DEVELOPMENT AND IMPLEMENTATION OF A CATEGORIZATION MODEL FOR THE EXOSKELETONS BASED ON THEIR DESIGN

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INSTITUTO TECNOL ´ OGICO Y DE ESTUDIOS SUPERIORES DE MONTERREY

CAMPUS CIUDAD DE M ´EXICO SCHOOL OF ENGINEERING AND SCIENCES

DEVELOPMENT AND IMPLEMENTATION OF A CATEGORIZATION MODEL FOR THE EXOSKELETONS BASED ON THEIR DESIGN

CHARACTERISTICS AND PRACTICAL PROJECTS

A DISSERTATION PRESENTED BY

JAVIER ALBERTO DE LA TEJERA-DE LA PE ˜ NA

SUBMITTED TO THE

SCHOOL OF ENGINEERING AND SCIENCES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR THE DEGREE OF

MASTER OF SCIENCE IN ENGINEERING SCIENCES

CIUDAD DE M ´EXICO, M ´EXICO , JUN 2020

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All Rights reserved

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Acknowledgements

I want to thank all those who were by my side throughout the development of this research project, as well as those whose work and advice allowed me to realize this work.

To my advisor, PhD. Mart´ın Rogelio Bustamante Bello, who not only believed in me, but also guided me throughout the research process even in moments and ways beyond the fulfillment of duty.

Thanks for their support and aid to:

• PhD. Ricardo Ambrosio Ram´ırez Mendoza

• PhD. Arturo Molina Guti´errez

• PhD. Javier Izquierdo Reyes

• PhD. Sergio Alberto Navarro Tuch

• PhD. Edgar Omar L´opez Caudana

• M.Sc. Luis Alberto Curiel Ram´ırez

• M.Sc. Ariel Alejandro L´opez Aguilar

• M.Sc. Rolando Bautista Montesano

• Prof. Jos´e Luis Pablos Hach

• Eng. Kevin Rogers C´ardenas Mogoll´on

• Eng. Scarlett Jazm´ın Z´u˜niga Ram´ırez

• Eng. Mar´ıa Fernanda Hern´andez Mondrag´on

• Eng. Rafael Tinajero Ayala Gonz´alez Arce

• Eng. Andr´es G´omez Esquivel

• Eng. Alejandro Garma Oehmichen

• Eng. Brayan Camilo Castro Sanchez

• Eng. Fitzgerald Leonard Gerardo Toro Quitian

• Eng. Juan Gasc´on Repull´es

• Eng. Eloi Pascual Belda

• Eng. Maximiliano Castellanos Andrade

• Eng. Jos´e Mar´ıa Flores Raigoitia

Thanks to the Instituto Tecnol´ogico y de Estudios Superiores de Monterrey Campus Ciudad de M´exico for giving me access to the facilities and resources necessary to carry out the project.

Thanks to the Centro de Investigaci´on en Microsistemas y Biodise˜no (CIMB) to provide the resources necessary for the realization of this work.

Thanks to the support of Novus “Factory 4.0 Application as a tool for teaching-learning of applied engineering”, coordinated by Dr. Jesús Vicente González Sosa, Tecnológico de Monterrey, on the production of this work.

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Dedication

To my parents, siblings, grandmother, and all my family,

Thank you for all your confidence, support, patience and encouragement. For helping and supporting me when I decided to take this path in my life, I am most grateful with you.

*****

To my life friends, Pablo, Carlos, Uriel, Gerardo, Montserrat, Ana, Ricardo, Andr´es, Abraham, Jorge, M´onica, Fernando and Raul,

Thank you for being with me in this time, while helping me to complete this stage of my life.

*****

To PhD. Mart´ın Rogelio Bustamante Bello who presented me this opportunity and guided me until the end of it, for being my advisor and changing the perspective of my life.

*****

To my lab colleagues and friends PhD. Sergio A. Navarro Tuch, PhD. Javier Izquierdo Reyes, MSc. Luis Alberto Curiel Ram´ırez, MSc. Ariel Alejandro L´opez Aguilar and MSc. Rolando Bautista Montesano, whose knowledge, perspective, and guidance led me to my research and a

day-to-day learning.

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Prologue

First of all, thank you for reading this master thesis work. Second, the reading of this thesis may appear strange at first sight. The structure followed in this thesis is based on the chronological order of events, since the beginning of the project and where it is heading to. This work is part of the ExoDUX (Exoskeletons Design and User Experience) project. All this work started with the development of exoskeletons and, the intention, was to keep up with these developments.

However, life presents opportunities that one must take, this project is an example of it.

There was an idea, to develop exoskeletons to help people who suffer from certain health problems, during the lecture of this document, the introduction gives this general idea. In the middle of the road followed, when I was starting to write an article about one of the exoskeletons developed, I found that many people are, currently, working with exoskeletons. But from all those people, there was just a small panorama of the exoskeletons’ definition. As in any other research area, it is necessary to compile the information needed to understand certain topics of the area, but in this case, such information was neither really known, nor complete. Also, this information can help to accelerate the development of exoskeletons.

This is the reason that this thesis is talking about two different topics. All this work was done during the masters stay and, even that there are two different topics, the research area is the same.

This document intends to justify the union of these topics, but more than that, it is all part of the same work.

I hope you enjoy reading this thesis and wakes an interest for the exoskeletons, just like it did with me.

Javier Alberto de la Tejera-de la Pe˜na

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Abstract

The exoskeletons are the future of the humankind. The humankind is in a constant pursuit of improve- ment for themselves, both physically and mentally. The human body has physical constraints in which no physical training can surpass, but our ingenious and imagination are making this possible. Several decades ago the first developments started, and nowadays, these developments, plus the improvements, are imperative for the humans in the following decades. The exoskeletons can assist or rehabilitate a person, leading this personalized technology to depend on the needs and abilities that each user has. The exoskeletons have a wide spectrum of opportunities in their design, due to the variety of situations in which a person needs an augmentation of their physical performance, thus the diversity of projects. An exoskeleton for sarcopenia was made for assisting the elderly who require help to perform their daily activities, and tested with electromyography (EMG) to analyze its functionality. On the other hand, an exoskeleton made for rehabilitation, machining the exoskeleton gives us a testing platform for other kinds of projects. Through the development of different exoskeletons and projects related to them, an opportunity area was found to formalize the exoskeletons’ topic, creating a model for the categorization of all the exoskeletons using their design characteristics and a further analysis for recommendations in their design. Besides, in this work are proposed tools, based on the design characteristics of exoskeletons, for the optimization of the exoskeleton design process.

