Is this the way we should approach sequences of motions for toolchanging
and the like? Comments, please.
HAL-BASED MOTION CONTROL
========================
Often, it's desirable to command a sequence of motions outside of g-code.
For instance, a number of movements may be required during a tool
change. The modifications proposed below allow for this kind of
control, and make 'halstreamer' an example component capable of
exercising this control. (It is anticipated that special-purpose
HAL components, rather than 'halstreamer', would command the tool change
motion in actual systems. It is up to an integrator to write an
appropriate component)
Motions in the external-position mode are performed in "exact stop" mode
(suitable for tool-change motions but probably not for machining), and
respect the machine's velocity and acceleration limits. It is hoped
that the implementation can re-use the so-called "free planner" which is
used in jogging.
NEW PINS ON THE MOTION CONTROLLER
=================================
motion.external-position-command BIT IN
When TRUE, the machine's position is controlled by the
external-position-<AXIS> pins. On the transition from TRUE
to FALSE, the machine returns at "traverse" speed to the
position it was in before this pin was asserted.
motion.external-position-<AXIS> FLOAT IN
(<AXIS> is one of X, Y, Z, A, B or C)
Drive with the requested position in machine coordinates
motion.position-<AXIS> FLOAT OUT
Driven with the current commanded position of the axis
motion.external-position-velocity FLOAT IN
Drive with the requested velocity.
motion.external-position-control BIT I/O
When the external position is reached, motion sets this pin TRUE.
CHANGES TO HALSTREAMER
======================
If the first letter of the streamer configuration string (cfg=) is '+',
then the new pin is created on a 'streamer' instance. Otherwise, the
'streamer' outputs one sample per invocation, as it does now.
streamer.<N>.next-sample BIT I/O
When this pin is TRUE, streamer outputs the next sample and sets this
pin FALSE
COMMANDING MOVEMENTS WITH HALSTREAMER
=====================================
The following illustrate how halstreamer can make a series of
coordinated movements, drawing a 2-unit square at 1 unit above the
machine origin at 5 units per minute. To begin the sequence, drive the
signal 'external-control' TRUE (for instance, with a 'halcmd setp').
# Additional HAL configuration
loadrt streamer depth=4 cfg=+bffff
net external-command motion.external-position-command streamer.0.pin.0
net external-x motion.external-position-x streamer.0.pin.1
net external-y motion.external-position-y streamer.0.pin.2
net external-z motion.external-position-z streamer.0.pin.3
net external-a motion.external-position-a motion.position-a
net external-b motion.external-position-b motion.position-b
net external-c motion.external-position-c motion.position-c
net external-vel motion.external-position-velocity streamer.0.pin.4
net external-control motion.external-position-control streamer.0.next-sample
# Sampler input file
# X Y Z vel (unit/sec)
1 -1.0 -1.0 1.1 10000.0
1 -1.0 1.0 1.0 0.08333
1 1.0 1.0 1.0 0.08333
1 1.0 -1.0 1.0 0.08333
1 -1.0 -1.0 1.0 0.08333
1 -1.0 -1.0 1.1 10000.0
0 0.0 0.0 0.0 0.0
OPEN QUESTIONS
==============
Q. Should feed override, adaptive feed, or feed-hold apply to these
motions?
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