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Introduction to System Dynamics 系统动力学入门教程 U.S. Department of Energy's Introduction to System Dynamics A Systems Approach to Understanding Complex Policy Issues Version 1.0 Prepared for: U.S. Department of Energy, Office of Policy and International Affairs, Office of Science & Technology Policy and Cooperation Adapted from Foundations of System Dynamics Modeling by: Michael J. Radzicki, Ph.D. Sustainable Solutions, Inc. Copyright © 1997 Designed by: Robert A. Taylor U.S. Department of Energy 注：本教程由学习型组织研修中心·中国学习型组织网（http://www.cko.com.cn） 打包编辑，仅供会员个人学习、研究参考，不得用于其他任何商业目的。未经允 许，不得发布、复制或传播本文件。 学习型组织研修中心·中国学习型组织网 http://www.cko.com.cn 编辑发布，2007 1 系统动力学入门教程 Index Overview ........................................................................................................................ 4 Chapter 1 Introduction .................................................................................................. 6 Origin of System Dynamics ............................................................................................... 6 System Dynamics and Energy Modeling .......................................................................... 11 Chapter 2 Why Model? ..................................................................................................25 Why Build Models in the First Place? .............................................................................. 25 Formal Models .......................................................................................................... 25 Mental Models ..........................................................................................................26 Combining Mental Models with System Dynamics ................................................. 27 Chapter 3 The Building Blocks .................................................................................... 29 Taking A Dynamic Perspective......................................................................................... 29 Time Paths ................................................................................................................ 29 Actual Data ............................................................................................................... 33 Seeing System Structure ................................................................................................... 39 Stocks and Flows ....................................................................................................... 39 Identifying Stocks and Flows ................................................................................... 40 Four Characteristics of Stocks ................................................................................. 40 Feedback ................................................................................................................... 47 Implicit and Explicit Goals ....................................................................................... 55 Archetypes ................................................................................................................ 58 Nonlinearity .............................................................................................................. 59 Implications of System Structure .................................................................................... 60 A System Problem and Its Symptoms are Separated By Time and Space ............... 60 Counterintuitive Behavior ........................................................................................ 62 Better Before Worse or Worse Before Better............................................................. 63 Policy Resistance ...................................................................................................... 64 Unpredictability ........................................................................................................ 65 Disequilibrium ......................................................................................................... 68 Chapter 4 Simple Structures ........................................................................................ 69 Exponential Growth, Exponential Decay, and Goal Seeking Behavior .......................... 69 Analytical Versus Simulated Solutions ..................................................................... 70 Exponential Growth ..................................................................................................76 Goal Seeking Behavior ............................................................................................. 90 Exponential Decay .................................................................................................... 93 System Oscillation ............................................................................................................97 S-Shaped Growth ............................................................................................................ 102 Chapter 5 The Modeling Process ................................................................................ 107 The Modeling Process .................................................................................................... 107 Management Flight Simulators ....................................................................................... 110 Chapter 6 Natural Gas Discovery Model ..................................................................... 114 Natural Gas Discovery Model: Reference Modes ............................................................ 114 学习型组织研修中心·中国学习型组织网 http://www.cko.com.cn 编辑发布，2007 2 系统动力学入门教程 Step-By-Step Re-Creation of the Natural Gas Discovery and Production Model ........... 116 Natural Gas Discovery and Production Model: First Cut ........................................ 116 Natural Gas Discovery and Production Model: Second Cut .................................... 119 Natural Gas Discovery and Production Model: Third Cut ..................................... 124 Natural Gas Discovery and Production Model: Fourth Cut ................................... 129 Natural Gas Discovery and Production Model: Fifth Cut ........................................ 133 Natural Gas Discovery and Production Model: Sixth Cut ....................................... 137 Policy Explorations with Natural Gas Model.................................................................. 142 Chapter 7 Next Steps ................................................................................................... 148 System Dynamics Resources .......................................................................................... 148 学习型组织研修中心·中国学习型组织网 http://www.cko.com.cn 编辑发布，2007 3 系统动力学入门教程 Overview The success or failure of a particular policy initiative or strategic plan is largely dependent on whether the decision maker truly understands the interaction and complexity of the system he or she is trying to influence. Considering the size and complexity of systems that public and private sector decision makers must manage, it is not surprising that the "intuitive" or "common sense" approach to policy design often falls short, or is counter-productive, to desired outcomes. This online book was written to introduce the concepts and "language" that make a systems-based study of such complex problems possible. Our intent is to provide the reader with a broad overview of the field of system dynamics, acquaint him or her with the fundamental stock-flow-feedback structures that determine the dynamic behavior in systems, and motivate the reader to begin analyzing problems dynamically and holistically. Knowing how to speak and think in terms of systems and interconnections is a critical step in effective policy design, policy implementation, and consensus building. In Chapter 1, Introduction, we provide some context for system dynamics by presenting a brief history of the field, beginning with Professor Jay W. Forrester's work at the Massachusetts Institute of Technology in the 1950's, through the present day. In addition, work related to energy policy is presented in some detail to provide the reader with examples of the type of issues that can be studied using system dynamics principles. In Chapter 2, Why Model?, we continue this discussion by exploring the question: "Why model at all?" Chapter 3, Building Blocks, presents the basic concepts behind the study of complex systems by first examining the patterns of behavior that real-world systems exhibit, and then discussing the structure that causes such patterns to emerge. This chapter can be thought of as the "language chapter" because it is here that the reader learns the concepts and terms required to construct the "theories" or "models" of their particular issues. With the concepts and language of system dynamics in hand, Chapter 4, Simple Structures, examines system behavioral types such as exponential growth or oscillation in greater detail. In this chapter, the reader is introduced to the concept of computer simulation. Current computer simulation technology allows decision-makers to easily construct models of a system's structure (including mathematical equations) to use in conducting policy experiments. In chapter 5, Basic Modeling Process, we share some thoughts and ideas about the process of constructing system dynamics models, from conceptual causal diagrams through detailed computer simulation models. Chapter 6, Natural Gas Discovery, reinforces the concepts introduced in the first five chapters by presenting a case-study based on a well-known system dynamics model of the U.S. natural gas
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