Drive glitching

VEX V5 Technical Support OFFICIAL Tech Support
1

This happened about half way thru our last competition.

The robot configuration is:

6 motor driving two 4" wheels and four 4" omni wheels.
The wheels are mounted on a hinged suspension.

Two motors drive the lift.
Two motors drive the intake.

When driving the robot for 10-20+ seconds the drive motors start jerking. (The motors start in the correct direction, rotate a small amount then stop. Not enough rotation to move the robot) This continues as long as we try to drive the robot.
After stopping for 10-20+ seconds we are able to drive for a short time again, then the drive motors start jerking again.

When the drive motors are jerking, the lift and intake operate normally.

We have:
Changed the microcontroller.
Changed the joystick.
Changed the power expander.
Bypassed the power expander and run the drive motors directly from the microcontroller.
Changed the motors.
Changed the program in the microcontroller.

This happend on wifi or tethered.

Any ideas on how to fix this?

2

Hello Net Robot,

Thanks for taking the time to contact us.
I believe you are overheating the thermal breakers in your Cortex, can you please confirm the following:

  1. What kind of motors do you have?

  2. Please elaborate in your motor configuration as below-
    Port 1
    Port 2
    Port 3
    Port 4
    Port 5
    Port 6
    Port 7
    Port 8
    Port 9
    Port 10

  3. Whats the status of the LEDs in your Joystick before and after the issue presents?

FYI: The Cortex has two thermal breakers, that will engage before the Cortex/motors overheat. The first breakers is located in ports 1-5 & the second breaker is located in ports 6-10. You must have all of your motors spread evenly across this two breakers to minimize the possibility of such breakers engaging.

Regards.

-Eli

3

Port 2 is connected to the A&B input on the power expander.
The power expander A output port is Y’d to the front and middle drive motor on the left side.
The power expander B port drives the back motor on the left side.

Port 3 is connected in a similar way to the right side motors.

Port 5 and 6 run the lift.
Port 7 and 8 run the intake.

All motors are 393s

4

Net robot,

Please confirm if the following is correct:

  1. All 393s

Port 1- n/c
Port 2- > Power Expander> Drive motors (left)
Port 3- > Power Expander> Drive Motors (right)
Port 4- n/c
Port 5- Lift
Port 6- Lift
Port 7- Intake
Port 8- Intake
Port 9- n/c
Port 10- n/c

  1. ?

I await your confirmation.
Regards.

-Eli

5

That is the correct configuration.

your first statement was correct.

  1. All 393s

Port 1- n/c
Port 2- > Power Expander> Drive motors (left)
Port 3- > Power Expander> Drive Motors (right)
Port 4- n/c
Port 5- Lift
Port 6- Lift
Port 7- Intake
Port 8- Intake
Port 9- n/c
Port 10- n/c

this was the configuration.

The center motors on the six wheel drive motor had too much load on them.
The load was reduced. the configuration was changed and now the robot runs well. The configuration is:

  1. All 393s

Port 1- Intake
Port 2- > Power Expander> Drive Motor A (Left)
Port 3- > Power Expander> Drive Motor B (Left)
Port 4- Left Motor
Port 5- Lift
Port 6- Lift
Port 7- > Power Expander> Drive Motor C (right)
Port 8- > Power Expander> Drive Motor D (right)
Port 9- Right Motor
Port 10- Intake

POWER MANAGEMENT IS IMPORTANT!

Thanks for the direction and information.

6