A Low‐cost Solution to Motion Tracking Using an Array of Sonar Sensors and an Inertial Measurement Unit A thesis presented to the faculty of the Russ College of Engineering and Technology of Ohio University In partial fulfillment of the requirements for the degree Master of Science Jason S. Maxwell August 2009 © 2009 Jason S. Maxwell. All Rights Reserved. 2 This thesis titled A Low‐cost Solution to Motion Tracking Using an Array of Sonar Sensors and an Inertial Measurement Unit by JASON S. MAXWELL has been approved for the School of Electrical Engineering Computer Science and the Russ College of Engineering and Technology by Maarten Uijt de Haag Associate Professor School of Electrical Engineering and Computer Science Dennis Irwin Dean, Russ College of Engineering and Technology 3 ABSTRACT MAXWELL, JASON S., M.S., August 2009, Electrical Engineering A Low‐cost Solution to Motion Tracking Using an Array of Sonar Sensors and an Inertial Measurement Unit (91 pp.) Director of Thesis: Maarten Uijt de Haag As the desire and need for unmanned aerial vehicles (UAV) increases, so to do the navigation and system demands for the vehicles. While there are a multitude of systems currently offering solutions, each also possess inherent problems. The Global Positioning System (GPS), for instance, is potentially unable to meet the demands of vehicles that operate indoors, in heavy foliage, or in urban canyons, due to the lack of signal strength. Laser‐based systems have proven to be rather costly, and can potentially fail in areas in which the surface absorbs light, and in urban environments with glass or mirrored surfaces. SONAR based systems, however, do not fall victim to any of the outlined problems above, and for this reason, is an area of navigation which requires further study and development. This thesis will cover techniques for localizing and classifying targets in a vehicles environment using a SONAR‐based system and an inertial measurement unit (IMU). The thesis will also cover the extension of these localization and classification techniques for the use of 3D motion detection and tracking of objects. Approved: _____________________________________________________________ Maarten Uijt de Haag Associate Professor School of Electrical Engineering and Computer Science 4 ACKNOWLEDGMENTS I would like to thank my advisor Dr. Maarten Uijt de Haag for suggesting this topic, as well as for providing assistance, guidance, and support throughout the entirety of this project and my time at Ohio University. I would also like to thank my committee members Dr. Frank Van Graas, Dr. Michael Braasch, and Gene Kaufman for their assistance and support in regards to this project. Thanks to Robert Widmer for assisting in the development of the hardware systems, as well as the discussion of our projects as a whole. Thanks also go out to Justin Mamrak for discussing and troubleshooting different hardware problems that arouse from time to time. I would like to thank Chereice Maxwell for her support and help while I was working long hours testing and writing; and finally, I would like to thank my parents and family for their support throughout this project and my entire college career. 5 TABLE OF CONTENTS Page Abstract .......................................................................................................................................................... 3 Acknowledgments ..................................................................................................................................... 4 List of Tables ................................................................................................................................................ 8 List of Figures .............................................................................................................................................. 9 List of Acronyms ...................................................................................................................................... 12 Chapter 1: Introduction ........................................................................................................................ 13 1.1. Motivation ....................................................................................................................... 13 1.2. Problem Statement ...................................................................................................... 14 1.3. Proposed Solution ....................................................................................................... 14 1.4. Scope ................................................................................................................................. 15 1.5. Assumptions ................................................................................................................... 15 1.6. Overview of Thesis ...................................................................................................... 16 Chapter 2: Background ......................................................................................................................... 17 2.1. Overview of SONAR .................................................................................................... 17 2.2. Overview of Inertial Measurement Unit ............................................................ 19 2.3. Biological Inspiration ................................................................................................. 20 2.4. 2D Target Classification ............................................................................................ 21 2.4.1. Vector Receiver .......................................................................................... 21 2.4.2. 2D Array ........................................................................................................ 22 2.4.3. Target Classification ................................................................................. 23 6 2.5. 3D Target Localization and Classification ......................................................... 29 2.5.1. 3D Sonar Array ........................................................................................... 29 2.5.2. 3D Target Localization ............................................................................ 30 2.5.3. 3D Target Classification .......................................................................... 32 Chapter 3: System Design .................................................................................................................... 35 3.1. Hardware ......................................................................................................................... 35 3.1.1. SONAR Units ................................................................................................ 35 3.1.2. SONAR Array ............................................................................................... 37 3.1.3. Inertial Measurement Unit .................................................................... 38 3.1.4. Computer System ...................................................................................... 38 3.1.5. System Communication Bus ................................................................. 38 3.2. Hardware Integration and Interfacing ............................................................... 40 3.3. Adjustments for Systemetic Sources of Error ................................................. 40 3.3.1. Accounting for System Delay Errors Due to Noise on the Communication Bus ................................................................................................. 41 3.3.2. Delay Between Transmission and Reception on Separate SONAR Units ................................................................................................................ 42 3.3.3. Reducing IMU Errors................................................................................ 42 3.3.4. Addressing SONAR Unit Synchronization Errors ........................ 43 Chapter 4: Motion Tracking ............................................................................................................... 45 4.1. Identifying Potentially Moving Objects .............................................................. 45 4.1.1. Stationary Identification Process ....................................................... 45 7 4.1.2. Moving Identification Process .............................................................. 46 4.2. Moving Object Velocity and Position Estimations ......................................... 48 4.2.1. Target Velocity Estimation .................................................................... 48 4.2.2. Target Location Tracking and Future Position Prediction ...... 49 Chapter 5: Test Results and Analysis ............................................................................................. 55 5.1. Individual SONAR Unit Measurement Accuracy and Stability Tests ..... 55 5.2. Object Localization Tests .......................................................................................... 60 5.3. Object Classification Tests ....................................................................................... 63 5.4. Stationary Motion Detection, Tracking, and Prediction .............................. 65 5.5. Moving Platform Motion Detection ...................................................................... 76 5.5.1. Application of Zero‐Velocity Update ................................................. 76 5.5.2. IMU and SONAR Integration for Moving Platform Motion Detection