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Thread: Point optimisation: how to

  1. #101
    Join Date
    Mar 2012
    Akron, Ohio USA


    I'm not nit-picking here but that phrase "in real time" is interesting.

    If the points going in are not in any particular order and the controller reorders them and possibly adds points how can that be "real time"?

    You get what I mean?

    I would think that the controller would need all the points in a frame to optimize them.

    By the time it takes to send a frame of points, at least one frame of time would have elapsed.

    Last edited by james; 01-22-2015 at 15:15.
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  2. #102
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Join Date
    May 2007
    A lab with some dripping water on the floor.


    Digital servo amps break down into two classes. I'm going to split them using a crude definition of a DSP term, " Determinism."

    Determinism is sort of the ability to remember the past in a filter.

    Non Deterministic amps work with a narrow "slice" of time and cannot remember the past nor anticipate the future. This is your common analog amp, and those digital amps that are configured to emulate a classical analog feedback loop. These take a single command element and process it. They often have both analog and digital input capabilities. Ie you can hook one to an ILDA analog signal or latch in a single digital word at a time.
    They offer improvments in speed or accuracy and often can be configured or tuned on the fly.

    Deterministic Amps are smart. They can remember the past and reasonably predict a small portion of the future, based on the incoming command as well as the past path. They have memory depth and are often DSP based. You can pass them a set of digital words representing the desired points or vectors and they will compute the time step and execute the path optimally. They can often execute something like a batch file. Usually they also have software allowing them to control the laser that does the materials processing. This allows them to deliver constant energy per unit of travel in a marking situation. Often they have multiple modes that can be stored in memory. Most of them can revert to something that emulates a non-deterministic Amp.

    Almost all digital amps use a standard, classic, analog Galvo. There are a few out there that support a non-standard Galvo with a digital position sensor based on a absolute encoder. The later are very rare, and generally used in semiconductor processing.

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