Cascade control has many potential benefits:
- It will catch certain load changes sooner and correct for them faster.
- It will effectively linearize the secondary variable.
- It can and should shorten the natural period of the primary loop.
- Some instrumentation tricks can be played.
For more information on these subjects and others you may refer to a booklet "Controller Tuning and Control Loop Performance, a Primer" , which is available in the US for $17, postpaid if prepaid. It has sold 29,740 copies to date. Control Engineering Magazine has referred to it as "PID Without the Math".
Information may be found at
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A page on Companion Software ($11) is there also.
If you wish, I could e-mail you the same information.
David W. St. Clair Straight-Line Control Co.