Control Performance Criteria Research Articles

Design of Linear Functional Observer for MIMO LTI systems

paper presents an efficient technique to design reduce order linear functional observer for linear time invariant systems. Assuming the existence of linear state feedback controller to achieve stability or some control performance criteria of the linear system, a design procedure is proposed for reconstruction of the state feedback control action. The attractive features of the proposed design procedure are that the resulted linear state functional state observer is of a very low order and it requires information of a small number of outputs. The proposed observer asymptotically converges to any number of linear functions. Numerical examples are considered to illustrate the properties of the observer.

Implementation of quality control performance criteria and approved guidelines for upgrading of clinical chemistry laboratory procedures in Alexandria University hospitals

The aim of the present work was to assess the quality of work in Clinical Pathology Department, Alexandria Main University Hospital, Egypt; as regards the pre-analytical and analytical phases of testing; for later accreditation. This evaluation was performed using inspection sheets that were designed according to the CAP 2006 recommendations. All checklist questions that could not be answered “yes” were considered deficiencies and had to be corrected before being accredited. The questions were classified into ten groups; each group contained a number of questions concerning one of the pre-analytical and analytical assessment activities. We ranked our results into 4 categories according to the degree of fulfillment. The total number of questions that were answered “no” at the start and the end of the study accounted for 64/101 (63.4%) and 34/101 (33.7%) questions respectively. Most of the deficiencies were detected in the pre-analytical phase of the testing process; the first two checklists were used for the evaluation of this phase. At the start of the study, the degree of requirements fulfillment in checklist I and II were 0% and 21.1% respectively. By the end of the study the degree of fulfillment became, 85.7% and 63.2% respectively. Average number of sample rejection due to different causes was evaluated before and after implementing CAP recommendations; these causes include haemolysis, clotted serum, quantity not sufficient, and lost samples; the percentage of rejected samples before implementing CAP recommendations was 15.8%, 1.81%, 0.70%, and 0.51% respectively, while after implementing CAP recommendations it was 7%, 0.77%, 0.08%, and 0.05%, respectively. We concluded that the presence of standardized protocol for the pre-analytical activities had improved the quality of samples received by the lab, and we also concluded that accreditation allows laboratories to evaluate their performance, their compliance with the requirements of the accrediting association, and their ability to improve the accuracy of the patient results they provide.

Iterative minimization of [formula omitted] control performance criteria

Data-based control design methods most often consist of iterative adjustment of the controller’s parameters towards the parameter values which minimize an H 2 performance criterion. Typically, batches of input–output data collected from the system are used to feed directly a gradient descent optimization — no process model is used. A limiting factor in the application of these methods is the lack of useful conditions guaranteeing convergence to the global minimum; several adaptive control algorithms suffer from the same limitation. In this paper the H 2 performance criterion is analyzed in order to characterize and enlarge the set of initial parameter values from which a gradient descent algorithm can converge to its global minimum.

Stochastic model reference predictive temperature control with integral action for an industrial oil-cooling process

This paper presents a stochastic model reference predictive control (SMRPC) approach to achieving accurate temperature control for an industrial oil-cooling process, which is experimentally modeled as a simple first-order system model with given long time delay. Based on this model, the stochastic model reference predictive controller with control weighting and integral action is derived based on the minimization of an expected generalized predictive control (GPC) performance criteria. A real-time adaptive SMRPC algorithm is proposed and then implemented into a stand-alone digital signal processor (DSP). Experimental results show that the proposed control method is capable of giving accurate and satisfactory control performance under set-point changes, fixed load and load changes.

Design and Tuning of Fuzzy Control Surfaces with Bezier Functions

Abstract Design and Tuning a fuzzy logic controller (EEGs) are usually done in two stages. In the first stage, the structure of a FLC is determined based on physical characteristics of the system. In the second stage, the parameters of the FLC are selected to optimize the performance of the system. The task of tuning FLCs can be performed by a number of methods such as adjusting control gains, changing membership functions, modifying control rules and varying control surfaces. A method for the design and tuning of FLCs through modifying their control surfaces is presented in this paper. The method can be summarized as follows. A fuzzy control surface is modeled with Bezier functions. Shapes of the control surface are then adjusted through vazying Bezier parameters. A Genetic Algorithm (GA) is used to search for the optimal set of parameters based on the control performance criteria. Simulation results on vazious control systerns show the effectiveness of the proposed method.

