Re: Higher performance systems

Leslie,

Ah, a topic near and dear to me just right now! The conundrum is
vector path fidelity and a constant vector velocity are mutually
exclusive.

To accurately follow a path means you have to decelerate to a stop at
the end of every line segment which is irritatingly slow and noisy.

You can "round" line segment nodes to keep a constant contouring
velocity. It is a computational nightmare though, having to insert
arcs between nodes whose start and end angles and radii depend on a
given axis set acceleration and velocity. The "on the fly"
trignometry and path look-ahead schemes get real ugly real fast.

I have come up with a method that neatly sidesteps those problems
entirely; it is computationally trivial and acts automatically. In
effect, the faster you go, the "rounder" the nodes are.

The method outputs a moving average of velocity, effectively
integrating velocity with time. A step change in velocity gives a
ramped change, a ramped velocity results in an S-shaped velocity
profile.

As you probably know the G2002 is up and running using this
algorithm, now on 3-D moves (XYZ). The results are very pretty indeed.

Mariss




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Leslie M. Watts"
<leswatts@a...> wrote:

> Mariss,
> I think of the accel in terms of minimum corner radii.
>
> Radius= velocity squared/acceleration
>
> ... for more calculator fun.
>
> With 20 amps x 70 volts peak one can move a lot of
> mass pretty quickly!
>
> I certainly agree with you and Jon that you won't
> get to 1000 ips with a 5 TPI ballscrew!
>
> Leslie M.Watts
> L M Watts Furniture
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