Hi murray70,

I thought the encoders were absolute, and the drives output normal incremental encoder signals?
Sounds like they are magnetic/hall sensors which would be an absolute method providing a few analog cycles per revolution which are then highly interpolated and output as incremental encoder signals. Also does some tricks to detect and reduce distortion, non-uniformity in the magnets and so forth. Possibly could be related to what you noticed and thought might be caused by the motor poles. But now I'm thinking it might be the encoder poles.


Tom would this quick reversal mess up the whole tuning process? Confuse all the calculations going on in Kflop? I remember reading somewhere that a big advantage of higher resolution encoders was that the controller can detect changes in speed faster and control the servo better. If changes in speed are that important, kinda seems like that would cause a big problem? Or maybe its too small an amount to matter that much?
Hard for me to say. Good velocity measurement helps stabilize a servo. To measure velocity from a position sensor one must basically take the derivative by computing delta position/delta time. Taking the derivative of a noisy signal becomes even more noisy. But then if the noise is very high frequency passing it through a low pass filter will reduce it. It depends how high of frequency the noise is compared to the real oscillations that should be damped. You can see the Output (green) is not responding much to the high frequency in the error, but more to the lower frequency variations in the error.