A Smith-like control design for performance enhancement of systems with RHP zeros

Qing Guo Wang, Xiang Lu, Tong Heng Lee

Research output: Contribution to journalArticlepeer-review


Motivated by the common non-minimum phase property of dead time and right-half-plane (RHP) zero, this paper presents a Smith-like scheme for control of systems with RHP zeros. It is shown that RHP zeros and possible dead time can be removed from the characteristic equation of the scheme so that the control design is greatly simplified, and enhanced performance is achievable. By model reduction, a unified design with a single tuning parameter is presented for processes of different order. The relationships between the time domain specifications and the tuning parameter are developed to ease the design trade-off. Simulation examples are presented to demonstrate the effectiveness of the proposed scheme. For robustness, it is shown that our design ensures a gain margin of 2 and phase margin of π/3, as well as 100% perturbation of the RHP zero or uncertain time delay of ΔL ≤ τ/0.42.

Original languageEnglish
Pages (from-to)128-138
Number of pages11
JournalJournal of Chemical Engineering of Japan
Issue number2
Publication statusPublished - 20 Feb 2007
Externally publishedYes


  • Desired closed-loop response
  • Right-half-plane zero
  • Smith predictor

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering


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