Which of the following controller is preferred in secondary controller of cascade control system
b. Pl c. PID
d. Any of the above can be used
Cascade control is a multiloop control structure used in process industry to improve control under immeasurable disturbances and to enhance single-loop control performance. In Fig. 2, C1 represents the primary (master) controller, C2 is the secondary (slave) controller, P1 is the primary controlled system, and P2 is the secondary controlled system. Signals r1 and r2 are the primary and the secondary reference values, y1 and y2 are the primary and the secondary controlled outputs, e1 and e2 are the primary and the secondary control errors, u2 is the manipulated variable that results from the control input calculated by the secondary controller influenced by the disturbance d1, and d2 is also a disturbance.
Any of the above can be used