IN DEGREE PROJECT TECHNOLOGY,FIRST CYCLE, 15 CREDITS

, STOCKHOLM SWEDEN 2018

Motorized tensioner system for prosthetic hands

FELIX HARDELL

JONAS TJOMSLAND

KTH ROYAL INSTITUTE OF TECHNOLOGYSCHOOL OF INDUSTRIAL ENGINEERING AND MANAGEMENT

Motorized tensioner system for prosthetic hands

FELIX HARDELLJONAS TJOMSLAND

Bachelor’s Thesis at ITMSupervisor: Nihad SubasicExaminer: Nihad Subasic

TRITA-ITM-EX 2018:54

Abstract

Modern research in prosthetic devices and other assis-tive technologies are constantly pushing boundaries. Whilethe technology is impressive, it is still inaccessible for thegreater part of the people in need of it. Advanced devicesare often extremely expensive and require regularly main-tenance from professionals. Enabling the Future is a globalnetwork of volunteers and was founded to face these prob-lems. They design and 3D-print mechanical prosthetics forpeople in need all over the world.

Most of the designs used by Enabling the Future are purelymechanical and do not implement motors. The purposeof this thesis was to take a new approach to the designand construction of low-cost motorized prosthetic hands.By distancing all the electronic components from the hand,including the motor, the project aimed to create a devicecompatible with all current designs of the Enabling the Fu-ture community.

To conceptualize this approach a demonstrator was con-structed and tested. It utilized a muscle sensor which al-lowed users to control the hand by tightening their mus-cles. The distance between the electronic components andthe prosthetic hand measured approximately one and a halfmeters and still transfered enough force, from the motor tothe hand, to deliver an adequate grip strength.

KeywordsMechatronics, Haptics, Prosthetics, 3D Printing.

Referat

Modern forskning inom protestillverkning och andrahandikapphjälpmedel gör kontinuerligt stora framsteg. Trotsatt tekniken är imponerade är den fortfarande otillgängligför den största del människor som behöver den. Avancera-de hjälpmedel är ofta extremt dyra och kräver kontinuer-ligt underhåll från yrkesverksamma. Enabling the Future,ett globalt nätverk av volontärer, grundades för att utma-na dessa problem. De konstruerar och tillverkar 3D-skrivnamekaniska proteser för människor med behov över hela värl-den.

De flesta konstruktioner som används av Enabling the Fu-ture är helt mekaniska och använder inga motorer. Syftetmed detta kandidatexamensarbete var att med nya tillvä-gagångssätt konstruera en billig motoriserad handprotes.Genom att placera all elektronik på en distans från han-den, inklusive motorn själv, var tanken att skapa ett systemsom är kompatibelt med de konstruktioner som Enablingthe Future använder.

För att förverkliga detta konstruerades en prototyp somtestats. Prototypen använde sig av en muskelsensor somlät användaren kontrollera proteshanden genom att spän-na sin arm. Distansen mellan de elektriska komponenternaoch protesen var ungefär en och en halv meter, samtidigtsom tillräckligt stor kraft kunde transporteras för att stängahanden med ett tillräckligt grepp.

NyckelordMekatronik, Haptik, Proteser, 3D Printning.

Acknowledgements

First we would like to thank the KTH staff. Specifically, our supervisor NihadSubasic for all lectures, support and feedback and the lab assistants for answeringquestions. We would also like to thank Staffan Qvarnström and Tomas Östberg forcomponents as well as ideas about the construction.

Secondly, we would like to thank our fellow KTH students. This includes, themechatronic master students one year ahead of us, for all their help, and all ourfriends in the same year who gave us feedback during the seminars and elsewhere.

Finally, we would like to thank the e-NABLE community for its existence. Allsupport provided by this community to people without financial possibilities inneed of prosthetic devices is invaluable.

Jonas Tjomsland and Felix HardellStockholm, May 2018

List of Abbreviations

EMG Electromyography

e-NABLE Enabling the Future

DC Direct Current

GAR Spiral-bound galvanized

PLA Polylactic Acid

PM Permanent Magnet

PWM Pulse With Modulation

SEK Swedish Kronor

STR Stainless-steel strands

USD US Dollar

List of Figures

1.1 An early sketch of how the tensioner system could be constructed, drawnon reMarkable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Simple explanation of the whippletree mechanism, drawn on reMarkable. 42.2 Illustration of a brushed motor, drawn on reMarkable. . . . . . . . . . 62.3 Schematic diagram of an H-bridge in two different states, drawn in

Keynote. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.1 Sketch of control box, drawn on reMarkable. . . . . . . . . . . . . . . . 103.2 Schematic diagram of all electronic components, drawn in Keynote. . . 113.3 A software flowchart explaining the setup and main loop of the system,

created in Keynote. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.1 Time from when the human test subject started closing their hand untilthe prosthetic hand had reached the end position. Figure was created inMATLAB R2017a. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Contents

1 Introduction 11.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Theory 42.1 Prosthetic hand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2 Whippletree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.3 Bowden cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.4 EMG-sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.5 Electric motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.5.1 Brushed PM DC motor . . . . . . . . . . . . . . . . . . . . . 62.5.2 H-bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Demonstrator 83.1 Problem formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2 Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2.1 Prosthetic hand . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2.2 Whippletree . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2.3 Cable house mounting . . . . . . . . . . . . . . . . . . . . . . 93.2.4 Wire clamp grip . . . . . . . . . . . . . . . . . . . . . . . . . 93.2.5 Control box . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.3.1 Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.3.2 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.3.3 Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.3.4 Motor driver . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.3.5 EMG-sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.3.6 Micro switch . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4 Results 14

4.1 Conducted experiments . . . . . . . . . . . . . . . . . . . . . . . . . 144.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5 Discussion and conclusion 165.1 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.2 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6 Recommendations and future work 18

Bibliography 20

Appendices 21

A Arduino Code 22

B Flexy Hand 2 26

C Redesign of Flexy Hand 2 arm part 27

D Finger configuration of whippletree 28

E Compression spring 29

F Price list of all components 30

G Motor datasheet 31

H Micro switch datasheet 34

I EMG-sensor datasheet 36

J Motor driver datasheet 45

Chapter 1

Introduction

1.1 BackgroundIn 2011, the World Health Organization estimated that close to 30 million peoplein developing countries were in need of some kind of prosthetic device [1]. Many ofthese are victims of conflicts or deceases not present in more developed countries.Low income in combination with inadequate health services increases the magnitudeof the problem. Furthermore, people in other parts of the world are facing similarchallenges. In the US, nearly two million people are living with limb loss [2]. Evenwith better welfare and financial conditions, the problem is severe.

Additionally, not only is the demand for an initial prosthetic device increasing,but every recipient needs several replacements and repairs during a lifetime. Arough estimate concludes that every 6-12 months for children and every 3-5 yearsfor adults, a replacement is necessary [3]. It is therefore not surprising that a tra-ditional middle-class family may be unable to afford prosthetic devices when theprice range for a prosthetic arm is 3,000 to 30,000 US Dollars (USD) [4].

Enabling the Future (e-NABLE) [5], a global network of volunteers, are workinghard to tackle these problems. By using 3D-printing and open source design, theycreate low cost upper limb assistive devices for people in need. Their designs areoften purely mechanical and do not contain any electric parts. Some projects out-side the e-NABLE community have tried a different approach, such as: Tact [6],Dextrus [7] and Limbitless [8], which uses small actuators to close and open the fist.In these projects all parts are integrated into the device itself, thus making themmobile and easy to use. However, such solutions require user customization andcould lead to the device being more difficult to repair and replace.

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CHAPTER 1. INTRODUCTION

1.2 PurposeThe purpose of this project was to challenge the traditional approaches used whencreating myoelectric prosthetic devices. To demonstrate this, the objective was toproduce a working prototype with cheap and easily accessible components, possibleto build by the amateur maker.

The following research questions were investigated:

• Can a replaceable and mobile myoelectric system be built to transfer motionfrom a distant motor to a prosthetic hand?

• Can such a system be built with cheap and easily accessible components?

1.3 ScopeDue to limitations in time and budget, some restrictions were applied to this project.There was a given budget of 1000 Swedish Kronor (SEK) from KTH Royal Instituteof Technology on top of components and parts supplied by the machine constructiondepartment itself. While this was a relatively small budget it was also a reasonableamount to ensure that the projects solution could be available to everyone. Fur-thermore, a mechatronic implementation was at focus so little consideration wastaken to solid mechanics, manufacturing and design.

