Autotuning of PID Controllers : Relay Feedback Approach

by Yu, Cheng-Ching

• ISBN13: 9783540762508
• ISBN10: 3540762507
• Format: Hardcover
• Copyright: 1999-05-01
• Publisher: Springer Verlag

Summary

Recognising the benefits of improved control, this book aims to provide simple and yet effective methods of improving controller performance. It bridges the gap between the conventional tuning practice and new generations of autotuning methods. Practical issues facing controller tuning are treated, such as measurement noises, process nonlinearity, load disturbances, and multivariable interaction, and tools are also given. Numerous worked examples and case studies are used to illustrate the autotuning procedure, and MATLAB programs to execute autotuning steps are given. This book is intended to be an independent learning tool, and is particularly invaluable to practitioners and scientist, as well as graduate and undergraduate students. The reader will therefore find it useful, particularly as it is applicable to engineering practice

Table of Contents

Introduction	1	(6)
PID Control	1	(3)
Relay Feedback Identification	4	(1)
Summary	5	(1)
References	5	(2)
Relay Feedback	7	(18)
Experimental Design	7	(3)
Direct Tuning Rules	10	(2)
Approximate Transfer Functions	12	(10)
Simple Approach	13	(2)
Improved Algorithm	15	(2)
Parameter Estimation	17	(1)
Examples	18	(4)
Conclusions	22	(1)
References	22	(3)
Improved Relay Feedback	25	(24)
Analysis	25	(10)
Ideal (on-off) relay feedback	25	(3)
Saturation relay feedback	28	(5)
Potential problem	33	(2)
Improved Experimental Design	35	(4)
Selection of the slope of saturation relay	35	(3)
Procedure	38	(1)
Applications	39	(8)
Conclusions	47	(1)
References	47	(2)
Systems with Unstable Zeros or Poles	49	(18)
Problem Description	49	(11)
Examples	49	(3)
System Analyses	52	(1)
Open-Loop Stable Systems	52	(3)
Open-Loop Unstable Systems	55	(5)
Frequency Domain Analyses	60	(3)
Discussion	63	(3)
Conclusions	66	(1)
References	66	(1)
Multivariable Systems	67	(42)
Concept	67	(4)
SISO Autotuning	67	(1)
MIMO Autotuning	68	(3)
Theory	71	(10)
Sequential Design	71	(3)
Process Characteristics	74	(4)
Sequential Identification	78	(3)
Controller Tuning	81	(6)
Potential Problem in Z-N Tuning	81	(1)
Modified Z-N Method	82	(2)
Performance Evaluation---Linear Model	84	(3)
Properties	87	(8)
Convergence	88	(1)
Tuning sequence	89	(3)
Problem of Variable Pairing	92	(2)
Summary of Procedure	94	(1)
Applications	95	(8)
Moderate-Purity Column	95	(3)
High-Purity Column	98	(2)
T4 Column	100	(3)
Conclusion	103	(1)
References	103	(6)
Load Disturbance	109	(20)
Problems	109	(3)
Step change versus continuous cycling	109	(2)
Effect of load change on relay feedback test	111	(1)
Analyses	112	(10)
Causes of errors	112	(4)
Output-biased relay feedback system	116	(1)
Derivation of bias value (δo)	117	(1)
Effect of load disturbance	117	(3)
Opposite effect from output-biased relay	120	(2)
Summary of Procedure	122	(1)
Applications	123	(5)
Linear system	124	(2)
Binary distillation column	126	(2)
Conclusions	128	(1)
References	128	(1)
Process Nonlinearity	129	(24)
pH Control	129	(1)
Gain Scheduled Autotune Variation (g-ATV)	130	(9)
Process Description	130	(2)
Modeling Titration Curve	132	(1)
Experimental Design for Titration Curve Identification	133	(3)
Nominal Tuning with Nonlinear Compensation	136	(1)
Summary of Procedure	137	(2)
Experimental	139	(12)
Instrumentation and Control	139	(2)
Model Validation	141	(3)
Experimental Results	144	(1)
Titration Curve Identification	144	(2)
g-ATV	146	(5)
Conclusions	151	(1)
References	151	(2)
Controller Monitoring	153	(24)
Relay with Hysteresis and Lc,max	153	(6)
Relay Feedback Systems	153	(3)
Relay with Hysteresis	156	(1)
A Framework for Monitoring	157	(2)
On-Line Search for Lc,max	159	(5)
Linear Assumption	159	(3)
Formulation	162	(1)
Procedure	162	(1)
Limitations and extensions	163	(1)
Selection of Hysteresis Width	164	(1)
Noise-Free Systems	164	(1)
Systems with Noise	164	(1)
Applications	165	(7)
Linear Systems (Noise-Free)	165	(2)
Nonlinear Distillation Example	167	(3)
Linear System (with Noise)	170	(2)
Conclusion	172	(1)
References	173	(4)
Autotuning for Plantwide Control Systems	177	(28)
Recycle Plant	177	(3)
Control Structure Design	180	(11)
Unbalanced Schemes	180	(1)
Column Overwork	180	(3)
Reactor Overwork	183	(2)
Balanced Scheme	185	(2)
Controllability	187	(2)
Operability	189	(2)
Controller Tuning for Entire Plant	191	(10)
Tuning Steps	192	(1)
Inventory Control	192	(1)
Ratio Control	193	(2)
Quality Loop	195	(1)
Closed-Loop Performance	196	(5)
Conclusion	201	(1)
References	201	(4)
Guidelines for Autotune Procedure	205	(16)
Process Characteristics	205	(2)
Load Disturbance	205	(1)
Nonlinearity	206	(1)
Noise	206	(1)
Available Relays	207	(1)
Specifications	208	(9)
Direct Tuning	209	(2)
Model-Based Tuning	211	(1)
Multiloop System	212	(5)
Summary	217	(1)
Conclusion	218	(3)
A MATLAB programs for different kinds of relays	221