Realtime - PC
Digital control of converters requires a platform for hard realtime control software, that is usually provided by a DSP system. Unfortunately these systems are not standardized and usually come along with a rather impressive price tag attached to it. Let's imagine you want to try some unoptimized pre-beta control algorithms and need a recording of more values than can be passed through a dual-ported-RAM on a standard (cheap) DSP board. In other words, in terms of performance you really need some beef up front, while you do not belong to the group of well heeled customers who do not ask for the price anyways. You need to come up with an alternative. The cheapest hardware platform that is widely available is the standard PC. It has lots of CPU power, unlimited RAM, multiple sources for i/o cards and realtime operating systems and a really low price.
On these pages we will offer some information about how to build a platform for digital control based upon standard hardware components.
be patient, it will be here soon
Since standard operating systems are designed for maximum overall throughput, they are not able to deal with hard limits imposed by critical realtime tasks. Of course the multi-media timing has to be accurate enough to provide the 25 frames per second, but a missed frame does not cause much damage. Since we are not in the aerospace business, examples of liquid fuel rocket control are a little far-fetched. But imagine that your converter gets out of control. There are various safety devices for that case, but it is still something you might not appreciate in the lab. You will need a realtime operating system that allows you to take full control of your target hardware. We did a survey on them, that you can use as a starting point.
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In order to insure that the controlwords get to the converter at the exactly calculated time, some external device is needed that handles this kind of timing for the PC. A timer card was developped and tested, that suits our requirements for various applications. More detailed information will soon be available. Contact me.
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This information is purely for the people who have been given the task to get a PC-system up and running:
1) do not mind your coworkers making fun of you
2) do not believe people who say 'it's quite easy and can be done in a minute'
3) do not give up
In case you need help, contact me.