In order to limit the workload and keep the project within the time constraint, pre-fabricated solutions were prioritized over "Do it yourself" methods. This includedthe acquired EMG-sensor, the stepper motor driver and the predesigned prosthetichand.

At the end of the project, the prosthetic hand was required to open and closewhen the user activated it by muscle contraction. The actuator needed to be ableto keep track of its current position thereby controlling the strength of the grip.

1.4 MethodFirst of all a literature study was conducted. A set of traditional prosthetic construc-tions were researched, including different mechanical, sensor, actuator and manufac-turing techniques. Areas such as soft robotics, haptic technology, electromyographyand 3D-printing were investigated.

A conceptual idea of the demonstrator was made, based on the literature studyand the limitations, followed by a final formulation of the research questions. Sub-sequently, the parts for a prosthetic hand were 3D-printed and testing was conducted

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CHAPTER 1. INTRODUCTION

Figure 1.1. An early sketch of how the tensioner system could be constructed,drawn on reMarkable.

to decide the performance of sensors and actuators. This, combined with experi-mentation with a shifter cable, resulted in a conceptual sketch, see figure 1.1.Following this, a prototype based on the sketch was assembled and an iterativeprocess started. All parts of the system were meticulously tested and quality as-sured which led to modifications in the design as well as replacement of electricalcomponents. Finally, a fully functional demonstrator was constructed and used fortesting.

3

Chapter 2

Theory

2.1 Prosthetic handThe prosthetic hands developed in the e-NABLE community mainly consist of 3D-printed parts. Each finger has tensile hinges between non-tensile parts in order tooperate. To make the prosthetic able to close, artificial tendons from the tip of allfingers are used. The hand closes when the tendons are pulled.

2.2 WhippletreeA whippletree mechanism distributes forces evenly through linkages. On one sideloads are applied through wires and on the other side a tension can be applied. Inthe case of prosthetics, the fingers work as load. If a finger cannot move due toan obstacle, the other fingers will keep on moving which increases the grip of thehand [9]. Since the thumb usually works against the other fingers alone, the force tothe thumb should be largest of all fingers. This can be achieved by using differentdistance relations between different connection in the whippletree, see figure 2.1.

Figure 2.1. Simple explanation of the whippletree mechanism, drawn on reMark-able.

4

CHAPTER 2. THEORY

2.3 Bowden cableA Bowden cable is made of several layers in a specific configuration surrounding awire. A cable housing with a steel interior and plastic exterior is usually used asouter layer. When the wire is pulled, tension is added to the cable while maintaininga static housing.

In bikes, where Bowden cables are used as shifter cables, Teflon is sometimes usedas an extra layer between the wire and the metal interior due to low friction andshifting performance. Furthermore, Teflon does not require lubrication which isotherwise needed. The wire is usually made from spiral-bound galvanized (GAR)or stainless-steel strands (STR). The STR offers greater resistance to corrosion butare usually more expensive than GAR [10].

At the end of the cable there is an end cap which can be configured in differentways. In order to avoid contamination from dirt or water, an open-end cap shouldbe avoided. Instead one option could be sealed end caps with an internal rubberO-ring which keeps the housing clean while offering low friction.

2.4 EMG-sensorElectromyography (EMG) is the measuring of muscle contractility or the electricalactivity in response to nerve stimulation of a muscle [11]. It has traditionally onlybeen used in medical research and diagnosis, however, as a result of the latestdevelopments within embedded systems and integrated systems design the use ofEMG has become one of the most common solutions for controlling and steeringprosthetic devices. It works, briefly speaking, by measuring the voltage differencebetween a pair of electrodes placed on a muscle and a third electrode placed at areference point, preferably a bony part of the users body.

2.5 Electric motorElectric motors convert electricity into rotation which can be transferred into linearmotion by different techniques. Either by using a lead screw as the motor shaftwith a nut along the axis or by other solutions such as a bobbin and wire. Themaximum amount of torque, MN , a Direct Current (DC) Motor can carry whileremaining within its temperature rating is given by

MN = K2ΦN · IN (2.1)

where IN is the current, K2 is a constant and Φ is the magnetic flux. The magneticflux is constant when a Permanent Magnet (PM) is used. The angular velocity, ω,

5

CHAPTER 2. THEORY

on the other hand, is given by

E = K2Φ · ω (2.2)

where E is the counter-electromotive force. [12]

2.5.1 Brushed PM DC motorA PM DC brush motor can be simply described with four components: stator, ro-tor, brushes and commutator, see figure 2.2. A magnetic field is generated by thestator containing a permanent magnet. The rotor is made up of windings, whichare energized sequentially. When current runs through the windings a magneticfield is produced. The poles of the magnetic field of the windings are attracted tothe opposite poles of the magnetic field of the stator.

By carefully switching the direction of the current in the rotor windings it is possibleto control the motor. This process, called commutation, is achieved by attachinga commutator on the rotor. When the motor turns, carbon brushes slide over dif-ferent segments of the commutator supplying a charge to that segment. Differentsegments are connected to different parts of the winding which allows the rotor tocontinue the turning.

Figure 2.2. Illustration of a brushed motor, drawn on reMarkable.

6

CHAPTER 2. THEORY

2.5.2 H-bridgeA H-bridge is an electronic circuit that allows current to flow across a load in eitherdirection. This process is controlled by opening and closing switches, see figure 2.3.When the load is a DC motor, one H-bridge is enough in order to run the motorboth forward and backwards. In the case of a Bipolar Stepper Motor, which haveno center taps on their windings, two H-bridges are necessary to perform the samemotion. H-bridges are often integrated into Stepper Motor Drivers [13].

Figure 2.3. Schematic diagram of an H-bridge in two different states, drawn inKeynote.

7

Chapter 3

Demonstrator

3.1 Problem formulationTo validate the functionality and usability of the system, a demonstrator was con-structed. The demonstrator had to be able to transfer force from the motor, throughthe bowden cable, to the prosthetic hand. On top of this, it had to consist of easilyaccessible and low-cost components.

3.2 Mechanics

3.2.1 Prosthetic handFlexy Hand 2, a design created by Steve Woods [14] and widely used in the e-NABLEcommunity, was chosen for the demonstrator, see Appendix B. All printable partswere printed on an Ultimaker 3D printer. The non-tensile parts in Polylactic Acid(PLA) material and the tensile hinges in a more flexible material called Filaflex.Standard fishing line, capable of carrying a weight of 30 kg, was used as artificialtendons.

The upper part of a Flexy Hand 2, where the tendons are usually fastened, wasredesigned for the purpose of this project. By doing this, space for the Whippletreemechanism was allocated and a custom made fastening system for the Bowden cablecould be implemented, see Appendix C.

A more detailed description of the assembly process, as well as all printable files forthe Flexy Hand, can be found on the e-NABLE website [14].

3.2.2 WhippletreeThe whippletree design used in the demonstrator was the V.2 Flexy Fingers whip-pletree [15]. It was chosen because it was easy to 3D print in PLA material and itworked by distributing the force evenly between two inputs.

8

CHAPTER 3. DEMONSTRATOR

In this demonstrator only one whippletree was used with the pinky and ringfinger connected to the middle finger as one input and the index finger connectedto the thumb as the other input. For a more detailed explanation see Appendix D.

3.2.3 Cable house mountingTo mount the cable house in both ends plastic ferrules were attached. This is a so-lution commonly used in bicycles as a conversion between entire housing and singlesteel wire. The ferrules both repels dirt and restricts the housing from moving inwrong directions.

In the mounting closest to the hand, between the plastic ferrule and the arm part, acompression spring was integrated. This allowed the hand to stay open independentof how the wrist joint was moved, see Appendix E.

3.2.4 Wire clamp gripIn each end of the Bowden cable a wire clamp grip was used. A wire clamp gripcreated a loop-end of the cable which allowed the fishing line to be easily con-nected. Depending on the placement of the loop-end the entire cable length couldbe adjusted.

3.2.5 Control boxAll the electronic components, except for the EMG-sensor, were placed in a smallcontrol box. Initially the box was intended to be small and mobile, thus enablingthe user to carry it in a backpack or similar. However, due to time constraints, asimpler and bigger version was chosen. Priority was placed on getting the systemto work.

