Hi everybody, I already have a very complex LabVIEW program with several loops running at the same time and I now want to include a cascade control in it. I created the cascade control itself first (see attached VI) and it works fine itself. But when I implement it in my main program (where I need it) it slows down the whole program: ( Maybe it's because of the local variables? But I don't know any other other solution. I'm new to this, so I would be very happy if anybody can help me! The VI which I attached is a little bit confusing (SORRY!), but basically you only need to look at the two while loops on the bottom and at the PID controller in case "F" of the case structure. The PID controller in case "F" is the controller of the outer loop of the cascade control. It's output ("setpoint") enters the inner loop (see while loop on the left/bottom), which consists of a second PID controller with a filter and (in the feedback) a modell for a PT1 + delay time. So the inner loop should work as a smith predictor. The output of the inner loop (FiO2) enters the modell "lunge" (see while loop at the right/bottom), which consists also of a PT1 + time delay. Finally the ouput of the modell "lunge" will be subtracted from the input of the first PID controller in case "F" (closed loop). Maybe I will post a draw of it later for better understanding. I'm looking forward to your suggestions how to make the control loop faster. Thanks in advance! Steffi

LabVIEW

Hi Steffi,

sorry for the long break. I attach a little part of the vi as a picture.

Mike

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