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acknowledgments.tex
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%----------Danksagung/Acknowledgments-------------------------------------------------------------- %----------Danksagung/Acknowledgments--------------------------------------------------------------
\addsec{Acknowledgments} \addsec{Acknowledgments}
Helo Hello (:

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chap1/introduction.tex
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\subsection{Motivation} \section{Motivation}
In recent years, computers are used to some extend in almost every industry in \label{sec:label}
Europe \cite{eurostat_ent_w_comp} and China \cite{iresearch_ent_w_comp}. This
leads to the conclusion, that also other countries must have a high usage of
computers in corporations. Furthermore, according to a statistic published by
\citeauthor{itu_hh_w_comp} in 2019, nearly half of the worldwide households have
access to at least one computer \cite{itu_hh_w_comp}. One of the most used
devices for data input while operating a computer is the keyboard
\parencite[22]{handbook_chi}. Therefore, people who use a computer, either at
home or to fulfill certain tasks at work, are also likely to use a keyboard. An
important part of a keyboard is the keyswitch also called keyboard key or
key. Those keyswitches use, depending on the manufacturer or keyboard type,
different mechanisms to actuate a keypress. More commonly used mechanism to date
are scissor switches, mostly used in laptop keyboards, rubber dome and membrane switches,
often used in low- to mid-priced keyboards, and mechanical switches which are
the main switch type for high-end and gaming keyboards
\cite{ergopedia_keyswitch}. Depending on the mechanism and type of key used, it
is possible that different force has to be applied to the key to activate
it. Normally, the force required to activate a key is identical for each key
across the keyboard. However, previous research has shown, that there is a
disparity in force generated by different fingers
\cite{bretz_finger_force}. This raises the question, why there are no keyboards
for personal or work related use cases with adjusted actuation forces per finger
or even customizable keyboards, where an individual can select the actuation
force for each keyswitch individually.
In recent decades, computers and other electronic devices have become an
indispensable part of everyday life. Computers are used in almost every industry
\cite{iresearch_ent_w_comp, eurostat_ent_w_comp} and almost half of the
worldwide households have access to at least one computer \cite{itu_hh_w_comp}.
Even 153 years after the first typewriter was patented \cite{noyes_qwerty, }
people still use keyboards as their main way to input data into a computer
\parencite[22]{handbook_chi}, \cite{broel_dektop_or_smartphone}. A potential
problem while interacting with a computer through the usage of a keyboard are
rapid movements of the fingers over a prolonged time.
Input tasks are not only restricted to pure data entry but also include complex
inputs required by games.
Prolonged usage of computers can lead to serious diseases % In recent years, computers are used to some extend in almost every industry in
% Europe \cite{eurostat_ent_w_comp} and China \cite{iresearch_ent_w_comp}. This
% leads to the conclusion, that also other countries must have a high usage of
% computers in corporations. Furthermore, according to a statistic published by
% \citeauthor{itu_hh_w_comp} in 2019, nearly half of the worldwide households have
% access to at least one computer \cite{itu_hh_w_comp}. One of the most used
% devices for data input while operating a computer is the keyboard
% \parencite[22]{handbook_chi}. Therefore, people who use a computer, either at
% home or to fulfill certain tasks at work, are also likely to use a keyboard. An
% important part of a keyboard is the keyswitch also called keyboard key or
% key. Those keyswitches use, depending on the manufacturer or keyboard type,
% different mechanisms to actuate a keypress. More commonly used mechanism to date
% are scissor switches, mostly used in laptop keyboards, rubber dome and membrane switches,
% often used in low- to mid-priced keyboards, and mechanical switches which are
% the main switch type for high-end and gaming keyboards
% \cite{ergopedia_keyswitch}. Depending on the mechanism and type of key used, it
% is possible that different force has to be applied to the key to activate
% it. Normally, the force required to activate a key is identical for each key
% across the keyboard. However, previous research has shown, that there is a
% disparity in force generated by different fingers
% \cite{bretz_finger_force}. This raises the question, why there are no keyboards
% for personal or work related use cases with adjusted actuation forces per finger
% or even customizable keyboards, where an individual can select the actuation
% force for each keyswitch individually.
% In recent decades, computers and other electronic devices have become an
% indispensable part of everyday life. Computers are used in almost every industry
% \cite{iresearch_ent_w_comp, eurostat_ent_w_comp} and almost half of the
% worldwide households have access to at least one computer \cite{itu_hh_w_comp}.
% Even 153 years after the first typewriter was patented \cite{noyes_qwerty, }
% people still use keyboards as their main way to input data into a computer
% \parencite[22]{handbook_chi}, \cite{broel_dektop_or_smartphone}. A potential
% problem while interacting with a computer through the usage of a keyboard are
% rapid movements of the fingers over a prolonged time.
