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Sirish L Shah - One of the best experts on this subject based on the ideXlab platform.
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detection and quantification of valve Stiction by the method of unknown input estimation
IFAC Proceedings Volumes, 2009Co-Authors: Saneej B Chitralekha, Sirish L Shah, J PrakashAbstract:Abstract Valve Stiction is one of the most common causes of oscillations in industrial process control loops. Such oscillations can degrade the overall performance of the loop and eventually the final product quality. The detection and quantification of valve Stiction in industrial process control loops is thus important. From previous studies in the literature, a sticky valve has been shown to have a distinct signature of the Stiction phenomena in its valve positioner data. However, the position of the modulating control valves is seldom available. We consider the problem of estimating the valve position as an unknown input estimation problem. In this work, we propose a novel application of the unknown input estimator in order to estimate the valve position given a linear model of the process and closed loop input-output data. Using the estimated valve position data, we can detect and also quantify the amount of Stiction. We demonstrate the efficacy of the method through simulation examples where a sticky valve is deliberately introduced in the closed loop using a two-parameter Stiction model available in the literature. An industrial case study is also presented in which the algorithm accurately detects and quantifies Stiction in a level control loop of a power plant.
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diagnosis of process nonlinearities and valve Stiction data driven approaches
2008Co-Authors: M Schoukat A A Choudhury, Sirish L Shah, Nina F ThornhillAbstract:Higher-Order Statistics.- Higher-Order Statistics: Preliminaries.- Bispectrum and Bicoherence.- Data Quality - Compression and Quantization.- Impact of Data Compression and Quantization on Data-Driven Process Analyses.- Nonlinearity and Control Performance.- Measures of Nonlinearity - A Review.- Linear or Nonlinear? A Bicoherence-Based Measure of Nonlinearity.- A Nonlinearity Measure Based on Surrogate Data Analysis.- Nonlinearities in Control Loops.- Diagnosis of Poor Control Performance.- Control Valve Stiction~- Definition, Modelling, Detection and Quantification.- Different Types of Faults in Control Valves.- Stiction: Definition and Discussions.- Physics-Based Model of Control Valve Stiction.- Data-Driven Model of Valve Stiction.- Describing Function Analysis.- Automatic Detection and Quantification of Valve Stiction.- Industrial Applications of the Stiction Quantification Algorithm.- Confirming Valve Stiction.- Plant-wide Oscillations - Detection and Diagnosis.- Detection of Plantwide Oscillations.- Diagnosis of Plant-wide Oscillations.
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Stiction definition modelling detection and quantification
Journal of Process Control, 2008Co-Authors: M Shoukat A A Choudhury, Mridul Jain, Sirish L ShahAbstract:Abstract Stiction or high static friction is a common problem in spring-diaphragm type control valves, which are widely used in the process industry. Recently, there have been many attempts to understand, define, model and detect Stiction in control valves. There are several methods for detecting Stiction, but quantification of the actual amount of Stiction still remains a challenge. This paper discusses briefly the definition and modelling of Stiction. Then it demonstrates a new method to detect and quantify the actual amount of valve Stiction using routine operating data. The proposed method is completely data-driven. No additional excitation or experimentation of the plant is required.
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Stiction – definition, modelling, detection and quantification
Journal of Process Control, 2007Co-Authors: M.a.a. Shoukat Choudhury, Mridul Jain, Sirish L ShahAbstract:Abstract Stiction or high static friction is a common problem in spring-diaphragm type control valves, which are widely used in the process industry. Recently, there have been many attempts to understand, define, model and detect Stiction in control valves. There are several methods for detecting Stiction, but quantification of the actual amount of Stiction still remains a challenge. This paper discusses briefly the definition and modelling of Stiction. Then it demonstrates a new method to detect and quantify the actual amount of valve Stiction using routine operating data. The proposed method is completely data-driven. No additional excitation or experimentation of the plant is required.
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Automatic detection and quantification of Stiction in control valves
Control Engineering Practice, 2006Co-Authors: M.a.a. Shoukat Choudhury, Nina F Thornhill, Sirish L Shah, David S. ShookAbstract:Stiction is a common problem in spring-diaphragm type valves, which are widely used in the process industry. Although there have been many attempts to understand and detect Stiction in control valves, none of the current methods can simultaneously detect and quantify Stiction. Conventional invasive methods such as the valve travel test can easily detect Stiction, but are expensive and tedious to apply to hundreds of valves to detect Stiction. Thus there is a clear need in the process industry for a non-invasive method that can not only detect but also quantify Stiction so that the valves that need repair or maintenance can be identified, isolated and repaired. This work describes a model free method that can detect and quantify Stiction that may be present in control valves using routine operating data obtained from the process. No additional excitation or experimentation of the plant is required. Over a dozen industrial case studies have demonstrated the wide applicability and practicality of this method as an useful diagnostic aid in control loop performance monitoring.
M.a.a. Shoukat Choudhury - One of the best experts on this subject based on the ideXlab platform.
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Control Valve Stiction Compensation - Part II: Performance Analysis of Different Stiction Compensation Methods
Industrial & Engineering Chemistry Research, 2019Co-Authors: Ahaduzzaman Nahid, Ashfaq Iftakher, M.a.a. Shoukat ChoudhuryAbstract:Control valves are important elements of control loops. Stiction in control valves limits the performance of control loops. It decreases the life of control valves. Minimizing the negative impact of sticky control valves can improve the performance of control loops. This is the second part of a two-part study on control valve Stiction compensation. In the first part, a novel Stiction compensation method has been proposed. This second part compares the performance of the proposed Stiction compensator described in Part I with six other important Stiction compensators that have appeared in the literature. The proposed compensator performs better than any of the other six compensators.
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Control Valve Stiction Compensation - Part I: A New Method for Compensating Control Valve Stiction
Industrial & Engineering Chemistry Research, 2019Co-Authors: Ahaduzzaman Nahid, Ashfaq Iftakher, M.a.a. Shoukat ChoudhuryAbstract:Valve Stiction is a hidden menace in process control loops. The presence of Stiction in control valves limits the control loop performance. Compensation of its effect is beneficial before the sticky valve can be sent for maintenance. This work is the first of a two part study on control valve Stiction compensation. This part proposes a novel Stiction compensation method while the second part compares the performance of this proposed Stiction compensation method with some of other compensation methods appeared in literature. The proposed compensator is developed based on reduction of control action and addition of an extra pulse of finite energy as required. A method for estimating an appropriate parameter for reducing controller action has been developed. The proposed Stiction compensator has been extensively evaluated using MATLAB Simulink environment. The compensator has also been implemented in a pilot plant experimental set-up. It has been found to be successful in removing valve Stiction induced osci...
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Stiction Quantification based on Time and Frequency Domain Criterions
IFAC-PapersOnLine, 2015Co-Authors: Feng Qian, M.a.a. Shoukat ChoudhuryAbstract:Abstract Valve Stiction is one of the most common causes for poor performance in industrial control loops. Therefore, a non-invasive method which can detect and quantify Stiction is urgently needed in the process industry. Most of the current Stiction estimation methods use time domain criterion, e.g. Mean Square Error, to jointly identify the Stiction and process model parameters. However, Stiction induced oscillation is a phenomenon which has some specific characteristics in the frequency domain. Thus, extracting frequency domain information in the routine operation data will provide a more reliable and accurate Stiction estimation. In this work, under the framework of Hammerstein model identification and global optimization, a new Stiction quantification method based on time and frequency domain criterions is proposed. Several simulation case studies are demonstrated to validate the proposed method.
