5i20 & 7i33 puzzle

Hello All,
I'm having a head-scratching moment here. I have a 5i20 & 7i33 connected to a chinese analog servo drive & motor.
I have used PnCconfig to write a .ini file using tkemc. If I set position display to actual and turn the motor, the display counts up
& down OK. I have set the following error values to 100mm If I enable the servo, I can jog back & forward, but, if I open hal meter
and display the following error, the error just goes up or down but doesn't return to zero when I stop jogging. If I jog for more than 100mm
then it faults out with following error. It seems to me as if the servo loop isn't closed somehow, but I can jog, so it sort of says the
servo loop is working. Anyone?

TIA,
Dave Winter.

What version of linuxcnc are you using?
Can you post your INI and HAL file (or the whole config file)

You don't mention encoder feedback but does it count up and down too?

Chris M

Hello,
I thought that I was using 2.7.14 but the splash screen when it starts up says 2.7.0 The servo motor & drive are 3 phase
brushless, the encoder is built into the rear of the motor, as is usual these days. On the 5i20 board there are 2 red LEDs which are
on when I start the PC and go out when I start up LCNC. There is something stirring in the back of my mind which thinks there should
be a green LED on on the 5i20 when LCNC is up & running, but there isn't ? Attached is my config folder ( are they folders or
directories in Linux? )

Thanks again,
Dave.

If you remove the:

setp pid.x.maxerror .0005
setp pid.y.maxerror .0005
setp pid.z.maxerror .0005
setp pid.s.maxerror .0005

Statements from the hal file, things should work better.

Hello Peter,
Looks like that did the trick. I also found lots of settings in my servo drives that needed changing, accel & decel ramps were set to S-shaped, need to be linear and as fast as possible, let LCNC handle the axis ramping. One thing I did find that surprised me was I have all the gains except P set to zero. The drives have an integrator in the speed & torque loops, and if you set any I gain in LCNC
it completely messes things up. I might be able to use FF0 gain to reduce the steady state following error.
Thanks for your help,

Dave.

Typically for velocity mode drives LinuxCNC only needs FF1 and P and perhaps a bit of FF2

Basically FF1 should be adjusted to null error during constant speed motion
FF2 should be adjusted to minimize the error during acceleration and deceleration
and P should be as high as you can get without becoming unstable

Thanks again Peter.

Dave.