|Improved Cascade Control System for a Class of Unstable Processes with Time Delay
Cheng-qiang Yin*, Hong-tao Wang, Qun Sun, and Ling Zhao
International Journal of Control, Automation, and Systems, vol. 17, no. 1, pp.126-135, 2019
Abstract : "An improved cascade control scheme is proposed based on modified Smith predictor for controlling
a class of unstable processes with time delay. The proposed control structure consist three controllers of which
the secondary loop has one controller and the primary loop has two controllers. The secondary loop controller is
designed according to Internal Model Control (IMC) principles. The primary loop set point tracking controller and
disturbance rejection controller are designed using the same procedure based on modified Smith predictor control
structure. An analytical method on the basis of the Internal Model Control design principle is adopted for the two
controllers which reduces complexity in design. The two controllers in primary loop are designed as proportional,
integral and derivative (PID) controller cascaded with a lead-lag filter. Moreover, suitable values are recommended
for the three controllers based on extensive simulations. Simulations studies are carried out to demonstrate the
effectiveness of the proposed method."
Cascade control, modified Smith predictor, PID controller, time delay, unstable process.