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Frequency analysis and compensation of valve Stiction in cascade control loops
Journal of Process Control, 2014Co-Authors: Chen Li, M.a.a. Shoukat Choudhury, Biao Huang, Feng QianAbstract:Abstract Valve Stiction is often a common problem in control loops and Stiction induced oscillation is the main cause of poor performance in control systems. Cascade control is extensively applied in process industry as an effective strategy to restrain disturbances and compensate process nonlinearities. In recent years many studies have been performed on the detection and quantification of valve Stiction in single feedback control loops. However, there is a lack in developing a mechanism which can analyze Stiction induced oscillation in cascade control loops. This work focuses on the frequency analysis of Stiction induced oscillations in cascade control loops and proposes a mechanism of oscillation compensation through outer and inner controller tuning. The effect of oscillation compensation by changing control strategies is also discussed. The theoretical analysis is evaluated through simulation examples and a pilot-scale flow-level cascade control experiment.
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Stiction – definition, modelling, detection and quantification
Journal of Process Control, 2007Co-Authors: M.a.a. Shoukat Choudhury, Mridul Jain, Sirish L ShahAbstract:Abstract Stiction or high static friction is a common problem in spring-diaphragm type control valves, which are widely used in the process industry. Recently, there have been many attempts to understand, define, model and detect Stiction in control valves. There are several methods for detecting Stiction, but quantification of the actual amount of Stiction still remains a challenge. This paper discusses briefly the definition and modelling of Stiction. Then it demonstrates a new method to detect and quantify the actual amount of valve Stiction using routine operating data. The proposed method is completely data-driven. No additional excitation or experimentation of the plant is required.
Raghunathan Rengaswamy - One of the best experts on this subject based on the ideXlab platform.
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On the Detection of Valve Nonlinearities in Otherwise Linear Closed-Loop Systems
IEEE Transactions on Automatic Control, 2017Co-Authors: Tim Spinner, Babji Srinivasan, Raghunathan RengaswamyAbstract:Previous works introduced control valve Stiction detection and quantification methods for closed-loop systems based on the identification of a Hammerstein element between the feedback controller and plant output signals. These techniques each rely upon the fact that the presence of valve Stiction introduces nonlinearities in the closed-loop system, yet, little theoretical discussion has been presented which explains the conditions under which these methods will succeed or fail in properly detecting valve Stiction. Therefore, the present work uses frequency domain analysis to provide a theoretical investigation of the identification of Stiction in otherwise linear closed-loop systems. In this way, the failure of Hammerstein Stiction detection techniques to positively identify valve Stiction in certain systems in which it known to be present can be explained accordingly.
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A Reliability Measure for Model Based Stiction Detection Approaches
IFAC Proceedings Volumes, 2012Co-Authors: Babji Srinivasan, Timothy Michael Spinner, Raghunathan RengaswamyAbstract:Abstract Stiction in control valves is one of the long-standing problems in the process industries which lead to oscillations in closed loop systems. Numerous methods have been developed to detect Stiction in linear closed-loop systems. Almost all of these methods utilize the fact that the presence of Stiction in control valves introduces nonlinearities in the closed loop control system. However, there exists no measure of reliability for the results provided by these techniques. In this work, using frequency domain analysis of closed loop systems, a measure of reliability is developed for model based Stiction detection approaches.
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Stiction identification in nonlinear process control loops
Computers & Chemical Engineering, 2010Co-Authors: Ulaganathan Nallasivam, S. Babji, Raghunathan RengaswamyAbstract:Abstract Nearly 20–30% of all process control loops oscillate due to Stiction resulting in productivity losses. Thus, detection and quantification of Stiction in control valves using routine operating data is an important component of any automated controller performance monitoring application. Many techniques have been proposed for the detection and quantification of Stiction. However, most of the approaches assume that the underlying process is linear; very little work is available for nonlinear processes. In this paper, Volterra model-based technique is investigated for the detection of Stiction in closed-loop nonlinear systems. The advantages of the proposed method are: (i) it can be used to detect Stiction in nonlinear systems and (ii) requires no prior information on whether the loop is linear or nonlinear. Results obtained from simulation and industrial case studies demonstrate the utility of the proposed methodology.
