PID Tuning Method Based on IMC for Inverse-Response Second-Order Plus Dead Time Processes

Round 1

Reviewer 1 Report

The paper is somewhat interesting for the field of the PID controller tuning based on IMC for inverse-response second-order systems with dead time. The main shortcoming of the paper is that the proposed tuning method has as a starting point two relatively long and unlikely expressions (25) and (26) of a tuning factor, obtained by the first two authors in 2015 in the reference [44],  a journal without international prestige in the control field. In addition, the proposed method is predominantly theoretical and relatively complicated, with limited possibilities to be applied in practice. However, it can be improved by making some additions and corrections such as:

• Insertion of some recent references from the last years ( for example: Cirtoaje V. A Practical Unified Algorithm of P-IMC Type, Processes, 2020, 8(2) , 165).
• Specifying the PID controller parameter values (Kc, Ti and Td) for each method (CCV, WN, ZN and CCCC ) applied to the process parameters sets P1,…,P5.

Author Response

We would like to thank the reviewer for the insightful comments provided in order to improve the paper. Please find attached the response to all points.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments on “PID tuning method based on IMC for inverse-response second-order plus dead time processes” by D. Castellanos-Cardenas et al.

 

PID control tuning rule is proposed for the process of G(s)=K(-hs+1)exp(-qs)/((t₁s+1)(t₂s+1)). IMC-PID tuning rule is utilized. The IMD-PID tuning rule has a design parameter t_c representing the approximate closed-loop time constant. Here, a new relation t_c = m_OF t_cult, where t_cult is the minimum t_c maintaining the stability, is suggested for the design parameter. A correlation rule for the optimal m_OF is also suggested. The factor m_OF can be considered as a stability margin. My recommendation is positive. Comments are as follows.

[1] The optimal solution for m_OF is dependent on the process changes, specifically, load change and set-point change. It is needed to state the process changes for optimization of Eq. (13).

[2] Here, to obtain m_OF, a new design parameter of weight on the input movements is suggested. This design parameter is somewhat artificial and seems not familiar to users. Instead of the weight for optimization, m_OF itself representing the stability margin may be better for the design parameter.

[3] The base PID tuning rule used is the IMC-PID method. Because the IMC method is based on the pole-zero cancellation, its performances can be poor for processes with small dead times. In this regard, example processes with both small h and q (for example, h=0.1 and q=0.01 for t₁=1) had better be included to show the wide applications of the proposed method.

Comments for author File: Comments.docx

Author Response

We would like to thank the reviewer for the insightful comments provided in order to improve the paper. Please find attached the response to all points.

Author Response File: Author Response.pdf