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List of Tables

4.1 Stakeholders analysis . . . 27

5.1 Summation of the total power used in each test by each muscle. . . 68

5.2 Results of the paired sample t-test between each pair of muscles . . . 70

5.3 Summary of the t-tests results. . . 71

5.4 Classification of exoskeletons from 2014 to 2019 (PART I) . . . 73

5.5 Classification of exoskeletons from 2014 to 2019 (PART II) . . . 74

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List of Figures

1.1 Layout of this work presented in this document. . . 5 2.1 Exoskeletons from the XIX century, created by Nicholas Yagn and patented in 1889 on the

left (A), in 1890 on the center (B) and Kelley’s exoskeleton on the right (C) from the XX century, called Pedomotor, which aid in the activities of walking and running [Yagn, 1889;

Yagn, 1890] [Kelley, 1919] . . . 7 2.2 Exoskeleton created by General Electric in 1965, named ”Hardiman I”, was one of the

pioneers of the exoskeletons powered by electrical and hydraulic actuators on the left [Makinson, 1971]. Exoskeleton created by Neil J. Mizen and patented in 1969 on the right, created using servo-motors and using mechanisms to distribute the energy for the movement [Mizen, 1969] . . . 8 2.3 Exoskeleton created by R. Radulovic for the arm (left (A)) [Radulovic et al., 1980], ex-

oskeleton created by Jean-Louis Chareire created as a leg-propulsion device (center (B)) [Chareire, 1989] and an exoskeleton made by Dick and Edwards as a human bipedal device (right (C)) [Dick and Edwards, 1991], the left most exoskeleton was powered by pneumatic systems, while the center and right most were powered by mechanical systems . 9 2.4 Exoskeleton created by Kenneth Boldt, made to be used in the full body, while using

hydraulic systems and controlled by a microprocessor [Boldt, 1994] . . . 10 2.5 BLEEX project (left) showing the final device with an external load [Zoss et al., 2005]

and the quasi-passive exoskeleton (right) while also carrying an external load [Walsh et al., 2007] . . . 11 2.6 The ”ARMin III” exoskeleton made for the rehabilitation of the shoulder (on the left) and

the Wrist exoskeleton prototype (WEP) (on the right). . . 12 3.1 The three full body exoskeletons described in this section were found on patents, Bujold’s

exoskeleton on the left, Maddry’s exoskeleton in the center and the Guardian® XO®

exoskeleton on the right. . . 15 3.2 The WAKE-up exoskeleton alpha version on the left and Zhang’s exoskeleton on the cen-

ter, showing the full structure to use it and the H1 exoskeleton on the right. . . 17 3.3 The AIRGAIT exoskeleton on the left and the INDEGO exoskeleton on the right . . . 18

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3.4 The CLEVERarm rehabilitation exoskeleton on the left and the AIRFRAME assistance

exoskeleton for industrial use on the right. . . 19

3.5 The soft robotic glove for assistance and rehabilitation, created by Wyss Institute and the School of Engineering and Applied Sciences at Harvard . . . 20

3.6 The pneumatic brace with extension assist made for the knee in patients with osteoarthritis (on the left) and the AssistOn-Ankle exoskeleton (on the right). . . 21

3.7 Heo’s classification for hand exoskeletons . . . 22

4.1 Percentage of the people who have been diagnosed with sarcopenia . . . 28

4.2 Percentage of the people who do any exercise . . . 28

4.3 From the previous answer, the percentage of the different activities performed . . . 29

4.4 The decision matrix comparing the three preliminary concepts . . . 30

4.5 Block diagram to control the exoskeleton through EMG . . . 31

4.6 General Structure of the ICARUS exoskeleton in CAD . . . 32

4.7 ICARUS exoskeleton model . . . 32

4.8 General Structure of the second iteration of the ICARUS exoskeleton in CAD . . . 33

4.9 Basic design of the dual channel EMG amplification system . . . 34

4.10 Final prototype of the ICARUS exoskeleton . . . 34

4.11 Methodology followed on the Exoskeleton Manufacturing Project. . . 35

4.12 Pieces design in a CAD software for their future assembly in an exoskeleton . . . 36

4.13 Final CAD model structure of a rehabilitation exoskeleton . . . 37

4.14 Original and modified piece in the bending stress test. . . 37

4.15 Original and modified piece in the deformation test. . . 38

4.16 A) Piece machined in a CNC machine, B) Gears printed in 3D and C) Piece manufactured manually . . . 38

4.17 Final prototype of the rehabilitation exoskeleton . . . 39

4.18 Activities which represent a greater trouble for performing, according with the surveys made to possible users. . . 41

4.19 TRIZ diagram showing the parameters analyzed. . . 42

4.20 The three concepts for the HERMES design, a mechanical spring based exo-suit (A), a mechanical double spring based exo-suit (B) and a soft robotic design exo-suit (C). . . 43

4.21 Unpowered exoskeleton design, created by Carnegie Mellon University and North Car- olina State University [Collins et al., 2015]. . . 45

4.22 HERMES exo-suit being worn on the right lower limb. . . 46

4.23 (A) Frontal view of the pulley adjustment straps between the segments of the knee, (B) Lateral view of the pulley adjustment straps between the segment of the knee, (C) Lateral view of the foot adjustment, (D) Frontal view of the foot adjustment and (E) Lateral view of the mechanism attached to the hip. . . 47

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exo-suit. . . 49

4.25 Raw data obtained from one of the subject, showing the 8 muscles on which the electrodes were placed. . . 50

4.26 Data previously plotted with a digital band pass filter. . . 51

4.27 Plots with the previous data already normalized with the z-score. . . 52

4.28 Final plots of the data with the RMS filter already used. . . 53

4.29 State of the art timeline of 75 exoskeletons. . . 58

4.30 Model proposal for the General Categorization of the Exoskeletons. . . 62

5.1 Graphical stages of the EMG signal processing on a single muscle. . . 65

5.2 Graphs obtained from the raw data of the fifth test with the HERMES exo-suit . . . 66

5.3 Power/time graphs of the fifth test. . . 66

5.4 Graphs obtained from the raw data of the fourteenth test with the HERMES exo-suit . . . 67

5.5 Power/time graphs of the fourteenth test. . . 67

5.6 Q-Q Plots of each muscle with the 24 results compiled. . . 69

5.7 Statistics of the body part focused category. . . 75

5.8 Statistics of the structure category. . . 77

5.9 Statistics of the action category. . . 77

5.10 Statistics of the powered technology category. . . 78

5.11 Statistics of the purpose category. . . 79

5.12 Statistics of the application area category. . . 80

5.13 Table comparing the different classes of the exoskeletons, using the categorization model, and giving a level of recommendation for each comparative. . . 81

5.14 Decision tree showing all the categories of the categorization model in several stages for developing an exoskeleton. . . 83

A.1 QFD Analysis . . . 99

A.2 Safety Analysis . . . 100

A.3 Basic design of the dual channel EMG amplification system . . . 101

A.4 PCB design for the four EMG channels of a single limb . . . 102

A.5 ICARUS exoskeleton poster . . . 103

B.1 Poster of the Rehabilitation Exoskeleton Manufacturing . . . 107

C.1 Safety Analysis of the HERMES exo-suit. . . 108

C.2 Poster of the HERMES project until the development of the prototype. . . 109

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Chapter 1

Introduction

The exoskeletons are the future of the humankind. The humankind is in a constant pursuit of improve- ment for themselves. However, the physical capabilities of a human have a limit, in which no training, resistance or will power can exceed. Given that the human body has certain physical limits, a new method for improving the human body has to be done. The exoskeletons are a great solution for the improve- ment of humankind because they can assist a user to complete a task while enhancing its performance.

