# Preface

My motivation for writing this textbook originates from several years teaching mechanical engineering at British Columbia Institute of Technology (BCIT). Several references specifically pertinent to the bachelor-level course System Design (MECH 8230) are available, but those existing resources and textbooks fail to fully meet the course requirement and curriculum—mainly the combination of related fundamentals and modern engineering software applications. Students at the bachelor level have been forced to consult with several sources. An opportunity became available through a call from the government of British Columbia and supported by BCIT to develop textbooks as open education resources and to make them available to students.

This textbook, *Engineering Systems Dynamics: Modelling, Simulation, and Design*, presents effective system modelling methods, mainly bond graph (BG), and the application of a relevant engineering software tool, 20-sim. As well, we have created an affordable, open education resource for students and professionals in the field.

This textbook emphasizes the fundamentals of modelling methods—including Lagrangian and BG—and introduces a software tool for modelling and simulation to support the design of common engineering systems. In this approach, time-consuming effort of manipulating and extracting system equations, and writing computer codes for integrating and finding their solution are secondary. We believe that our approach helps both students and professionals currently working in the field to become more productive engineers. Screen-recorded video files of selected worked-out examples help the reader understand the topic and applications for real-world engineering systems.

This book comprises the following 11 chapters:

**Chapter 1: ****Introduction** gives the definition of modelling, some background on the role of modelling for simulation and design, and the history of BG method.

**Chapter 2: ****Lagrangian Mechanics** discusses the background foundation of the energy-based Lagrangian method of modelling, its formulation, and several worked-out examples to demonstrate the applications of this method along with their system equations solutions using 20-sim.

**Chapter 3: ****Bond Graph Modelling Method** gives a full description of the BG method, its related structure, generalized variables including power variables effort and flow, nine basic elements, and causality-definition and assignment rules. This chapter is the foundation for learning BG method and prepares the reader to learn and apply BG method.

**Chapter 4: Building Bond Graph Models: Procedure and Application** gives guidelines and procedure of how to build a BG model and how to assign causalities. A step-by-step approach with worked-out examples demonstrates application of the procedure.

**Chapter 5: ****Introduction to 20-sim Software Tool** introduces the software package 20-sim and details its features for building BG models and simulation for systems. This chapter includes examples and solutions, including screen-recorded video files of the solution steps using 20-sim.

**Chapter 6: ****Bond Graph Models for Complex Mechanical Systems** gives more worked-out examples for selected complex mechanical systems including rotational and 2D rigid body motion. This chapter includes several examples and their solutions including screen-recorded video files of the solution steps using 20-sim.

**Chapter 7: ****Bond Graph Models for Electrical Systems** discusses the application of BG method to electrical circuits and systems and the related sign convention for current and voltage. This chapter includes several worked-out examples for selected electrical systems including screen-recoded video files of the solution steps using 20-sim.

**Chapter 8: ****Bond Graph Models for Hydraulic Systems** discusses the application of BG method to hydraulic systems and the related definitions for effort and flow in these types of systems. This chapter gives the derivation for hydraulic inertance, capacitance, and resistance, as well as several worked-out examples for selected hydraulic systems, including screen-recorded video files of the solution steps using 20-sim.

**Chapter 9: ****Bond Graph Models for Multi-Domain Systems** gives several worked-out examples of the application of BG method to systems consisting of multi-energy domains, including screen-recorded video files of the solution steps using 20-sim.

**Chapter 10: ****Frequency Analysis: Bode Plots and Transfer Function** discusses the methods of analyzing systems in frequency domain vs. time domain and details the application of the Bode method for plotting power and phase of selected input/output signals related to a given system. This chapter includes several worked-out examples, including screen-recorded video files of the solution steps using 20-sim.

**Chapter 11: ****Miscellaneous Topics** collects all related and supporting topics to help the reader’s understanding of the subject. The topics include extraction of system equations from BG models, the derivative and algebraic loop, conjugate variables, and pseudo bond graph. The chapter also includes worked-out examples where necessary**.**

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Mehrzad Tabatabaian, PhD, PEng

Vancouver, BC

October 2021

*The publisher recognises and respects all marks used by companies, manufacturers, and **developers as a means to distinguish their products. All brand names and product names **mentioned in this book are trademarks or service marks of their respective companies. Any **omission or misuse (of any kind) of service marks or trademarks, etc. is not an attempt to **infringe on the property of others.*