I am trying to configure two PID controllers whose outputs go to a single output signal selector for control of a valve. One of the controllers will be in normal use, while the other is a limit controller.
I have connected the backcalc output from the analogue output block to the backcalc in of the signal selector and the backcalc out from the signal selector to the backcalc in for each of the PID controllers. I would have expected this to prevent the non-selected controller from winding up to maximum under integral action. This is not happening. Is there something I need to modify in the PID controller to enable wind-up protection of the unselected controller.
I can of course construct some logic external to the PID controllers to perform this function, but I would have thought the output signal selector would inherently have this function.
Regards
Jeff Richards
In reply to Andre Dicaire: