School of Information Technology and Electrical Engineering ACTIVE BALANCE FOR A HUMANOID ROBOT By Toby Daniel Low The School of Information Technology and Electrical Engineering The University of Queensland Submitted for the degree of Bachelor of Engineering (Honours) in the division of Computer System Engineering 29 th October 2003 Page 1 Daniel Toby Low Lab 311, University of Queensland St. Lucia, Brisbane QLD 4067, Australia. 29 th October 2003 Head School of Information Technology and Electrical Engineering, The University of Queensland St. Lucia QLD 4067 Dear Professor Kaplan, In accordance with the requirements of the Degree of Bachelor of Engineering (Honours) in the School of Information Technology and Electrical Engineering, I would like to submit the following thesis entitled —Active Balance of a Humanoid Robot“ This thesis was performed under the supervision of Dr Gordon Wyeth. I declare that this work submitted in this thesis is that of my own, except work that has been acknowledged in text and footnotes, and has not been previously submitted for a degree at The University of Queensland or any other institution. Yours Sincerely, Daniel Toby Low Page 2 TABLE OF CONTENTS ABSTRACT............................................................................................................................................ 7 ACKNOWLEDGEMENTS................................................................................................................... 8 CHAPTER 1 INTRODUCTION .......................................................................................................... 9 1.1 WHY HUMANOID ROBOTS EXIST?................................................................................... 9 1.2 ROBOCUP COMPETITION................................................................................................... 9 1.3 ROBOT BALANCING.......................................................................................................... 10 1.4 CHAPTER OUTLINE ........................................................................................................... 10 CHAPTER 2 LITERATURE REVIEW ............................................................................................ 12 2.1 BACKGROUND INFORMATION....................................................................................... 12 2.1.1 KEY CONCEPTS AND TERMINLOGY ......................................................................... 12 2.1.2 TYPES OF WALKING.................................................................................................... 13 2.1.3 BALANCE MODELS...................................................................................................... 14 2.1.4 CONTROL CONCEPTS AND TERMINLOGY............................................................... 15 2.2 THE —GUROO“ PROJECT.................................................................................................... 16 2.2.1 OVERVIEW .................................................................................................................... 16 2.2.2 PREVIOUSLY DEVELOPED BALANCE SYSTEM ....................................................... 17 2.3 EXISTING HUMANOID ROBOTS...................................................................................... 18 2.3.1 —WABIAN“..................................................................................................................... 18 2.3.2 THE HONDA HUMANOID ROBOT.............................................................................. 19 2.4 OTHER CONTROL AND BALANCE TECHNIQUES........................................................ 20 2.4.1 DIRECT ANGULAR MOMENTUM FEEDBACK.......................................................... 20 2.4.2 FEEDBACK, FEEDFORWARD AND FUZZY CONTROL............................................ 21 2.5 BALANCE CONTROL SYSTEM APPROACH .................................................................. 21 CHAPTER 3 SPECIFICATIONS ...................................................................................................... 22 3.1 PURPOSE .............................................................................................................................. 22 3.2 GOAL..................................................................................................................................... 22 3.3 METHODOLOGY................................................................................................................. 23 3.4 CONSTRAINTS .................................................................................................................... 24 3.5 CONTRIBUTIONS................................................................................................................ 25 CHAPTER 4 MODELLING THE HUMANOID ROBOT .............................................................. 26 4.1 CHOOSING A MODEL ........................................................................................................ 26 4.1.1 COMPARING THE MODELS........................................................................................ 26 4.1.2 THE CHOSEN MODEL ................................................................................................. 26 4.2 TWO-MASS INVERTED PENDULUM MODEL................................................................ 27 4.2.1 HUMAN ROBOT TRANSLATION.................................................................................. 27 4.2.2 FORMULATING THE DYNAMIC DIFFERENTIAL EQUATIONS............................... 28 4.2.3 BALANCE MODEL STATE-SPACE EQUATIONS........................................................ 30 CHAPTER 5 BALANCE CONTROL SYSTEM .............................................................................. 32 5.1 OBTAINING THE TRANSFER FUNCTIONS .................................................................... 32 5.1.1 LINEARISING THE SYSTEM......................................................................................... 32 5.1.2 CONVERTING TO A SISO SYSTEM.............................................................................. 34 5.2 CONTROL SYSTEM DESIGN............................................................................................. 36 5.2.1 ROOT LOCUS DESIGN................................................................................................. 36 5.2.2 MODELLING MOTOR CHARACTERISTICS ............................................................... 38 5.3 MATLAB SIMULATION RESULTS ................................................................................... 41 5.3.1 LINEAR AND NON-LINEAR TIME RESPONSES ......................................................... 41 5.3.2 REFINEMENTS TO THE DESIGN................................................................................ 42 Page 3 CHAPTER 6 ATTITUDE BEHAVIOURS........................................................................................ 43 6.1 POSTURE ATTITUDE CONTROL...................................................................................... 43 6.2 COG ATTITUDE CONTROL............................................................................................... 43 CHAPTER 7 SOFTWARE DESIGN AND IMPLEMENTATION................................................. 45 7.1 SIMULATION USING DYNAMECHS................................................................................ 45 7.1.1 CURRENT SIMULATION DESIGN............................................................................... 45 7.1.2 IMU SENSOR DESIGN.................................................................................................. 46 7.1.3 SIMULATION INPUT FORCE DESIGN ....................................................................... 47 7.2 SOFTWARE DESIGN METHODS....................................................................................... 48 7.2.1 HIGHER LEVEL DESIGN ............................................................................................. 48 CHAPTER 8 SIMULATION RESULTS AND REFINEMENTS ................................................... 50 8.1 PRELIMINARY SIMULATION RESULTS......................................................................... 50 8.1.2 MORE REFINEMENTS.................................................................................................. 51 8.2 FINAL SIMULATION RESULTS ........................................................................................ 52 8.2.1 STEP RESPONSE RESULTS ......................................................................................... 52 8.2.2 COG CONTROL RESULTS ........................................................................................... 52 8.2.3 POSTURE CONTROL RESULTS................................................................................... 53 8.3 POSTURE WITH ANKLE CONTROL................................................................................. 55 8.3.1 SIMPLE ANKLES BEHAVIOURS.................................................................................. 55 8.3.2 POSTURE WITH ANKLE CONTROL RESULTS........................................................... 56 CHAPTER 9 HARDWARE IMPLEMENTATION ......................................................................... 58 9.1 IMU SPECIFICATIONS ....................................................................................................... 58 9.2 IMU SOFTWARE AND HARDWARE DESIGN................................................................. 58 9.3 REAL HARDWARE RESULTS ........................................................................................... 59 9.3.1 INITIAL