9

CHAPTER 3. DEMONSTRATOR

The DC motor and micro switch were placed in the main room of the box. Whenthe motor was working the fishing line was rolled up on a small 3D-printed bobbin.The micro switch told the system when the wire clamp reached the wall, therebyindicated that the hand was fully opened. Two pockets, dimensioned for eight AAbatteries, were placed on the outside of the box. The Bowden cable was attachedto one of the walls and a small hole allowed the wire to enter the box, see figure 3.1.

Figure 3.1. Sketch of control box, drawn on reMarkable.

10

CHAPTER 3. DEMONSTRATOR

3.3 Electronics

3.3.1 WiringThe demonstrators electronic components were connected as illustrated in figure 3.2.

Figure 3.2. Schematic diagram of all electronic components, drawn in Keynote.

3.3.2 Power supplyThe Arduino Uno uses 5V as operating voltage, but is recommended to have aninput voltage of 7-12V when using the barrel jack. As power source eight AA bat-teries were connected in series, together delivering 12V, to the Arduino. The chosenmotor was preferably used with 24V. To increase the voltage for the motor eightnew AA batteries, supplying 12V, were connected in series with the first eight bat-teries. AA batteries were chosen due to accessibility and price.

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CHAPTER 3. DEMONSTRATOR

It should be noted that the batteries supplying both the Arduino and the mo-tor run out before the batteries only supplying the motor run out. Such a solutionfor the batteries was however considered better than other options, see Chapter 6.

3.3.3 MotorThe DMN29BA-002, a 24V DC brush motor, was chosen as motor for the demon-strator, see Appendix G. The selected model consists of both a DC motor as wellas a worm drive. This choice was based on the earlier described restrictions, seeChapter 1, as well as desired torque. To transfer the rotary motion to a linearmotion a self-designed bobbin was attached to the D-shaped motor shaft.

3.3.4 Motor driverSTMicroelectronics‚ L298 was deemed to be the best solution for a motor driver.It has a dual H-bridge, able to power two DC motors or one unipolar or bipolarstepper motor. See Appendix J.

Since the demonstrator only consisted of one DC motor, it can be argued that thisimplementation was unnecessarily complicated. One should, however, know thatL298 is cheap, easy-to-use and accessible. In addition to this, it supports steppermotors which can be implemented if the DC motor would break.

3.3.5 EMG-sensorMyoWare’s muscle Sensor AT-04-001 was chosen because of its low price point to-gether with great usability and out-of-the-box features, see Appendix I.

Since the EMG sensor only reacts to electronic impulses the prosthetic was bothopened and closed by the user tightening their muscle. This also made it possiblefor the user to relax their hand while the prosthetic hand was closed.

3.3.6 Micro switchTo keep track of when the prosthetic hand was entirely open a micro switch, Goobay10185 from Wentronic, was implemented. See Appendix H. The micro switch wasinstalled where the Bowden cable entered the Control box. When the motor releasedthe fishing line, the hinges retracted the fingers back which closed the micro switch.

3.4 SoftwareThe software of the tensioner system was split into two parts. Firstly, a setup pro-cess was initiated followed by the main loop which continued until the system wasturned off.

12

CHAPTER 3. DEMONSTRATOR

Briefly speaking, the setup process checked and adjusted the position of the handwhen the system was turned on. In the main loop, the Arduino read the EMGSensor’s value and when that reached a predetermined threshold the motor startedto pull the wire for a specific length of time. Subsequently, it entered its next stage,constantly reading the EMG value to determine whether to open the hand again.When the value from the EMG sensor yet again reached its threshold, the motor ro-tated in the opposite direction, thus opening the hand. See figure 3.3 for a thoroughexplanation of the process.

Figure 3.3. A software flowchart explaining the setup and main loop of the system,created in Keynote.

13

Chapter 4

Results

4.1 Conducted experimentsBefore assembling the entire demonstrator, experiments were conducted on differentmodule configurations. This was done to reduce the risk of failure in the final prod-uct, by carefully making sure all components were working individually as intended.

The first experiment was to investigate how large the force had to be in orderto close the prosthetic hand alone completely. To test this, a spring balance wasattached to the whippletree connection of the artificial tendons. A spring balancemeasures in kilograms but can easily be converted into Newtons. The spring bal-ance was pulled until it reached its end position, i.e. the hand was entirely closed,and the weight was measured.

As a continuation of the first experiment, the second experiment aimed for anunderstanding on how much force the motor was able to transfer through the restof the tensioner system. In the Bowden cable end, otherwise connected to the whip-pletree, a spring balance was attached. The spring balance was fixed and the motorthe motor pulled the wire in the opposite direction. The current was kept at amaximum of 1.2A and with a 24V supply.

When each module had been finalized and assembled into the demonstrator, de-lays in the entire system were tested. A human test subject, without any limblosses, was chosen. The test subject had the EMG sensor placed on their forearmand and was instructed to close their hand randomly 30 times in a row. This means15 times closing the prosthetic and 15 times opening it. The time from when thetest subject started closing their hand until the prosthetic had closed was measuredand then the time to open again was also measured. Note that there was no loadin the hand when these tests were carried out.

14

CHAPTER 4. RESULTS

4.2 Results

Test Weight [kg]1 5.52 5.43 5.5

Table 4.1. Weight to fully close the prosthetic hand alone.

Test Weight [kg]1 11.52 12.03 11.7

Table 4.2. Weight possible to transfer through tensioner system from motor.

Figure 4.1. Time from when the human test subject started closing their hand untilthe prosthetic hand had reached the end position. Figure was created in MATLABR2017a.

15

Chapter 5

Discussion and conclusion

5.1 DiscussionThe force needed to close the hand alone, see Table 4.1, was significantly higher thanfirst expected. This led to several adjustments of the initial construction. Threedifferent motors were tested with gear implementations.

When the final prototype was completed the tensioner system was able to transferforce well above what the hand alone could, see Table 4.2. However, by subtractingthe weight the tensioner system could transfer from the weight required to close theprosthetic hand alone, the grip strength was calculated to just over 6 kg.

According to a European study from 2014, the average grip strength among sixyear old girls was 8.1 kg, while boys in the same age had an average grip strength of9.1 kg [16]. Since many of the recipients in the e-NABLE community are children,a motorized system delivering 6 kg could be deemed sufficient by users.

Time delays may prove to be a problem, as closing the hand without any load tookalmost 2.4 seconds on average, see Figure 4.1. This would probably be perceivedas very slow for a user in the beginning, until the user becomes accustomed to it.Opening the hand was much faster and probably has a more reasonable time period.

There is no doubt that a system which can transfer motion from a distance to aprosthetic hand is possible to create. By using a Bowden cable this can be achievedwithout keeping the system stretched along one direction. Such a system can bebuilt for less than 1330 SEK, equivalent to 152 USD, as of May 20 2018, see Ap-pendix F.

The construction of such system is quite complicated and requires time, even byonly replicating this project. Therefore many improvements need to be done beforea system like this can be performed on a larger scale in the e-NABLE community.

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CHAPTER 5. DISCUSSION AND CONCLUSION

5.2 ConclusionsA replaceable and mobile myolectric system can be build to transfer motion from adistant motor to a prosthetic hand.

It is possible to say that a motorized version of the e-NABLE prosthetic mightbe possible to make in larger scales without an unreasonable price tag. However,such system is complicated to build and needs improvements.

17

Chapter 6

Recommendations and future work

It is important to once again point out that there were restrictions in this project,making the design options in some cases limited.

As seen in the results, the demonstrator required large torques at reasonable speedin order to operate properly. This, in combination with a low price target, led toproblems when choosing the motor. If a motor was too weak, a gear was needed,providing a slow and more complicated system. If a motor with high torque waschosen, the price increased. The noise level from the motor was also taken intoconsideration. This lead to a compromise between many factors which might haveaffected the overall performance of the system. A possibility would be to furtherinvestigate different motor solutions to implement in the system.

Instead of using 16 AA batteries in series to supply the motor with 24V, otherpower supply solutions could be interesting to evaluate. Notice that the systemneeds both enough current and voltage, leading to a high torque as well as rea-sonable rotational speed, see Equation 2.1 and 2.2. One solution is to use otherbattery types, supporting higher voltage and still offering enough ampere hours.Another solution is a step-up converter, which was actually tested in this construc-tion. A step-up converter offers the possibility to increase the voltage, i.e. speed, byreducing the current, i.e. torque, proportionally. If this is implemented ensure thatthe step-up conversion is completed before the current enters the H-bridge. It isalso important to investigate for how long the power supply might be able to workuntil the need for charging or changing.

