Created Date: April 22,2010

Created by: Tinker

It took a little searching but I found this in the sureservo manual:

"When power is first applied to the servo drive,

control algorithms detect the motor's rotor

position through sensors imbedded in the motor.

Feedback to the drive of the UVW signals for

commutation is via the ABZ encoder signal wires.

Following rotor position sensing, the drive

automatically switches to encoding for

commutation control. "

At the risk of over simplifying, the controler trys wiggling the amature a bit and checks what the response is. That may not be as bad as it sounds, since I think it can determine the direction of rotation in about 5 arcminutes, how much it actualy turns the armature I don't know.

Created Date: April 23,2010

Created by: Do-more PE

Since the encoder is 10kppr, I would think that the motor movement would be imperceptible since the drive already knows which direction the motor turns based on the encoder signal and it only needs to get a change in signal on the A, B, or Z pulse to know which direction it is going.

So you would be talking about maybe an arcsecond of movement if that.

Created Date: April 27,2010

Created by: gkaufman

At power up, the UVW signals are present and they provide a low resolution "absolute position " feedback that tells the servo drive the electrical position of the servo motor rotor (electrical position is different from mechanical position due to multiple pole pairs in most servo motors - if the motor was 2 pole then electrical position would be equal to mechanical position). No movement of the rotor is necessary to initialize the torque angle in the servo drive. The torque of the servo motor is proportional to the sin of the angle so there is plenty of torque to start the initial motion even if the torque was off by as much as 45 electrical degrees (70% of peak torque would be available in this case). After power-up, the UVW signals are automatically switched over to the high resolution quadrature "incremental position " data and the once per revolution reference marker signal. As soon as the servo drive detects the first occurance of the encoder marker signal the torque angle is adjusted in the servo drive to the near perfect value. The servo motor manufacturer mechanically aligns the marker pulse to provide the near perfect torque angle during manufacturing of the motor. If the motor encoder were to be removed or replaced then this alignment process must be repeated.

Created Date: August 04,2010

Created by: gkaufman

With the SureServo system, the UVW encoder signals are present at power-up for about 0.5 seconds. This gives the servo drive enough time to detect rough position of the servo motor rotor. After about 1/2 second, the motor encoder automatically switches over to high resolution ABZ data signals which the servo drive uses for real-time commutation of the brushless servo motor. With the first occurance of the Z signal (marker pulse) the rotor angle inside the drive is set to the exact value. Hope this answers your question.