Stabilization of linear autonomous systems of differential equations with distributed delay

Consideration is given to the problem of optimal stabilization of differential equation systems with distributed delay. The optimal stabilizing control is formed according to the principle of feedback. The formulation of the problem in the functional space of states is used. It was shown that coefficients of the optimal stabilizing control are defined by algebraic and functional-differential Riccati equations. To find solutions to Riccati equations, the method of successive approximations is used. The problem for this control law and performance criterion is to find coefficients of a differential equation system with distributed delay, for which the chosen control is a control of optimal stabilization. A class of control laws for which the posed problem admits an analytic solution is described.

Multisensor switching control strategy with fault tolerance guarantees

In this paper we propose a novel fault tolerant multisensor switching strategy for feedback control. Each sensor of the proposed multisensor scheme has an associated state estimator which, together with a state feedback gain, is able to individually stabilise the closed-loop system. At each instant of time, the switching strategy selects the sensor–estimator pair that provides the best closed-loop performance, as measured by a control-performance criterion. We establish closed-loop stability of the resulting switching scheme under normal (fault-free) operating conditions. More importantly, we show that closed-loop stability is preserved in the presence of faulty sensors if a set of conditions on the system parameters (such as bounds on the sensor noises, maximum and minimum values of the reference signal, etc.) is satisfied. This result enhances and broadens the applicability of the proposed multisensor scheme since it provides guaranteed properties such as fault tolerance and robust closed-loop stability under sensor fault. The results are applied to the problem of automotive longitudinal control.

ON THE SHAPE OF H2 PERFORMANCE CRITERIA

An H2 control performance criterion dependent on a controller parameter vector is analyzed from the point of view of evaluating the domain of attraction of its global minimum when a gradient-based algorithm is used in tuning the parameters. The objective of this analysis is twofold: (i) examine how some design parameters of the criterion can be used to enlarge the domain of attraction; (ii) examine how the minimization of a sequence of intermediate criteria can possibly lead to the global minimum of the original criterion without the danger of entrapment in a local minimum.

Risk aversion predictive control

Abstract A quality-controlled predictive control method, suitable for control of fast, remote systems subject to significant communication delays, is developed. Each move is quality controlled in that it independently satisfies a risk-based control performance criterion. The method is found to be capable of mitigating the ill effects of highly nonstationary delay distributions while providing good control performance for milder nonstationarity. It is demonstrated on simplified predictive control (SPC) of a single-input, single-output process. SPC is preferred here due to its simplicity and well-conditioned dependence of both the sampling time and its single parameter. © 2006 ISA-The Instrumentation, Systems, and Automation Society.

Optimal prefiltering in iterative feedback tuning

Iterative feedback tuning (IFT) is a data-based method for the iterative tuning of restricted complexity controllers. A special experiment in which a batch of previously collected output data is fed back at the reference input allows one to compute an unbiased estimate of the gradient of the control performance criterion. We show that, by performing an optimal filtering of the data that are fed back, one can minimize the asymptotic variability of the control performance cost and, hence, minimize the average performance degradation that results from the randomness of the data. The expression of the optimal filter is derived, and a simulation illustrates the benefits that result from using this optimal filter as compared to the use of the classical constant filter.

Application of model predictive control and dynamic analysis to a pilot distillation column and experimental verification

The steady-state and dynamic behaviour of a binary packed distillation column have been simulated using a stagewise approach. The model solutions have been obtained employing modified equilibrium including efficiency and non-equilibrium transfer unit. This work compares an experimental and a theoretical analysis of the steady-state and dynamic behaviour of a packed distillation column using a 0.08 m ID pilot-scale tower distilling a mixture of methanol–water. The packed distillation column was divided into four stages based on McCabe–Thiele method. For control studies, reflux ratio was chosen as a manipulated variable, so the effect of the perturbation on reflux ratio to the overhead temperature was examined. Theoretical and experimental results were compared in order to see the validity of the stagewise approximation. The application of two types of model based control system was considered theoretically, viz PID and dynamic matrix control (DMC). First-order plus dead time model and convolution model were used for step test in the control applications. Performance of these control systems were tested using control performance criterion. These control systems were also compared with open-loop dynamic behaviour and each other.

