Hello,
Background: I'm trying to build a punch press with a "head clear"
sensor. Whenever the "tip" of the press passes a certain height, a
sensor is triggered and the metal sheet should be moved to the position
of the next punch (before the tip reaches the bottom of the movement -
the punching motor is not stopped between punches).
Punching speed is at most 300 ppm. I have about 100-150 milliseconds of
clear time to move the sheet. Currently, the "head clear" signal is
implemented as a motion.digital-in-XX pin, and I can use a standard
Gcode for a given job:
G91
...
M66 P0 L1 Q999
M64 P0
G0 X1
M65 P0
M66 P0 L1 Q999
M64 P0
G0 X1
M65 P0
...
I'm using the digital output as a debugging aid, and checking through
halscope that movement only happens while that output signal is low.
I have a machine already working like this for over a year, without any
problems, but I'm trying to improve punching speed (identifying all
places where there is a delay).
The critical delay is the EMC task cycle time. When comparing the input
and output signals, there are two situations:
1- [TASK]CYCLE_TIME = -0.001: The times between an M66 and M64 commands
are in the range of 2-25 milliseconds. Average seems to be about 7 ms,
but there's a lot of jitter.
2- [TASK]CYCLE_TIME = 0.001: The range is in 15-20 ms. Much less jitter,
but (in my mind) a very height delay (which should have been 1 millisecond).
When running negative CYCLE_TIME and debug mode, min and max cycle time
is 0.0003 to 0.180 seconds (output after program exit) so, a lot of jitter.
Internally, the task cycle is controlled by an RCS_TIMER. Waiting
(AFAIK) is done by the followin line in libnml/os_intf/_timer.c
(function esleep()):
...
if (select(0, NULL, NULL, NULL, &tval) < 0) {
...
Now, these are all my findings so far. I'm guessing the "select* call
isn't really waiting on the appropriate timeout. I assume the task cycle
thread will have some jitter due to the different types of commands it
executes, however 15ms jitter seems an awfull lot. If I could reduce it
to 5ms (at least on the EMC_TASK_EXEC_WAITING_FOR_IO case) I'd already
be pretty happy.
Any tips on how I can proceed next?
Thanks.
--
Matheus Degiovani
Gigatron Software e Treinamentos Ltda.
(18) 3649-4045
MSN: [email protected]
--
CrĂticas ou Sugestões? Ligue para Ouvidoria Gigatron: (18) 3649-4048
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