Controller Design and Stability Analysis of Intensification Process using Analytical Exact Gain-Phase Margin approach

Abstract

Controllable intensified process has received immense attention by the researchers in order to deliver the benefit of process intensification to be operated in a desired way in order to provide a more sustainable process towards reduction of environmental impact, improve of intrinsic safety and process efficiency. This paper proposed the Exact Gain and Phase Margin (EGP) through analytical method to develop suitable controller design for intensified system using PID controller formulation and it was compared to conventional Direct Synthesis Methods (DS), Internal Model Control (IMC) and Industrial IMC method in terms of the performance and stability analysis. Simulation results showed that EGP method provides good setpoint tracking and disturbance rejection as compared to DS, IMC and Industrial IMC while retaining overall performance stability as time delay increases. The Bode Stability Criterion was used to determine the stability of the open-loop transfer function of each method and the result demonstrated decrease in stability as time delay increases for controller design using DS, IMC and Industrial IMC and hence control performance degrades. On the other hand, the proposed EGP controller maintains the overall robustness and control performance throughout the increase of time delay and outperform the other controller design methods at higher time delay. Another highlight of this work is that the proposed EGP controller design method provides overall overwhelming control performance with lower overshoot and shorter rise time compared to other controllers when process time constant is smaller in magnitude (τp =0.01 and 0.1) than the instrumentation element, which is one of the major concerns during the design of intensified controllers, resulting in a higher order of overall system. The desired selection of gain margin and phase margin were suggested at 2.5 to 4 and 60° – 70° respectively for a wide range of control condition for intensified process where higher instrumentation dynamic would be possible achieve robust control as well. As a result, the proposed EGP method controller is thought to be more reliable design strategy for maintaining the overall robustness and performance of higher order and complex systems that are highly affected by time delay and high dynamic response of intensified processes.