architecture for control of stations around an index wheel

[ned]

I've just started a new job that is asking me to use LabVIEW in a different application than I've programmed in the past, and I'm looking for suggestions. I'm working on a system that has several stations around an index wheel. At one station a vial is filled, then rotated to the next station where the contents are verified, then the vial is capped, etc. I'm trying to decide what software architecture to use for this.

My original thought was that each station would act as its own subsystem, and communication would occur using two notifiers: the index wheel system would send one notification when it is in position, and each other subsystem would send a notification back when it completed (indicating success or an error). However, there is an existing system here already that uses PLCs and a sequencer (perhaps I have the term wrong) that rotates through a circle each cycle and triggers outputs across all subsystems along the way (one output might turn on at 5 degrees, another at 30 degrees, etc), which makes it easy to see when something goes wrong because it is possible to step through it by advancing the sequencer more slowly. I'm considering using a similar technique in my LabVIEW code.

Does anyone have experience with a similar system, and if so, can you comment on your experience? Did you use one of these two approaches or something else entirely?

[LAVA 1.0 Content]

QUOTE(ned @ Sep 17 2007, 07:21 AM)

Does anyone have experience with a similar system, and if so, can you comment on your experience? Did you use one of these two approaches or something else entirely?

I would make 2 suggestions. The first would be to seriously investigate teststand and if you do not know it, take some courses on it. The built in sequencing architecture and the ability to easily parallel operations will make your life MUCH easier. Also, learning teststand is a valuable tool.

Secondly, if you can't make a successful pitch for teststand, once upon a time I made a very powerful architecture that used the OpenG Message Queue and several parallel running 'Engines'. Each engine was a consumer of a unique Message on the Q that were fired off in parallel. Each engine would then process it's message/command in parallel and return to the central system w/ status at the end via the built in notifier to the OG MsgQ.

This station was not an indexer station, but implemented the architecture that you are speaking of.