Nevertheless, the exoskeletons are an extensive topic, and, to understand the topic, a formal definition is mandatory.

The formal definition of the exoskeletons is the following, the exoskeletons are devices that augment the performance of a wearer, which are essentially anthropomorphic, also are used and worn by a user, for whom was designed [Herr, 2009]. The objective of the exoskeletons is to augment the human performance, for which the human augmentation refers to the enhancement of human capabilities and capacity through the use of technology and science [Cearley et al., 2019].

The exoskeletons have many designs, due to the wide spectrum of cases in which can be used. Each exoskeleton is different from all the others, providing a specific help to a specific user. Even when two exoskeletons are designed to aid a specific body part and a specific user, the design method, powered technology, action, and structure can be different, thus the spectrum of possibilities for exoskeletons.

Just to clarify, this is not the only research field in which the term exoskeleton is used, in other research fields the exoskeletons have a different definition and are used for protection as a barrier [Andersen, 2009].

In this work, the exoskeletons that are only to be covered are for augmenting the physical performance of humans.

Coming back to our main topic, the exoskeletons have been in development since the XIX century, in which one of the oldest registers of exoskeletons dates. This register is a patent from the United States, but the device was created in the former Russian Empire by Nicholas Yagn. The way of describing the device was as an ”Apparatus for Facilitating Walking, Running and Jumping” and another register from the same creator ”Apparatus for Facilitating Walking and Running” [Yagn, 1890; Yagn, 1889].

As previously seen, the exoskeleton development has occurred since the XIX century, and, is far

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from over. In the future, the use of the exoskeletons will be imperative for the humankind, not only for rehabilitation of certain pathologies, contusions, degeneracy or malformations; but also, for assisting in the workplace, when it has physical work, or in the home for different tasks, such as climbing the stairs, in order to avoid the fatigue. This is corroborated by the global research and advisory firm, Gartner, stating that the human augmentation is one of the top strategic technology trends for the future [Cearley et al., 2019]; one of the ways of achieving the human augmentation, is with the use of exoskeletons.

This work consists of a formal definition to classify all the different exoskeletons by doing a categorization of all the general sub-sections that the exoskeletons have, done with the analysis of an extensive state of the art of different exoskeletons, the development of an exoskeleton testing platform and, also, the development of a soft exoskeleton made for assisting the elderly with a state of decreased skeletal muscle mass and skeletal muscle strength, also called sarcopenia [Akishita et al., 2018].

In the modern era, the world population is aging due to different factors. From 1990 to 2013, the global share of older people (people aged 60 years or over) increased from 9.2 % to 11.7 %, respectively [United Nations Department of Economic and Social Affairs Population Division, 2013]. These numbers reflect the evolution of more than two decades of the population’s age, but the last United Nations’ report describes that this number has increased. According with the United Nations, the people aged 65 years or over in the 2019 were 703 million persons, being a 9 % of all the population (excluding all the people aged less than 65 years, in contrast with the 2013 report) and projecting a rise to 1.5 billion or 16 % of the population by 2050 [UN DESA’s Population Division, 2019], in other words, one in every six people in the world will be 65 years or older.

Moreover, in terms of countries, only in the United States in 2017, there were approximately 49.2 million people aged 65 years old and over; projecting that in 2060 there will be around 98 million [The Administration for Community Living, 2018]. An alarming scenario is currently in front of us, due to the aging process of the population and its expected growth, with all the complications, pathologies and degeneration which impacts directly in this population sector. This scenario can be directly damped by the research and development of technology (R&D) to assist such population in each of the health issues that may affect them; it is imperative to act in favor to avoid this scenario before the level of urgency surpasses the available resources.

As a consequence of the world population aging, sarcopenia is one of the main concerns for the future of health, because it is one of the main complications that the elderly face. Likewise, the sarcopenia is a high burden for the economy of a country, due to the high healthcare costs.

The sarcopenia is a declining state of muscle mass, strength, and physical function; but these declines are due to sedentary-lifestyles, multimorbidity, and adiposity [Shaw et al., 2017]. Among the most important factors for the development of sarcopenia are the nutrition and physical activity. Specifically, the resistance training, in physical activity, is more beneficial for muscle strength and functionality rather than light physical activity. Nevertheless, both are beneficial, due to the circumstances, to slow the development of sarcopenia [Shaw et al., 2017].

In 2000, in the United States was estimated that the sarcopenia had a healthcare cost of $18.5 billion

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Introduction 3 dollars, representing about 1.5 % of total healthcare expenditures for that year [Janssen et al., 2004]. As previously seen, the population has been increasing, not only all the population, but also the people aged 65 years or over; thus, the cases of sarcopenia had been increasing too. The sarcopenia is estimated to affect about 30 % of people over 60 years old and more than 50 % of people over 80 years, as calculated in 1998 [Baumgartner et al., 1998].

1.1 Motivation

The presented previous costs represent only the direct expenditures of the sarcopenia. Nevertheless, as mentioned by Beaudart, these costs are not the real ones, because sarcopenia is associated with multi- ple comorbidities [Beaudart et al., 2014], and may have an effect on obesity [BAUMGARTNER, 2006], type II diabetes mellitus [Castaneda et al., 2000] and osteoporosis [Gillette-Guyonnet et al., 2000]. Thus, Janssen’s estimation is missing all the indirect expenditures, for which the estimation would rise. There- fore, sarcopenia is a high-cost health issue that may arise due to demographic circumstances in the near future, thus the importance of damping it.

Thence, this health issue presents a big area of opportunity for the research and development of technologies whose intention is damping the sarcopenia by the use of exoskeletons. Although, this presents a bigger picture of the exoskeletons’ area, laying the foundation of the exoskeletons, by creating different designs and experimenting with them.

The creation of different exoskeletons has a background, motivated by the search for solving different health issues. One person cannot create all the exoskeletons to solve the different health issues, but creating tools which its use optimize their designing process, is a step forward to solve these health issues.

1.2 Problem Statement and Context

As previously mentioned, the development of sarcopenia could be decreased with physical activity [Shaw et al., 2017]. Unfortunately, the people who experience sarcopenia have an advanced age which limits the physical activities able to perform. Thus, the need to develop technological solutions to solve this problem. Such as exoskeletons, to solve the problem.

The development of exoskeletons has brought a new revolution in the wearables market. Similar to the modern era with the fourth industrial revolution on how it is altering the way we live, work, and relate to others [Schwab, 2015]. Nowadays, new technologies are changing the way we see and interact with the world.

The exoskeletons are a research area that has great importance for the future. The exoskeletons are not limited to decrease the development of sarcopenia, but, it is just limited to the imagination of the researchers and people who develop them, to aid people who might need one.

After designing an exoskeleton for the sarcopenia, a lack of information regarding the basics of the exoskeletons was found. In other words, the exoskeletons area has not been formalized yet, which means

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that the foundations of this area haven’t been set still, creating an opportunity to research this aspect.

Contributing to the development of one of the technologies areas that will require the humankind in the near future.

1.3 Research Question

With the current exoskeleton developments, which should be the ideal categorization to properly classify all the exoskeletons in existence, based on their design characteristics?

