Re: Tangential movement function design

Hello,

You use the ATAN function. Provide for old_vect_dir and
curr_vect_dir, comparing to get delta_dir. This last is important
because sometimes you'll want to lift the knife to rotate rather than
rotating it IN the material. (Even though it's only a few thou in, it
can still make a mess of the vinyl...) You set a discriminator value
above which the vertical move is called before rotation.

Anyway, the other gotcha's are the boundaries around and "through" 0
degrees (3 o'clock) So include some boundary checks. And initialise
at 0. You don't need the quadrant info. ATAN is good for the whole
360, once you take care of "zero crossings"

I have some old Powerbasic code I developed for this, but it's on a
machine which hasn't seen a 120v sine wave for quite awhile<G>

Use ATAN, and you'll probably have your solution before I can find a
cord for the old box...

Hope this helps,

Ballendo


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "kdoney_63021"
<kdoney_63021@y...> wrote:

> I need to be able to move my Z axis in a rotary direction to

maintain

> a tangential perspective to my X and Y motion. Like putting a pizza
> cutter on my Z axis with a moving table design. I need to move the
> cutter in the proper direction (tangent) to the expected motion.
>
> I tried to avoid this complication by using a free floating drag
> knife design but I need to be able to reverse direction immediately
> and the radius on the drag knife is too large.
>
> I can easily attach a rotary axis to my Z and have the movement
> available but I need a general mathematical function for

calculating

> the required angle. I was thinking a simple differential equation
> could output the required tangent but I simply have not been able

to

> program the function in C to take into account reversal of

direction

> or undefined tangents. The ones I have problems with would be like:
>
> last position x=0 y=0
> current position x = 2 y = 1 current Z angle is 33 degrees
> move to x=2 y = 6
> or
> last position x=0 y=0
> current position x = 2 y = 1 current Z angle is 33 degrees
> move to x = -2 y = -6.
>
> Does anyone have the function(s)? They don't have to be in C.