Convert from Anilam Crusader M to EMC 2

Next, I plan to confirm that all limit switches are still present in the circuit, and test the x and y axis as well. Finally, I plan to generate a reference signal and attempt to move all axis.

My goal during this upgrade will be to use all existing hardware. It appears that no-one has successfully done this, but I don't know why this shouldn't be possible. Anilam had a functional control after all. From reading other posts, my understanding is that drives get a tach feedback, and the motion controller gets (relatively low resolution) position feedback from "glass scales". I know of one successful Anilam to EMC via PPMC, although he had to add rotary encoders. I would like to avoid this, or at least understand why my current set-up won't work.

I am open to various motion control options at this point, my preference would go to whatever can drive my current hardware most efficiently for a reasonable cost.

Update on Progress:

- Confirmed function of all limit switches (single switch per axis--activated by dual fixed cams...one on each end of travel of the axis)...Done. E-stop will not reset if limit switch is tripped, system will e-stop if limit is reached while running.

- There is a spare terminal (P8) on the Anilam PCB 803 (see pic). If you bring pin 13 to gnd (pin14), the servos will enable upon e-stop reset. I wired in a momentary switch to this terminal so that I could keep my finger on a "deadman switch" while testing.

- Confirmed power up of all drives...done. There is no drift to the z axis, but some small very slow drift to the x and y.

- wired a 9V battery (see pic) to provide a 0 to ~3 V signal into the drives. To do this, I used pins 1-6 of the same terminal (P8) of PCB 803. I also needed to pull the connector from the Anilam control board that was outputting voltage. (PCB 502) Confirmed that I can drive both directions and stop. Done. Interesting that I can get rid of the small drift on x and y by applying a small control voltage. (seems like a good sign). I confirmed that positive voltage to the red wires give positive axis movement (from tool reference)

- checked tachs by measuring voltage across wires. I was surprised that this worked with the power off. I attempted to crank the axis as fast as I could, but I imagine that this is not as fast as they used to move when the controller worked. I measured about 5V max on the x and y, but saw up to 10V on the Z. The Z appears to have much more reduction, so I believe I could get the motor spinning faster with the mechanical advantage that I could use on that axiz. I am concerned that a 0-10V analog input is not a large enough range. I would not be surprised if the tach's output 0-15V like the signal input to the drives. If no 0-15V input is available, I will likely have to step down the voltage to make use of what is available. There is no convienent way to get this signal out as the tach's go directly into the drive. I needed to stick probe wires into the back of the connector to measure. TODO: confirm that the drive wasn't affecting this signal, unplug the connector and test again.

- I was surprised to see that with the axis moving in a positive direction (from tool reference) the tach sent a negative voltage.

Even with ability to read the tachometer,you are still 'dead reckoning' between scale counts and with enough idle time you will drift until you hit a scale count. So when idle I suspect all you will accomplish is to lower the frequency of the +-1 count dither that you normally get with digital encoder feedback systems. It should work well when moving if implemented correctly though.

As Andy mentioned, a negative tachometer reading in a positive direction is expected since the tachometer is negative feedback
(the negative tachometer output is summed with the positive command voltage when moving in a positive direction)

Its easy to extend the 7I87 input range (adding a 100K input resistor will increase the range to +-20V)

Sure thats what dead reckoning is, but there will always be accumulative errors so the position will drift when idle.

It may actually be that you dont care about the tachometer voltage above a volt or so, since you can use encoder velocity signals for interpolation when moving at any reasonable rate.
So maybe a +- 1V full scale range might be better (with some input clamping method)

All in all I wonder if adding a high resolution rotary encoder to the ballscrew end is not going to be better ultimate solution

I have to wonder how the original hardware handled it. Did the tack signal go to just the drive or the drive and control? If it only went to the drive, and the drive is handling the velocity loop, then might the corser scale feed back to the control be enough?

Just the ponderings of a person who doesn't realy know what they are talking about.

I'm going through almost exactly the same upgrade path myself - 0.01mm resolution linear scales, Anilam crusader II control, analogue drives with tach feedback.

I can confirm that on my Crusader control the tach feedback only went to the drives. The encoders connected straight back to one of the Crusader boards while the analogue control signals came from a different board to the drives.

On careful inspection of the wiring schematic and detailed testing of what pin went where I managed to deduce that the majority of the pins on the massive round multi pin plug did nothing at all. One impressive looking 26 conductor ribbon cable in the control box turned out to only actually have 5 wires doing anything at all.