I recently came across concept of auto /manual mode for PID controllers. I was wondering why two modes are required. PID is intended to change output according to set point and auto regulate during disturbances. Can just one mode not be used for both changing set point and regulation? why two separate circuits?
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I recently came across concept of auto /manual mode for PID controllers.I think it's a good idea to give us the (link to the) document.
I assume it tells you "what" is auto and manual.
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The linked article discusses specific details of controllers manual to automatic switching and is obviously not intended to teach basic terms of control engineering. Nevertheless it gives you an idea about the purpose of mode switching, if you just read it thoroughly.
Consider that a controller is not necessarily always active. It may be activated and deactivated at times. Manual mode means that a controller is deactivated, in other words not reacting on set point and process value variations. Instead the controller output ("manipulated value") is either hold at a defined initial value or controlled by a different source. "Bumpless" is a keyword in mode switching, start controller operation without any unwanted excursions of the manipulated value.