In some unusual cases the micro switch did not work properly. This was becausethe retraction of the Flexy Hand 2 hinges was too small to successfully retract theentire tensioner system as well as the micro switch. A solution to this would be touse a micro switch with less resistance needed to close.

18

CHAPTER 6. RECOMMENDATIONS AND FUTURE WORK

The chosen MyoWare Muscle Sensor was very easy to implement, but in relation toother components rather expensive, see Appendix F. The subsequent costs relat-ing to this component further increase if the electrodes need to be changed often.Muscle sensor implementations that can be removed and reused more easily wouldbe preferred.

The control box used in the demonstrator was from the beginning of the projectaimed to fit inside a backpack. Due to time limits such implementation was nevertested. A future experiment would be to reduce the entire box size and shape itbetter for a backpack.

Fishing line has many benefits, it can be rolled up on a bobbin easily and is al-ready widely used as artificial tendons in the e-NABLE community. However, theuse of fishing line can result in difficulties in small spaces, such as inside the controlbox, where knots need to be strong.

3D printing was seen as a good choice since most users in the e-NABLE communityhave access to this technology. It would be recommended for future projects tocontinue to create solutions possible to 3D-print.

The Flexy Hand 2 is a popular design which worked well in this project. However,after some testing it was noticed that, the thumb closed faster than the remainingfingers. This led to some difficulties when grabbing different objects. The problemwas probably a result of the whippletree configuration but this was never investi-gated further.

As a final note, the authors would like to point out that the mechanics of thisproject were complicated. However, choosing parts went quite fast and the elec-tronics and programming went even faster.

19

Bibliography

[1] WHO. (2011). World report on disability, [Online]. Available: http://www.who . int / disabilities / world _ report / 2011 / report . pdf. (Accessed:2018.02.13).

[2] Amputee Coalition. (2012). Limb loss statistics, [Online]. Available: https://www.amputee-coalition.org/limb-loss-resource-center/resources-filtered/resources- by- topic/limb- loss- statistics/limb- loss-statistics/. (Accessed: 2018.02.13).

[3] E. Strait, “Prosthetics in developing countries”, Prosthetic Resident, p. 3,2006.

[4] G. McGimpsey and T. C. Bradford, “Limb prosthetics services and devices”,Bioengineering Institute Center for Neuroprosthetics Worcester PolytechnicInstitution, 2008.

[5] (2011). Enabling the future, [Online]. Available: http://enablingthefuture.org/about/. (Accessed: 2018.02.20).

[6] P. Slade, A. Akhtar, M. Nguyen, and T. Bretl, “Tact: Design and performanceof an open-source, affordable, myoelectric prosthetic hand”, in Robotics andAutomation (ICRA), 2015 IEEE International Conference on, IEEE, 2015,pp. 6451–6456.

[7] J. Gibbard. (2013). Dextrus hand, [Online]. Available: http://www.openhandproject.org/dextrus.php. (Accessed: 2018.02.21).

[8] UCFArmory. (2014). Limbitless arm, [Online]. Available: http://enablingthefuture.org/upper-limb-prosthetics/the-limbitless-arm/. (Accessed: 2018.02.21).

[9] J. Diamond. (2015). Whippletree in e-nable hand, [Online]. Available: https://www.youtube.com/watch?v=dW5B_CeJtd8. (Accessed: 2018.02.21).

[10] Jagwire. (2018). Inner wire guide, [Online]. Available: https://jagwire.com/guides/inner-wire. (Accessed: 2018.02.22).

[11] K. R. Mills, “The basics of electromyography”, Journal of Neurology, Neuro-surgery & Psychiatry, vol. 76, no. suppl 2, pp. ii32–ii35, 2005, issn: 0022-3050.doi: 10.1136/jnnp.2005.069211. eprint: http://jnnp.bmj.com/content/76/suppl_2/ii32.full.pdf. [Online]. Available: http://jnnp.bmj.com/content/76/suppl_2/ii32.

20

BIBLIOGRAPHY

[12] H. Johansson, P.-E. Lindahl, R. Meyer, M. Grimheden, W. Sandqvist, andM. Paulson, Elektroteknik. Institution for Machine Design, Stockholm: KTHIndustrial engineering and Management, 2013.

[13] D. W. Jones. (1995). Control of stepping motors, [Online]. Available: http:/ / homepage . divms . uiowa . edu / ~jones / step / index . html. (Accessed:2018.02.22).

[14] (2011). Flexy hand 2, [Online]. Available: http://enablingthefuture.org/upper-limb-prosthetics/the-flexy-hand/. (Accessed: 2018.04.01).

[15] (2015). V.2 flexy fingers, [Online]. Available: https://www.thingiverse.com/thing:1108085. (Accessed: 2018.04.01).

[16] P. D. M.-E. et al, “Physical fitness reference standards in european children:The idefics study”, International Journal of Obesity, pp. 57–66, 2014.

21

Appendix A

Arduino Code

// Motorized Tens ioner System For Pro s th e t i c Hands// A Bachelor t h e s i s in Mechatronics at KTH Royal I n s t i t u t e o f Technology// Jonas Tjomsland & Fe l i x Harde l l// May 2018

// I n i t i a l i z i n g v a r i a b l e s :

// Hand :// I nd i c a t e s whether the hand i s opened (1 ) or c l o s ed ( 0 ) .i n t handState ;

// Motor :// Standby i s s e t to pin 13 :i n t STBY = 10 ;// Motor input 1 i s s e t to pin 12 :i n t motorInput1 = 9 ;// Motor input 2 i s s e t to pin 11 :i n t motorInput2 = 8 ;

// EMG senso r :// Output value from EMG sensor , between 0−1023:i n t emgValue ;// Threshold f o r EMG sensor va lue to a c t i v a t e motor :i n t thresho ldValue = 320 ;// EMG analog input i s s e t to pin A0 :char analogInputEmg = A0 ;

// Micro switch senso r :// Micro switch d i g i t a l input i s s e t to pin 13 :i n t switchInput = 13 ;

22

APPENDIX A. ARDUINO CODE

// Micro switch power i s provided from pin 4 :i n t switchPowerSource = 4 ;

// Move func t i on .// Takes d i r e c t i o n as input and r o t a t e s the motor . . .// in that d i r e c t i o n un t i l the stop func t i on i s c a l l e d .void move( i n t d i r e c t i o n )

// Sets standby to HIGH, enab l ing motor r o t a t i on :d i g i t a lWr i t e (STBY, HIGH) ;

// Clockwise r o t a t i on :i f ( d i r e c t i o n == 1)

d i g i t a lWr i t e ( motorInput1 , HIGH) ;d i g i t a lWr i t e ( motorInput2 , LOW) ;

// Counter c l o ckw i s e r o t a t i on :e l s e

d i g i t a lWr i t e ( motorInput1 , LOW) ;d i g i t a lWr i t e ( motorInput2 , HIGH) ;

// Stop func t i on .// Takes no input , s tops motor r o t a t i on .void stop ( )// Sets standby to LOW, d i s ab l i n g motor r o t a t i on :

d i g i t a lWr i t e (STBY, LOW) ;

// Setup func t i on .// I n i t i a l i z i n g a l l p ins and makes sure that . . .// hand i s in open po s i t i o n be f o r e main loop s t a r t s .void setup ( )

pinMode (STBY, OUTPUT) ;pinMode (motorInput1 , OUTPUT) ;pinMode (motorInput2 , OUTPUT) ;pinMode ( switchInput , INPUT) ;pinMode ( switchPowerSource , OUTPUT) ;

23

APPENDIX A. ARDUINO CODE

// Sets the switch power source ( pin 4) to HIGH:d i g i t a lWr i t e ( switchPowerSource , HIGH) ;

// Sets handsState to the switch pos i t i on , 1 or 0 :handState = d ig i ta lRead ( switchInput ) ;

// Open hand i f c l o s ed :i f ( handState == 0)

move ( 1 ) ;// Continuously read the switch po s i t i o n and stop . . .// r o t a t i on when the hand i s f u l l y opened :

whi l e (1 )

handState = d ig i ta lRead ( switchInput ) ;i f ( handState == 1)

// Stops motor r o t a t i on :stop ( ) ;handState = 1 ;break ;

de lay ( 1 0 0 ) ;

