softmotion read encoder velocity 0

[Massif]

     Dear,

My application is created with softmotion 10.0.0.1 and labview 2010 SP2.

My motor drive is correct. I read the encoder velocity with the softmotion's VI 'Read (encoder) Position'. 

When the motor is drive, the velocity read is correct.

When the motor's command velocity is zero (motor stop), the encoder velocity read is not zero.

The VI 'read (encoder) position' show the velocity between a up and a down of the encoder. The motor is servocontrol to zero with this up and this down.

Why the 'read (encoder) position' VI display not zero when the motor is servocontrol with the command stop i.e. velocity = zero?

  Regards

  Massif

[Guillaume_H]

Hi,

Thank you for posting on National Instruments forums.

First, could you please specify the magnitude of the variation from zero that you observe? If it is high, you might have a problem with your motor. Otherwise, it is some sort of an expect behavior.

Indeed, even when a motor is at a velocity equal to zero, it stills moves a little. It will be completely immobile only if you stop your application (i.e. only when no power source is connected to it). Therefore, if your encoder is precise, it can detect the small vibrations of your motor.

Also, you can refer to this tutorial: Reading Velocity http://zone.ni.com/devzone/cda/tut/p/id/4770

Using a lower resolution might be a valid workaround for this problem. You can also add a little subroutine forcing the velocity measurement to 0 when the position of your motor reaches a certain value.

I hope this information will help you.

Best regards,

[Massif]

Dear Guillaume,

My problems is due to the encoder resolution.

I'm going to preform some new tests with an encoder with lower resolution.

  Regards

Massif