1.4 Solution Overview

The path to answer the research question has many alternatives, herein is described as one of those alternatives. First, the development of exoskeletons is imperative to understand, from the practical point of view, these devices. Working, designing, using in experiments, and reading the state of the art of the exoskeletons, is an ideal way to understand and get experience from them. Once this stage is completed, the design characteristics must be analyzed, to find the sections in common, to classify all the exoskeletons. Having the design characteristics, the categorization can be designed; with further examples of how it should work with any kind of exoskeleton.

1.4.1 General Objective

• Create an ideal categorization to classify all the exoskeletons in existence, by using their design characteristics, from the completion of exoskeletons’ related projects of different sections to understand correctly the subject.

1.4.2 Particular Objectives

• Read and analyze the state of the art of the exoskeletons to understand the subject and create sections in common of different exoskeletons.

• Develop a project which includes the creation of an exoskeleton focused on people who have a degeneration and test its functionality.

• Manufacture an exoskeleton focused for rehabilitation, to use it as a platform testing for any future project.

• Once analyzed several different exoskeletons, design a categorization to classify all the exoskeletons in existence.

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Introduction 5

1.5 Layout

This document is divided into several chapters, each chapter gives a guideline to the development of this work. This work talks about the development of the exoskeletons, and from that development, the possible classification of the exoskeletons. Chapter 2 is mainly focused on the background necessary to understand this document, setting the beginnings of the exoskeletons. Chapter 3 is focused on the state of the art, but is separated into two main sections, the state of the art of the exoskeletons and the state of the art of exoskeletons’ classifications. Following this same structure, Chapter 4 firstly talks about the development of initial projects regarding the exoskeletons. The initial projects are separated into three different projects, ICARUS exoskeleton, Exoskeleton Manufacturing Project, and HERMES exoskeleton. The second part of Chapter 4 is focused on the classification of the exoskeletons, providing the identification of their main design characteristic areas and giving a model to classify the exoskeletons. The results are in Chapter 5, starting with the results from an experiment of using the HERMES exoskeleton. The second part of Chapter 5 describes the results of the classification with the model proposed. Also, in Chapter 5, all the results presented will be discussed. Finally, in Chapter 6 will be presented the conclusions and future work of this project. In the Appendixes, further details could be found for important parts of each project.

Figure 1.1: Layout of this work presented in this document.

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Background

This chapter describes the development of the exoskeletons since their first beginnings. In the beginning, there are presented some useful definitions to understand this topic and do not confuse it with similar devices. Later on, describing the exoskeleton developments are combined with the breakthrough of technology through the decades and new ideas that were taken from the influence of science fiction and imagination. The development and design of the exoskeletons started to change and adapt to the modern technology of that time. The development of exoskeletons is described until 2014, in which the state-of- the-art begins, analyzing the different exoskeletons that had been developed.

2.1 Important definitions

To properly understand this document, it is recommended that the reader understand the following definitions:

• Orthosis: externally applied device used to modify the structural and functional characteristics of the neuro-muscular and skeletal systems. [ISO 8549-1:1989, 1989]

• Orthoses: plural of orthosis.

• Prosthesis: externally applied device used to replace wholly, or in part, an absent or deficient limb segment. [ISO 8549-1:1989, 1989]

• Exoskeleton: device that augments the performance of an able-bodied wearer. [Herr, 2009]

• Exo-suit: exoskeleton with a soft structure.

These definitions are given to the reader to avoid any confusion with similar devices to the exoskeletons. All the exoskeletons are orthoses, however, they are powered orthoses. Also, do not confuse a prosthesis with an orthosis. In summary, the prosthesis replace a limb segment of the body, while the orthoses, are applied to a body part.

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Research development 7

2.2 Development of exoskeletons

The exoskeletons are not creations of the last few decades, as it could be thought. As previously mentioned, two of the firsts exoskeletons are traced to the XIX century, when the term exoskeleton had not been devised yet. The registers of the, nowadays called, exoskeletons were described as an ”apparatus for facilitating” certain activities; created in the former Russian Empire by Nicholas Yagn, these two devices helped the user to perform certain activities. Both devices were similar in terms of purpose, because one of the devices facilitated the user to walk and run [Yagn, 1889], while the other one facilitated the user to walk, run and jump [Yagn, 1890], thus, both devices having the purpose of assisting the user.

Figure 2.1: Exoskeletons from the XIX century, created by Nicholas Yagn and patented in 1889 on the left (A), in 1890 on the center (B) and Kelley’s exoskeleton on the right (C) from the XX century, called Pedomotor, which aid in the activities of walking and running [Yagn, 1889; Yagn, 1890] [Kelley, 1919]

These exoskeletons are some of the most antique designs of devices that augmented the human performance while wearing them. The operation of both devices was merely mechanical, using only springs and the design for the redistribution of the energy from the user to the movement, this type of actuation being passive. The objective of both devices was to decrease the fatigue of a person, while the person was wearing the device and performing one of the activities for which were created. These two devices are shown in Figure 2.1 (A & B).

These designs are part of the first precedent of the exoskeletons. Analyzing the designs, it’s possible to observe how the energy of other systems can be used for augmenting the physical performance of a person. Moreover, these designs set the starting point of the human augmentation through external

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systems. Back in the XIX century, the most common external actuators available were the mechanical systems. Nevertheless, the idea of a device that augments the physical performance of a user while wearing it was created. And, that idea will continue its evolution through the decades and centuries.

Three decades after the patents of Yagn, in 1919, another patent for a device which augmented the physical performance was made, called a ”Pedomotor”. It was created by L. C. Kelley, the purpose of this device was to assist walking, following the same passive action principle as Yagn. This device facilitated walking and running, while relieving of strain and fatigue the muscles used [Kelley, 1919]. In comparison, both designs, Yagn’s and Kelley’s, presented certain advantages and disadvantages.

For instance, Yagn’s design had more applications for his device but with a bigger sized device as seen in Figure 2.1. On the other hand, Kelley’s design sacrificed some applications, while reducing the device’s size, as seen in Figure 2.1 (C). This reduction in size set one of the first evolutions for the exoskeletons guiding them to the new eras.

As in any research area, there are periods in which there is not a constant development until a ”development boom” appears and more people are attracted to it. Once the origins of the exoskeletons are set, we can move through the following decades bringing only the most notorious exoskeletons developed to have their history and development evolution.

Figure 2.2: Exoskeleton created by General Electric in 1965, named ”Hardiman I”, was one of the pioneers of the exoskeletons powered by electrical and hydraulic actuators on the left [Makinson, 1971].

Exoskeleton created by Neil J. Mizen and patented in 1969 on the right, created using servo-motors and using mechanisms to distribute the energy for the movement [Mizen, 1969]

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Research development 9 This brings us to the 1960s, in which other exoskeletons’ development was on a breach. One of these exoskeletons was initiated in 1965 by General Electric, the US Army and Navy, it was named ”Hardiman I” and is pictured in Figure 2.2. This exoskeleton was a full-body powered device designed to augment the strength and endurance of the user by applying hydraulic and electrical systems [Makinson, 1971].