% Input tasks are not only restricted to pure data entry but also include complex
% inputs required by games.
% Prolonged usage of computers can lead to serious diseases
With the rising popularity of smartphones and other touchscreen devices % With the rising popularity of smartphones and other touchscreen devices
\cite{gs_statcounter_dmt_2020} which utilize virtual keyboards to fulfill a % \cite{gs_statcounter_dmt_2020} which utilize virtual keyboards to fulfill a
variety of tasks that also include data entry, e.g., writing text messages, % variety of tasks that also include data entry, e.g., writing text messages,
short emails, communicating on social media or web browsing % short emails, communicating on social media or web browsing

383
chap2/literature_review.tex
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@ -1,59 +1,79 @@
\section{Literature Review} \section{Literature Review}
To better understand which metrics and methods are meaningful in the domain of keyboards and especially when % To better understand which metrics and methods are meaningful in the domain of keyboards and especially when
To investigate whether or not solely the actuation force of individual keys can make a difference in terms of efficiency or satisfaction an .... % To investigate whether or not solely the actuation force of individual keys can make a difference in terms of efficiency or satisfaction an ....
\subsection{Keyboards and key switches} \subsection{Keyboards and key switches}
\begin{figure}[ht]
\centering
\includegraphics[width=1.0\textwidth]{images/keyboard_models.jpg}
\caption{Different keyboard models}
\label{fig:keyboard_models}
\end{figure}
Keyboards are well known input devices used to operate a computer. There are a Keyboards are well known input devices used to operate a computer. There are a
variety of keyboard types and models available on the market, some of which can variety of keyboard types and models available on the market, some of which can
be seen in Figure \ref{fig:keyboard_models}. The obvious difference between be seen in Figure \ref{fig:keyboard_models}. The obvious difference between
those keyboards in Figure \ref{fig:keyboard_models} is their general those keyboards in Figure \ref{fig:keyboard_models} is their general
appearance. What we see is mainly the general shape of the enclosure and the appearance. What we see is mainly the shape of the enclosure and the keycaps,
keycaps, which are the rectangular pieces of plastic on top of the actual which are the rectangular pieces of plastic on top of the actual keyswitches
keyswitches which indicate which letter, number or symbol, also known as which sometimes indicate which letter, number or symbol, also known as
characters, a keypress should send to the computer. These keycaps are mainly characters, a keypress should send to the computer. These keycaps are mainly
made out of the two plastics \gls{ABS} and \gls{PBT} which mainly differ in made out of the two plastics \gls{ABS} and \gls{PBT} which primarily differ in
feel, durability, cost and sound \parencite[8]{bassett_keycap}. Nowadays, there feel, durability, cost and sound \parencite[8]{bassett_keycap}.
are three main standards for the physical layout of keyboards namely ISO/IEC
9995 \cite{iso9995-2}, ANSI-INCITS 154-1988 \cite{ansi-incits-154-1988} and JIS \begin{figure}[ht]
X 6002-1980 \cite{jis-x-6002-1980}, that propose slightly different arrangements \centering
of the keys and some even alter the shape of a few keys. Figure \includegraphics[width=1.0\textwidth]{images/keyboard_layouts.png}
TODO\ref{fig:keyboard_ISO_ANSI_JSP} shows the layouts defined by the three \caption{The three major physical keyboard layouts all labeled with the
standards mentioned and shows the main differences. In addition to the physical alphanumeric characters of the most popular layout―\gls{QWERTY}
layout, there are also various layouts concerning the mapping of the physical \cite{wiki_kb_layouts}}
key to a character that is displayed by the computer. Most of the time, the \label{fig:keyboard_layouts}
mapping happens on the computer via software and therefore the choice of layout \end{figure}
is not necessarily restricted by the physical layout of the keyboard but rather
a personal preference. As seen in Figure TODO \ref{fig:keyboard_models}, there Nowadays, there are three main standards for the physical layout of keyboards
are also non standard physical layouts available which are often designed to namely ISO/IEC 9995 \cite{iso9995-2}, ANSI-INCITS 154-1988
improve the posture of the upper extremity while typing to reduce the risk of \cite{ansi-incits-154-1988} and JIS X 6002-1980 \cite{jis-x-6002-1980}, that
injury or even assist in recovering from previous \gls{WRUED} propose slightly different arrangements of the keys and some even alter the
\cite{ripat_ergo}. Those designs often split the keyboard in two halves to shape of a few keys. Figure TODO\ref{fig:keyboard_layouts} shows the layouts
reduce ulnar deviation and some designs also allow tenting of the halves or defined by the three standards mentioned and shows the main differences. In
provide a fixed tent which also reduces forearm pronation \cite{baker_ergo, addition to the physical layout, there are also various layouts concerning the
