The performance of an automatic PID controller tuning method based on relay feedback is studied in the presence of deterministic disturbances. It is found that the occurence of any static load disturbance could cause ...
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The performance of an automatic PID controller tuning method based on relay feedback is studied in the presence of deterministic disturbances. It is found that the occurence of any static load disturbance could cause significant errors in the estimates of the ultimate gain and period. However, the resultant asymmetry of the relay switching intervals can be used as an error indicator, or used to compute a self-corrective bias to restore accuracy of the estimates. This corrective bias is found to be functional even in the presence of moderate nonlinearity. A reliable self-biasing auto-tuner is thus resultant. The effect of a less common sinusoidal load could be more serious since it may not be detectable and hence more prior knowledge about its presence is required.
The pule placement design principle pruvides a good way of determining a closed loop system with desired properties. The method has been used in adaptive contexts for many years. A drawback of the method is, however, ...
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The pule placement design principle pruvides a good way of determining a closed loop system with desired properties. The method has been used in adaptive contexts for many years. A drawback of the method is, however, that the polynomial formulation mav lead to robustness problems because of the sensitivity with respect to the coefficients of the polynomials. Further, unless all process zeros are cancelled a set of linear equations has to be solved at each step in time. In this paper an attempt is made to avoid these two problems. The sensitivity of the polynomial formulation is avoided by parameterizing the model in the poles and zeros, which are estimated on-line. With the plant expressed in this form it is possible to parameterize the controller such that the solution of the Diophantine equation corresponds to the solution of a triangular system of equations. The controller parameters can thus be computed recursively without extensive computations
A self-contained statistical analysis of the Pisarenko method for estimating sinusoidal frequencies from signal measurements corrupted by white noise is presented. An explicit formula is provided for the asymptotic co...
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A self-contained statistical analysis of the Pisarenko method for estimating sinusoidal frequencies from signal measurements corrupted by white noise is presented. An explicit formula is provided for the asymptotic covariance matrix of the joint estimation errors of the minimum eigenvalue and the minimum eigenfilter coefficients of the data covariance matrix. Our theoretical results extend and reinforce previous results obtained by Sakai [1]. A comparison with the performance achieved by the Yule-Walker Method is also reported.
This paper presents general frequency domain criteria for the robust stability of systems with parametric uncertainities. The criteria are applied to the robust stability verification of LTI systems with or without ti...
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This paper presents general frequency domain criteria for the robust stability of systems with parametric uncertainities. The criteria are applied to the robust stability verification of LTI systems with or without time delays and of LTI systems operating under possibly nonlinear passive feedback.
An on-line scheme to fault detection in adaptive control systems is proposed by introducing Kullbaek Discrimination Information (KDI) as a detection index. When a physical parameter change due to a failure has occurre...
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An on-line scheme to fault detection in adaptive control systems is proposed by introducing Kullbaek Discrimination Information (KDI) as a detection index. When a physical parameter change due to a failure has occurred in a system under adaptive control, the failure effect will hardly be visible in the output performance because of the adaptation mechanism. Such a parameter change is also difficult to detect by monitoring the regulator parameters, which are determined by a recursive identification based on the direct approach. Since the failure effect is reflected as a change in the predictor model used for the adaptive control design, the fault detection leads to a model discrimination problem. It has been shown that the KDI can be used as an effective distortion measure for the model discrimination and the index can be applied in a modified form to detect a fault on-line. Simulation studies on a second order damped oscillatory system have been carried out to demonstrate the efficiency of the method.
Lower bounds for the stability margin of linear discrete systems computed from impulse response measurements are presented. These bounds are based on the connection between the weighted performance criteria and the Ly...
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Lower bounds for the stability margin of linear discrete systems computed from impulse response measurements are presented. These bounds are based on the connection between the weighted performance criteria and the Lyapunov equation. It is shown that positive definite matrices satisfying the Lyapunov equation for a stable system with unknown parameters can be computed from impulse response measurements. The lower bounds for the stability margin can be obtained from the eigenvalues of these matrices. The properties of the method presented are discussed and it is shown that the lower bounds can be improved by increasing the order of the weighting factor.< >
The estimation of sinusoidal frequencies by the overdetermined Yule-Walker (OYW) Method is considered. An explicit expression is derived for the asymptotic covariance matrix of the estimation errors. The effect of inc...
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The estimation of sinusoidal frequencies by the overdetermined Yule-Walker (OYW) Method is considered. An explicit expression is derived for the asymptotic covariance matrix of the estimation errors. The effect of increasing the number of Yule-Walker equations on estimation accuracy is analyzed. The asymptotic estimation accuracy of the OYW method is compared to the best achievable accuracy corresponding to the Cramér-Rao bound
A 500 MW unit superheater temperature control loop structure and parameters design using a state-space based CADCS package STAFCON is described. Special control loop structure with disturbance generator model is devel...
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A 500 MW unit superheater temperature control loop structure and parameters design using a state-space based CADCS package STAFCON is described. Special control loop structure with disturbance generator model is developed to increase disturbance compensation capabilities. Simulation results and brief STAFCON system description are also given.
An effective algorithm for the calculation of stability regions in the plane of two control parameters is proposed. The algorithm is suitable for small computers. In comparison with the classical technique, the derive...
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An effective algorithm for the calculation of stability regions in the plane of two control parameters is proposed. The algorithm is suitable for small computers. In comparison with the classical technique, the derived algorithm requires fewer manual calculations. The program and its short characteristic equation is included. Utilization of the program is illustrated on an example of an automatically controlled power system having a ‘forced’ excitation system.
It has been shown recently that a given MIMO system may be represented by several equivalent state-space representations, referred to as overlapping or pseudocanonical forms, instead of the unique observability (contr...
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It has been shown recently that a given MIMO system may be represented by several equivalent state-space representations, referred to as overlapping or pseudocanonical forms, instead of the unique observability (controllability) canonical form. The structure of a pseudocanonical form is determined by a set of pseudoobservability (-controllability) indexes, analogous to the observability (controllability) indexes determining the structure of the canonical form. A MIMO system can be represented by several different pseudocanonical forms, specified by their structure indexes. In this note, we give an upper bound on the admissible structure indexes of a given system in terms of a new set of invariants of this system. An illustrative example is included.
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