University of Nevada, Reno Biomorphic Hyper-Redundant Snake Robot: Locomotion Simulation, 3D Printed Prototype and Inertial-Measurement-Unit-Based Motion Tracking A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering By Weixin Yang Dr. Yantao Shen/Thesis Advisor December 2016 THE GRADUATE SCHOOL We recommend that the thesis prepared under our supervision by WEIXIN YANG Entitled Biomorphic Hyper-Redundant Snake Robot: Locomotion Simulation, 3d Printed Prototype And Inertial-Measurement-Unit-Based Motion Tracking be accepted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Yantao Shen, Ph.D, Advisor M. Sami Fadali, Ph.D, Committee Member Hung (Jim) La, Ph.D, Graduate School Representative David W. Zeh, Ph.D., Dean, Graduate School December, 2016 i ABSTRACT Snakes are one of the most successful species in the world due to the high adaptability in most environments of the earth. A snakebot is a biomorphic hyper- redundant robot that resembles a biological snake. Snakebots are most useful in situations where their unique characteristics give them an advantage in their locomotion environments. These environments tend to be long like pipes or highly cluttered like rubble. Thus, snake robots are currently being developed to assist search and rescue tasks in complex environments. This thesis proposes a detailed architecture to develop a snakebot including building its mathematical model based on statistical geometry analysis and kinematic force analysis; verifying the mathematical model using the numerical simulation; mechanical structure design of the robot; electric system and data transmission system design, and its locomotion data analysis and performance evaluation. In the thesis, we clearly demonstrate that the simulation results prove both the proposed mathematical model and the mechanical design of the robot; the IMU data analysis results agree with the simulation results. To increase the precision level of the IMU based motion tracking for the robot, the Kalman Filter and trapezoid integration algorithms were applied to the data processing and analysis. Finally, the achieved results validate the effectiveness of these applied algorithms. The developed snakebot promises huge potentials in future applications. In our future work, we’ll integrate sensors like camera, force sensing units, and others with the robot, so as to facilitate its control capability with sensor feedback functions. In addition, we will employ and test more powerful microprocessors to improve the real-time computing performance of the robot. Our goal is to make the snakebot an advanced intelligent mechatronic system for fulfilling future search and rescue tasks in the complex and challenging environments. ii Acknowledgments I would like to thank my thesis advisor Dr. Shen for his supervision. The door to Prof. Shen office was always open whenever I ran into a trouble spot or had a question about my research or writing. He consistently allowed this project to be my own work, but steered me in the right direction whenever he thought I needed it. Without his support, expertise, guidance, and most of all, patience, the completion of this thesis wouldn’t be possible. I would also like to thank Dr. Fadali and Dr. Hung for their support by serving on my thesis committee. Dr. Fadali helped me in fully understanding basic principles of random signal processing. With his great patience, Dr. Fadali also took his great efforts and his time to help revising my thesis. In addition, I would thank Dr. Hung for his help in the robotic class. The control algorithms taught in the class are essentially helpful to my research work in the thesis. Next, I would like to thank the following graduate students in our lab, Mr. Yudong Luo and Ms. Na Zhao. Their selfless sharing of experience and thoughtful discussions help me to solve many technical issues in the project. Ms. Na Zhao helped to design the mechanical structure of the robot with her patience and expertise. In addition, I would like to acknowledge that the research work was partially supported by NASA CAN grant # NNX13AN15A. Finally, I must express my very profound gratitude to my parents for providing me with unfailing support and continuous encouragement throughout my years of study and through the process of writing this thesis. This accomplishment would not be possible without their support. iii Dedication To my mother, Huazhi, my father, Yunchuan and my fiancée Aijing iv Contents 1 Introduction ............................................................................................................................. 1 1.1 Goal, Objectives, and Contribution ............................................................................. 1 1.2 Motivation ....................................................................................................................... 2 1.3 Organization ................................................................................................................... 3 2 Background ............................................................................................................................ 4 2.1 Modeling and analysis of snake robot locomotion ................................................... 4 2.2 Implementation of physical snake robots .................................................................. 5 2.2.1 Snake robots without contact force sensors ..................................................... 5 2.2.2 Snake robots with contact force sensors ......................................................... 11 2.2.3 Summary .............................................................................................................. 11 3 Snake Robot Mathematic Model ....................................................................................... 12 3.1 Static Analysis.............................................................................................................. 12 3.2 MATLAB Simulation .................................................................................................... 13 3.3 Kinematic Analysis ...................................................................................................... 18 4 Snake Robot Mechanical Model and Simulation ............................................................ 24 4.1 The Structure Model of Snake Robot ....................................................................... 24 4.2 Simulation Environment Setting ................................................................................ 26 4.3 2D Simulation ............................................................................................................... 27 4.3.1 Serpentine Locomotion Simulation ................................................................... 27 v 4.3.2 Serpentine Locomotion under Different Friction ............................................. 34 4.4 3D Snake Robot Sidewinding Locomotion Simulation .......................................... 36 5 Snake Robot’s Mechanical Structure and Integrated Electronic System Design ...... 40 5.1 Snake Robot Mechanical Design .............................................................................. 40 5.2 Voltage Booster and Adapter Boards....................................................................... 43 5.2.1 5V Booster & Charger ........................................................................................ 43 5.2.2 Parallel Charging ................................................................................................. 45 5.2.3 Adapter Boards .................................................................................................... 46 6 Remote Control and Locomotion Analysis. ..................................................................... 49 6.1 Wireless Communication ........................................................................................... 49 6.1.1 Xbee module ........................................................................................................ 49 6.1.2 Wireless Communication Protocol .................................................................... 50 6.2 Snake robot’s trajectory tracking model................................................................... 54 6.2.1 Trajectory tracking algorithm ............................................................................. 54 6.2.2 Snake robot’s absolute orientation (Euler vector) and visualization ............ 58 6.3 Tracking system noise processing and software compensation algorithm ........ 60 6.3.1 System noise analysis and processing ............................................................ 60 6.3.2 Noise processing algorithms ............................................................................. 62 6.3.3 Time domain and spectral analysis .................................................................. 62 6.3.4 Low-pass filter ...................................................................................................... 66 vi 6.3.5 IMU acceleration data calibration ..................................................................... 71 6.3.6 IMU baseline calibration ..................................................................................... 73 6.3.7 Kalman Filter ........................................................................................................ 81 6.4 Snake robot locomotion analysis .............................................................................