The ”Hardiman I” was developed to demonstrate the potential of a powered exoskeleton, that can be used to load and unload cargo [Makinson, 1971]. This exoskeleton is one of the most important of that decade, because it set the precedent of using different actuators in the exoskeletons in contrast with the previous exoskeletons used, which were mere mechanical, calling this type of actuation ”active”.

What’s more, the ”Hardiman I” was not a unique exoskeleton at that time. Another full-body powered exoskeleton was developed and then patented in 1969. This exoskeleton used servo-motors to power the movements of the wearer, followed by mechanisms to redistribute the movement [Mizen, 1969]. This device was called a ”powered exoskeletal device that functions as a ’Man Amplifier’”, which describes how the term exoskeleton was in the works and the formal term had not been devised yet. In Figure 2.2 is shown a picture of the full-body exoskeleton created by Mizen.

These two previous exoskeletons show how the developments of exoskeletons were in the works, the evolution of the design of exoskeletons and new actuators used, due to the time of their design.

In the following decades, the advances in science and technology brought the development of different research areas, the exoskeletons benefit from these advances. So that in the ’70s, ’80s, and ’90s decades,

Figure 2.3: Exoskeleton created by R. Radulovic for the arm (left (A)) [Radulovic et al., 1980], exoskeleton created by Jean-Louis Chareire created as a leg-propulsion device (center (B)) [Chareire, 1989] and an exoskeleton made by Dick and Edwards as a human bipedal device (right (C)) [Dick and Edwards, 1991], the left most exoskeleton was powered by pneumatic systems, while the center and right most were powered by mechanical systems

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the diversification of the exoskeletons spread for many specific uses. In the late ’70s and early ’80s, an exoskeleton focused on the arm was developed, consisting of a mobile arm support prototype powered by a pneumatic system, aiding the shoulder and elbow movement; in some cases, augmenting the muscular strength [Radulovic et al., 1980]. Figure 2.3 (A) portraits the design of Radulovic’s exoskeleton design.

Later on, in the late ’80s, a device was developed and patented by Jean-Louis Chareire. The ”Me- chanical Leg-Propulsion Assistance Device” can be compared with Yagn’s, due to the purposes of the devices. Chareire’s device was focused to give a leg-propulsion assistance, using mechanical systems and the initial movement of the wearer [Chareire, 1989], as portraited in Figure 2.3 (B).

Moreover, at the beginning of the 90’s decade, another exoskeleton was invented, called the ”Human Bipedal Locomotion Device”. This exoskeleton was focused to be worn in the full-body; however, it only was assisting the lower limbs. Propelled by mechanical systems, this device was designed for walking and running, allowing ”large steps” or ”having trampoline-like jumps” [Dick and Edwards, 1991]. This exoskeleton is shown in Figure 2.3 (C) and demonstrates a different approach of an exoskeleton compared with the ones we have already talked about.

From 1889 to 1991, these were one of the most remarkable exoskeletons at their respective times.

Figure 2.4: Exoskeleton created by Kenneth Boldt, made to be used in the full body, while using hydraulic systems and controlled by a microprocessor [Boldt, 1994]

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Research development 11 Nevertheless, the developments in science and technology from 1889 cannot be compared with the developments in 1991, taking big steps towards the advances in science and technology, with a further use of those advances in different research areas. Using the exoskeleton’s area as an example, at their beginnings, the exoskeletons were not even called with that term, and were developed with their respective technological constraints. Thus, the development of exoskeletons had a rough beginning, and nowadays are stronger than ever. With our current technological constraints in mind, we can design and develop better exoskeletons, suiting them to our current needs and prepare ourselves for a daily-use of them.

Following over the years, in the mid-’90s, another full-body exoskeleton was developed, using hydraulic systems for the movement and a microprocessor to control the actuators. Classified as an active exoskeleton, this design is shown in Figure 2.4. In 1994, this design was patented, acknowledging this design to advances in science and technology. Boldt’s exoskeleton demonstrates the incorporation of the state-of-the-art technology, at their respective time.

With the previous exoskeleton we close the XX century, having already two different centuries in which the exoskeletons existed. Moving on to the XXI century, there are many more designs to consider, however, this work will only present a review of several exoskeletons between 2014 and 2020.

In the XXI century, due to the advances in computers, the exoskeletons could be advanced in a parallel way. Among several exoskeletons, some important ones will be included. These exoskeletons are the

Figure 2.5: BLEEX project (left) showing the final device with an external load [Zoss et al., 2005] and the quasi-passive exoskeleton (right) while also carrying an external load [Walsh et al., 2007]

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Berkeley Lower Extremity Exoskeleton (BLEEX) and the ”quasi-passive exoskeleton” created by Conor Walsh. The BLEEX project was a lower limb exoskeleton capable of carrying its weight and an external load, with hydraulic actuators [Zoss et al., 2005]. In comparison, the ”quasi-passive exoskeleton” also was created to carrying an external load, however, the design of this exoskeleton transferred the payload through mechanical systems [Walsh et al., 2007]. Both exoskeletons designed for assisting the user in carrying an external load and are shown in Figure 2.5, on the left side is the BLEEX project and, on the right side, Walsh’s exoskeleton.

The development of exoskeletons is not limited to devices focused on the full body or the lower body, the exoskeletons can be designed to be attached to any segment of the body. Moreover, the continuous development of exoskeletons brought more applications to the devices and another purpose, now the exoskeletons can be designed for rehabilitating patients. This is the case of the ”ARMin III”, created in 2008, an arm therapy exoskeleton to rehabilitate the shoulder, which with an additional module, provided aid to the lower arm and the wrist, this exoskeleton is showed in (Figure 2.6). [Nef et al., 2009]

A couple of years later, in 2010, another exoskeleton was designed for the wrist. This exoskeleton explores the possibility to use a surface electromyography (EMG) signal to control the torque in the direction of motion of the wrist. The wrist exoskeleton prototype (WEP) was made to be used as an assistive device for the wrist and controlled by EMG attached to the arm of the user. This prototype is presented on Figure 2.6. [Khokhar et al., 2010]

Figure 2.6: The ”ARMin III” exoskeleton made for the rehabilitation of the shoulder (on the left) and the Wrist exoskeleton prototype (WEP) (on the right).

This chapter intended to present the developments of the exoskeletons from their beginning until the last few years, when the current state of the art begins. The developments of the exoskeletons have been limited to the available technology at the time they were created. Since the end of the XX century and beginning of the XXI century, the advances in technology have led the efforts to the beginning of the

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Research development 13 digital era, in which the exoskeletons have taken advantage of their designs and developments.

This set the precedent for the exoskeletons, but now it’s time for the current development of the exoskeletons in the state of the art. Thus, the following chapter will be centered on these current developments. Nevertheless, it is important to remark that this work is about the classification of the exoskeletons, thus, the most recent exoskeleton classifications will be presented. Separating the following chapter in two different sections.

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State of the Art

This chapter is centered on the state of the art of the exoskeletons. In this sense, this chapter is divided into two sections. The first part presents the exoskeletons from the last few years, specifically from 2014 to 2020, while dividing them in the parts on which are focused to help. In this part, just a few exoskeletons will be named, because the work in this area has been long and productive. The second part of this chapter is going to be for the analysis of the current exoskeleton’s classifications, describing the few classification in existence.