rempel_ergo}. Besides the exterior design of the keyboard, there is another mapping of the physical key to a character that is displayed by the
part of interest—the keyswitch. This component of a keyboard actually sends the computer. Most of the time, the mapping happens on the computer via software and
signal that a key is pressed down. There are different types of keyswitches therefore the choice of layout is not necessarily restricted by the physical
available to date. The more commonly available ones are scissor switches and layout of the keyboard but rather a personal preference. As seen in Figure
rubber dome switches which are both subsets of the membrane switches. Scissor \ref{fig:keyboard_models}, there are also non standard physical layouts
switches are often found in keyboards that are integrated into notebooks while available which are often designed to improve the posture of the upper extremity
rubber dome switches are mostly used in workplace keyboards. Both variants use a while typing to reduce the risk of injury or even assist in recovering from
rubber membrane with small domes underneath each key. When a key is pressed, the previous \gls{WRUED} \cite{ripat_ergo}. Those designs often split the keyboard
corresponding dome collapses and because the dome's inner wall is coated with a in two halves to reduce ulnar deviation and some designs also allow tenting of
conductive material, closes an electrical circuit \cite{ergopedia_keyswitch, the halves or provide a fixed tent which also reduces forearm pronation
peery_3d_keyswitch}. Another type of switches are mechanical \cite{baker_ergo, rempel_ergo}. Besides the exterior design of the keyboard,
keyswitches. These switches are frequently used in gaming and high quality there is another part of interest—the keyswitch. This component of a keyboard
workplace keyboards as well as by enthusiast along with prosumers which build actually sends the signal that a key is pressed. There are different types of
and then sell custom made keyboards to the latter audience \cite{bassett_keycap, keyswitches available to date. The more commonly available ones are scissor
ergopedia_keyswitch}. These keyswitches are composed of several mechanical switches and rubber dome switches which are both subsets of the membrane
parts which can be examined in Figure TODO\ref{fig:mech_keyswitch_dissas}. The switches. Scissor switches are often found in keyboards that are integrated into
housing is made up of two parts, the bottom and top shell. The actual mechanism notebooks while rubber dome switches are mostly used in workplace
consists of two conductive plates, which when connected trigger a keypress, a keyboards. Both variants use a rubber membrane with small domes underneath each
stainless steel spring which defines how much force has to be applied to the key. When a key is pressed, the corresponding dome collapses and because the
switch to activate it and a stem which sits on top of the spring and separates dome's inner wall is coated with a conductive material, closes an electrical
the two plates. When pressure is applied to the keycap, which is connected to circuit \cite{ergopedia_keyswitch, peery_3d_keyswitch}. Another type of switches
the stem, the spring gets contracted and the stem moves downwards and thereby are mechanical keyswitches. These switches are frequently used in gaming and
stops separating the two plates which closes the electrical circuit and sends a high quality workplace keyboards as well as by enthusiast along with prosumers
which build and then sell custom made keyboards to the latter audience
\cite{bassett_keycap, ergopedia_keyswitch}. These keyswitches are composed of
several mechanical parts which can be examined in Figure
\ref{fig:mech_keyswitches_dissas}. The housing is made up of two parts, the
bottom and top shell. The actual mechanism consists of two conductive plates,
which when connected trigger a keypress, a stainless steel spring which defines
how much force has to be applied to the switch to activate it and a stem which
sits on top of the spring and separates the two plates. The shape of the stem,
represented by the enlarged red lines in Figure
\ref{fig:mech_keyswitches_dissas}, defines the haptic feedback produced by the
keyswitch. When pressure is applied to the keycap, which is connected to the
stem, the spring gets contracted and the stem moves downwards and thereby stops
separating the two plates which closes the electrical circuit and sends a
keypress to the computer. After the key is released, the spring pushes the stem keypress to the computer. After the key is released, the spring pushes the stem
back to its original position \cite{bassett_keycap, peery_3d_keyswitch, back to its original position \cite{bassett_keycap, peery_3d_keyswitch,
ergopedia_keyswitch, chen_mech_switch}. Usually, mechanical keyswitches are ergopedia_keyswitch, chen_mech_switch}. Usually, mechanical keyswitches are
@ -63,15 +83,25 @@ be hot-swapped without soldering at all \cite{gmmk_hot_swap}. It is also
possible to equip an already existing \gls{PCB} with sockets to make it possible to equip an already existing \gls{PCB} with sockets to make it
hot-swappable \cite{te_connect}. hot-swappable \cite{te_connect}.
