Revisiting cascade control system and experimental analysis to PID setting for improved process control

Abstract

© 2017 American Scientific Publishers. All rights reserved. The single loop feedback control is commonly used in process control. However, overall performance can be further improved by using cascade control methodology. In this experimental research, FOPDTs of both inner and outer loop were developed through sequential tuning and simultaneous tuning methods. IMC tuning was applied for Sequential tuning method whereas the Multiscale and Enhance Cascade Control were applied for Simultaneous tuning. Interestingly, the result showed that simultaneous tuning provided near-optimized performance in controlling process, which only requires a single bump test for developing FOPDTs. Moreover, less tuning skill is required as the tuning method is guided by developed equations. Improved performance is identified through comparing result of both tuning methods as well as the optimized tuning by using Matlab-Simulink. It is concluded that the optimum PID tuning is fixed to PB = 4%, ti= 85(s) and td= 8.8(s) for outer loop and PB = 85%, and ti= 3.5(s) for inner loop. Cascade loop control ultimately improves both regulatory and servo control.