LinuxCNC-RIO - RealtimeIO for LinuxCNC based on FPGA (ICE40 / ECP5)

Mine works

Hello Meister

Since a week, I have been trying to set up a rotary axis A with a TangBob. It works at snail speed, but not at higher speed. I am always confronted with joint follow error of the axis.
I need the axis in a winder setup to wind bobbins. Hence A must rotate "endless" depending on the windings I want to achieve. I need to achieve at least 1000 rpm. There is no problem with a linear axis.
I have used rio-flow-gui to set up an open loop stepper type angular, 1600 micro steps. Scale in and scale out are set to 1600. Whatever I do with the ini parameters to achieve higher speeds it fails on the joint follow error.
As I do not understand the internal mechanics of the actual feedback that should confirm the requested speed, I am lost. Furthermore, I do not understand the fole of the PID, which should have no meaning for an open loop set up.
I also cannot find any example of my application to help me out.
Hence, I hope you can help me out to set up a rotary axis at 1000 rpm to overcome that joint follower error (in simulation mode and with the hardware (currently only with the Tangboard only - no ChinaBob attached).
Thanks a lot in advance.

Hi Mirko,

The external step generators are controlled by velocity commands, so they require a PID controller to convert the position into velocity commands.

To start with, set the error parameter for the rotary axis to 20 and the min-error to 2:

Flow -> StepDir plugin -> Joint -> General -> *error

I hope that sorts out the follow error for now.

You can also lower the acceleration parameter.
Most default settings are for linear axes and will not work well with rotary axes.

Thanks a lot for your immediate help! That has solved the problem and I can go ahead with the rest of the project.
By the way, I have changed a bit the PID parameters, which has improved the situation, but did not solved it.
FF1 = 1
FF=0.02
MAXOUTPUT=30000
(1000 rpm and high acceleration of 5500 works now)