Feedback Control

Philipp K. Janert was born and raised in Germany. He obtained a Ph.D. in Theoretical Physics from the University of Washington in 1997 and has been working in the tech industry since, including four years at Amazon.com, where he initiated and led several projects to improve Amazon's order fulfillment process. He is the author of two books on data analysis, including the best-selling "Data Analysis with Open Source Tools" (O'Reilly, 2010), and his writings have appeared on Perl.com, IBM developerWorks, IEEE Software, and in the Linux Magazine. He has contributed to CPAN and other open-source projects. He lives in the Pacific Northwest.

Foundations
Chapter 1 Why Feedback? An Invitation
A Hands-On Example
Hoping for the Best
Establishing Control
Adding It Up
Summary
Code to Play With
Chapter 2 Feedback Systems
Systems and Signals
Tracking Error and Corrective Action
Stability, Performance, Accuracy
Uncertainty and Change
Feedback and Enterprise Systems
Code to Play With
Chapter 3 System Dynamics
Lags and Delays
Dynamics in the Physical World and in the Virtual World
The Importance of Lags and Delays for Feedback Loops
Theory and Practice
Code to Play With
Chapter 4 Controllers
Block Diagrams
On/Off Control
Proportional Control
Integral Control
Derivative Control
The Three-Term or PID Controller
Code to Play With
Chapter 5 Identifying Input and Output Signals
Control Input and Output
Examples
Criteria for Selecting Control Signals
A Note on Multidimensional Systems
Chapter 6 Review and Outlook
The Feedback Idea
Iteration
Process Knowledge
Avoiding Instability
The Setpoint
Control, Not Optimization
Practice
Chapter 7 Theory Preview
Frequency Representation
The Transfer Function
Block-Diagram Algebra
PID Controllers
Poles of the Transfer Function
Process Models
Chapter 8 Measuring the Transfer Function
Static Input/Output Relation: The Process Characteristic
Dynamic Response to a Step Input: The Process Reaction Curve
Process Models
Other Methods of System Identification
Chapter 9 PID Tuning
Tuning Objectives
General Effect of Changes to Controller Parameters
Ziegler–Nichols Tuning
Semi-Analytical Tuning Methods
A Closer Look at Controller Tuning Formulas
Chapter 10 Implementation Issues
Actuator Saturation and Integrator Windup
Smoothing the Derivative Term
Choosing a Sampling Interval
Variants of the PID Controller
Nonlinear Controllers
Chapter 11 Common Feedback Architectures
Changing Operating Conditions: Gain Scheduling
Large Disturbances: Feedforward
Fast and Slow Dynamics: Nested or “Cascade” Control
Systems Involving Delays: The Smith Predictor
Case Studies
Chapter 12 Exploring Control Systems Through Simulation
The Case Studies
Modeling Time
The Simulation Framework
Chapter 13 Case Study: Cache Hit Rate
Defining Components
Measuring System Characteristics
Controller Tuning
Simulation Code
Chapter 14 Case Study: Ad Delivery
The Situation
Measuring System Characteristics
Establishing Control
Improving Performance
Variations
Simulation Code
Chapter 15 Case Study: Scaling Server Instances
The Situation
Measuring and Tuning
Reaching 100 Percent With a Nonstandard Controller
Dealing with Latency
Simulation Code
Chapter 16 Case Study: Waiting-Queue Control
On the Nature of Queues and Buffers
The Architecture
Setup and Tuning
Derivative Control to the Rescue
Controller Alternatives
Simulation Code
Chapter 17 Case Study: Cooling Fan Speed
The Situation
The Model
Tuning and Commissioning
Closed-Loop Performance
Simulation Code
Chapter 18 Case Study: Controlling Memory Consumption in a Game Engine
The Situation
Problem Analysis
Architecture Alternatives
Results
Simulation Code
Chapter 19 Case Study Wrap-Up
Simple Controllers, Simple Loops
Measuring and Tuning
Staying in Control
Dealing with Noise
Theory
Chapter 20 The Transfer Function
Differential Equations
Laplace Transforms
Using the Laplace Transform to Solve Differential Equations
The Transfer Function
What If the Differential Equation Is Not Known?
Chapter 21 Block-Diagram Algebra and the Feedback Equation
Composite Systems
The Feedback Equation
Block-Diagram Algebra
Limitations and Importance of Transfer Function Methods
Chapter 22 PID Controllers
The Transfer Function of the PID Controller
The Canonical Form of the PID Controller
The General Controller
Proportional Droop Revisited
Chapter 23 Poles and Zeros
Structure of a Transfer Function
Effect of Poles and Zeros
Pole Positions and Response Patterns
What to Do About Delays
Chapter 24 Root Locus Techniques
Construction of Root Locus Diagrams
Root Locus or “Evans” Rules
Angle and Magnitude Criteria
Practical Issues
Examples
Chapter 25 Frequency Response and the Bode Plot
Frequency Response
The Bode Plot
A Criterion for Marginal Stability
Other Graphical Techniques
Chapter 26 Topics Beyond This Book
Discrete-Time Modeling and the z-Transform
State-Space Methods
Robust Control
Optimal Control
Mathematical Control Theory
Appendices
Appendix Glossary
Appendix Creating Graphs with Gnuplot
Basic Plotting
Plot Ranges
Inline Transformations
Plotting Simulation Results
Summary
Appendix Complex Numbers
Basic Operations
Polar Coordinates
The Complex Exponential
Appendix Further Reading
Recommended Reading
Additional References
Mathematical Prerequisites
Colophon

»This book distills the theory into practical techniques for software enginieers.« Chris Nauroth, Hortonworks

»Read it - you'll build better systems!« Richard B. Kreckel, AREVA

»I am impressed. People who design and operate computer systems should know about control theory.«