ISA Transactions
Volume 44, Number 1
January 2005
A collection of articles about measurement and control systems in the process industries.
Characterization of a differential fiber Bragg grating sensor for oil-water boundary detection
By Peter LoPresti, Dilip Jali, Blake Carpenter, Michael Gersztenkorn
Department of Electrical Engineering, University of Tulsa, 600 South College Avenue, Tulsa, Oklahoma 74104, USA
Abstract
We investigate the operating characteristics of an oil-water boundary detector utilizing differential interrogation of fiber Bragg grating sensors. The system resolution is shown to be stable with respect to the choice of strain actuator and long-term temperature changes and changes in the initial strain on the fiber string. Fluid flow, particularly turbulent flow, is found to reduce system resolution significantly for the current system design. Improvements in the system design are required to minimize the effects of fluid flow and to accurately detect the presence of oil-water emulsions.
© 2005 ISA—The Instrumentation, Systems, and Automation Society.
A study of wavelet analysis based error compensation for the angular measuring system of high-precision test turntables
By Deng Huiyu, Wang Xinli, and Ma Peisun
Research Institute of Robot, Shang Hai Jiao Tong University, Shang Hai 200030, People’s Republic of China; Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
Abstract
An angular measuring system is the most important component of high-precision test turntables; its function and precision determine the turntable’s function and precision. The angular measuring system’s error was considered as a stationary signal in the past. An autocorrelation function and spectrum characteristics of the angular measuring system error are analyzed using the cyclostationary signal theory. The idea that the error in the angular measuring system is nonstationary is first put forward; theory is provided to reconstruct the angular measuring system’s error signal using wavelet analysis. The error signal is reconstructed using one-dimensional Mallat’s algorithm. The standard deviation between the reconstructed and the original signal is much less than the angular measuring system’s accuracy. The reconstruction signal is used to compensate the system error instead of the original error signal; the angular measuring system accuracy is improved.
© 2005 ISA—The Instrumentation, Systems, and Automation Society.
Linear mass balance equilibration: A new approach for an old problem
By J. Ragot, D. Maquin, and M. Alhaj-Dibo
Centre de Recherche en Automatique de Nancy, CNRS UMR 7039, 2, Avenue de la Forıˆt de Haye, 54516 Vandoeuvre Cedex, France
Abstract
Interval analyses are well known in the mathematics literature but have found few applications in control engineering. Based on the interval concept, we present here a methodology for data reconciliation and mass balance equilibration which is a very classical problem in mineral and chemical engineering. Indeed, this problem is solved with the view of inequality constraints which allows us to represent measurements by interval without particular knowledge and hypothesis about the density probability function of the measurement errors. As a main result, the paper gives a set of solutions for the reconciled data under an interval form and not only one solution as is the case with classical approaches.
© 2005 ISA—The Instrumentation, Systems, and Automation Society.
Observer design and stabilization for linear neutral delay systemsBy Bing Chen, James Lam, and Zidong Wang|
Department of Mathematics, Bohai University, Liaoning 121003, People’s Republic of China; Department of Mechanical Engineering, University of Hong Kong, Hong Kong, Hong Kong; and the Department of Information Systems and Computing, Brunel University, Uxbridge UB8 3PH, United Kingdom
Abstract
This paper focuses on the state observer design problem as well as the observer-based stabilization problem for linear neutral delay systems. The purpose of the former problem is to design an observer that guarantees the asymptotic stability of the estimation error dynamics. The existence condition for such an observer is established. The latter problem, which is the main problem studied in this paper, aims at designing an observer-based feedback controller, such that the closed-loop system is asymptotically stabilized. It is shown that the desired controller can be easily designed if there are solutions to several linear matrix inequalities. Finally, two simulation examples are given to demonstrate the validity and effectiveness of the proposed approach.
© 2005 ISA—The Instrumentation, Systems, and Automation Society.
Geometrical error compensation of machines with significant random errors
By Kok Kiong Tan, Sunan Huang
Department of Electrical and Computer Engineering, National University of Singapore, Singapore, SingaporeAbstract
In this paper, we present a new statistical approach towards soft geometrical error compensation of machines with significant errors. The approach, based on an analysis of the probability of the random error recurring, can reduce the adverse influence of random errors on the compensation of systematic errors. The proposed methodology is made up of three steps. First, error classes are defined from the error bands obtained from calibration. Second, the probability of the magnitude of random error belonging to each of these classes is computed based on the density of the data set within the class. Based on these probabilities, the most probable systematic part of the error measurement can be statistically deduced. Finally, the geometrical error compensation is carried out based on this value. Experimental results are provided for the linear error compensation of a single-axis piezo-ceramic motion system.
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