BasicMicro

Hi,
I just opened our robot (which was turned on but immobile for several hours), and realized that all 4 motors are quite hot (it's possible to touch them, but not for a long time).
There was no slope (the robot was in our office).
We use velocity control (so we were sending at 10Hz a command to set velocity to 0).

Do you have an idea why the 2 roboclaws (2x60A) are delivering so much power to the motors when the robot is not moving (and not on a slope).

Is it possible that it is due to some "small" oscillations of the motors around the "reference" position?
If so, is there a way to reduce those oscillations?
If not, what else could explain that the DC motors get so hot?

Thanks a lot in advance
Best regards
Felix

If you are using position control than that is exactly the cause of the motors being hot. Position control holds the position. You can add larger deadzone so you can get to a position where it wont power the motor but that will only work when there is no external force.

No I wasn't using position control, at least not explicitly : I was using velocity control with velocity=0.
Is velocity=0 equivalent to using position control with target equal to the position when the command is sent?

The ground is perfectly flat and horizontal (office floor), so there is no force acting on the motors due to gravity.

What might be possible, is that the front and back wheels for some reason didn't got exactly the same "reference" position, and that the front motors where trying to move a few millimeters in one direction while the back motors were trying to move a few millimeters in the other direction. As our wheels have good adherence to the ground, they might not have managed to slip to realign, and therefore the "combat" between the front and back motors never stopped : does that seem possible to you?

If so, which parameter should I modify to avoid this issue in future?

When you know you are stopped you can remove power from the motors all together by sending a 0 duty command to each. This will stop the velocity PID from controlling the motors and fighting each other if your suspicion is correct. I expect it is.