DESIGN AND DEVELOPMENT OF ROBUST HANDS FOR HUMANOID ROBOTS Anand Vazhapilli Sureshbabu Department of Bioengineering and Robotics and the iCub Facility Università degli Studi di Genova with Istituto Italiano di Tecnologia This dissertation is submitted for the degree of Doctor of Philosophy in Bioengineering and Robotics Istituto Italiano di Tecnologia March 2018 ANAND VAZHAPILLI SURESHBABU: Design and Development of Robust Hands for Humanoid Robots DOCTORAL SCHOOL: Department of Bioengineering and Robotics (XXIX Cycle) SUPERVISORS: Dr.Alberto Parmiggiani Dr.Giorgio Metta To my Mom, who found the strength to encourage me as she lay beating cancer, To Biene, whose love has given me a goal to run towards, To my family, the greatest support and strength in my life. Declaration I hereby declare that except where specific reference is made to the work of others, the contents of this dissertation are original and have not been submitted in whole or in part for consideration for any other degree or qualification in this, or any other University. This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration, except where specifically indicated in the text. This dissertation contains less than 65,000 words including appendices, bibliography, footnotes, tables and equations and has less than 150 figures. Anand Vazhapilli Sureshbabu March 2018 Acknowledgements “A boy who won’t stand up for himself becomes a man who can’t stand up to anything.” — Khaled Hosseini “...talent means nothing, while experience, acquired in humility and with hard work, means everything.” — Patrick Süskind I would like to start by thanking all the reviewers in the past and present who put in their valuable time and painstaking effort of going through my publications and thesis, and for giving their invaluable feedback. I would also like to start off by saying that I have come across countless precious individuals, during my nearly four years in Genova. If I forget to thank you, forgive me. My sincerest gratitude goes towards my advisors Giorgio and Alberto. Alberto, in particular has been a guiding force throughout these years, and having been his first student mentee, I guess we can say we grew up together to realise what a team needs to be, in both good times and bad. He was always there to criticize me and redirect my focus, when I went astray. I would also like to whole-heartedly thank my reviewers, Dr.Marco Controzzi and Dr.Markus Grebenstein, your feedback was invaluable to me. My PhD will not be where it is now without the help from our entire team at the iCub facility. In particular, I would like to thank Marco Maggiali, Luca Fiorio, Alessandro Scalzo and Roberto Puddu for providing their invaluable assistance. I would also like to thank Marcello Savoldi, my CREO and italian coach, who’s guidance helped me both personally and professionally: Grazie mille! I would also like to thank my current and past flatmates: Ninad, Silvio, Giovanni viii and Emy, who fed me and made our house a home by providing endless entertainment and companionship to this outsider. I also thank all my friends who supported me through good times and bad in the past three and a half years. My Vivlafrans group, for their unconditional support and the Party team for making Genova’s social encounters all the more fun. Den, Sandy, Giulio, Yue, Chri, Mati, Louis, Fanny, Dave.. the list goes on. I want to also thank my family. It has been 9 whole years since I left home. And not a day has gone by when I haven’t wished I was closer to you. I thank them for their patience, it must be the toughest thing for any parent to do: to have your children live far away from you. Please know that, I would return in an instant, if the opportunity does so arise. And finally, to Biene. For all her unconditional love and support these pasttwo years, and for giving me a family that is just ours. Abstract Robotic hands have been among the most researched and oft used branch of hu- manoid robotics. At the forefront of every humanoids research problem, is the prob- lem of grasping and manipulation. Designing a robotic hand that is efficient in cost, construction and performance is a very challenging task. Robotic hands are usually heavily customised within their requirements of