\begin{figure}[ht]
\centering
\includegraphics[width=1.0\textwidth]{images/mech_keyswitches_dissas.jpg}
\caption{Disassembled tactile, clicky and linear mechanical keyswitchs. The
red lines resemble the shape of the stem which is responsible for the haptic
feedback and thus, in combination with the strength of the spring, the
required actuation force}
\label{fig:mech_keyswitches_dissas}
\end{figure}
Mechanical keyswitches also have three main subcategories. Those categories Mechanical keyswitches also have three main subcategories. Those categories
primarily define if and how feedback for a keypress is realised: primarily define if and how feedback for a keypress is realised:
\begin{enumerate} \begin{enumerate}
\item \textbf{Tactile Switches} utilize a small bump on the stem to slightly \item \textbf{Tactile Switches} utilize a small bump on the stem to slightly
increase the force required immediately before and a collapse of force right increase and then instantly collapse the force required immediately before the
after the actual actuation happens. This provides the typist with a short actual actuation happens \cite{cherry_mx_brown}. This provides the typist with
noticeable haptic feedback and which should encourage a premature release of a short noticeable haptic feedback and which should encourage a premature
the key. An early study by Brunner and Richardson suggested, that this release of the key. An early study by Brunner and Richardson suggested, that
feedback leads to faster typing speeds and a lower error rate in both this feedback leads to faster typing speeds and a lower error rate in both
experienced and casual typists (n=24) \cite{brunner_keyswitch}. Contrary, a experienced and casual typists (n=24) \cite{brunner_keyswitch}. Contrary, a
study by Akagi yielded no significant differences in terms of speed and error study by Akagi yielded no significant differences in terms of speed and error
rate between tactile and linear keyswitches and links the variation found in rate between tactile and linear keyswitches and links the variation found in
@ -81,29 +111,41 @@ primarily define if and how feedback for a keypress is realised:
\item \textbf{Tactile and audible Switches (Clicky)} separate the stem into \item \textbf{Tactile and audible Switches (Clicky)} separate the stem into
two parts, the lower part also features a small bump to provide tactile two parts, the lower part also features a small bump to provide tactile
feedback and is also responsible for a distinct click sound when the actuation feedback and is also responsible for a distinct click sound when the actuation
happens. Gerard et al. noted, that in their study (n=24), keyboards with happens \cite{cherry_mx_blue}. Gerard et al. noted, that in their study
audible feedback increased typing speed and decreased typing force. This (n=24), keyboards with audible feedback increased typing speed and decreased
improvement could have been due to the previous experience of participants typing force. This improvement could have been due to the previous experience
with keyboards of similar model and keyswitch characteristic of participants with keyboards of similar model and keyswitch characteristic
\cite{gerard_keyswitch}. \cite{gerard_keyswitch}.
\item \textbf{Linear Switches} do not offer a distinct feedback for the \item \textbf{Linear Switches} do not offer a distinct feedback for the
typist. The activation of the keyswitch just happens after approximately half typist. The activation of the keyswitch just happens after approximately half
the total travel distance. The only tactile feedback that could happen is the the total travel distance \cite{cherry_mx_red}. The only tactile feedback that
impact of \gls{bottoming}, but with enough practice, typist can develop a could happen is the impact of \gls{bottoming}, but with enough practice,
lighter touch which reduces overall typing force and therefore reduces the typist can develop a lighter touch which reduces overall typing force and
risk of \gls{WRUED} \cite{gerard_keyswitch, peery_3d_keyswitch, fagarasanu_force_training}. therefore reduces the risk of \gls{WRUED} \cite{gerard_keyswitch,
peery_3d_keyswitch, fagarasanu_force_training}.
\end{enumerate} \end{enumerate}
The corresponding force-displacement curves for one exemplary keyswitch of each The corresponding force-displacement curves for one exemplary keyswitch of each
category are shown in Figure TODO\ref{fig:ks_fd_curves}. category by the manufacturer Cherry are shown in Figure
\ref{fig:ks_fd_curves}. The Operational position indicates the activation of the
keyswitch.
