LOW OUTPUT PID DAC

Hy,

I'm trying to setup a XYZ machine, as simple as I can for testing prupouses, but in the last 3 days my work gets moving minus than fernando alonso riding a mail box.

I'm using a 5i23+7i48+5I23_svss6_8 FW. When I ran the PNCCONF, I did the open loop test and everything Went OK. X encoder made good position measuring. I set 2.0 volt to output DAC on this test and que DAC gave 1.95 volt to X servoamplifier, so it moved at aprox 10mm/second.

But when I launch Linuxcnc/axis the DAC output is much lower. I checked all signal on the INI generated file, and set every speed limit I found to a highger value. The only speed parameter I can't find are these who are realted to homing sequence. These are not in the INI file, and in the PNCCONF I saw these was grayed out.

Some "item" is setting the PID output low, max +/-0.05 volt (externally measured). I always fall in joint following error if I set the jog speed slider high, like commanded position is non reachable for any reason (in low jog speed it moves w/o followin error, but moves are quite slow).

First I thought may be the system is not homed or same limit SW is pressed, limiting the max speed. But later observed that if I swich on the machine, but switch off the servo power, the halshow show X axis enabled, and then if I click on the "+" jog button (I have a small integral term on the PID) the DAC output increases and reach quite greater values, as it were not affected by the limiting "item".

In the PNCCONF the only signals configured for now are the xyz encoder and the xyz pwmgens. I have linear scales with ABZ output. All other stuff, including the "dog" homing or limit switches, are not configured for now, but I'll plan to connet them to a modbus TCP field device.

So this leads to the following:
-Is there a good site to debug how HAL is obtainig its output DAC?
-Why I cant set the homing sequence on pncconf?
-And how to start it once in axis enviroment?

Very thanks in advance, Mario JRL.

Sounds like you need to tune the PID settings.
Open loop test does not use PID - you are setting the DAC output directly.

Pncconf will gray out the homing options if you didn't select a home switch input on the mesa page.
What version of linuxcnc are you using?

Chris M

I've upgraded to 2.7 from 2.6. I've also noted PNCCONF gui is different in 2.7. But what hal signal can I watch to see if there is a limit switch tripped or something like that? (I've read the joint speed is quite decreased and the axis enable kkeps ON if a limit SW is tripped or in homing sequence, but not cutted off and axis disabled like CNC typical systems)

Thanks, Mario JRL

the items you mention can be a number of issues
if you have not set up enable or your soft limits then it cant shut off , as it does not know at what point etc
all hal signals are available in the hal configuration in axis and you can watch any , either by name or port input

check that your enable signal is changing at your breakout , it may only be that the approprate pin needs inverting in pncconf
especialy if using opto's as this invariably inverts the signal .

if a limit switch has tripped in linuxcnc then you would get a pop up warning , in most cases again the input or output requires inverting .

also for low output levels , check again your ini file for the voltages it has set . both as default and max and min per axis
if you care to post your config as an archive , moderators are more able to assist , rather than guess at possible problems