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Performance Monitoring and Fault Detection in Control Systems


M. Tyler

vol. AUT96-19

As the sophistication of systems used in chemical processing industries increases and demands for high quality products manufactured at low costs mount, the need for improved methods for automatic monitoring of processes arises. This is particularly true for systems operating under automatic control where the control system often acts to eliminate early warning signs of process changes. This thesis examines problems in the area of dynamic system monitoring, with emphasis on control systems. Problems in the areas of controller performance monitoring, estimation, and fault detection are considered. In the area of controller performance monitoring, techniques for assessing performance in a minimum variance framework are developed. In contrast to previous methods, the current approach is applicable to general systems, including unstable and nonminimum-phase plants and systems with unstable controllers. Through two simple examples, it is shown that significant errors may be encountered when information on the unstable poles and non-invertible zeros of a system is not properly included in the performance evaluation techniques. An alternative approach to evaluating deterioration in performance of control systems is formulated using a framework in which acceptable performance is expressed as constraints on the closed loop transfer function impulse response coefficients. Likelihood methods are used to determine if the constraints are met. This second approach can be applied to more general performance criteria than the minimum variance based method. The problem of constrained state estimation is pursued using Moving Horizon Estimation. It is shown that previous formulations of this estimation technique can be unstable when constraints on the innovations and estimated states are included. By expanding the constraint set and modifying the estimation objective, stability is guaranteed. The proposed algorithm can be implemented as a quadratic program.


Type of Publication:

(04)Technical Report

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% Autogenerated BibTeX entry
@TechReport { Xxx:1996:IFA_1505,
    author={M. Tyler},
    title={{Performance Monitoring and Fault Detection in Control
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