\begin{figure}[ht]
\centering
\includegraphics[width=1.0\textwidth]{images/ks_fd_curves.jpg}
\caption{Actuation graphs for Cherry MX BROWN \cite{cherry_mx_brown} | BLUE
\cite{cherry_mx_blue} | RED \cite{cherry_mx_red} switches. Tactile position marks the point where a haptic feedback happens, operational position marks the activation of the keyswitch and reset position is the point where the keyswitch deactivates again}
\label{fig:ks_fd_curves}
\end{figure}
All types of keyswitches mentioned so far are available in a myriad of actuation All types of keyswitches mentioned so far are available in a myriad of actuation
forces. Actuation force, also sometimes referred to as make force, is the force forces. Actuation force, also sometimes referred to as make force, is the force
required to activate the keyswitch \cite{radwin_keyswitch, required to activate the keyswitch \cite{radwin_keyswitch,
ergopedia_keyswitch}. That means depending on the mechanism used, activation ergopedia_keyswitch}. That means depending on the mechanism used, activation
describes the closing of an electrical circuit which then forwards a signal, describes the closing of an electrical circuit which forwards a signal, that is
that is then processed by a controller inside of the keyboard and then forwarded then processed by a controller inside of the keyboard and finally send to the
to the computer. The computer then registers the character depending on the computer. The computer then selects the corresponding character depending on the
layout used by the user. Previous studies have shown, that actuation force has layout used by the user. Previous studies have shown, that actuation force has
an impact on error rate, subjective discomfort, muscle activity and force an impact on error rate, subjective discomfort, muscle activity and force
applied by the typist \cite{akagi_keyswitch, gerard_keyswitch, applied by the typist \cite{akagi_keyswitch, gerard_keyswitch,
@ -144,23 +186,200 @@ capabilities for our experiment to reduce the effort required to equip each
keyboard with the required keyswitches and in case a keyswitch fails during keyboard with the required keyswitches and in case a keyswitch fails during
the experiment, decrease the time required to replace the faulty switch. the experiment, decrease the time required to replace the faulty switch.
\subsection{Measurement of keyboard related metrics} \subsection{Measurement of typing related metrics}
A common way to compare different methods concerning alphanumeric input in terms \label{sec:metrics}
of efficiency is to use one of many typing test applications which are Nowadays, a common way to compare different methods concerning alphanumeric
commercially available. Depending on the software used and the experimental input in terms of efficiency is to use one of many typing test or word
setup, users have to input different kinds of text, either for a predefined time processing applications which are commercially available. Depending on the
or the time is measured till the whole text is transcribed \cite{chen_typing_test}. software used and the experimental setup, users have to input different kinds of
text, either for a predefined time or the time is measured till the whole text
is transcribed \cite{chen_typing_test, hoffmann_typeright,
fagarasanu_force_training, akagi_keyswitch, kim_typingforces,
pereira_typing_test}. Text used should be easy to read for typists
participating in studies that evaluate their performance and are therefore is
chosen based on a metric called the \gls{FRE} which indicates the
understandability of text \cite{fagarasanu_force_training,
kim_typingforces, flesch_fre}. The score ranges from 0 which implies very poor reading
ease to 100 suggesting that the style of writing used causes the text to be very
easy to comprehend \cite{flesch_fre}. Immel proposed an adjusted formula of the
\gls{FRE} that is suitable for German text \cite{immel_fre} and can be seen in
(\ref{eq:fre_german}).
\begin{equation}\label{eq:fre_german}
FRE_{deutsch} = 180 - \underbrace{ASL}_{\mathclap{\text{Average Sentence Length}}} - (58,5 * \overbrace{ASW}^{\mathclap{\text{Average Syllables per Word}}})
\end{equation}
According to Flesch, the values retrieved by applying the formula to text can be
classified according to the ranges given in Table \ref{tbl:fre_ranges} \cite{flesch_fre}.
\begin{table}
\centering
\caption{Categories for different FRE scores to classify the understandability
of text \cite{flesch_fre}}
\label{tbl:fre_ranges}
\begin{tabular}{l|c}
\hline\hline
\multicolumn{1}{c|}{FRE} & Understandability \\
\hline
\multicolumn{1}{c|}{0 - 30} & Very difficult \\
30 - 50 & Difficult \\
50 - 60 & Fairly difficult \\
60 - 70 & Standard \\
70 - 80 & Fairly easy \\
80 - 90 & Easy \\
\multicolumn{1}{r|}{90 - 100} & Very easy \\
\hline
\end{tabular}
\end{table}
There are several metrics to measure the performance of typists. Typical methods
to measure speed are
\begin{enumerate}
\item \textbf{\Gls{WPM}}
\begin{equation}\label{eq:wpm}
WPM = \frac{|T| - 1}{S} * 60 * \frac{1}{5}
\end{equation}
In Eq. (\ref{eq:wpm}), $|T|$ is the length of the transcribed text, $S$ the
time in seconds taken to transcribe $T$, $\frac{1}{5}$ the average word length
and $60$ the conversion to minutes. $|T| - 1$ counteracts the first input
which starts the timer in many typing tests \cite{mackenzie_metrics}.
