Answered: Poor "zero" on two wire motors

We recently installed several 269 motors on opposing sides on the drive to our robot.

In autonomous we could not set them to a “neutral” position in which there was no bias signal. This was observed when all power was removed (a zero motor setting) and the robot allowed to “roll” to a stop. It did not roll straight, it swerved to one side. This was because, even though a zero setting was sent, the motors had a bias signal in one direction. You could feel this simply by trying to turn either wheel attached directly to a motor.

Since the motors were on opposite sides, the bias caused one side to resist going backwards and the other motor encouraged it to go backwards, hence a torque on the robot.
Since this ws entirely in autonomous, not transmitter trim was involved. New motor controllers were used.

Quite frankly it appears like a cheap and nasty motor design. It makes programming in autonomous more of a challenge, but you would expect when a zero siganl is sent there should be no resistance to trurning, except for the mechanical resistance of gears within the motor.

Should this be occuring?

We are working to improve the motor performance in future versions of the CORTEX Master Code and apologize for the inconvenience. You should be able to widen the dead band via your User Code as a temporary work around.