Analysis of Load Frequency Control Performance Assessment Criteria

This paper presents the development and application of an analytic framework for the formulation and evaluation of control performance criteria in load frequency control (LFC). The framework is constructed so as to explicitly represent the uncertainty in the measured variables in LFC and to use metrics that are meaningful for the structure of the problem. The framework makes effective use of probability and random processes concepts to develop rather general criteria for LFC performance assessment. In fact, the NERC criteria CPS1 and CPS2 are special cases of the criteria of the framework. The paper thus provides an analytic rationale for the NERC control performance criteria. Analysis of the CPS1 and CPS2 criteria shows that, under conditions that are typically in effect in North American interconnections, the two criteria are redundant. Consequently, there is good analytical basis for not requiring the application of CPS2 once CPS1 is satisfied. Numerical results with four interconnections are given to illustrate the analytic results. The framework is a powerful construct that may be used to construct new criteria for LFC performance assessment.

Analysis of load frequency control performance assessment criteria

This paper presents the development and application of an analytic framework for the formulation and evaluation of control performance criteria in load frequency control (LFC). The framework is constructed so as to explicitly represent the uncertainty in the measured variables in LFC and to use metrics that are meaningful for the structure of the problem. The framework makes effective use of probability and random processes concepts to develop rather general criteria for LFC performance assessment. In fact, the NERC criteria CPS1 and CPS2 are special cases of the criteria of the framework. The paper thus provides an analytic rationale for the NERC control performance criteria. Analysis of the CPS1 and CPS2 criteria shows that, under conditions that are typically in effect in North American interconnections, the two criteria are redundant. Consequently, there is good analytical basis for not requiring the application of CPS2 once CPS1 is satisfied. Numerical results with four interconnections are given to illustrate the analytic results. The framework is a powerful construct that may be used to construct new criteria for LFC performance assessment.

Expert System Technology for MPC Supervision and Adaptation

The framework of a MPC supervisory and adaptation system using expert system technology is described in this paper. Instead of focusing on one particular type of controller performance criteria, the proposed framework emphasizes on the integrity of the controllers as a whole. It includes different monitoring tools to classify the current control scenarios and a heuristic-based adaptation mechanism to “intelligently” respond to the change in environment. The framework, together with a DMC type MPC, has been successfully implemented in G2™ environment. Encouraging results have been observed.

AGC logic based on NERC's new Control Performance Standard and Disturbance Control Standard

Presented in this paper are the design and simulation results of a new AGC logic. The new logic is specifically designed to work under NERC's new Control Performance Standard and Disturbance Control Standard with improved effectiveness and efficiency. The old Control Performance Criteria and the new Control Performance Standard are briefly described and compared. The considerations in constructing a simulation environment are included. Texas Utilities Electric Company (TU), in a joint effort with the University of Texas at Arlington, has begun implementation of this new AGC logic.

Investigating the Incidence of type i errors for chronic whole effluent toxicity testing using Ceriodaphnia dubia

AbstractThe risk of Type I error (false positives) is thought to be controlled directly by the selection of a critical p value for conducting statistical analyses. The critical value for whole effluent toxicity (WET) tests is routinely set to 0.05, thereby establishing a 95% confidence level about the statistical inferences. In order to estimate the incidence of Type I errors in chronic WET testing, a method blank‐type study was performed. A number of municipal wastewater dischargers contracted 16 laboratories to conduct chronic WET tests using the standard test organism Ceriodaphnia dubia. Unbeknownst to the laboratories, the samples they received from the wastewater dischargers were comprised only of moderately hard water, using the U.S. Environmental Protection Agency's standard dilution water formula. Because there was functionally no difference between the sample water and the laboratory control/dilution water, the test results were expected to be less than or equal to 1 TUc (toxic unit). Of the 16 tests completed by the biomonitoring laboratories, two did not meet control performance criteria. Six of the remaining 14 valid tests (43%) indicated toxicity (TUc > 1) in the sample (i.e., no‐observed‐effect concentration or IC25 < 100%). This incidence of false positives was six times higher than expected when the critical value was set to 0.05. No plausible causes for this discrepancy were found. Various alternatives for reducing the rate of Type I errors are recommended, including greater reliance on survival endpoints and use of additional test acceptance criteria.

