Detection and Diagnosis of Stiction in Control Loops

Transcription

1 Mohieddine Mali Biao Huang Editors with M.A.A. Shoukat Choudhury, Peter He, Alexander Horch, Manabu Kano, Nazmul Karim, Srinivas Karra, Hidekazu Kugemoto, Kwan-Ho Lee, S. Joe Qin, Claudio Scali, Zhengyun Ren, Maurizio Rossi, Timothy Salsbury, Sirish L. Shah, Ashish Singhal, Nina F. Thornhill, Jin Wang and Yoshiyuki Yamashita Detection and Diagnosis of Stiction in Control Loops State of the Art and Advanced Methods <ÖSp rineer g<

2 Contents List of Contributors Abbreviations and Acronyms xxv xxix 1 Introduction 1 Mohieddine Mali and Biao Huang 1.1 Motivation Typical Valve-controlled Loop Stiction Phenomenon and Related Effects Input-Output Relation of Valves Under Stiction Limit Cycles due to Stiction Typical Observations in Control Loops with Sticky Valves Industrial Examples of Loops with Stiction Summary and Conclusions 18 Part I Stiction Modelling and Oscillation Detection 2 Stiction Modelling 21 M.A.A. Shoukat Choudhury, Nina F. Thornhill, Manabu Kano and Sirish L. Shah 2.1 Introduction Physics-based Stiction Modelling Data-driven Stiction Modelling One-parameter Stiction Model Two-parameter Stiction Model Choudhury's Stiction Model Simulation of the Stiction Model Kano's Stiction Model Comparison Between Choudhury's and Kano's Stiction Models Similarities Differences 32 xvii

3 xviii Contents Comparisons Using an Industrial Example Summary and Conclusions 35 3 An Alternative Stiction-modelling Approach and Comparison of Different Stiction Models 37 Q. Peter He, Jin Wang and S. Joe Qin 3.1 Introduction He's Two-parameter Model Three Data-driven Models Implementation of the First-principles Model Comparison of Data-driven Models Further Investigation of Valve Stiction He's Three-parameter Model Simulation Results An Industrial Example Summary and Conclusions Appendix: Proof of the Equivalence Between He's Two-parameter and Three-parameter Model 58 4 Detection of Oscillating Control Loops 61 Srinivas Karra, Mohieddine Jelali, M. Nazmul Karim and Alexander Horch 4.1 Introduction Root-causes for Oscillatory Control Loops Poor Process and Control System Design Aggressive Controller Tuning Non-linearities in Control-loop Hardware External Oscillatory Disturbances Characterisation of Oscillations Auto-covariance Function Power Spectrum Strength of Oscillations Techniques for Detection of Oscillations in Control Loops Detection of Spectral Peaks Regularity of Large Enough Integral of Absolute Error Regularity of Upper and Lower IAEs and Zero-crossings Decay-ratio Approach of the Auto-correlation Function Regularity of Zero-crossings of the Auto-correlation Function Spectral Envelope Method Critical Evaluation of Oscillation-detection Methods Features of Industrial Control-loop-oscillation Detection Detection Test Examples Signal with Coloured Noise Signal with One Predominant Oscillation Signal with Dampened Oscillation 85

4 Contents xix Signal with Multiple Oscillations Signal with Intermittent Oscillations Comprehensive Oscillation Characterisation Industrial Case Studies Oscillating Flow Control Loop Unit-wide Oscillation Caused by a Sensor Fault Plant-wide Oscillation Caused by a Valve Fault Summary and Conclusions 100 Part II Advances in Stiction Detection and Quantification 5 Shape-based Stiction Detection 103 Manabu Kano, Yoshiyuki Yamashita and Hidekazu Kugemoto 5.1 Introduction Method Description Method A Method В Method С Key Issues Simulation Results Application to Industrial Loops Ill 5.6 Summary and Conclusions Stiction Detection Based on Cross-correlation and Signal Shape Alexander Horch 6.1 Introduction The Cross-correlation Function Industrial Examples Loop Interaction I Loop Interaction II Flow Control Loop I Flow Control Loop II Level Control Theoretical Explanation Correlation for Oscillating External Disturbances Tight Tuning Correlation in the Presence of Stiction Conclusions (Cross-correlation Method) Stiction Detection for Integrating Processes Detection in Integrating Loops - Basic Idea Differentiation and Filtering Sample Histogram Distribution for the Stiction Case Distribution for the Non-stiction Case Examples Level Control Loop with Stiction 142

5 xx Contents Level Control Loop Without Stiction Level Control Loop with Deadband Self-regulating Processes Flow Control Loop with Stiction Flow Control Loop Without Stiction Loops with Dominant P-control Summary and Conclusions Curve Fitting for Detecting Valve Stiction 149 Q. Peter He and S. Joe Qin 7.1 Introduction Method Description Sinusoidal Fitting Triangular Fitting Stiction Index Key Issues Simulation Results Application to Industrial Loops Summary and Conclusions A Relay-based Technique for Detection of Stiction 165 Claudio Scali and Maurizio Rossi 8.1 Introduction Trends of Different Variables Method Description Basic Idea Stiction Index Fitting Procedure Fitting Algorithm Simulation Results Nominal Case Presence of Noise Application to Plant Data Summary and Conclusions Shape-based Stiction Detection Using Area Calculations 183 Timothy I. Salsbury and Ashish Singhal 9.1 Introduction Method Description Theoretical Basis Stiction Detection Hypothesis Test Noise Effects and Practical Implementation Key Issues Simulation Results Application to Industrial Loops 200