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Stiction Identification in Nonlinear Process Control Loops
IFAC Proceedings Volumes, 2009Co-Authors: Ulaganathan Nallasivam, Babji Srinivasan, Raghunathan RengaswamyAbstract:Abstract Abstract Nearly 20–30% of all process control loops oscillate due to Stiction and lead to loss of productivity. Thus, the detection and quantification of Stiction in control valves using just the raw operating data is an important component of any automated controller performance monitoring application. Many techniques have been proposed for the detection and quantification of Stiction. Pattern based identification approaches use unique shapes of the PV and OP data to identify Stiction. Other approaches that include some measure of nonlinearity index have also been used to identify Stiction. A solution technique for Stiction detection in nonlinear processes with known process models is also available. In this paper, one possible approach to detect Stiction in nonlinear process control loops with unknown process models is discussed.
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ACC - Blind identification of Stiction in nonlinear process control loops
2008 American Control Conference, 2008Co-Authors: N. Ulaganathan, Raghunathan RengaswamyAbstract:Stiction in control loops lead to oscillations and loss of productivity. Timely detection of Stiction in control valves can be used in scheduling valve maintenance and deployment of compensation techniques to reduce their impact. Several approaches have been proposed for detection of Stiction. Data-based approaches use unique shapes of the PV and OP data to identify Stiction. Approaches based on nonlinearity detection have also been used to identify Stiction. Yet another approach uses a Hammerstein model structure identification for detecting Stiction. Most of these approaches are restricted to linear processes. In this paper, possible approaches to detect Stiction in nonlinear process control loops are discussed.
Biao Huang - One of the best experts on this subject based on the ideXlab platform.
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Frequency analysis and compensation of valve Stiction in cascade control loops
Journal of Process Control, 2014Co-Authors: Chen Li, M.a.a. Shoukat Choudhury, Biao Huang, Feng QianAbstract:Abstract Valve Stiction is often a common problem in control loops and Stiction induced oscillation is the main cause of poor performance in control systems. Cascade control is extensively applied in process industry as an effective strategy to restrain disturbances and compensate process nonlinearities. In recent years many studies have been performed on the detection and quantification of valve Stiction in single feedback control loops. However, there is a lack in developing a mechanism which can analyze Stiction induced oscillation in cascade control loops. This work focuses on the frequency analysis of Stiction induced oscillations in cascade control loops and proposes a mechanism of oscillation compensation through outer and inner controller tuning. The effect of oscillation compensation by changing control strategies is also discussed. The theoretical analysis is evaluated through simulation examples and a pilot-scale flow-level cascade control experiment.
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Compensation of control valve Stiction through controller tuning
Journal of Process Control, 2012Co-Authors: M. Ale Mohammad, Biao HuangAbstract:Abstract Despite numerous studies on modeling and detection of static friction (Stiction) in control valves, compensation methods for this problem are limited. In this work, a Stiction compensation framework is proposed which is based on the oscillation condition introduced in [17] . This condition was used as a tool to predict occurrence and severity of Stiction-induced oscillations in control systems. The aim of this paper is to suggest re-tuning guidelines for controllers with regard to the presence of Stiction in the control valve, to eliminate or reduce oscillations. A variety of processes and controllers are studied and recommendations are made in order to eliminate the Stiction-induced oscillations. For oscillations that cannot be removed, the proposed method will reduce the frequency and magnitude of oscillations. This compensation framework has also been validated using two different pilot-scale experiments with different types of processes and an industrial control system.
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Estimation of distribution function for control valve Stiction estimation
Journal of Process Control, 2011Co-Authors: Biao HuangAbstract:Abstract There are many methods for detection and estimation of control valve Stiction. There exists, however, to the best of authors’ knowledge, no method to determine the statistical property of the Stiction detection and estimation. The challenge lies in the memory nonlinearity of the Stiction that creates difficulty in determining statistical property of the estimation. In this work, a bootstrap based approach is used to estimate the statistical distribution of Stiction parameter estimation. The method is applied to a simulation example as well as several industry data sets to demonstrate its effectiveness.