// Main loop :// See so f tware f l owchar t in Appendix f o r thorough exp l enat i on o f p roce s s .void loop ( )

// Reads the EMG sensor va lue :emgValue = analogRead ( analogInputEmg ) ;

// I f EMG value i s over t r e sho l d and hand i s open −> c l o s e hand :i f ( ( emgValue > thresho ldValue )&&(handState == 1))

// Runs motor in counter c l o ckw i s e d i r e c t i o n :

move ( 0 ) ;// Runs f o r 2200 ms , t h i s need to be customized . A longe r . . .// r o t a t i on time r e s u l t s in a s t r onge r g r ip :

de lay ( 2200 ) ;

24

APPENDIX A. ARDUINO CODE

// Stops motor r o t a t i on :stop ( ) ;handState = 0 ;

// Reads the EMG sensor va lue :emgValue = analogRead ( analogInputEmg ) ;

// I f EMG value i s over t r e sho l d and hand i s c l o s ed −> open hand :i f ( ( emgValue > thresho ldValue )&&(handState == 0))

move ( 1 ) ;

// Continuously read the switch po s i t i o n and . . .// stop r o t a t i on when the hand i s f u l l y opened :

whi l e (1 )

// Sets handsState to the switch pos i t i on , 1 or 0 :handState = d ig i ta lRead ( switchInput ) ;i f ( handState == 1)

// Stops motor r o t a t i on :stop ( ) ;handState = 1 ;break ;

de lay ( 1 0 0 ) ;

25

Appendix B

Flexy Hand 2

BILL OF MATERIALSITEM

NUMBER DESCRIPTION NUMBEROFF

1-1 THUMB PROXIMAL PHALANX 11-2 THUMB DISTAL PHALANX 12-1 INDEX PROXIMAL PHALANX 12-2 INDEX MIDDLE PHALANX 12-3 INDEX DISTAL PHALANX 13-1 LONG PROXIMAL PHALANX 13-2 LONG MIDDLE PHALANX 13-3 LONG DISTAL PHALANX 14-1 RING PROXIMAL PHALANX 14-2 RING MIDDLE PHALANX 14-3 RING DISTAL PHALANX 15-1 SMALL PROXIMAL PHALANX 15-2 SMALL MIDDLE PHALANX 15-3 SMALL DISTAL PHALANX 16 HAND BODY 17 PALMAR DIGITAL 48 PROXIMAL AND DISTAL INTERPHALANGEAL 11EXPLODED VIEW

2-3

3-3

4-3

5-3

2-2

3-2

4-25-2

2-1

3-1

4-1

5-1

6

1-2

1-1

7

8

8

8

8

8

26

Appendix C

Redesign of Flexy Hand 2 arm part

Entire design is available as open source on assistivetech.se. As seen in the picturebelow, the part is supposed to be printed in PLA and then thermoformed.

27

Appendix D

Finger configuration of whippletree

1 2 3 4 5

Finger configuration in the demonstrator

1. Thumb2. Index finger3. Middle finger4. Ring finger5. Pinky finger

28

Appendix E

Compression spring

1

2

3

Compression spring in use

29

Appendix F

Price list of all components

This project was aiming for users in a 3D-printing community. Therefore, no 3D-printing materials nor 3D-printers have been taken into consideration when doingthis price list. The same goes for soldering, which was also needed.

Price ListComponent Model Price

(SEK)Website

Microcontroller Arduino Uno Rev. 3 250 www.kjell.comMotor DMN29BA-002 250 (1)Motor driver L298 79 www.electrokit.comEMG sensor MyoWare Muscle Sensor 332 www.sparkfun.comEMG nodes Muscle Sensor Surface

EMG Electrodes (6-pack)43 www.sparkfun.com

Micro switch Goobay 10185 19 www.electrokit.comElectric wires 15 (1)Bowden cable 150 www.sportson.seSpring 15 (1)Fishing line Power Pro 135m (30 kg) 5 www.fiske.se (2)AA-batteries (LR6) 20-pack 70 www.kjell.comBattery hold-ers

2x(8x AA med batterikon-takt)

100 www.kjell.com

Total 1328

(1) Was provided by the Department of Machine Design at KTH Royal Instituteof Technology. Prices have been estimates according to market value as of May 202018.

(2) The entire fishing line costed 269 SEK. Only 2.5 out of 135 meters were used.

30

Appendix G

Motor datasheet

31

DMN29SeriesSpecification

Outline

DMN29

DMN29BA 3.0 12 7.8 1.11 0.42 3700 0.07 5000 30 4.17 90 0.20

DMN29BB 3.0 24 7.8 1.11 0.21 3700 0.05 5000 30 4.17 90 0.20

TYPE

RATED NO LOAD STALLWEIGHT

g lbTORQUE CURRENT SPEEDVOLTAGEOUT PUT

mN・mVW oz・in ACURRENTA

SPEEDr/min r/min mN・m oz・in

TORQUE

TORQUE0

0 10 20 30 40

0

1000

2000

3000

4000

5000

6000

7000

5 10 15 20 25 30 35mN・m

SPEEDCURRENT

CURRENT

SPEED

RED HOLDER

CW

（＋）

（－）

BLACK HOLDER

oz・in

100 200 300 gf・cm0

0.8

2.4

2.0

SPEED （r/min）

CURRENT(A) : 24V

0

0.4

1.2

1.0

2.8 1.4

CURRENT(A) : 12V

1.6 0.8

1.2 0.6

0.4 0.2

CURRENT, SPEED-TORQUE CURVE CONNECTION

24.6

(0.969)

(RED)(+)TERMINAL

(BLACK)(-)TERMINAL

2-M2.6DEPTH 3MAX(0.118 MAX)

HOLEφ(0.098dia.)2.5 10

(0.394)

NAME PLATE P.C.D=φ16(P.C.D=0.63dia. )

±0.2

±0.008

0.8

2-φ(2-0.047dia. )

±0.2

±0.008

1.2

２－2.8×0.5t

6.2

1.5

(+)(-) TERMINAL DETAILED DRAWING

DIMENSIONS Unit mm(inch)

φ

-0.01

02.5

12

2.7

38.8(1.528)

3.2

φ10

φ

-0.1 0

10

φ27.8

(1.094dia.)

φ29

(1.142dia.)

(0.098dia. )

(0.394dia.)

(2-0.110×0.02t )

0-0.0004

(0.394dia. )

0-0.004

(0.126)

(0.106)

(0.032) (0.244)

(0.059)

(0.472)

DC Brush Motors DMN29 Motor

14(0.551)

(0.866±0.012 )

22(0.866)

03 DMN Series

※

SPEEDCURRENT

Outline

Outline

DMN29BL

AIntermittent Operation

21.5 (0.847)

5 (0.197)

15.5 (0.61)

10.5(0.413)

±0.1

5

φ -0.02

0 6φ10

4-0.5 (4-0.02)

17.9 (0.705) (RED)

(+)TERMINAL

(BLACK)(-)TERMINAL

NAMEPLATE

DMN29BA-002, 003

φ1.2

HOLEφ 0+0.13

±0.5

2-2.8

(0.3594dia.)

(2-0.11 )

(1.142dia.)

(3.937)

(0.047dia.)

(0.217)

(0.736) (0.638)

(0.236)

(0.276)

±0.02

(0.197±0.004 )

(0.315 )

0-0.0008

7

3.2

φ29

φ10

56.8

100

5.518.7

6

16.2

φ-0.02

08

Specification

GEARRATIO

※Rotation of gearbox shaft is in reverse of rotation　of motor.

78.9

RATED TORQUE

0.190

N・m

27.8

oz・in r/min

SPEED

56

DMN29BA-002DMN29BA-003

LIntermittent Operation

Specification

※Enter the required reduction ratio in the .※Enter the required voltage A or B in the .

WEIGHT：140g 0.31 lb

WEIGHT：250g 0.55 lbGEARRATIO

30

50

120

150

200

255

RATED TORQUE

0.14

0.23

0.56

0.69

0.92

0.98

N・m

19.5

32.0

77.9

90.8

131

139

oz・in r/min

123

74.0

30.8

24.7

18.5

15.3

DMN29BL

DIMENSIONS Unit mm(inch)

DIMENSIONS Unit mm(inch)

(1.417)

(0.047dia.)(2-0.11dia.±0.02)

(2-0.13dia.)

(0.394dia.)

