Re: Re: Suggestion for Version 1.0 motion application API...

On Mon, 10 May 2004, Walter Verdonck wrote:

> > [...]
> > A Path is a sequence of ViaPoints; 
> 
> Isn't this a quite restricted definition? To me, a Path is more like a
> trajectory, e.g. a sinusoid, which specifies the relation between time
> and position.
> 
The Path is fully defined by the ViaPoints, _and_ by the behaviour of
the Components in the _application_. The (choice of) behaviour is not
part of the data flow, the path-influencing information in the ViaPoints
is.

If you want a sinusoid there are various alternatives:
- the ViaPoint contains the parameters of the sinusoid (amplitude,
  phase, time duration,..., but also spatial direction in which to
  execute the sinusoid), and a property that identifies the ViaPoint
  as a sinusoidal one. The _application_ will generate the sinusoid,
  provided its Generator has the corresponding functionality.
- the Path contains ViaPoints that are sampled from a sinusoid. The
  ViaPoint's information can be more than just tangent direction and
  velocity: also higher order parameters are possible; hence, the sinusoid
  could be approximated to any desired accuracy. That's what happens in
  most current machine tools, I guess.
- the ViaPoint could describe a "process" which results in the
  generation of a sinusoid.

[...]
> If I understand this well, a ViaPoint is the point you want to reach
> exactly, sometimes called the Precision Point. Does your definition 
> also include fly-by points, i.e. point you want to approach with a
> certain velocity or within a certain tolerance?

Absolutely! Tolerances etc are (could be) _parameters_ of the ViaPoint.
So, there will be a large collection of ViaPoints (or Paths, etc.). This
is, in my opinion, nothing more but a faithful reflection of the
reality...
Note that part of the information of the resulting path is contained in
the Generator of the application! The same ViaPoint given to different
interpolators can result in different trajectories.

I know there is still a lot of filling-in-the-ViaPoint-details to do :-)

Herman