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 (PID) 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.