(1.142dia.)

(1.165)

(0.551)

(0.709)

(4.075)

(0.394dia.)

(1.693)

(0.126)

2-φ3.5

φ1.2±0.52-2.8

3.2

φ29φ10

36

1843

103.5

29.6

1431(1.22)

HOLE

(2.236)(0.126)

4-M4DEPTH 6MAX(4-M4DEPTH 0.236MAX)

24.6(0.969)

66.5(2.618)

±0.330

38 (1.496)

12

±0.3

224

30(0.158)(1.181)

4(0.158)

(BLACK)(-)TERMINAL

(RED)(+)TERMINAL

16(0.63)

(0.472)

SPEED

DC Brush Motors DMN29 Motor

(0.236dia -0.0008)

0

(0.118dia.+0.004)0

14(0.551)

14(0.551)

14(0.551)

(1.181±0.012)

(0.866

(0.866±±0.012

0.012 ))

(0.866±0.012 )

22(0.866)22(0.866)22(0.866)

04DMN Series

Appendix H

Micro switch datasheet

34

Appendix I

EMG-sensor datasheet

36

Measuring muscle activation via electric potential, referred to as electromyography (EMG), hastraditionally been used for medical research and diagnosis of neuromuscular disorders. However,with the advent of ever shrinking yet more powerful microcontrollers and integrated circuits, EMGcircuits and sensors have found their way into prosthetics, robotics and other control systems.

3-lead Muscle / ElectromyographySensor for Microcontroller Applications

FEATURES NEW - Wearable Design NEW - Single Supply

+3.1V to +5.9V Polarity reversal protection

NEW - Two Output Modes EMG Envelope Raw EMG

NEW - Expandable via Shields NEW - LED Indicators Specially Designed For Microcontrollers Adjustable Gain

1 - Power Supply, +Vs2 - Power Supply, GND3 - Output Signal, SIG

Sensor Layout

What is electromyography?

EMAIL: support@advancer.co

Raw EMG Signal - 7Shield Power (output) - 8

Shield GND- 9

www.AdvancerTechnologies.com

© 2015-2016

4 - Mid Muscle Electrode Pin

5 - End Muscle Electrode Pin

6 - Reference Electrode PinReference Electrode Cable

Adjustable Gain (SIG Output Only)

Mid Muscle Electrode Snap

End Muscle Electrode Snap

MyoWare™ Muscle Sensor (AT-04-001) DATASHEET

APPLICATIONS Video games Robotics Medical Devices Wearable/Mobile Electronics Prosthetics/Orthotics

Power Switch

Note: Isolator model is only a suggestion.

Setup Configurations (Arduino is shown but MyoWare is compatible with most development boards)

a) Battery powered with isolation via no direct external connections

b) Grid powered with USB isolation

Note: Since no component is connected to electrical grid, further isolation is not required. It is also acceptable to power the MCU with a battery via the USB or barrel ports.

EMAIL: support@advancer.co www.AdvancerTechnologies.com

REC

OM

MEN

DED

© 2015-2016

(No

te: A

rdu

ino

an

d b

att

erie

s n

ot

incl

ud

ed. A

rdu

ino

set

up

is o

nly

a

n e

xam

ple

; sen

sor

will

wo

rk w

ith

nu

mer

ou

s o

ther

dev

ices

.)

USB Isolator(Adafruit 2107)

REC

OM

MEN

DED

c) Battery powered sensor, Grid powered MCU with USB isolation

Setup Configurations (cont’d)

d) Grid powered. Warning: No isolation.

Note: This configuration has no isolation. Usually safe but rare situations could create a current loop to the electrical grid.

EMAIL: support@advancer.co www.AdvancerTechnologies.com

© 2015-2016

Note: Isolator model is only a suggestion.

USB Isolator(Adafruit 2107)

REC

OM

MEN

DED

Setup Instructions

1) Thoroughly clean the intended area with soap to remove dirt and oil2) Snap electrodes to the sensor’s snap connectors

(Note: While you can snap the sensor to the electrodes after they’ve been placed on the muscle, we do not

recommend doing so due to the possibility of excessive force being applied and bruising the skin.)

3) Place the sensor on the desired musclea. After determining which muscle group you want to target (e.g. bicep, forearm,

calf), clean the skin thoroughlyb. Place the sensor so one of the connected electrodes is in the middle of the

muscle body. The other electrode should line up in the direction of the muscle length

c. Peel off the backs of the electrodes to expose the adhesive and apply them to the skin

d. Place the reference electrode on a bony or nonadjacent muscular part of your body near the targeted muscle

4) Connect to a development board (e.g. Arduino, RaspberryPi), microcontroller, or ADCa. See configurations previously shown

Example Sensor Location for Bicep

EMAIL: support@advancer.co www.AdvancerTechnologies.com

© 2015-2016

Note: Not To Scale

Why is electrode placement important?

EMAIL: support@advancer.co www.AdvancerTechnologies.com

Raw EMG output

Innervation Zone

Correct PlacementMidline of the muscle belly between an innervation zone and a myotendon junction

Midline Offset

Myotendon Junction

Position and orientation of the muscle sensor electrodes has a vast effect on the strength ofthe signal. The electrodes should be place in the middle of the muscle body and should bealigned with the orientation of the muscle fibers. Placing the sensor in other locations willreduce the strength and quality of the sensor’s signal due to a reduction of the number ofmotor units measured and interference attributed to crosstalk.

© 2015-2016

RAW EMG vs EMG Envelope

Our Muscle Sensors are designed to be used directly with a microcontroller. Therefore, oursensors primary output is not a RAW EMG signal but rather an amplified, rectified, andintegrated signal (AKA the EMG’s envelope) that will work well with a microcontroller’sanalog-to-digital converter (ADC). This difference is illustrated below using arepresentative EMG signal. Note: Actual sensor output not shown.

RAW EMG Signal

Rectified EMG Signal

Rectified & IntegratedEMG Signal

EMAIL: support@advancer.co www.AdvancerTechnologies.com

Reconfigure for Raw EMG Output

This new version has the ability to output an amplified raw EMG signal.To output the raw EMG signal, simply connect the raw EMG signal pin to your measuring device instead of the SIG pin.

Connect

© 2015-2016

Note: The RAW output is centered about an offset voltage of +Vs/2, see above. It is important to ensure +Vs is the max voltage of the MCU’s analog to digital converter. This will assure that you completely see both positive and negative portions of the waveform.

Note: The amplification for the RAW output is not adjustable via the GAIN potentiometer.

Connecting external electrode cables

Re

fEn

dM

idd

le

EMAIL: support@advancer.co www.AdvancerTechnologies.com

© 2015-2016

This new version has embedded electrode snaps right on the sensor board itself, replacing the need for a cable. However, if the on board snaps do not fit a user’s specific application, an external cable can be connected to the board through three through hole pads shown above.

MiddleConnect this pad to the cable leading to an electrode placed in the middle of the muscle body.EndConnect this to the cable leading to an electrode placed adjacent to the middle electrode towards the end of the muscle body.RefConnect this to the reference electrode. The reference electrode should be placed on an separate section of the body, such as the bony portion of the elbow or a nonadjacent muscle

Adjusting the gain

We recommend for users to get their sensor setup working reliably prior to adjusting the gain. The default gain setting should be appropriate for most applications.To adjust the gain, locate the gain potentiometer in the lower left corner of the sensor (marked as “GAIN”). Using a Phillips screwdriver, turn the potentiometer clockwise to increase the output gain; turn the potentiometer counterclockwise to reduce the gain.

Note: In order to reduce the required voltage for the sensor, the redesign switch out a JFET amplifier for a CMOS amplifier. However CMOS amplifiers tend to have slower recovery times when saturated. Therefore, we advise users to adjust the gain such that the output signal will not saturate the amplifier.

Electrical Specifications

Parameter Min TYP Max

Supply Voltage +3.1V +3.3V or +5V +6.3V

Adjustable Gain Potentiometer, Rgain

(G = 201 * Rgain / 1 kΩ)0.01 Ω 50 kΩ 100 kΩ

Output Signal Voltage EMG EnvelopeRaw EMG (centered about +Vs/2)

0V0V

----

+Vs+Vs

Input Impedance -- 110 GΩ --

Supply Current -- 9 mA 14 mA

Common Mode Rejection Ratio (CMRR) -- 110 --

Input Bias -- 1 pA --

EMAIL: support@advancer.co www.AdvancerTechnologies.com

Dimensions

© 2015-2016

0.82(20.7)

2.06 (52.3)

2 x 0.125” DIA. Thru Hole

1.75 / (44.4)

0.019(5.0)

1.93 / (49.1)

0.51(13.0)

Appendix J

Motor driver datasheet

45

L298

Jenuary 2000

DUAL FULL-BRIDGE DRIVER

Multiwatt15

ORDERING NUMBERS : L298N (Multiwatt Vert.) L298HN (Multiwatt Horiz.)

