Re: Windows timing subroutines, how do they work?

David,

Has happened already. Conventional constant contouring techniques
use "look-ahead" schemes and complex math to move at a constant
velocity along a concatened line segment path.

The G101 uses a velocity-word stream to the step pulse engine. This
allows for a unique and very simple constant contouring method I
call "look-behind". Simply put, the generated velocity-words (along
the concatenated path, no accel/decel) are passed thru a moving
average filter whose output goes to the pulse engine.

Some advantages over conventional techniques is this method requires
no analysis of the line-segment coordinate data, uses only add,
subtract and division by powers of 2 (bit right-shift). It natively
adapts to the requested vector velocity, automatically increasing the
rounding at line-segment nodes the faster it goes. The filter can be
switched in and out on the fly to allow accel/decel where sharp
direction changes are required.

If you want to see it run, please see www.geckodrive.com, go to
the 'support' page and pick the very last item listed (video). The
pen in the video is tracing at 300 IPM on a 6" by 6" XY stage having
5 TPI screws. The motors are 3A/phase PK268s at 24VDC. The drives are
G201s. It could go much faster but the screws sound very unhappy
above 1,500 RPM.

The file is about 5 megabytes so having a broadband connection is a
real plus.

Mariss



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ibewgypsie"
<ibewgypsie@h...> wrote:

> What is probably needed? One Timing generator running at a obscene
> speed, smaller processors that get a bluetooth into buffer dump for
> distance or usb, or? Each processor handles one axis, reading the
> encoder to adjust it's own loop-feedback, running pulse ratio per

main

> engine. All interpolated, All with a error out line back to main
> source to err-out. Each axis dedicated to itself. Then here-we-go..
> Look ahead software that processes speed changes per gcode line and
> pid's it all to that frequency to make desired end of line

directional

> changes without losing it's interpolation between axis. Ramp up,

Ramp

> down each line is not a good way to machine, but the only thing I

have

> saw on my machine.
>
> Will it happen, probably not.
>
>
>
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <thom@t...> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis"
> > <mariss92705@y...> wrote:
> > > In my opinion it should not be the task of a PC to do

the 'donkey

> > > work' of generating step pulses be it Linux, DOS or Windows.

That is

> > > a task that belongs to dumb dedicated hardware.
> > >
> > > A PC is an 'intelligence engine'. It's task is to do a lot of

math

> > > and make decisions. Its output product should go to a 'pulse

engine',

> > > hardware finely tuned to the task of generating of producing

pure and

> > > clean frequencies on demand from the PC.
> > >
> > > These are tasks are so diametrically opposed it's like using a

claw

> > > hammer for a screwdriver. In a pinch you can do it but it's not
> > > pretty.
> > >
> > > That also pretty much surmises what I have seen from most PC

based

> > > CNC programs. The step pulse phase jitter is horrible even from

the

> > > most popular out there. The motors sound like a barrel of

agitated

> > > monkeys and I have the scope pixs to prove it.
> > >
> > > If things are going to be done right, the PC has to interface

to some

> > > kind of step pulse engine.
> > >
> > > The 'agitated monkey' part. Motors that sound like that are

being

> > > robbed of their potential torque especially at high speeds.

Phase

> > > modulation imposes unnecessary torque demands (infinite

impulse

> > > functions) on the motors. Said more simply, you pay for all

that

> > > noise in performance.
> > >
> > > Mariss
> > >
> > >
> > The problem in the past and currently in the present, is that

there is

> > no "standard" for an external pulse generator so you end up

having to

> > buy a "system" that is composed of software and matching

hardware.

> > Your options start to dwindle and if you want/need/desire to

change

> > the software you have to throw away the entire system. It would

be

> > like every car manufacturer deciding to use non-standard tires

that

> > only they provided or each TV network broadcating in a different
> > format so you had to buy a set specifically for their signal

format.

> > From a pure engineering standpoint it might make sense to hand off
> > signal processing to another circuit like a DSP card, but it

needs to

> > have an open set of standards that ANY software company could

write

> > to. If it's going to end up as a PC perhipheral then it needs to

have

> > drivers or open standards that make it useful with different
> > programs. Show me a pulser card that is not single source, has

open

> > standards and is supported by multiple vendors (especially MACH)

and

> > I'll get in line to buy one.