Experimental evaluation of an augmented IMC for nonlinear systems

Performance of internal model control (IMC), which is affected by the inevitable errors in the model used, can be improved by augmented IMC (AuIMC) having an additional feedback of process/model mismatch through a suitable gain. This paper presents a detailed study on real-time control of an open-loop stable single-input-single-output (SISO) nonlinear system by AuIMC. The AuIMC structure is first analyzed theoretically to show its robustness and performance characteristics, followed by its experimental evaluation on pH control of a neutralization process. The experimental results show that significantly improved control is obtained by the AuIMC compared to the standard IMC.