L298P (PowerSO20)

BLOCK DIAGRAM

.OPERATING SUPPLY VOLTAGE UP TO 46 V.TOTAL DC CURRENT UP TO 4 A . LOW SATURATION VOLTAGE.OVERTEMPERATURE PROTECTION.LOGICAL "0" INPUT VOLTAGE UP TO 1.5 V(HIGH NOISE IMMUNITY)

DESCRIPTION

The L298 is an integrated monolithic circuit in a 15-lead Multiwatt and PowerSO20 packages. It is ahigh voltage, high current dual full-bridge driver de-signed to accept standard TTL logic levels and driveinductive loads such as relays, solenoids, DC andstepping motors. Two enable inputs are provided toenable or disable the device independently of the in-put signals. The emitters of the lower transistors ofeach bridge are connected together and the corre-sponding external terminal can be used for the con-

nection of an external sensing resistor. An additionalsupply input is provided so that the logic works at alower voltage.

PowerSO20

®

1/13

PIN CONNECTIONS (top view)

GND

Input 2 VSS

N.C.

Out 1

VS

Out 2

Input 1

Enable A

Sense A

GND 10

8

9

7

6

5

4

3

2

13

14

15

16

17

19

18

20

12

1

11 GND

D95IN239

Input 3

Enable B

Out 3

Input 4

Out 4

N.C.

Sense B

GND

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

VS Power Supply 50 V

VSS Logic Supply Voltage 7 V

VI,Ven Input and Enable Voltage –0.3 to 7 V

IO Peak Output Current (each Channel)– Non Repetitive (t = 100µs)–Repetitive (80% on –20% off; ton = 10ms)–DC Operation

32.52

AAA

Vsens Sensing Voltage –1 to 2.3 V

Ptot Total Power Dissipation (Tcase = 75°C) 25 W

Top Junction Operating Temperature –25 to 130 °CTstg, Tj Storage and Junction Temperature –40 to 150 °C

THERMAL DATA

Symbol Parameter PowerSO20 Multiwatt15 Unit

Rth j-case Thermal Resistance Junction-case Max. – 3 °C/W

Rth j-amb Thermal Resistance Junction-ambient Max. 13 (*) 35 °C/W

(*) Mounted on aluminum substrate

1

2

3

4

5

6

7

9

10

11

8

ENABLE B

INPUT 3

LOGIC SUPPLY VOLTAGE VSS

GND

INPUT 2

ENABLE A

INPUT 1

SUPPLY VOLTAGE VS

OUTPUT 2

OUTPUT 1

CURRENT SENSING A

TAB CONNECTED TO PIN 8

13

14

15

12

CURRENT SENSING B

OUTPUT 4

OUTPUT 3

INPUT 4

D95IN240A

Multiwatt15

PowerSO20

L298

2/13

PIN FUNCTIONS (refer to the block diagram)

MW.15 PowerSO Name Function

1;15 2;19 Sense A; Sense B Between this pin and ground is connected the sense resistor tocontrol the current of the load.

2;3 4;5 Out 1; Out 2 Outputs of the Bridge A; the current that flows through the loadconnected between these two pins is monitored at pin 1.

4 6 VS Supply Voltage for the Power Output Stages.A non-inductive 100nF capacitor must be connected between thispin and ground.

5;7 7;9 Input 1; Input 2 TTL Compatible Inputs of the Bridge A.

6;11 8;14 Enable A; Enable B TTL Compatible Enable Input: the L state disables the bridge A(enable A) and/or the bridge B (enable B).

8 1,10,11,20 GND Ground.

9 12 VSS Supply Voltage for the Logic Blocks. A100nF capacitor must beconnected between this pin and ground.

10; 12 13;15 Input 3; Input 4 TTL Compatible Inputs of the Bridge B.

13; 14 16;17 Out 3; Out 4 Outputs of the Bridge B. The current that flows through the loadconnected between these two pins is monitored at pin 15.

– 3;18 N.C. Not Connected

ELECTRICAL CHARACTERISTICS (VS = 42V; VSS = 5V, Tj = 25°C; unless otherwise specified)

Symbol Parameter Test Conditions Min. Typ. Max. Unit

VS Supply Voltage (pin 4) Operative Condition VIH +2.5 46 V

VSS Logic Supply Voltage (pin 9) 4.5 5 7 V

IS Quiescent Supply Current (pin 4) Ven = H; IL = 0 Vi = L Vi = H

1350

2270

mAmA

Ven = L Vi = X 4 mA

ISS Quiescent Current from VSS (pin 9) Ven = H; IL = 0 Vi = L Vi = H

247

3612

mAmA

Ven = L Vi = X 6 mA

ViL Input Low Voltage(pins 5, 7, 10, 12)

–0.3 1.5 V

ViH Input High Voltage(pins 5, 7, 10, 12)

2.3 VSS V

IiL Low Voltage Input Current(pins 5, 7, 10, 12)

Vi = L –10 µA

IiH High Voltage Input Current(pins 5, 7, 10, 12)

Vi = H ≤ VSS –0.6V 30 100 µA

Ven = L Enable Low Voltage (pins 6, 11) –0.3 1.5 V

Ven = H Enable High Voltage (pins 6, 11) 2.3 VSS V

Ien = L Low Voltage Enable Current(pins 6, 11)

Ven = L –10 µA

Ien = H High Voltage Enable Current(pins 6, 11)

Ven = H ≤ VSS –0.6V 30 100 µA

VCEsat (H) Source Saturation Voltage IL = 1AIL = 2A

0.95 1.352

1.72.7

VV

VCEsat (L) Sink Saturation Voltage IL = 1A (5)IL = 2A (5)

0.85 1.21.7

1.62.3

VV

VCEsat Total Drop IL = 1A (5)IL = 2A (5)

1.80 3.24.9

VV

Vsens Sensing Voltage (pins 1, 15) –1 (1) 2 V

L298

3/13

Figure 1 : Typical Saturation Voltage vs. Output Current.

Figure 2 : Switching Times Test Circuits.

Note : For INPUT Switching, set EN = HFor ENABLE Switching, set IN = H

1) 1)Sensing voltage can be –1 V for t ≤ 50 µsec; in steady state Vsens min ≥ – 0.5 V.2) See fig. 2.3) See fig. 4.4) The load must be a pure resistor.

ELECTRICAL CHARACTERISTICS (continued)

Symbol Parameter Test Conditions Min. Typ. Max. Unit

T1 (Vi) Source Current Turn-off Delay 0.5 Vi to 0.9 IL (2); (4) 1.5 µs

T2 (Vi) Source Current Fall Time 0.9 IL to 0.1 IL (2); (4) 0.2 µs

T3 (Vi) Source Current Turn-on Delay 0.5 Vi to 0.1 IL (2); (4) 2 µs

T4 (Vi) Source Current Rise Time 0.1 IL to 0.9 IL (2); (4) 0.7 µs

T5 (Vi) Sink Current Turn-off Delay 0.5 Vi to 0.9 IL (3); (4) 0.7 µs

T6 (Vi) Sink Current Fall Time 0.9 IL to 0.1 IL (3); (4) 0.25 µs

T7 (Vi) Sink Current Turn-on Delay 0.5 Vi to 0.9 IL (3); (4) 1.6 µs

T8 (Vi) Sink Current Rise Time 0.1 IL to 0.9 IL (3); (4) 0.2 µs

fc (Vi) Commutation Frequency IL = 2A 25 40 KHz

T1 (Ven) Source Current Turn-off Delay 0.5 Ven to 0.9 IL (2); (4) 3 µs

T2 (Ven) Source Current Fall Time 0.9 IL to 0.1 IL (2); (4) 1 µs

T3 (Ven) Source Current Turn-on Delay 0.5 Ven to 0.1 IL (2); (4) 0.3 µs

T4 (Ven) Source Current Rise Time 0.1 IL to 0.9 IL (2); (4) 0.4 µs

T5 (Ven) Sink Current Turn-off Delay 0.5 Ven to 0.9 IL (3); (4) 2.2 µs

T6 (Ven) Sink Current Fall Time 0.9 IL to 0.1 IL (3); (4) 0.35 µs

T7 (Ven) Sink Current Turn-on Delay 0.5 Ven to 0.9 IL (3); (4) 0.25 µs

T8 (Ven) Sink Current Rise Time 0.1 IL to 0.9 IL (3); (4) 0.1 µs

L298

4/13

Figure 3 : Source Current Delay Times vs. Input or Enable Switching.

