Controller design for integrating processes with inverse response and dead time based on standard forms

In chemical engineering, processes exhibiting an initial response to a step input change in the opposite direction of the final steady state can frequently be encountered. Processes exhibiting such characteristics are called inverse response processes and warrant a closer look. In addition, inverse response processes can include an integrator in their transfer function model. In the literature, there are only a few studies addressing control of integrating processes with inverse response. Existing design methods, usually, suggest the use of well-known proportional-integral-derivative (HD) controllers for the control of inverse response processes with an integrator. However, it has been proven by studies in the literature that PID controllers results in unsatisfactory closed-loop performances for integrating processes. Addition of inverse response makes the control of an integrating process more difficult to control. On the other hand, it has been shown that PI-PD controllers perform in very satisfactory closed-loop responses for a class of processes, including integrating processes as well. This paper gives the use of PI-PD controllers to improve the closed-loop performance of integrating processes with inverse response. Simulation examples are provided to illustrate the superiority of the proposed method over the existing ones.