The Cascade Control Architecture
ABSTRACT: Two popular control strategies for improved disturbance rejection performance are cascade control and feed forward with feedback trim. Improved performance comes at a price. Both strategies require that additional instrumentation be purchased, installed and maintained. Both also require additional engineering time for strategy design, tuning and implementation. The cascade architecture offers alluring additional benefits such as the ability to address multiple disturbances to our process and to improve set point response performance.
An Implementation Recipe for Cascade Control
ABSTRACT: When improved disturbance rejection performance is our goal, one benefit of a cascade control (nested loops) architecture over a feed forward strategy is that implementing a cascade builds upon our existing skills. Implementation is a familiar task because the procedure is essentially to employ our controller design and tuning recipe twice in sequence.
A Cascade Control Architecture for the Jacketed Stirred Reactor
ABSTRACT: Our control objective for the jacketed stirred reactor process is to minimize the impact on reactor operation when the temperature of the liquid entering the cooling jacket changes. We have previously explored the modes of operation and dynamic CO-to-PV behavior of the reactor. We also have established the performance of a single loop PI controller and a PID with CO Filter controller in this disturbance rejection application. Here we consider a cascade architecture as a means for improving the disturbance rejection performance in the jacketed stirred reactor.
Cascade Disturbance Rejection in the Jacketed Stirred Reactor
ABSTRACT: Our control objective for the jacketed stirred reactor is to maintain reactor exit stream temperature at set point in spite of disturbances caused by a changing cooling liquid temperature entering the vessel jacket. In previous articles, we have established the design level of operation for the reactor and explored the performance of a single loop PI controller and a PID with CO Filter controller in meeting our control objective. We also have proposed a cascade control architecture for the reactor that offers potential for improving disturbance rejection performance. We now apply our proposed architecture following the implementation recipe for cascade control. Our goal is to demonstrate the implementation procedure, understand the benefits and drawbacks of the method, and explore cascade disturbance rejection performance for this process.