cost, shape, function, features, plat- form, etc. This thesis aims at trying to identify the different aspects to robotic hand design and tries to find ways to do it well and in cost-efficient ways. The first four chapters in this thesis sets up the problem, tries to identify theright inspirations when it comes to mimicking nature, goes through the different hands that exist in literature and tries to identify some of its key features which make it successful. An evaluation index is then proposed to compare hands across domains and to find where the key focus of these hands lie. It also acts as a list of ‘best practices’ when it comes to adding features in a robotic hand. The core of the thesis aims at developing two diverse hands, connected by a similar design philosophy. The hands had to incorporate novel manufacturing technologies, accurate sensors and new features while making them extremely cost-efficient. First, a wrist is designed and constructed, which provides the requisite range of motion and the support required for the hand to be mounted upon. Later, a simple two digit underactuated hand is constructed with a plethora of cost-effective features and is studied. Both the wrist and the hand are built as part of a new humanoid robot, the R1. Finally, the lessons learnt are noted and an experimental prototype hand for the iCub robot is designed and constructed. This aims at taking the features present in the R1 hand and adapting it for the iCub platform, while addressing the existing problems in the iCub hand. This experimental prototype introduces new technologies, never tried before on the iCub platform, all the while making the entire design process cost-efficient. Contents Contents xi List of Figures xvii List of Tables xxi Nomenclature xxi 1 Introduction1 1.1 Artificial Hands in Society and Science . .2 1.1.1 Medicine . .3 1.1.2 Domestic Robots . .3 1.2 Research Platforms . .5 1.2.1 The iCub Platform . .5 1.2.2 R1 Humanoid . .5 1.3 Research Objectives . .6 1.4 Thesis Structure . .7 1.5 Publications . .9 2 Hands in Nature 11 2.1 Animal Manus . 11 2.1.1 Special Features . 12 2.2 Human Hands . 14 2.2.1 The Human Wrist . 15 2.3 Human Hand Anatomy . 16 2.3.1 The Bones of the Human Hand . 16 2.3.2 Joints . 17 2.3.3 Pulley System in Fingers . 18 xii Contents 2.3.4 Arches . 18 2.4 Main Functions . 19 2.4.1 Prehensile Manipulation . 20 2.4.2 Non-prehensile Manipulation . 22 2.4.3 Communication . 22 2.4.4 Exploration . 24 2.5 Nomenclature . 25 2.6 Goals . 26 3 Review on robotic hands 27 3.1 A General Timeline of Robotic Hands . 27 3.1.1 Robotic Hands . 28 3.1.2 Evolution of rapid prototyped robotic hands . 34 3.2 Types of Hands by Function . 38 3.3 A Qualitative Analysis on Robotic Hands . 39 3.3.1 The Key Features . 43 3.3.2 Comparison of Key Aspects . 48 3.4 Technical guidelines . 52 4 A New Evaluation Index 55 4.1 Motivation . 55 4.2 A New Evaluation Index . 56 4.3 The FFP Index . 58 4.3.1 Form . 59 4.3.2 Control Features . 65 4.3.3 Performance . 69 4.3.4 Subjective Weighting . 72 4.4 A Case Study . 73 4.4.1 Form . 73 4.4.2 Features . 74 4.4.3 Performance . 74 4.5 Final Design Guidelines . 77 4.5.1 Technical Requirements . 77 5 The R1 Wrist 79 5.1 Overview . 79 Contents xiii 5.2 Conceptual Design . 80 5.2.1 Requirements . 81 5.2.2 Kinematic Structure Selection . 82 5.2.3 Load Path Analysis . 83 5.3 Embodiment Design . 85 5.3.1 Hardware . 85 5.3.2 Electronics . 87 5.4 Evaluation . 88 5.4.1 Cost Evaluation . 89 5.4.2 Payload . 89 5.4.3 Range of Motion . 90 5.4.4 Performance Analysis . 90 6 The R1 Hand 95 6.0.1 Design philosophy . 95 6.1 Conceptual Design . 96 6.1.1 Kinematics . 97 6.1.2 Series Elastic Elements . 97 6.2 Embodiment Design . 101 6.2.1 Hardware . 101 6.2.2 Friction Management . 102 6.2.3 Coupling and Actuation . 102 6.2.4 Design of the Series Elastic Elements . 103 6.2.5 Electronics . 104 6.3 Evaluation . 107 6.3.1 Performance Analysis . 108 6.3.2 Grasp Force Sensing . 109 6.3.3 Load Response . 110 6.3.4 Grasping Analysis . 111 6.3.5 Robustness . 111 6.3.6 Weight . 112 6.3.7 FFP Evaluation - R1 hand . 112 7 The iCub Plastic Hand 115 7.0.1 Lessons Learnt from the R1 Hand . 115 7.0.2 The iCub Hand . 116 xiv Contents 7.1 Conceptual Design . 117 7.1.1 Kinematics . 118 7.1.2 Overall Design . ..