\item \textbf{\Gls{AdjWPM}} is especially useful if participants are allowed to
make mistakes and at the same time not forced to correct them. This method adds
an adjustable factor to lower the \gls{WPM} proportionally to the uncorrected
error rate $UER := [0;1]$ defined in Eq. (\ref{eq:uer}). The exponent $a$ in
Eq. (\ref{eq:cwpm}) can be chosen depending on the desired degree of correction
\cite{mackenzie_metrics}.
\begin{equation}\label{eq:cwpm}
AdjWPM = WPM * (1 - UER)^{a}
\end{equation}
\item \textbf{\Gls{KSPS}} measures the raw input rate of a typist by capturing
the whole input stream including backspaces and deleted characters ($IS$)
\cite{mackenzie_metrics}.
\begin{equation}\label{eq:ksps}
KSPS = \frac{|IS| - 1}{S}
\end{equation}
\end{enumerate}
In addition to speed, the error rate of typists can be measured with the
following two methods
\begin{enumerate}
\item \textbf{\gls{CER}} is the ratio of erroneous input that got fixed
($IF$) to any character typed during transcription, including $IF$
\cite{soukoreff_metrics}.
\begin{equation}\label{eq:cer}
CER = \frac{|IF|}{|T| + |IF|}
\end{equation}
\item \textbf{\gls{UER}} is the ratio of erroneous input that was \textbf{not}
fixed ($INF$) to any character typed during transcription, including $IF$
\cite{soukoreff_metrics}.
\begin{equation}\label{eq:uer}
UER = \frac{|INF|}{|T| + |IF|}
\end{equation}
\end{enumerate}
In several other studies, in addition to the metrics mentioned so far, \gls{EMG}
data was captured to evaluate the muscle activity or applied force while typing
on completely different or modified hardware \cite{kim_typingforces,
fagarasanu_force_training, gerard_audio_force, gerard_keyswitch, martin_force,
rose_force, rempel_ergo, pereira_typing_test}. \gls{EMG} signals, are captured
with the help of specialized equipment that utilize electrodes which are either
placed onto the skin above the muscles of interest (non-invasive) or inserted
directly into the muscle (invasive). The disadvantage of non-invasive surface
level electrodes is the lacking capability to capture the distinct signal of one
isolated muscle \cite{reaz_emg}. Nevertheless, because this type of electrode is
more likely to find acceptance among participants and is also easier to apply by
non-medically trained researchers, it finds wide adoption among studies
\cite{takala_emg}. To make \gls{EMG} data comparable across subjects, it is
necessary to conduct initial measurements where each individual participant is
instructed to first completely relax and then fully contract (\gls{MVC}) the
muscles of interest. These values are used to normalize further data obtained in
an experimental setting. The mean signal yielded by complete relaxation is
subtracted to reduce noise and the \gls{MVC} is used to obtain the individuals
percentage of muscle activity (\%MVC or EMG\%) during tests \cite{halaki_emg,
takala_emg, rempel_ergo}. Muscles typically measured during typing exercises
are the \gls{FDS}, \gls{FDP} and \gls{ED}. The main function of the \gls{FDS}
and \gls{FDP} is the flexion of the medial four digits, while the \gls{ED}
mainly extends the medial four digits. Therefore, these muscles are primarily
involved in the finger movements required for typing on a keyboard
\cite{netter_anatomy, kim_typingforces, gerard_keyswitch, gerard_audio_force}.
A method frequently used to measure applied force is to place one or multiple
load cells under the keyboard \cite{gerard_keyswitch, rempel_ergo,
bufton_typingforces}. Load cells are electronic components that are able to
convert applied force to an electrical signal. This signal usually gets
amplified by specialized circuits and then further processed by a micro
controller, computer or other hardware \cite{johnson_loadcell}.
