Re: Re: Re: Re: BDI and servos

>    From: Bob Simon <bsimon@...>

<s>

> I have one question. Are there user available (.ini file?) parameters
> to establish where the controller breaks smooth motion and applies a
> deceleration/acceleration before continuing with the next block? Many
> controllers call this "auto exact stop" or something like that. The
> parameter usually represents an angle (deg or rad). If this angle is
> exceeded, the controller will insert a standard end of move
> deceleration and accelerate in the next move. I've seen more
> complicated schemes that adjust the decel/accel proportional to the
> departure angle. One system even uses an angle table. Most proportional
> schemes seem to be overkill...IMO.

Hi Bob.

Um.... Here's what Tom Kramer, the author of the interpreter, says about
path modes.

-----snips from RS274NGC-----
3.5.14 Set Path Control Mode - G61, G61.1, and G64

Program G61 to put the machining center into exact path mode, G61.1 for
exact stop mode, or G64 for continuous mode. It is OK to program for the
mode that is already active. See Section 2.1.2.16 for a discussion of
these modes.

2.1.2.16 Path Control Mode

The machining center may be put into any one of three path control
modes: (1) exact stop mode, (2) exact path mode, or (3) continuous mode.
In exact stop mode, the machine stops briefly at the end of each
programmed move. In exact path mode, the machine follows the programmed
path as exactly as possible, slowing or stopping if necessary at sharp
corners of the path. In continuous mode, sharp corners of the path may be
rounded slightly so that the feed rate may be kept up. See Section 3.5.14
and Section 4.3.5.3

The canonical machining functions share with the RS274 language the
simplifying assumption that machine dynamics can be almost ignored. That
is, in this model, acceleration and deceleration do not occur. Components
of the machining center can be told to move at a specific rate, and that
rate is imagined as being achieved instantaneously. Stopping is also
imagined as instantaneous. This model obviously does not correspond with
reality. The control modes provided here provide some compensation for
this lack of consideration of dynamics.
-----end-----

G61.1 might work out a bit like you are thinking but being able to change
path mode based on some arbitrary ini value isn't there... yet.

Ray