6 Contents xxi Temperature Control Loop with Stiction from a Building Automation System Temperature Control Loop with Stiction from a Pulp and Paper Plant Summary and Conclusions Estimation of Valve Stiction Using Separable Least-squares and Global Search Algorithms 205 Mohieddine Jelali 10.1 Introduction Basic Approach Identification Model Structure: Hammerstein Model Linear Model Stiction Model Identification Approach Separable Least-squares Estimator Global Search Algorithms Key Issues Model Structure Selection Time-delay Estimation Determination of Initial Parameters and Incorporation of Constraints Simulation Studies First-order-plus-time-delay Process Integrating Process with Time Delay Industrial Case Studies Loop CHEM 25: Pressure Control Loop Loop PAP 2: Flow Control Loop Loop CHEM 24: Flow Control Loop with Setpoint Changes Loop POW 2: Level Control Loop Loop POW 4: Level Control Loop Loop MIN 1: Temperature Control Loop Loop CHEM 70: Flow Control Loop with External Disturbances Summary and Conclusions Stiction Estimation Using Constrained Optimisation and Contour Map 229 Kwan Ho Lee, Zhengyun Ren and Biao Huang 11.1 Introduction Stiction Model of Control Valve General Conception Physical Model of Valve Sticion Kano's Valve-stiction Model Choudhury's Valve-stiction Model 232

7 Contents He's Valve-stiction Model Existing Stiction-detection Methods Open-loop Methods Closed-loop Methods Discussion of Existing Methods Closed-loop Stiction Detection and Quantification Basic Principle and Important Steps Stiction Detection and Quantification Procedure Search Space of Stiction-model Parameters Constrained Parameter-search Techniques Advantages Stiction Detection: Identifiability Analysis Heuristic Illustration of Closed-loop Identifiability Identifiability Analysis for Closed-loop Systems with Valve Stiction Simulations Industrial Applications Illustrative Industrial Examples Comparative Study Graphical User Interface Summary and Conclusions 265 Oscillation Root-cause Detection and Quantification Under Multiple Faults 267 Srinivas Karra and M. Nazmul Karim 12.1 Introduction Preliminaries and Brief Review of Model-based Oscillation Diagnosis Root-cause for Oscillations and Compensation Techniques Oscillation Diagnosis and Root-cause Quantification Challenges to be Addressed Overview of the Root-cause Detection and Quantification Methodology Revisiting Control-valve Characteristics Under Stiction Oscillation Detection and Diagnosis Methodology Process-model Identification Under Non-stationary Disturbances Identification of EARMAX Model Illustrative Example: Identification Under Non-stationary Disturbance Root-cause Detection and Quantification OP-PV Model Identification Methodology Identification of Controller Transfer Function Oscillation Root-cause Detection and Quantification Methodology 280

8 12.6 Illustrative Example: Oscillation Diagnosis Under Various Faulty Situations Stiction Oscillatory External Disturbance Aggressive Controller Tuning Stiction and Oscillatory External Disturbance Stiction and Aggressive Controller Tuning Oscillatory External Disturbance and Aggressive Controller Tuning Stiction, Aggressive Controller Tuning and Oscillatory External Disturbance Industrial Case Studies Control Loop Control Loop Control Loop Summary and Conclusions 293 Comparative Study of Valve-stiction-detection Methods 295 Mohieddine Mali and Claudio Scali 13.1 Introduction Selected Methods Industrial Control Loops Involved in the Study Application Results and Discussion Application Results Synthesis and Discussion Efficiency of the Techniques, Problems and Countermeasures Comparison on 20 Loops with Known Problems Selected Examples Graphical User Interface Suggestions Summary and Conclusions Appendix: Tables of Results of the Comparative Study 324 Conclusions and Future Research Challenges 359 Biao Huang, Mohieddine Jelali and Alexander Horch 14.1 Summary of the Book Future Research Challenges Stiction Modelling Oscillation Detection Stiction Detection and Estimation Stiction Control 365

9 xxiv Contents Appendix A Evaluated Industrial Control Loops 367 Appendix В Review of Some Non-linearity and Stiction-detection Techniques 371 B.l Bicoherence Method 371 B.l.l Non-Gaussianity Index 372 B.1.2 Non-linearity Index 373 B.1.3 Total Non-linearity Index 374 B.1.4 Ellipse Fitting 374 B.2 Surrogates Analysis 374 B.2.1 Surrogate Data Generation 375 B.2.2 Non-linear Predictability Index 376 References 377 Contributor Biographies 383 Index 389