Lastly, subjective metrics e.g., comfort, usability, user experience, fatigue
and satisfaction, are evaluated based on survey data collected after
participants used different input methods \cite{kim_typingforces,
bell_pauseboard, bufton_typingforces, pereira_typing_test, iso9241-411}. In
their study, Kim et al. used a survey provided by the \gls{ISO} which is
specifically designed to evaluate different keyboards in terms of user
satisfaction, comfort and usability \cite{kim_typingforces, iso9241-411}. This
survey poses a total of twelve questions concerning e.g., fatigue of specific
regions of the upper extremity, general satisfaction with the keyboard,
perceived precision and uniformity while typing, etc., which are presented on a
seven-point Likert-scale \cite{iso9241-411}. Further, studies concerning the
usability and user experience of different text entry methods used the \gls{UEQ}
or \gls{UEQ-S} to evaluate the differences in those categories \cite{nguyen_ueq,
olshevsky_ueq, gkoumas_ueq}. While the full \gls{UEQ} provides a total of 26
questions divided into six scales (attractiveness, perspicuity, efficiency,
dependability, stimulation and novelty), the \gls{UEQ-S} only features 8
questions and two scales (pragmatic and hedonic quality). Because of the limited
explanatory power of the \gls{UEQ-S}, it is recommended to only use it, if there
is not enough time to complete the full \gls{UEQ} or if the participants of a
study are required to rate several products in one session
\cite{schrepp_ueq_handbook}.
\subsubsection{Relevance for this thesis}
Measuring metrics related to data entry tasks can be performed with the help
several commercially available tools and equipment. Especially muscle activity
has to be measured with appropriate tools and accurate placement of the
electrodes is important to ensure quality results \cite{takala_emg, halaki_emg,
kim_typingforces, gerard_keyswitch}. Metrics related to performance such as
\gls{WPM}, \gls{CER} and \gls{UER} are well defined and can be applied in almost
any experimental setup concerning the transcription of text
\cite{soukoreff_metrics, mackenzie_metrics}. In addition to the measured data,
questionnaires can help to gather subjective feedback about the keyboards and
thereby reveal differences that cannot be easily acquired by a device or formula
\cite{rowley_surveys}.
\subsection{Satisfaction while using a keyboard}
\subsection{Text understandability / FRE}
\subsection{Crowdsourcing / Observer Bias} \subsection{Crowdsourcing / Observer Bias}
\subsection{Keyboard usage} As shown by the previous research in Section \ref{sec:metrics}, it is common
\subsection{Keyswitch types} practice in research related to typing to present a text that has to be
- Rubber dome transcribed by the participant. Usually, the text was chosen by the researcher
- Mechanical switches (Why linear -> rubberdome is not tactile nor has audible feedback) or already available through the used typing test software. If the
\subsection{Muscle activity / EMG measurements} understandability of text is of concern, the binary choice of, is understandable
\subsection{Finger strength} or not, made by the researcher could lead to a phenomenon called the observer
\subsection{Traditional methods} bias \cite{hrob_observer, berger_observer}. Thus, the text could potentially be
\subsection{Alternative methodology} to difficult to understand for the participants if not evaluated with e.g. the
- Available Methods (Impact vs load) \gls{FRE} or other adequate formulas. Further, if there is previous knowledge
- Load cells about the requested participants, the researcher could subconsciously select
text that is familiar to, or well received by some of the subjects and could
thereby conceivably influence the outcome \cite{hrob_observer, berger_observer}.
The same problem arises, if the typing test software already provides such texts
but the researcher has to select some of them for the experiment. Further, the
difficulty of the provided texts should be verified to ensure accurate results
across multiple treatments. A possible solution for this problem is
crowdsourcing.
Howe CONTINUE
\cite{howe_crowdsource}. If there are automated checks for text
difficulty in place, this method completely excludes the researcher from the
text selection process.
\subsubsection{Relevance for this thesis}
% \subsection{Keyboard usage}
% \subsection{Finger strength}
% \subsection{Traditional methods}
% \subsection{Alternative methodology}
% - Available Methods (Impact vs load)
% - Load cells

7
chap3/implementation.tex
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@ -1,5 +1,6 @@
\section{Typing Test} \section{Implementation}
\label{sec:label} \label{sec:label}
\subsection{Typing Test Platform}
\section{Finger strength measurement device} \label{sec:label}
\subsection{Finger strength measurement device}
\label{sec:label} \label{sec:label}

11
chap4/methodology.tex
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@ -1,5 +1,6 @@
\section{Research Approach} \section{Methodology}
