Ind. Eng. Chem. Res. 2006, 45, 4019
4019
Preface: Relay Feedback in Control Design Relay systems can be traced back to their classical configurations. In the 1950s, relays were mainly used as amplifiers, but such applications are now obsolete, because of the development of electronic technology. In the 1960s, relay feedback was applied to adaptive control. One prominent example of such applications is the self-oscillating adaptive controller developed by Minneapolis Honeywell, which uses relay feedback to attain a desired amplitude margin. This system was tested extensively for flight control systems, and it was also used in several missiles. It was in the 1980s that Astrom applied the relay feedback method to auto-tune proportional-integral-derivative (PID) controllers for process control and triggered a resurgence of interest in relay methods, including extensions of the method to a variety of complex systems, including time-delay systems, nonminimum phase systems, unstable systems, and multivariable and nonlinear systems. Because of its simplicity of use, to which practicing engineers can relate, relay feedback methods for control design have found their way into industrial control. Many industrial control products are now equipped with relay feedback functionality, to enable control automatic tuning. Extension of the simple approach to performance assessment, nonlinearity modeling, and robust control has also been proposed and developed. This special issue aims to capture and report recent advances made in the field, and the trend that will likely be carried on from this point. From a good number of papers submitted, after thorough peer review, 10 papers were accepted for publication in this special issue. It is hoped that this special issue will further ignite interest in this field, to propel even greater progress in the use of the relay in control engineering.
Prof. Kok Kiong Tan* Department of Electrical and Computer Engineering, National UniVersity of Singapore, 4 Engineering DriVe 3, Singapore 117576 IE068003T
* To whom correspondence should be addressed. Tel: 65-65162110. Fax: 65-67791103. E-mail:
[email protected]. 10.1021/ie068003t CCC: $33.50 © 2006 American Chemical Society Published on Web 05/31/2006
