Estun Servo Tuning

[MRW]

I am trying to tune some estun EMJ motors here and there are a few things that I do not quite understand. TB234 says this

"These numbers reflect 10mm-12mm pitch ballscrew and 160000 counts/rev of the motor. To figure out an appropriate Kp and Ki value divide 160000 by your counts/rev of the motor and multiply by Kp and Ki values above to get ballpark values"

My machine has an 8mm pitch ballscrew and the encoders have 4194304 counts/rev. What I do not understand from the instruction above is how to get the ballpark values for Kp and Ki as according to that mathamatical equation if I figured right, it would always be "1" regardless of the encoder count/per rev, is that what this is trying to say or am I missing something?

Thanks again,

[AcornJosh]

Don't worry about that, just use the suggested values (TB291) for your drive, maybe lower them slightly.
Set the max RPM based on your motor specs. F1 setup, F3 config, F4 PID, F8 Drive, F1 Drive PID.
Now focus on tuning KV1. Once this is dialed in, you can try tweaking Kp and Ki.

Setting the Max RPM in F1 Drive PID sets these parameters. From manual.
15.3.150 Parameters 357–364 –– Axis Drive Max RPM for Axes 1-8
These parameters allow you to set the drive/motor max rate capability (in RPMs) for use by the PIDalgorithm for the calculation of the axis KV1 contribution. This value is independent from the axis MaxRate setting in the Jog Parameters menu, which is used by the control software. However, for those axeswhose corresponding parameters are set to 0 (the default) the the PID algorithm will use the axis MaxRate setting in the Jog Parameters for the calculation of the axis KV1 contribution. These parameters areintended for 3rd party velocity mode drives that have a different max rate setting than that of the controlsoftware

[MRW]

Ok Ill try this.
At the moment all axis motors when they are in the run state they hover back and forth about (i'm guessing 10deg.) and do not stay stable. What could be causing this? or does this all have to do with the tuning issues?

[tblough]

That is called "dither" and is definitely related to tuning. Once you have the motors tuned, that should be reduced to plus or minus a couple of encoder counts which should not even be visible.

[MRW]

Ok great, The other issue I am having is that as soon as I try to run the tuning program F2 The axis starts and then stops with a encoder read error. What can I do to change this so I can start moving things around and actually tune these motors? Nothing seems to work for me and I still wonder if this is a drive setting related issue. I cannot get anything to change. I have paid for support but all they say is to go and follow the tech bulletin which I have tried many times only to get 0 results. Looks like I just wasted a bunch a money for support that I cant get any help with.

SOMEONE PLEASE HELP ME OUT. This is starting to drive me crazy!

[AcornJosh]

Are you able to jog an axis without it throwing a fault message? The system should work with the basic settings. You need to get the drives jogging and working before you try to tune.

[MRW]

I can jog all axis manually as long as I keep the Rev/inch at 1. Otherwise it faults out with an encoder position error.

[tblough]

Encoder position error means the control commanded the axis to move, let's say 1", but the encoder reported the distance moved as something other than 1". This means that either the motor revs/inch are wrong, or the encoder counts per rev are wrong, or both are wrong.

The other possibility is that the control does not have the bandwidth to handle 4 million counts per rev at more than 1" per minute. You should definitely change the motor encoder resolution to something more reasonable like 4000 to 20000 counts per rev.

[MRW]

Ok would that explain to than why if I tell it to go .25" which should be 4 revs. that it turns 16 rounds instead?

[AcornJosh]

The Encoder only measures motor revolutions. The control has no idea how many inches you moved, It only sees how many turns of the motor. The Turn ratio (revs per inch) are what converts the encoder feedback into your DRO inches.

Does the axis jog if you keep the feedrate turned down low?

Are you sure your have the encoder counts set the same between the estun and the oak? This is based on pn200 on the estun.