How to setup Chinese AASD Servo electronic gearing

[Neale]

Quick question (although it might be a long answer!)...

The reason for using electronic gearing here is because you want to include the controller in the feedback loop but it can't handle the encoder pulse rate (as I understand it). In this case, is there an argument for using step/dir signals to the servo controller (which most of the ones I've looked at seem to support)? OK, controller is out of the loop but the servo controller can handle the encoder feedback itself, possibly with some kind of built-in auto-tuning (guessing here) and maybe give better overall performance? Or maybe I've misunderstood completely and this is about using analogue input controllers?

[JAZZCNC]

The reason for using electronic gearing here is because you want to include the controller in the feedback loop but it can't handle the encoder pulse rate (as I understand it). . . . . . . .. . . . . . Or maybe I've misunderstood completely and this is about using analogue input controllers?

Yep your miles off Neale.!! . . . . . . . Did you watch the video because I'm struggling to see how you came to that conclusion because think I made it pretty clear what the problem was.?

This as nothing to do with Closing the loop or if using Step/Dir or Analog it applies to both.

But I'll explain it here in text for you and anyone else who's not sure what was meant in the video.

To get the full 3000Rpm from the these servo's which have encoders with 10,000 pulses per rev the motion controller needs to output 500Khz frequency. 10,000 * 3000 =30,000,000 pulses per minute / 60sec = 500,000 pulses per sec or 500Khz.

Most of the low to middle range motion controllers only provide 100 or 125Khz and the parallel port only allows at best 50khz and still be stable.
This means with the only 100khz you won't get the full RPM out of the motors. So to get the full RPM the drives provide electronic gearing.
It does this by taking the incoming pulses and applies a ratio based on the gearing ratio that you program into the drive based on how short on pulses you are to the 500Khz needed for full speed.

The cost of doing this is that you lose some of the resolution the encoders provide. For instance, with a 5:1 ratio, our encoder count becomes 2000 not 10,000 and it's this value you use to calculate the steps per setting. So, for instance, say using a 5mm pitch screw the resolution drops from 0.0005 to 0.0025. No big deal because we had an excess resolution to start with.

So the point of the video was how to calculate the electronic gearing and program it into the drive because it's a calculation based on a formula that is about as clear as mud.!

Regards the comment about Step/Dir then yes they will take both Step/Dir and analog. The drives also provide an Encoder output that can be used by motion controller to close the loop if it provides this feature. Some controllers allow this for both Step/Dir and analog, however, most Step/dir controller don't. In which case the loop is closed between motor and drive.
All Analog controllers take Encoder feedback because they can not work without it.