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using HAL to correct axis errors
8 years 8 months ago #105999
by pgf
using HAL to correct axis errors was created by pgf
This is a topic of some shame -- the axes on my home-built X-Y mill aren't square to one another, and they've been that way for a very long time. Sigh.
When I built the mill (mid-90s?) it didn't occur to me that I might not get the axis alignment exactly correct on the first try, and I provided no means for adjustment. So yes, I've been living with this for forever. You might guess, correctly, that I don't use the mill much.
It occurred to me that there was probably a way to fix this error from within linuxcnc, and sure enough I found this post:
forum.linuxcnc.org/10-advanced-configura...on-with-2-7-11#99833
which proposes a simple HAL component to work around an uneven table.
So I'd like to try it, but I'm stuck.
Based on that post of Andy Pugh's, my component looks like:
It builds and installs fine with halcompile. But then what? There's obviously some other configuration required to get this into the pipeline.
As an initial step, I've added a line with
to the file "custom.hal" in my mill's config directory. When I fire up linuxcnc, it quickly dies. While I didn't expect the component to actuall work, I didn't expect it to kill the whole system so quickly! 
Clearly I'm missing something basic that I didn't glean from a quick read through the HAL docs. The logs aren't terribly useful, except perhaps that they're so short -- perhaps that's meaningful..
Debug:
and print:
Any suggestions appreciated!
paul
When I built the mill (mid-90s?) it didn't occur to me that I might not get the axis alignment exactly correct on the first try, and I provided no means for adjustment. So yes, I've been living with this for forever. You might guess, correctly, that I don't use the mill much.
It occurred to me that there was probably a way to fix this error from within linuxcnc, and sure enough I found this post:
forum.linuxcnc.org/10-advanced-configura...on-with-2-7-11#99833
which proposes a simple HAL component to work around an uneven table.
So I'd like to try it, but I'm stuck.
Based on that post of Andy Pugh's, my component looks like:
Code:
component nonsquare_table;
license "GPL"; // GPL v2 or later
pin in float x-in;
pin in float y-in;
pin out float y-out;
function _;
;;
FUNCTION(_){
y_out = y_in + 0.0095 * x_in; // approx 3/32" in 10"
}
It builds and installs fine with halcompile. But then what? There's obviously some other configuration required to get this into the pipeline.
As an initial step, I've added a line with
Code:
loadrt nonsquare_table.ko
Clearly I'm missing something basic that I didn't glean from a quick read through the HAL docs. The logs aren't terribly useful, except perhaps that they're so short -- perhaps that's meaningful..Debug:
22841
PID TTY STAT TIME COMMAND
Stopping realtime threads
Unloading hal components
and print:
RUN_IN_PLACE=no
LINUXCNC_DIR=
LINUXCNC_BIN_DIR=/usr/bin
LINUXCNC_TCL_DIR=/usr/lib/tcltk/linuxcnc
LINUXCNC_SCRIPT_DIR=
LINUXCNC_RTLIB_DIR=/usr/realtime-3.4-9-rtai-686-pae/modules/linuxcnc
LINUXCNC_CONFIG_DIR=
LINUXCNC_LANG_DIR=/usr/share/linuxcnc/tcl/msgs
INIVAR=inivar
HALCMD=halcmd
LINUXCNC_EMCSH=/usr/bin/wish8.5
INIFILE=/home/pgf/linuxcnc/configs/my-mill/my-mill.ini
PARAMETER_FILE=linuxcnc.var
TASK=milltask
HALUI=
DISPLAY=axis
Starting LinuxCNC server program: linuxcncsvr
Loading Real Time OS, RTAPI, and HAL_LIB modules
Killing task linuxcncsvr, PID=22841
Removing HAL_LIB, RTAPI, and Real Time OS modules
Removing NML shared memory segments
Any suggestions appreciated!
paul
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