Figure 4 : Switching Times Test Circuits.

Note : For INPUT Switching, set EN = HFor ENABLE Switching, set IN = L

L298

5/13

Figure 5 : Sink Current Delay Times vs. Input 0 V Enable Switching.

Figure 6 : Bidirectional DC Motor Control.

L = Low H = High X = Don’t care

Inputs Function

Ven = H C = H ; D = L Forward

C = L ; D = H Reverse

C = D Fast Motor Stop

Ven = L C = X ; D = X Free RunningMotor Stop

L298

6/13

Figure 7 : For higher currents, outputs can be paralleled. Take care to parallel channel 1 with channel 4 and channel 2 with channel 3.

APPLICATION INFORMATION (Refer to the block diagram)1.1. POWER OUTPUT STAGE

The L298 integrates two power output stages (A ; B).The power output stage is a bridge configurationand its outputs can drive an inductive load in com-mon or differenzial mode, depending on the state ofthe inputs. The current that flows through the loadcomes out from the bridge at the sense output : anexternal resistor (RSA ; RSB.) allows to detect the in-tensity of this current.

1.2. INPUT STAGE

Each bridge is driven by means of four gates the in-put of which are In1 ; In2 ; EnA and In3 ; In4 ; EnB.The In inputs set the bridge state when The En inputis high ; a low state of the En input inhibits the bridge.All the inputs are TTL compatible.

2. SUGGESTIONS

A non inductive capacitor, usually of 100 nF, mustbe foreseen between both Vs and Vss, to ground,as near as possible to GND pin. When the large ca-pacitor of the power supply is too far from the IC, asecond smaller one must be foreseen near theL298.

The sense resistor, not of a wire wound type, mustbe grounded near the negative pole of Vs that mustbe near the GND pin of the I.C.

Each input must be connected to the source of thedriving signals by means of a very short path.

Turn-On and Turn-Off : Before to Turn-ON the Sup-ply Voltage and before to Turn it OFF, the Enable in-put must be driven to the Low state.

3. APPLICATIONS

Fig 6 shows a bidirectional DC motor control Sche-matic Diagram for which only one bridge is needed.The external bridge of diodes D1 to D4 is made byfour fast recovery elements (trr ≤ 200 nsec) thatmust be chosen of a VF as low as possible at theworst case of the load current.

The sense output voltage can be used to control thecurrent amplitude by chopping the inputs, or to pro-vide overcurrent protection by switching low the en-able input.

The brake function (Fast motor stop) requires thatthe Absolute Maximum Rating of 2 Amps mustnever be overcome.

When the repetitive peak current needed from theload is higher than 2 Amps, a paralleled configura-tion can be chosen (See Fig.7).

An external bridge of diodes are required when in-ductive loads are driven and when the inputs of theIC are chopped ; Shottky diodes would be preferred.

L298

7/13

This solution can drive until 3 Amps In DC operationand until 3.5 Amps of a repetitive peak current.

On Fig 8 it is shown the driving of a two phase bipolarstepper motor ; the needed signals to drive the in-puts of the L298 are generated, in this example,from the IC L297.

Fig 9 shows an example of P.C.B. designed for theapplication of Fig 8.

Fig 10 shows a second two phase bipolar steppermotor control circuit where the current is controlledby the I.C. L6506.

Figure 8 : Two Phase Bipolar Stepper Motor Circuit.

This circuit drives bipolar stepper motors with winding currents up to 2 A. The diodes are fast 2 A types.

RS1 = RS2 = 0.5 Ω

D1 to D8 = 2 A Fast diodes VF ≤ 1.2 V @ I = 2 Atrr ≤ 200 ns

L298

8/13

Figure 9 : Suggested Printed Circuit Board Layout for the Circuit of fig. 8 (1:1 scale).

Figure 10 : Two Phase Bipolar Stepper Motor Control Circuit by Using the Current Controller L6506.

RR and Rsense depend from the load current

L298

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Multiwatt15 V

DIM.mm inch

MIN. TYP. MAX. MIN. TYP. MAX.

A 5 0.197

B 2.65 0.104

C 1.6 0.063

D 1 0.039

E 0.49 0.55 0.019 0.022

F 0.66 0.75 0.026 0.030

G 1.02 1.27 1.52 0.040 0.050 0.060

G1 17.53 17.78 18.03 0.690 0.700 0.710

H1 19.6 0.772

H2 20.2 0.795

L 21.9 22.2 22.5 0.862 0.874 0.886

L1 21.7 22.1 22.5 0.854 0.870 0.886

L2 17.65 18.1 0.695 0.713

L3 17.25 17.5 17.75 0.679 0.689 0.699

L4 10.3 10.7 10.9 0.406 0.421 0.429

L7 2.65 2.9 0.104 0.114

M 4.25 4.55 4.85 0.167 0.179 0.191

M1 4.63 5.08 5.53 0.182 0.200 0.218

S 1.9 2.6 0.075 0.102

S1 1.9 2.6 0.075 0.102

Dia1 3.65 3.85 0.144 0.152

OUTLINE ANDMECHANICAL DATA

L298

10/13

DIM.mm inch

MIN. TYP. MAX. MIN. TYP. MAX.

A 5 0.197

B 2.65 0.104

C 1.6 0.063

E 0.49 0.55 0.019 0.022

F 0.66 0.75 0.026 0.030

G 1.14 1.27 1.4 0.045 0.050 0.055

G1 17.57 17.78 17.91 0.692 0.700 0.705

H1 19.6 0.772

H2 20.2 0.795

L 20.57 0.810

L1 18.03 0.710

L2 2.54 0.100

L3 17.25 17.5 17.75 0.679 0.689 0.699

L4 10.3 10.7 10.9 0.406 0.421 0.429

L5 5.28 0.208

L6 2.38 0.094

L7 2.65 2.9 0.104 0.114

S 1.9 2.6 0.075 0.102

S1 1.9 2.6 0.075 0.102

Dia1 3.65 3.85 0.144 0.152

Multiwatt15 H

OUTLINE ANDMECHANICAL DATA

L298

11/13

JEDEC MO-166

PowerSO20

e

a2 A

E

a1

PSO20MEC

DETAIL A

T

D

1

1120

E1E2

h x 45

DETAIL Alead

sluga3

S

Gage Plane0.35

L

DETAIL B

R

DETAIL B

(COPLANARITY)

G C

- C -

SEATING PLANE

e3

b

c

NN

H

BOTTOM VIEW

E3

D1

DIM.mm inch

MIN. TYP. MAX. MIN. TYP. MAX.

A 3.6 0.142

a1 0.1 0.3 0.004 0.012

a2 3.3 0.130

a3 0 0.1 0.000 0.004

b 0.4 0.53 0.016 0.021

c 0.23 0.32 0.009 0.013

D (1) 15.8 16 0.622 0.630

D1 9.4 9.8 0.370 0.386

E 13.9 14.5 0.547 0.570

e 1.27 0.050

e3 11.43 0.450

E1 (1) 10.9 11.1 0.429 0.437

E2 2.9 0.114

E3 5.8 6.2 0.228 0.244

G 0 0.1 0.000 0.004

H 15.5 15.9 0.610 0.626

h 1.1 0.043

L 0.8 1.1 0.031 0.043

N 10 (max.)

S

T 10 0.394(1) "D and F" do not include mold flash or protrusions.- Mold flash or protrusions shall not exceed 0.15 mm (0.006").- Critical dimensions: "E", "G" and "a3"

OUTLINE ANDMECHANICAL DATA

8 (max.)

10

L298

12/13

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the conse-quences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. Nolicense is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in thispublication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMi-croelectronics products are not authorized for use as critical components in life support devices or systems without express writtenapproval of STMicroelectronics.

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L298

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TRITA ITM-EX 2018:54

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