Feedback Control for Computer Systems. Introducing Control Theory to Enterprise Programmers (e-book) Katowice

How can you take advantage of feedback control for enterprise programming? With this book, author Philipp K. Janert demonstrates how the same principles that govern cruise control in your car also apply to data center management and other enterprise systems. Through case studies and hands-on simulations, you...ll learn methods to solve several control issues, including mechanisms to spin up more servers automatically when web traffic spikes.Feedback is ideal for controlling large, complex systems, but its use in software engineering raises unique issues. This book provides basic theory and lots of practical advice for programmers with no previous background in feedback control.Learn feedback concepts and controller designGet practical techniques for implementing and tuning controllersUse feedback “design patterns" for common control scenariosMaintain a cache...s “hit rate" by automatically adjusting its sizeRespond to web traffic by scaling server instances automaticallyExplore ways to use feedback principles with queueing systemsLearn how to control memory consumption in a game engineTake a deep dive into feedback control theory Spis treści: Feedback Control for Computer Systems Preface What Is Feedback? Why This Book? How to Read This Book Conventions Used in This Book Using Code Examples Safari Books Online How to Contact Us Acknowledgments I. Foundations 1. Why Feedback? An Invitation A Hands-On Example Hoping for the Best Establishing Control Adding It Up Summary Code to Play With 2. Feedback Systems Systems and Signals Tracking Error and Corrective Action Stability, Performance, Accuracy The Setpoint Uncertainty and Change Feedback and Feedforward Feedback and Enterprise Systems Code to Play With 3. System Dynamics Lags and Delays Forced Response and Free Response Transient Response and Steady-State Response Dynamics in the Physical World and in the Virtual World Dynamics and Memory The Importance of Lags and Delays for Feedback Loops Avoiding Delays Theory and Practice Code to Play With 4. Controllers Block Diagrams On/Off Control Proportional Control Why Proportional Control Is Not Enough Integral Control Integral Control Changes the Dynamics Integral Control Can Generate a Constant Offset Derivative Control Problems with Derivative Control The Three-Term or PID Controller Code to Play With 5. Identifying Input and Output Signals Control Input and Output Directionality of the Input/Output Relation Examples Thermal Control 1: Heating Situation Input Output Commentary Item Cache Situation Input Output Commentary Server Scaling Situation Input Output Commentary Controlling Supply and Demand by Dynamic Pricing Situation Input Output Commentary Thermal Control 2: Cooling Situation Input Output Commentary Criteria for Selecting Control Signals For Control Inputs For Control Outputs A Note on Multidimensional Systems 6. Review and Outlook The Feedback Idea Iteration Process Knowledge Avoiding Instability The Setpoint Control, Not Optimization II. Practice 7. Theory Preview Frequency Representation The Transfer Function Block-Diagram Algebra PID Controllers Poles of the Transfer Function Process Models 8. Measuring the Transfer Function Static Input/Output Relation: The Process Characteristic Practical Considerations Dynamic Response to a Step Input: The Process Reaction Curve Practical Aspects Process Models Self-Regulating Process Accumulating Process Self-Regulating Process with Oscillation Non-Minimum Phase System Other Methods of System Identification 9. PID Tuning Tuning Objectives General Effect of Changes to Controller Parameters ZieglerNichols Tuning Semi-Analytical Tuning Methods Practical Aspects A Closer Look at Controller Tuning Formulas 10. Implementation Issues Actuator Saturation and Integrator Windup Preventing Integrator Windup Setpoint Changes and Integrator Preloading Smoothing the Derivative Term Choosing a Sampling Interval Variants of the PID Controller Incremental Form Error Feedback Versus Output Feedback The General Linear Digital Controller Nonlinear Controllers Error-Square and Gap Controllers Simulating Floating-Point Output Categorical Output 11. Common Feedback Architectures Changing Operating Conditions: Gain Scheduling Gain Scheduling for Mildly Nonlinear Systems Large Disturbances: Feedforward Fast and Slow Dynamics: Nested or Cascade Control Systems Involving Delays: The Smith Predictor III. Case Studies 12. Exploring Control Systems Through Simulation The Case Studies Modeling Time Control Time Simulation Time The Simulation Framework Components Plants and Systems Controllers Actuators and Filters Convenience Functions for Standard Loops Generating Graphical Output 13. Case Study: Cache Hit Rate Defining Components Cache Misses as Manufacturing Defects Measuring System Characteristics Controller Tuning Simulation Code 14. Case Study: Ad Delivery The Situation Measuring System Characteristics Establishing Control Improving Performance Variations Cumulative Goal Gain Scheduling Integrator Preloading Weekend Effects Simulation Code 15. Case Study: Scaling Server Instances The Situation Measuring and Tuning Reaching 100 Percent With a Nonstandard Controller Dealing with Latency Simulation Code 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 17. Case Study: Cooling Fan Speed The Situation The Model Tuning and Commissioning Closed-Loop Performance Simulation Code 18. Case Study: Controlling Memory Consumption in a Game Engine The Situation Problem Analysis Architecture Alternatives A Nontraditional Loop Arrangement A Traditional Loop with Logarithms Results Simulation Code 19. Case Study Wrap-Up Simple Controllers, Simple Loops Measuring and Tuning Staying in Control Dealing with Noise IV. Theory 20. The Transfer Function Differential Equations Laplace Transforms Properties of the Laplace Transform Using the Laplace Transform to Solve Differential Equations A Worked Example The Transfer Function Worked Example: Step Response Worked Example: Ramp Input The Harmonic Oscillator What If the Differential Equation Is Not Known? 21. Block-Diagram Algebra and the Feedback Equation Composite Systems The Feedback Equation An Alternative Derivation of the Feedback Equation Block-Diagram Algebra Limitations and Importance of Transfer Function Methods 22. PID Controllers The Transfer Function of the PID Controller The Canonical Form of the PID Controller The General Controller Proportional Droop Revisited A Worked Example 23. Poles and Zeros Structure of a Transfer Function Effect of Poles and Zeros Special Cases and Additional Details Complex conjugate poles Multiple poles Poles on the imaginary axis Pole/zero cancellations Pole Positions and Response Patterns Dominant Poles Pole Placement What to Do About Delays 24. Root Locus Techniques Construction of Root Locus Diagrams Root Locus or Evans Rules Angle and Magnitude Criteria Practical Issues Examples Simple Lag with a P Controller Simple Lag with a PI Controller 25. Frequency Response and the Bode Plot Frequency Response Frequency Response in the Physical World Frequency Response for Transfer Functions A Worked Example The Bode Plot A Criterion for Marginal Stability Other Graphical Techniques 26. Topics Beyond This Book Discrete-Time Modeling and the z-Transform State-Space Methods Robust Control Optimal Control Mathematical Control Theory V. Appendices A. Glossary B. Creating Graphs with Gnuplot Basic Plotting Plot Ranges Inline Transformations Plotting Simulation Results Summary C. Complex Numbers Basic Operations Polar Coordinates The Complex Exponential D. Further Reading Recommended Reading Additional References Mathematical Prerequisites Index Colophon Copyright