Cascade Control Strategy

Hi dear Steemians...
I am going to present to you series of "Process Control Strategies" in the form of images..

Today I will show you Cascade Control images.

When atleast two controllers are used and each Controller is sensing the different aspect of the same process, then these controllers are said to be in the Cascade Control Mode. If flow of a liquid in the tank is being controlled by a valve and Flow controller is again being controlled by a Level Controller then Level controller and Flow Controllers are said to be in the Cascade Mode.

Here is a simple feedBack controlled loop for an ordinary Process...

Here is Cascade Control for the same process.

Here main purpose is that to achieve more Stability for the Primary Controller which in turn controls the secondary controller and secondary controller be very fast/very less lag time in comparison to primary controller to achieve best usage of Cascade Control.

For Example here Flow/opening of valve is being controlled by Level Controller by sending the Setpoint Value and Measured (Process) Value being generated by Flow Controller. Ultimate control lies with the Level Controller.

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