3.1 Modern exoskeletons (2014-2020)

The exoskeletons presented in this first section are focused on several parts of the body and have many types of actuation, giving them a broader area of application, in contrast with the exoskeletons of the past.

3.1.1 Full body Exoskeletons

In the state of the art, there are few exoskeletons focused on the full body. This is due to the applications in which the exoskeleton can be useful because designers/inventors prefer to develop an exoskeleton for a specific task, rather than developing complex exoskeletons to be used in different tasks.

The first full-body exoskeleton was developed by Alain Bujold and patented in 2016. This is an exoskeleton to be worn by a user and to transfer the load from the head, neck, and/or torso of the user to the ground. The patent describes a passive exoskeleton in three interconnected sections and, these sections, comprise members that form the structure. According to Bujold, the exoskeleton transfer partially to the ground the load carried by the head, neck, and/or torso, reducing the load supported by the user [Bujold et al., 2016]. This exoskeleton is presented in Figure 3.1 A.

The second full-body exoskeleton was developed by Connor J. Maddry and patented in 2019. This is a pneumatic and electromyographic exoskeleton, designed with a rigid frame. This exoskeleton is controlled by electromyographic (EMG) sensors and then the pneumatic actuators are activated. According to Maddry, the exoskeleton does not require the connection to a power grid, enhancing the outcomes and

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State of the Art 15 applications of the same in real case scenarios [Maddry, 2019]. This exoskeleton is presented in Figure 3.1 B.

The last full-body exoskeleton spent many years in development and in the late 2019 an alpha version was released to certain members of the company. This exoskeleton is the Guardian® XO®, an exoskeleton that augments the strength of the user enabling up to 200 pounds and having 24 degrees of freedom (DOF) [Martindale, 2020]. According to the manufacturing company of this exoskeleton, Sarcos, this exoskeleton relieves of fatigue or strain to the users and can be applied in different scenarios in which a regular worker needs to lift and transport heavy load. The Guardian® XO® exoskeleton is presented in Figure 3.1 C.

Figure 3.1: The three full body exoskeletons described in this section were found on patents, Bujold’s exoskeleton on the left, Maddry’s exoskeleton in the center and the Guardian® XO® exoskeleton on the right.

Furthermore, we can see that the development of full-body exoskeletons is not a trend nowadays.

For instance, at the beginning of exoskeletons, the common sense would give us a trend to have a full- body exoskeleton, due also by the name given. However, the reality is different. The exoskeletons are developed, nowadays, for different health problems or to avoid health problems, thus the necessity of having exoskeletons focused on a certain body part. Nevertheless, the trend of thoughts in the modern world still is with the full-body exoskeleton, because it is the easiest way to imagine a new technology, mainly talking about the older generations.

3.1.2 Lower body Exoskeletons

Nowadays, the lower body exoskeletons are the most common. There are exoskeletons for the complete lower body (hip and both lower limbs), for only one lower limb, for knee, for ankle, among others. In this section, we will only discuss the exoskeletons that are focused for the complete lower body, both

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lower limbs or one lower limb, due to the classification, any other exoskeleton for a specific joint or limb (referring to only one segment of the body), will be discussed in section 3.1.4.

To know the reason that the lower body exoskeletons are the most common, we need to focus on the problems or disabilities for which are made. For instance, the cerebral palsy (CP) as a motor disability [Rossi et al., 2014], unilateral lower limb movement disorders due to hemiplegia, apoplexy or accidents [Zhang et al., 2016], or movement disability caused by neurological pathologies such as spinal cord injury (SCI), stroke or traumatic brain injury [Dao et al., 2017; Bortole et al., 2013], also, to assist leg mobility [Dalley et al., 2018]. All these disabilities have a direct impact on the people suffering from them, the lower body exoskeletons are the most common due to the necessity of these people to have mobility and do not spend their entire lives in a wheelchair or a bed.

Some examples of lower limb exoskeletons are the following:

• The ”WAKE-up” exoskeleton, made by Rossi, Patan`e, Del Sette, and Cappa, is targeted for patients aged 5-8 years and is focused to assist the drop foot gait working, due to cerebral palsy (CP) as a motor disability. This exoskeleton was not only made for cerebral palsy, but the locomotion rehabilitation of pediatric subjects with neurological diseases. This device is a bi-articular assisted orthosis consisting of two modules that can be used together or alone, which can be seen in Figure 3.2 A. The working principle of this device is the torque transmission in the actuation system, which is based on a series elastic actuator (SEA) allowing variations of joint stiffness for ankle rotations.

[Rossi et al., 2014]

• Zhang’s rehabilitation exoskeleton, made by Zhang, Liu, Li, Zhao, Yu, and Zhu, changes the condition of how to use an exoskeleton. This design is made for patients with unilateral lower limb movement disorders, in other words, that has movement disorder in one lower extremity. The exoskeleton has a walk-assisting platform for safety and anti-gravity support, giving a full control environment for any patient that needs to use it, as presented in Figure 3.2 B. The operation of the device consists of detect and track the healthy leg, which is later used as the control input for the other leg. This exoskeleton, as the previous one, uses a series elastic actuator (SEA), due to the torque output can be accurately detected in the healthy leg and calculate the assistive torque for the other leg. [Zhang et al., 2016]

• The H1 rehabilitation exoskeleton was designed to assist overground gait training for people who had suffered a stroke and have deficits in gait coordination. The device is a bilateral exoskeleton, meaning that it is for both lower limbs, and has six degrees of freedom. This exoskeleton was designed by Bortole, del Ama, Rocon, Moreno, Brunetti, and Pons and is presented in Figure 3.2 C.

This exoskeleton has an adaptative trajectory control that guides the patient’s limb within a desired path. Also, an admittance control strategy that allows the platform to capture the movements of the user during assistive training and replicate it during active training. [Bortole et al., 2013]

• The AIRGAIT is an exoskeleton created by the Shibaura Institute of Technology. It is powered by

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State of the Art 17

Figure 3.2: The WAKE-up exoskeleton alpha version on the left and Zhang’s exoskeleton on the center, showing the full structure to use it and the H1 exoskeleton on the right.

pneumatic artificial muscle actuators. This exoskeleton, as Zhang’s exoskeleton, uses an external structure to carry the bodyweight of the patient, as seen in Figure A. The complete system consists of the structure, a variable treadmill, and the lower limb gait training exoskeleton. The exoskeleton covers the thigh at the lower end of the hip joint and until the lower end of the knee and is actuated with pneumatic artificial muscles and controlled by a CompactRIO. [Dao and Yamamoto, 2018]

• The INDEGO exoskeleton is a modular powered orthosis focused for individuals with mobility impairment, created by Parker Hannifin company. Nowadays, it is already a product, and as seen in Figure 3.3 B. This exoskeleton is powered by a rechargeable lithium-ion battery pack and has paired brushless DC (BLDC) motors and geared transmission to distribute the movement. The INDEGO has been made for the activities of standing, walking, and sitting, also with the transition between these activities. These transitions occur when the exoskeleton monitors the users’ movement of their arms and a stability aid. Also, adding a mobile application to customize the triggering of the transitions, to be more communicated to the user. [Dalley et al., 2018]

3.1.3 Upper body Exoskeletons

Upper body exoskeletons are less common and known due to the issue of carrying, for instance, the exoskeleton to several places while wearing it. The lower body exoskeletons are made to be worn and help the user to perform certain activities, which include mobility from one place to another. In contrast,

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Figure 3.3: The AIRGAIT exoskeleton on the left and the INDEGO exoskeleton on the right

the upper body exoskeletons do not have that advantage, because they are often used in static places or environments. The following exoskeletons will exemplify this reasoning.

