Re: Jog wheel

[Brian Pitt <bfp-at-earthlink.net>]

Hi Ray

a few comments thrown in

> Handwheel
>
> Now the handwheel problem is not quite so simple.  Rather than the
> continuous jog as in the suggested stuff above, we would use incremental
> jog and the increment would determine the multiplier to be used with each
> pulse/push.
>
right... 
except the incremental handwheel would be easier than dealing with all
the keyboard quirks and the calibration and timing on the analog joystick etc.

> But now any motion command issued by the emc has a speed and an endpoint so
> this would seem to work okay but what happens in the case of a handwheel
> where a second or third jog command is issued while the first one hasn't
> yet completed it's move.  

this one came up on the CCED list last time
it should ,yes,should  ignore the extras if it is already jogging

on many machines with MPGs you can hear/feel the larger increments as 
a bunch if startstops but the small increments will blend together and feel
like a smooth motion

> Normally the endpoint of an incremental jog
> command is computed from the current position to the position of the axis
> with the increment added or subtracted.  So what would normally happen is
> that whenever the second motion command is recognized by the task module,
> it will take the current location and add the increment.  Thus not all
> increments or handwheel steps will be the same length.  

sure they would 
it has to finish one before it can take another so they
would either be the same size or be skipped over
at the end of the move it would always stop on a multiple of 
the increments from the start point even if a few were skipped

> Only those issued
> after the previous has been completed will move the axis the full increment
> distance. So spinning the handwheel rapidly during a jog will only get you
> a bit further than the next to last one executing.
>
exactly 
the axis will stop as soon as you stop ,just like a normal handwheel
this is what we want to happen

> This behavior could be altered if we wrote a routine that captured the
> pulses of the handwheel and add them up while a jog command is being
> executed.  Then when the current motion command completes, it would issue a
> single command with the distance value as the number of pulses times the
> increment and set the count to zero again.
>
so if the jog increment was set at .1 and you gave the wheel two quick turns
you would get an axis movement of 20 inches ,with no way to stop it except
smashing the E-Stop switch
ummm... 
thats probably not the behavior we really want ;-)

Brian