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