What are the advantages and disadvantages of Cascade control?

processcontrol

#1

Advantages of Cascade control Loop-

-Isolating the slow outer loop from valve problems and some disturbances.
Fast inner loop take care of these.

Disadvantages of cascade control loop.

-Additional measurement required.
-Additional control required.So controller tuning of secondary controller is required.

When to use cascade control loop?

-Inner loop should be faster (3 times) than outer loop.

What is the tuning sequence of cascade control?

First tune the inner loop
Enable cascade control
Tune the outer loop