Part IV : Enhancements to Single-Loop PID Feedback Control
@ Control enhancements are chosen based on the following criteria:
• Reinforce principles: ‘strong’ control theory
• Demonstrate practice
• Apply process insight: understanding of process equipment and operating
conditions
Chapter 14 Cascade Control
@ Cascade design criteria
Cascade uses an additional measurement of a process variable to assist in the control system
Ex. Stirred-tank heat exchanger with cascade control
S1. Cascade control is superior to single-loop control
S2. Cascade controller
S3. Two controller names
@ Rejection of stochastic secondary disturbance
Cascade control
Cascade examples
1. Packed-bed reactor
2. Heater exchanger
3. Pressure control
@ Distributed decision making by cascade structure