Performance assessment of PID control loops based on IMC tuning rule

In industrial feedback control loops, setpoint changes are often in the form of step, ramp or other general types, and controllers are usually restricted to the PID form. This paper establishes the lower bounds of integrated absolute errors (IAEs), based on the widely-used internal model control (IMC) principle, from closed-loop responses subject to these setpoint changes. Taking the lower bound as a benchmark, an IMC-IAE-based index is proposed to assess the performance of PID controllers. Numerical and experimental examples, as well as an industrial case study, are provided to verify the lower bound as the performance benchmark, and to illustrate the effectiveness of using the proposed index for performance assessment of PID control loops. ? 2011 IFAC.EI