• The first exoskeleton was named CLEVERarm, this exoskeleton was created by Soltani-Zarrin, Zeiaee, Eib, Langari, and Tafreshi, collaborating between the Texas A&M University in College Station, TX USA and University at Qatar. The CLEVERarm is the acronym of ”Compact, Low- weight, Ergonomic, Virtual/Augmented Reality Enhanced Rehabilitation arm”. This exoskeleton was made to rehabilitate patients who had suffered a stroke, leading to varieties of disability. The CLEVERarm, presented in Figure 3.4 A, has a structure to remain static in a certain place, only allowing the movement of the arm while the user is wearing it. This exoskeleton has 8 degrees of freedom (DOF) supporting the motion from the shoulder. throughout the upper limb, until the wrist.

Finally, the CLEVERarm is controlled with a CompactRio RealTime and FPGA. [Soltani-Zarrin et al., 2017]

• The AIRFRAME is another upper-body exoskeleton, made by Levitate Technologies Inc. This has a particular distinction, because nowadays it is a product and was developed for industrial use. In contrast with the CLEVERarm, this exoskeleton is made to be used in any industrial environment and does not stay in a static place, this is an assistance exoskeleton, which allows to the user perform certain activities with less effort. The AIRFRAME allows the user to carry certain loads (e.g. tools) in their arms and the weight of the load is redistribute through the body of the user to reduce the

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State of the Art 19 complete weight supported by the back. [Vinoski, 2019] The AIRFRAME is shown in Figure 3.4 B.

Figure 3.4: The CLEVERarm rehabilitation exoskeleton on the left and the AIRFRAME assistance exoskeleton for industrial use on the right.

3.1.4 Exoskeletons for specific body segment or joint

The last section in how the exoskeletons can be separated, according to the body part for which are focused, is for a specific body segment or joint. This section describes the exoskeletons that do not have a big size and are made exclusively for a certain body part (e.g. hand, ankle, finger), due to the physical condition of the user. This section will describe one exoskeleton for the hand, one exoskeleton for the knee, and one for the ankle, the spectrum of choices to develop an exoskeleton following this section is wide.

• The first exoskeleton in this section is a soft robotic glove, this globe was developed to be used for assistance or for rehabilitation, with the flexibility to use at home. This exoskeleton was made by Polygerinos, Wang, Galloway, Wood and Walsh, researchers from the Wyss Institute, and the School of Engineering and Applied Sciences at Harvard. This is a kind of exoskeleton made exclusively for all the user’s necessities, because this exoskeleton can be used at home, meaning that the user does not need to attend a rehabilitation clinic/institute. If this wasn’t enough, this exoskeleton was also developed to be used for assistance and rehabilitation with a soft actuation. In reality, this exoskeleton may seem simple, as seen in Figure 3.5, but it is not. And, it was made specially to be used and not forgetting it in a laboratory. [Polygerinos et al., 2015]

• The second exoskeleton changes from the hand to the knee, this exoskeleton is called pneumatic brace with extension assist. Specifically this device is not considered an exoskeleton by the involved

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Figure 3.5: The soft robotic glove for assistance and rehabilitation, created by Wyss Institute and the School of Engineering and Applied Sciences at Harvard

researchers, because this device is made only for a joint and some people may not consider it as an exoskeleton, this device is presented in Figure 3.6. Nevertheless, this device is an exoskeleton, because it fulfills all the requirements to be an exoskeleton. This device is a pneumatic unloader bracing with extension assistance, it is made to delay the need for knee surgery by reducing pain and improving the movement of the articulation. After testing this device, it was found that the mean quadriceps and hamstrings muscles’ strength increased. [Cherian et al., 2015]

• The last exoskeleton of this chapter is focused on the ankle, having the purpose of rehabilitating the ankle of a user by using a series elastic actuator (SEA). This exoskeleton is named ”AssistOn- Ankle” and is presented as a reconfigurable exoskeleton, as shown in Figure 3.6. This device was created by the Faculty of Engineering and Natural Sciences of Sabanc University. This exoskeleton uses the SEA to achieve a high-fidelity force/impedance control and active backdriveability. The AssistOn-Ankle was studied to evaluate an active and passive range of motion of the human ankle, follow trajectories in the ankle for user exercises, provide assistance in tracking exercises, and have a partial weight support. [Erdogan et al., 2017]

These are some of the exoskeletons that are remarkable in the state of the art, however, there are many more exoskeletons in existence. Each of the previous sub-sections comprises the exoskeletons focused to assist certain parts of the body, creating one way of classifying these devices. The following section 3.2 is going to talk about some state of the art classifications of the exoskeletons.

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State of the Art 21

Figure 3.6: The pneumatic brace with extension assist made for the knee in patients with osteoarthritis (on the left) and the AssistOn-Ankle exoskeleton (on the right).

3.2 Researches about the classification of exoskeletons

This section is going to talk about the researches done, respecting the classification of exoskeletons. There are several ways to classify an exoskeleton, and some of these articles, talk about ways of differentiating the exoskeletons according to their characteristics, however, the characteristics are incomplete for a general classification. In the last few years there had been some classification of exoskeletons, each one describing certain characteristics or uses of the exoskeleton. In chronological order, this chapter will present the articles which classify, in some way, the exoskeletons.

3.2.1 Herr’s Classification

The eldest article, in this section, was published in 2009 and created by Hugh Herr. Hugh Herr is one of the modern exoskeletons pioneer, one of the best definitions of the exoskeleton was given by him. This article describes the classification, challenges, and future directions of the exoskeletons, but we are going only to focus on the classification. According to Herr, one way to separate the exoskeletons is in:

• Series-limb exoskeletons

• Parallel-limb exoskeletons for load transfer

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• Parallel-limb exoskeletons for torque and work augmentation

• Parallel-limb exoskeletons that increase human endurance [Herr, 2009]

3.2.2 Heo’s Classification

This classification was only made for the hand exoskeletons, however, it is one of the most complete classifications found in the literature and it was published in 2012. This article describes a comprehensive review of hand exoskeletons for both, rehabilitation and assistance, from basic hand biomechanics to actuator technologies. The classification of this article is presented in the following Figure 3.7.

Figure 3.7: Heo’s classification for hand exoskeletons

This review only specializes in hand exoskeletons, hence, the lack of more categories and classes for its classification. [Heo et al., 2012]

3.2.3 Gopura’s Classification

This article reviews the development of hardware systems of active upper-limb exoskeletons. This article is really important, because it talks about a formal classification, however, the implementation for only active upper limb exoskeletons limits the potential of the classification. This article was made by R.A.R.C.

