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.
Steve
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When I still could have...