Comments on “Synthesis of PID controller for unstable and integrating processes”—Chemical Engineering Science 64 (2009) 2807–2816

In the above-mentioned paper [Chemical Engineering Science 64 (2009) 2807–2816], the problem of synthesis of PID controller for unstable and integrating processes is considered. Analytical PID controller tuning rules are proposed by a correct approximation function using desired closed-loop response technique. However, we find that there exist some mistakes and misprints in this paper. This note points out the flaw of the commented paper.