Servo and positioning

[zdzisio1980]

Hello,

I'm new. I have stupid question. We consider following situation. We have got a servo motor (for example: Pittman 14204) which have encoder with resolution 2,000 (8,000 after decoding x4). It means that 1 impulse from encoder is equivalent to revolution of motor's shaft of 0.045 degree (=360/8000) .
Can we really positioning motor's shaft with precision equal +/- 0.045 degree? Do construction of servo motor allow to this?

Thanks for any answer and sorry for my poor English )

[vger]

zdzisio,
Yes and no... the thing is that with the encoder connected back to the motion control, any error in the commanded position will produce a drive to get the servo to go to the commanded positon. With a commanded count position of 1467 for example, the servo will drive toward that position, when it approches that position, the motion control will slow down the drive and stop when that positon is reached. If the position changes (hand wheel moved for example) the motion control sees the error and drives it back to where it should be. So the servo / motion control combination when properly tuned will enable this accurate positoning.

Steve

[ServoChris]

Just a small Addition:

Some fanuc Encoders I have worked on, using serial data, have over 1 million counts per revolution. So I would say yes, the motors are and can be that accurate.

Chris