame of the robot, either accidentally or intentionally.

[ratdude747]

What speed controllers? if victors, are they calibrated right?

if jags, PWM, serial CAN, or 2CAN?

also, if known, what programming language?

[Al Skierkiewicz]

King,
Jaguars (old Tan color) were notorious for failing in one direction that year. When you say that the robot stops functioning, are you saying that the Crio reboots or the robot simply will not go in reverse? Are you using dual motor transmissions? If so are you absolutely sure of the wiring to each motor? It is possible that one of the motors is wired backwards. When you reverse you suddenly add a short (both motors go into stall) drawing upwards of 200 amps. Although unlikely, it is possible for the motors to be able to drive in one direction but not at full speed. Of course if you add a defective Jag that is open in forward but functions normally in reverse, this result is possible. I suggest you remove the wiring to one motor on each side and see if the robot moves in both directions. Note which direction the wheels turn for a forward movement on the joysticks. Then swap motors on both sides and try again. Do the motors cause the same direction of movement as the first test? I have also seen debris in a transmission that allows movement in one direction but locks the transmission in the other direction. You should be able to simulate this without power, moving the robot by hand.

[vhcook]

Did you test on the floor or on blocks (or both)?

[mesamb1]

You said you can spin. With the mecanum wheels that sounds like the wheels can spin backwards, but not when the joystick tells it to go backwards. I would think code, but there could be a joystick short

[LemmingBot]

Check the C-rio, we just had a problem with our 2011 bot that sounds alot like yours, we think that it was a combination of inflicted damage and a slightly defective unit. Try swapping the rio out with a different one and see if that fixes it.

[kinganu123]

Originally Posted by Alan Anderson

What does "properly grounded" mean to you? Absolutely nothing should be electrically connected to the frame of the robot, either accidentally or intentionally.

well, everything is mounted on wood and whatever isn't used isn't connected to the PD board
Furthermore, we put a multimeter to the frame and got a reading of 0.0

Originally Posted by Ninja_Bait

However, since all the wheels work independently and the bot only crashes when they all drive backwards, I'd say it's safe to blame code. I can't think of any other reason that would cause the bot to act like that.

I'm starting to think that too, but motorsafety isn't throwing any errors and everythings SEEMS to be fine in terms of code. all it is is creating a robotdrive, joystick, and driving via inputs from joystick

Originally Posted by ratdude747

What speed controllers? if victors, are they calibrated right?

if jags, PWM, serial CAN, or 2CAN?

also, if known, what programming language?

Victors
what do you mean by "calibrated right"
and we are using Java

Originally Posted by Al Skierkiewicz

King,
Jaguars (old Tan color) were notorious for failing in one direction that year. When you say that the robot stops functioning, are you saying that the Crio reboots or the robot simply will not go in reverse? Are you using dual motor transmissions? If so are you absolutely sure of the wiring to each motor? It is possible that one of the motors is wired backwards. When you reverse you suddenly add a short (both motors go into stall) drawing upwards of 200 amps. Although unlikely, it is possible for the motors to be able to drive in one direction but not at full speed. Of course if you add a defective Jag that is open in forward but functions normally in reverse, this result is possible. I suggest you remove the wiring to one motor on each side and see if the robot moves in both directions. Note which direction the wheels turn for a forward movement on the joysticks. Then swap motors on both sides and try again. Do the motors cause the same direction of movement as the first test? I have also seen debris in a transmission that allows movement in one direction but locks the transmission in the other direction. You should be able to simulate this without power, moving the robot by hand.

we are using Victors and i THINK single transmissions
the cRIO doesn't reboot upon failing
i'll check everything else you've said, thanks!

Originally Posted by vhcook

Did you test on the floor or on blocks (or both)?

Both

Originally Posted by mesamb1

You said you can spin. With the mecanum wheels that sounds like the wheels can spin backwards, but not when the joystick tells it to go backwards. I would think code, but there could be a joystick short

can't be the joystick because we tried our xbox and an older joystick

Originally Posted by LemmingBot

Check the C-rio, we just had a problem with our 2011 bot that sounds alot like yours, we think that it was a combination of inflicted damage and a slightly defective unit. Try swapping the rio out with a different one and see if that fixes it.

its a relatively new cRIO (we bought it a while ago, but it was only for show on a testboard that we later stripped), but I'll have the team replace it

[Jim Wilks]

Originally Posted by kinganu123

well, everything is mounted on wood and whatever isn't used isn't connected to the PD board
Furthermore, we put a multimeter to the frame and got a reading of 0.0

Would that be a reading of 0.0 ohms = bad or 0.0 volts = good? A value without units is meaningless.

[PAR_WIG1350]

Originally Posted by kinganu123

Furthermore, we put a multimeter to the frame and got a reading of 0.0

The lack of units has already been mentioned, but I have another question.
You put a multimeter to the frame and what? If both probes were on the frame, the resistance would be 0.0, or close to 0.0, as would the voltage (due to the fact that the resistance is 0). The proper way to test for electrical continuity problems is to , with the meter set to measure in kOhms, place one probe on the frame while the other one is placed on the cRIO chassis, the back of the axis camera, motor controller outputs, and the PD board inputs (Make sure the robot is off, or preferably, the battery is out of the robot. ). If the meter displays infinity (usually a 1 at the far left of the display) in all cases described above, but 0.0 when the probes make contact with each other, then the electrical system is likely not shorted to the frame.