Gopura and published in 2016. There are some parts of importance in this article, such as the classification.

Also, the author presents the milestones of evolution of upper-limb exoskeletons, separating them in several generations, according to their development year. Gopura’s classification is the following:

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State of the Art 23

• The applied segment: separating the exoskeletons for the part of the upper limb for which are focused

• Degrees of Freedom (DOF): number of active joints

• Method of actuation: type of actuators used

• Method of power transmission: type of mechanism or method for the transmission of power

• Application domain: intended application for the exoskeleton

• Linkage configuration: describes if the exoskeleton is serial, parallel or hybrid

• Control method: describes of the control method used in the exoskeleton [Gopura et al., 2016]

3.2.4 Voilqu´e’s Classification

The next classification is focused on the industrial exoskeletons, created by Voilqu´e and published in 2019.

This paper classifies the industrial exoskeletons in three categories: awkward posture and movements, heavy workload manipulation, and assembly effort assistance; but also, in other categories involving the design and not only the application of the exoskeleton. The other categories are: according to continent source, development status, mass, targeted body part support, actuation type, energy source, and the proposed industrial needs. However, this article does not stop there, because it also has a structural analysis, a kinematic diagram, and a connectivity graph, for a further structural analysis to measure the structural complexity of the exoskeletons. [Voilque et al., 2019]

3.2.5 Sanchez-Villama ˜nan’s Analysis

The last article in this section is not focused in a classification, but in reviewing the mechanical design prin- ciples of the lower limb exoskeletons. This article was made by Maria del Carmen Sanchez-Villama˜nan, among others, and published in 2019. The review analyses 52 lower limb wearable exoskeletons, focusing on three aspects of compliance: actuation, structure, and interface attachment components. Moreover, the article highlights the drawbacks and advantages of the exoskeletons, suggesting promising research lines;

with a further set of datasheets containing the technical characteristics of the reviewed exoskeletons. All this is analyzed to provide any researcher with an overview of the lower limb exoskeletons in existence.

[Sanchez-Villama˜nan et al., 2019]

The previous articles presented advances on how to classify the exoskeletons, however, their classifications lack the areas to properly classify any exoskeleton, referring not only to a specific class, but all the exoskeletons in existence. Those articles talk about specific areas in which their classifications worked, given that their works were not been focused on the creation of any classification. Also, the categories in

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which each article classifies the exoskeletons are different from the others, thus the lack of a comparison table between the articles. Demonstrating the dispersion of the areas of the exoskeletons.

In the following chapter, similar to this chapter, will be divided into the development of the projects made for this specific document, involving the exoskeletons, and the analysis and development of a general categorization for an exoskeleton.

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Chapter 4

Design and Development

The project presented in this work started with the development of an exoskeleton for the lower limbs and having as a purpose assist the elderly persons who suffer from Frailty Syndrome. This was the first approach of this project to the development of exoskeletons. Starting in an unknown path, leading to the pursuit of knowledge of the exoskeletons, since their very first beginnings until the modern exoskeletons.

This chapter will describe the full development of this project, since the beginning with projects involving exoskeletons until the formalization of the exoskeletons topic, with the general categorization for the exoskeletons.

4.1 Initial Projects

This section is divided into three different projects, each one involving the development of a project related to exoskeletons. These initial projects were used to set the foundations of the understanding of exoskeletons and their modern applications.

4.1.1 ICARUS Project

One of the main complications of the elderly persons is the Frailty Syndrome. This problem was the reason which started the ICARUS project. Initializing with the needs which the elderly people might have, applying those needs to real engineering solutions. Finding the optimal solution to be an exoskeleton.

From the beginning, the ICARUS project started as the final career project of a multidisciplinary team, with students of the Bachelor on Bio-medical Engineer, Telecommunication and Electronics Engineer, Mechanical Engineer, Mechatronics Engineer and Industrial Designer. The goal of the project was to develop an exoskeleton system to aid patients with lower limb muscle weakness by boosting their residual movement and improving their balance, giving them part of their autonomy back. To achieve that goal, some objectives must be accomplished. Such as analyzing the bio-mechanics involved in sitting down and standing up, designing a system to boost the residual movement of the patient, designing the electronics

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for the control of the actuators and electromyography activation, construction of a functional prototype and testing of the prototype. [Cervantes et al., ]

The justification of this project was the high percentage of elderly people suffering from frailty syndrome and the increment of elderly people in the following decades. However, after the project was initiated, there was a change, instead of focus the project on people who suffer from frailty syndrome, which was changed to people who suffered from sarcopenia. This due to the correct terminology and to have a broader path of research.

4.1.1.1 ICARUS Design Process

The design process in this project started with the information search of the exoskeletons that existed at that moment, finding several exoskeletons for many different health issues; but not only for health issues, also to prevent other health issues. Moreover, the findings in this search included exoskeletons focused for many body parts, not only the lower limbs, as the intention of this project.

In order to sustain the research and development of this project, a disease state fundamentals research was done. Containing the study of the normal morphophysiology of the musculoskeletal system and how it is affected by the sarcopenia. This disease state fundamental consisted on the research of the physiology, in terms of the normal anatomy, passing through the bones, muscles, and joints of the lower limbs; the normal physiology, which are the physical anatomy of skeletal muscle and the general mechanism of muscle contraction, for this purposes.

Moreover, the pathophysiology of the health problem to attack and the clinical presentation, which throws some important considerations. Consisting of the loss of muscle mass. Depending on the age of the person, is the percentage of muscle mass that will lose. Estimating that, from the age of 30, it is lost between 3-8% of muscle mass per decade; however, other studies show that the muscle peak muscle strength of a person is maintained until the age of 45-50 years old, from where muscle strength starts to decline at a rate of 12-15% per decade, and growing that rate through the decades [Serra Rexach, 2006].

Furthermore, the disease state fundamental needs also the integration of the clinical outcomes, which include the morbidity, mortality, and clinical trials. Another important section is the epidemiology, in- cluding the prevalence and incidence of the disease state. Finalizing this fundamentals research with the economic impacts, dividing them into the direct medical costs and the indirect costs.

To continue the design process, a stakeholder analysis must be done. To know the organizations and people who might be interested in the ICARUS. Identifying five different stakeholders: the patient, the physiotherapist, the support group for the patients, the healthcare institutions, and the geriatrician. In the following Table 4.1 is shown the benefit and primary cost, net impact, and the key factors of each stakeholder.

After the stakeholders have been analyzed, the following step is to analyze the treatment options.

Searching the existing treatments for patients suffering from the sarcopenia and making an analysis of the benefits and risks of each treatment. The treatments are separated into categories, these being: Walking support, physical activity, nutrition, hormone therapy, and pharmacologic.

DEVELOPMENT AND IMPLEMENTATION OF A CATEGORIZATION MODEL FOR THE EXOSKELETONS BASED ON THEIR DESIGN

INSTITUTO TECNOL ´ OGICO Y DE ESTUDIOS SUPERIORES DE MONTERREY