\section{Analysis of available mechanical keyswitches} \subsection{Research Approach}
- Why have we chosen these switches \subsection{Market analysis of available mechanical keyswitches}
\section{Preliminary telephone interview} \subsection{Preliminary telephone interview}
\section{Preliminary study of finger strength} \subsection{Preliminary study of finger strength}
% armstrong measurments of finger strength

6
chap5/results.tex
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@ -1 +1,5 @@
results \section{Results}
A rapid method that creates many corrected errors, has efficient error correction, and leaves
few uncorrected errors can still be considered a successful method, since it produces
accurate text in relatively little time. pp. 56 MacKenzie
\label{sec:label}

3
chap6/discussion.tex
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@ -1 +1,2 @@
Discussion \section{Discussion}
\label{sec:label}

3
chap6/recommendations.tex
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@ -1 +1,2 @@
Recommendations \section{Recommendations}
\label{sec:label}

3
chap7/conclusion.tex
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@ -1 +1,2 @@
Conclusion \section{Conclusion}
\label{sec:label}

3
chap7/future_work.tex
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@ -1 +1,2 @@
Future work \section{Future work}
\label{sec:label}

3
chap7/limitations.tex
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@ -1 +1,2 @@
limitlimitss \section{Limitations}
\label{sec:label}

21
glossary.tex
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@ -1,11 +1,12 @@
%----------Glossar/Glossary------------------------------------------------------------- %----------Glossar/Glossary-------------------------------------------------------------
\newacronym{KB}{KB}{Keyboard} \newacronym{KB}{KB}{Keyboard}
\newacronym{EMG}{EMG}{Electromyography} \newacronym{EMG}{EMG}{electromyography}
\newacronym{MVC}{MVC}{maximum voluntary contraction}
\newacronym{CTS}{CTS}{Carpal Tunnel Syndrome} \newacronym{CTS}{CTS}{Carpal Tunnel Syndrome}
\newacronym{RSI}{RSI}{Repetitive Strain Injury} \newacronym{RSI}{RSI}{Repetitive Strain Injury}
\newacronym{FRE}{FRE}{Flesch Reading Ease Score} \newacronym{FRE}{FRE}{Flesch Reading Ease Score}
\newacronym{VAS}{VAS}{Visual Analog Scale} \newacronym{VAS}{VAS}{visual analog scale}
% Mulcles alive p. 189 % Mulcles alive p. 189
% Atlas of Human Anatomy p. 433 % Atlas of Human Anatomy p. 433
\newacronym{FDS}{FDS}{flexor digitorum superficialis} \newacronym{FDS}{FDS}{flexor digitorum superficialis}
@ -15,6 +16,16 @@
\newacronym{ABS}{ABS}{acrylonitrile butadiene styrene} \newacronym{ABS}{ABS}{acrylonitrile butadiene styrene}
\newacronym{WRUED}{WRUED}{work related upper extremity disorders} \newacronym{WRUED}{WRUED}{work related upper extremity disorders}
\newacronym{PCB}{PCB}{printed circuit board} \newacronym{PCB}{PCB}{printed circuit board}
\newacronym{WPM}{WPM}{Words per Minute}
\newacronym{AdjWPM}{AdjWPM}{Adjusted Words per Minute}
\newacronym{KSPS}{KSPS}{Keystrokes per Second}
\newacronym{CER}{CER}{Corrected Error Rate}
\newacronym{UER}{UER}{Uncorrected Error Rate}
\newacronym{KSPC}{KSPC}{Keystrokes per Character}
\newacronym{UEQ-S}{UEQ-S}{short version of the user experience questionnaire}
\newacronym{UEQ}{UEQ}{user experience questionnaire}
\newglossaryentry{cN}{ \newglossaryentry{cN}{
@ -29,6 +40,10 @@ description={Gram: 1 g $ \approx $ 0.97 cN}
name={gf}, name={gf},
description={Gram-force: 1 gf = 1 g} description={Gram-force: 1 gf = 1 g}
} }
\newglossaryentry{QWERTY}{
name={QWERTY},
description={Keyboard layout commonly used in the US and many other countries}
}
\newglossaryentry{QWERTZ}{ \newglossaryentry{QWERTZ}{
name={QWERTZ}, name={QWERTZ},
description={Keyboard layout commonly used in Germany} description={Keyboard layout commonly used in Germany}
@ -41,5 +56,5 @@ description={Describes the scenario when the typist does not release the key bef
\newglossaryentry{Topre}{ \newglossaryentry{Topre}{
name={Topre}, name={Topre},
description={Topre switches are keyswitches produced by the Japanese company Topre Corporation description={Topre switches are keyswitches produced by the Japanese company Topre Corporation}
} }

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409
ref_shelf.bib
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@ -67,8 +67,6 @@ url = {https://www.realforce.co.jp/en/products/},
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} }
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4
thesis.tex
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@ -188,8 +188,8 @@
\cleardoublepage \cleardoublepage
%Anhänge/Appendices %Anhänge/Appendices
\include{appendices} % \include{appendices}
\cleardoublepage % \cleardoublepage
%------------------------------------------------------------------------------------ %------------------------------------------------------------------------------------
%----------------DOKUMENTENENDE - END OF DOCUMENT------------------------------------ %----------------DOKUMENTENENDE - END OF DOCUMENT------------------------------------