Jaguar will not go backwards

[Cody Trey]

Our bot is running a four motor mechanum drive

all of our motors will go forward, but when we try to go back, one or two of them will not turn, any ideas?

ask any questions you think may be relivant

[Vikesrock]

Are these tan Jags by any chance? Failure in one direction only is a know failure mode of the Tan Jags.

[Cody Trey]

they are tan, is there any way to fix this problem?

[Vikesrock]

Originally Posted by Cody Trey

they are tan, is there any way to fix this problem?

If it is a Jaguar hardware failure there is no competition legal way to repair it. Check and make sure that the lights on the Jaguars affected are changing the way you expect when powering in the direction that doesn't work. If the Jaguar light behaves properly, but the motor doesn't turn it's time to replace the Jag.

[Cody Trey]

ok, i'll get that checked

[RyanN]

It was a problem with the U6 Gate Driver. Many teams had the problem if it was thermally shocked by heavy current from going from full reverse to full forward nearly instantly.

There was a design change, and that problem is now fixed.

[EricVanWyk]

Check to make sure the two limit switch jumpers are installed before you replace the Jags.

[nighterfighter]

Originally Posted by Vikesrock

If it is a Jaguar hardware failure there is no competition legal way to repair it. Check and make sure that the lights on the Jaguars affected are changing the way you expect when powering in the direction that doesn't work. If the Jaguar light behaves properly, but the motor doesn't turn it's time to replace the Jag.

How might one fix this, and use it as a practice jag?

[Vikesrock]

Originally Posted by nighterfighter

How might one fix this, and use it as a practice jag?

You would have to replace the U6 Gate Driver. I believe the chip used is obsolete and difficult or impossible to come by. Not sure if there is a pin compatible replacement that could be found or not.

[DonRotolo]

Another troubleshooting technique is to remove all circuit breakers for the Jaguars except the one being tested. If that changes the problem check wiring.

[Al Skierkiewicz]

Originally Posted by nighterfighter

How might one fix this, and use it as a practice jag?

In some cases the failure was so spectacular that the circuit board was burned through. You need to contact Luminary Micro to see if it can be fixed or simply replace with a newer version.

[Cody Trey]

we have found out that it is not the jag. we have switched it out for other jags and same problem, we also checked the gear box, and re-greased it, the motor will go backwards and forwards when direct battery power is applied. We believe that is may be a problem in the code. we used c++ to program using the built in mecanumDrive->HolomicDrive(speed, direction, twist) function.

[The Lucas]

Originally Posted by Cody Trey

we used c++ to program using the built in mecanumDrive->HolomicDrive(speed, direction, twist) function.

It looks like you are using Polar not Cartesian style Mecanum. You need to supply a direction (calculate using 2 axis) , not an axis for the direction parameter. Are you doing that?

I would recommend for debuging using MecanumDrive_Cartesian() so you can just plug in an axis to each parameter. Just drive it forward and reverse to test the jags. Sorry if anything is misspelled, I am typing on my mobile without consulting docs

[Cody Trey]

I am unfamiliar with MecanumDrive_Cartesian() could you please explain this more in depth. like what the parameters are?

[Ether]

Originally Posted by Cody Trey

I am unfamiliar with MecanumDrive_Cartesian() could you please explain this more in depth. like what the parameters are?

If you have C++ installed, the WPI Library source code is on your hard disk.

void RobotDrive::MecanumDrive_Cartesian(float x, float y, float rotation, float gyroAngle)

X and Y are your joystick axes for Strafe(X) and Forward/Reverse(Y) respectively.

"rotation" is for turning (yaw rate) and can come from the twist axis of a 3-axis joystick.