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Stiction estimation using constrained optimisation and contour map
2010Co-Authors: Kwan Ho Lee, Zhengyun Ren, Biao HuangAbstract:A closed-loop method for valve-Stiction detection and quantification based on Hammerstein modelling is discussed. A suitable model structure of valve Stiction is chosen prior to conducting valve-Stiction detection and quantification. Given the Stiction-model structure, a bounded search space of a Stiction model is defined and a constrained optimisation problem is performed. The best unknown Stiction-model parameters are found by satisfying a mean-squared error criterion within a space of valve Stiction model parameters. For this purpose, a multi-start adaptive random search is used. The proposed strategy not only detects but also quantifies valve Stiction. The validity of the proposed method is illustrated through industrial examples. Also, the closed-loop identifiability issue is addressed.
Jin Wang - One of the best experts on this subject based on the ideXlab platform.
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Valve Stiction Quantification Method Based on a Semiphysical Valve Stiction Model
Industrial & Engineering Chemistry Research, 2014Co-Authors: Jin WangAbstract:Valve Stiction is one of the most common equipment problems that can cause poor performance in control loops. Consequently, there is a strong need in the process industry for noninvasive methods that can not only detect but also quantify Stiction. In this work, on the basis of a physical and a semiphysical model, a new valve Stiction signature is proposed. Industrial evidence is provided to validate the new valve Stiction signature. Although valve Stiction is a stochastic phenomenon that can not be exactly described by any deterministic model, the revised valve signature provides a better description of sticky valve behavior, particularly when valve Stiction is severe. On the basis of the revised valve Stiction signature, a noninvasive, simple, and robust valve Stiction quantification method is proposed using the routine operation data and limited process knowledge. The proposed quantification method estimates the Stiction parameters, namely, static friction and dynamic or kinetic friction, without requiring the valve position signal. Quantification is accomplished by using linear and nonlinear least-squares methods which are robust and easy to implement. The properties of the proposed algorithm are investigated using simulated case studies of first order plus time delay processes, and the performance of the method is compared to other Stiction quantification methods using 20 industrial cases.
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ACC - Quantification of valve Stiction based on a semi-physical model
2013 American Control Conference, 2013Co-Authors: Jin WangAbstract:Valve Stiction is one of the most common equipment problems that can cause poor performance in control loops. Consequently, there is a strong need in the process industry for non-invasive methods that can not only detect but also quantify Stiction. In this work, a semi-physical valve Stiction model is derived from the analysis of the dynamic response of a physical model. Based on the semi-physical model, we propose a noninvasive valve Stiction quantification method using the routine operating data from the process. The algorithm is proposed to estimate the Stiction parameters, namely static friction and dynamic or kinetic friction, without requiring the valve position signal. Quantification is accomplished by using linear and nonlinear least-squares methods which are robust and easy to implement. Several simulation examples, including both self-regulating and integrating processes with different degrees of Stiction, are used to demonstrate the effectiveness of the method.
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a curve fitting method for detecting valve Stiction in oscillating control loops
Industrial & Engineering Chemistry Research, 2007Co-Authors: Jin Wang, Martin Pottmann, Joe S QinAbstract:Many control loops in process plants perform poorly because of valve Stiction as one of the most common equipment problems. Valve Stiction may cause oscillation in control loops, which increases variability in product quality, accelerates equipment wear, or leads to control system instability and other issues that potentially disrupt the operation. In this work, data-driven valve Stiction models are first reviewed and a simplified model is presented. Next, a Stiction detection method is proposed based on curve fitting of the output signal of the first integrating component after the valve, i.e., the controller output for self-regulating processes or the process output for integrating processes. A metric that is called the Stiction index (SI) is introduced, based on the proposed method to facilitate the automatic detection of valve Stiction. The effectiveness of the proposed method is demonstrated using both simulated data sets based on the proposed valve Stiction model and real industrial data sets.
