Dual-loop PID control strategy for ramp tracking and ramp disturbance handling for unstable CSTRs

Abstract Control strategies designed for step signals fail when applied for ramp tracking and ramp disturbance rejection. Hence, this work presents a novel dual-loop control technique for ramp tracking and ramp disturbance rejection in unstable systems. To begin with, first the unstable process is stabilized using a proportional-derivative (PD) compensator (in the internal loop). This PD compensator was created utilising the direct synthesis approach. Using the loop shaping approach, a proportional-integral-derivative controller (in the outer-loop) is then developed to integrate stabilised plant dynamics. Simulations are done using standard unstable CSTR (Continuous Stirred Tank Reactor) plant models by applying step/ramp reference signals and disturbances. The proposed control strategy shows a satisfactory servo and regulatory response than the existing designs while dealing with step and ramp types of signals. Lastly, a performance summary is also presented on different errors.