Y axis moves!! Tuning the DMM servos - overview

As I've got the Y axis bolted together and the belt is fitted and tensioned, I thought it would be rude not to flash up the controller and give it a spin.

The program I have loaded in the memory makes a variety of X, Y and Z moves but it's clear that the default PID settings for my Dyn2 drives are somewhat "suboptimal". It seems to have a bad case of the DTs or possibly Parkinson's.

Link to the servo drives here. And the software download page.

The DMM servo tuning software is designed to help with the process but it requires some calculations to determine the ideal settings. For now, I just fiddled about and ended up with a better ie more stable result.

I'll come back to this when I've done the sums and have something to go on. The CNCdrives tuning software that supports the brushed servos on The Shiz has some nice features that display the demand and actual motor movement, so you can observe how the overshoot and steady state error are affected by the settings. I suppose the DMM boys are taking the more theoretically correct approach by calculating the moment of inertia etc and calculating the appropriate gains.

This is how they describe the process:

Back in Jan 2016, I started a spreadsheet to do these calcs. I'll need to review them and finalise the values. Looks as if I got a little way along the road with it, although it is rather devoid of the calculations and actual values. Details, I know!

I can use their example values in my spreadsheet to check my sums make sense.

Update:

In fact, it seems the software has been updated since I made my copy on the network. The latest version looks a lot less flakey, judging by the manual.

Here's the autotune page. I ran it OK but I have to say the resulting settings (gains of 8, 7 and 1) seem some way off the mark.

I over rode the settings manually using the slightly snazzier screen:

Clearly some work to be done on my part....