MODEL SET IDENTIFICATION IN FREQUENCY‐DOMAIN AND ITS APPLICATION TO JOINT DESIGN WITH ROBUST CONTROL

In this paper, we propose a new model set identification method for robust control, which determines both nominal models and uncertainty bounds in frequency‐domain using periodgrams obtained from experimental data. This method also gives less conservative model sets when we have more experimental data, which is one of the distinguished features compared with the existing model set identification methods. To this end, first, we construct a new noise model set in terms of periodgrams, which consists of hard‐bounded (or deterministic) noises but takes account of a low correlation property of noise signals, simultaneously. Then, based on the noise model, we show how to compute the nominal models and the upper bounds of modeling error via convex optimization, which minimize given cost functions. Furthermore, by introducing a weighting function compatible with control performance criterion into the identification cost function, we consider a joint design method of the proposed model set identification and H∞ control. Numerical examples show the effectiveness of the proposed method.

Decentralized control of interconnected electric power systems in competitive markets

This paper investigates the prospects of decentralized control in the emerging competitive electricity markets. The weaknesses of current control performance criteria for dealing with such markets are discussed and it is hypothesized that decentralized control, providing full control over economically independent electrically interconnected areas, is necessary in such markets. To study the feasibility of such a decentralization rigorously, a state space decomposition method is introduced and applied to the model of an interconnected system. As a result it is shown that, in electric power systems, regardless of the number and location of the tie lines and implemented control schemes, the frequency and phase of each area are in the controllable subspaces of all areas in the interconnection. This shows that, if decentralization is to be achieved, flexible links which decouple the phases of areas must be utilized. The side effects of such implementations are also discussed.

CPC revisited [power system control

For over 20 years, the North American Electric Reliability Council Operating Committee's (NERC-OC) Performance Subcommittee has been using the Control Performance Criteria (CPC) to evaluate the control performance of NERC's control areas. A new, more comprehensive CPC criteria is being put through its trial period by the Performance Subcommittee. The author reviews how the current CPC was developed, implemented, and used to date. >

Selection of candidate quality control isolates and tentative quality control ranges for in vitro susceptibility testing of yeast isolates by National Committee for Clinical Laboratory Standards proposed standard methods

The National Committee for Clinical Laboratory Standards has developed a proposed standard method for in vitro antifungal susceptibility testing of yeast isolates (National Committee for Clinical Laboratory Standards, document M27-P, 1992). In order for antifungal testing by the M27-P method to be accepted, reliable quality control (QC) performance criteria must be developed. In the present study, five laboratories tested 10 candidate QC strains 20 times each against three antifungal agents: amphotericin B, fluconazole, and 5-fluorocytosine. All sites conformed to the M27-P standards and used a common lot of tube dilution reagents and RPMI 1640 broth medium. Overall, 98% of MIC results with amphotericin B, 95% with fluconazole, and 92% with 5-fluorocytosine fell within the desired 3-log2 dilution range (mode +/- 1 log2 dilution). Excellent performance with all three antifungal agents was observed for six strains: Candida albicans ATCC 90028, Candida parapsilosis ATCC 90018, C. parapsilosis ATCC 22019, Candida krusei ATCC 6258, Candida tropicalis ATCC 750, and Saccharomyces cerevisiae ATCC 9763. With these strains, 3-log2 dilution ranges encompassing 94 to 100% of MICs for all three drugs were established. Additional studies with multiple lots of RPMI 1640 test medium will be required to establish definitive QC ranges.