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@ -2,7 +2,7 @@
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\label{sec:methodology}
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\subsection{Research Approach}
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Because of the controversial findings about the impact of key actuation forces
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|
on speed \cite{akagi_keyswitch, loricchio_force_speed} and the fact, that
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on speed \cite{akagi_keyswitch, loricchio_force_speed} and the fact that
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keyboard related work can increase the risk for \gls{WRUED} \cite{ccfohas_wrued,
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pascarelli_wrued}, we decided to further investigate possible effects of
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different actuation forces and even a keyboard equipped with non-uniform
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@ -12,16 +12,16 @@ non-uniform actuation forces on these metrics. Therefore, we first asked
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seventeen people about their preferences, experiences and habits related to
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keyboards to get a better understanding on what people might prefer as a
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baseline for the design of the adjusted keyboard (keyboard with non-uniform
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actuation forces) and to complement the findings obtained through our literature
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review. Further, we collected information about available mechanical keyswitches
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on the market. Additionally, we conducted a small preliminary experiment with 6
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subjects, where we measured the peak forces each individual finger of the right
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hand was able to apply to distinct keys in different locations. We then created
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the design for the adjusted keyboard based on those measurements. Lastly, an
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experiment with twenty-four participants was conducted, where we compared the
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performance and user satisfaction while using four different keyboards,
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including our adjusted keyboard. Figure \ref{fig:s4_flow} presents a brief
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overview of the consecutive sections.
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actuation forces) as well as to complement the findings obtained through our
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literature review. Further, we collected information about available mechanical
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|
keyswitches on the market. Additionally, we conducted a small preliminary
|
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|
experiment with 6 subjects, where we measured the peak forces each individual
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|
finger of the right hand was able to apply to distinct keys in different
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|
locations. We then created the design for the adjusted keyboard based on those
|
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|
measurements. Lastly, an experiment with twenty-four participants was conducted,
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|
where we compared the performance and user satisfaction while using four
|
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|
different keyboards, including our adjusted keyboard. Figure \ref{fig:s4_flow}
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|
presents a brief overview of the consecutive sections.
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\begin{figure}[H]
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\centering
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@ -60,7 +60,7 @@ described by the seven who already experienced pain were the wrist
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review \cite{ergopedia_keyswitch, peery_3d_keyswitch}. Nine answered that they
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|
use a notebook (scissor-switches, membrane), six stated that they use an
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external keyboard with rubber dome switches and only two responded that they use
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a keyboard featuring mechanical keyswitches. The average, self-reported, usage
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|
a keyboard featuring mechanical keyswitches. The average―self-reported―usage
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|
ranged between half an hour and 10 hours with a mean of 4.71 hours. It is
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|
important to note, that a study by Mikkelsen et al. found, that self-reported
|
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|
durations related to computer work can be inaccurate
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|
@ -112,7 +112,7 @@ To evaluate the impact of an adjusted keyboard\footnote{keyboard with
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|
non-uniform actuation forces} on performance and satisfaction we first needed
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to get an understanding on how to distribute keyswitches with different
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|
actuation forces across a keyboard. Our first idea was to use a similar approach
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to the keyboard we described in Section \ref{sec:lr_sum}, were the force
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to the keyboard we described in Section \ref{sec:lr_sum}, where the force
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|
required to activate the keys decreased towards the left and right ends of the
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|
keyboard. This rather simple approach only accounts for the differences in
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|
finger strength when all fingers are in the same position, but omits possible
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@ -125,14 +125,14 @@ distributed as follows: computer science students (3/6), physiotherapist (1/6),
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user experience consultant (1/6) and retail (1/6). All Participants were given
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|
|
instructions to exert maximum force for approximately one second onto the key
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|
mounted to the measuring device described in Section
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|
\ref{sec:force_meas_dev}. We also used a timer to announced when to press and
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\ref{sec:force_meas_dev}. We also used a timer to announce when to press and
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|
when to stop. We provided a keyboard to every participant, which was used as a
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|
reference for the finger position before every measurement. To reduce order
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|
effects, we used a balanced latin square to specify the sequence of rows (top,
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|
home, bottom) in which the participants had to press the keys
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|
\cite{bradley_latin_square}. Additionally, because there were only six people
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|
available, we alternated the direction from which participants had to start in
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|
such a way, that every second subject started with the little finger instead of
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|
such a way that every second subject started with the little finger instead of
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|
the index finger. An example of four different positions of the finger while
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|
performing the measurements for the keys \textit{Shift, L, I} and \textit{Z} can
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|
be observed in Figure \ref{fig:FM_example}.
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@ -180,7 +180,7 @@ key can be seen in Eq. (\ref{eq:force_example}).
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|
AF_{P} = GFR * MAF_{P} = 3.23 \frac{g}{N} * 10.45\,N \approx 33.75\,g
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|
\end{equation}
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We then assigned the each theoretical actuation force to a group that resembles
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|
We then assigned each theoretical actuation force to a group that resembles
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|
|
a spring resistance which is available on the market or can be adjusted to that
|
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|
|
value. We matched the results from Table \ref{tbl:finger_force} to the groups
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|
|
representing the best fit shown in Table \ref{tbl:force_groups}.
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|
@ -231,7 +231,8 @@ representing the best fit shown in Table \ref{tbl:force_groups}.
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|
corresponding keyswitch in the following row. The columns indicate the label
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|
|
of the scale on the measuring device which can be seen in Figure
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|
|
\ref{fig:FM_example}. \textit{↑} stands for the shift key. \textit{F5} :=
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|
little finger, ..., \textit{F2} := index finger}
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|
little finger, \textit{F4} := ring finger, \textit{F3} := middle finger,
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|
|
\textit{F2} := index finger}
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|
|
\label{tbl:finger_force}
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|
|
\end{table}
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|
@ -255,11 +256,12 @@ representing the best fit shown in Table \ref{tbl:force_groups}.
|
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|
|
\caption{Categorization of theoretical actuation forces acquired with
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|
|
Eq. (\ref{eq:actuation_forces}), into groups of more commonly available
|
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|
|
|
stiffnesses of springs. The rows indicate which finger is used to press the
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|
|
key. \textit{F5} := little finger, ..., \textit{F2} := index finger}
|
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|
key. \textit{F5} := little finger, \textit{F4} := ring finger, \textit{F3}
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|
|
:= middle finger, \textit{F2} := index finger}
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|
\label{tbl:force_groups}
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|
|
|
|
\end{table}
|
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|
We simply mirrored the results of the right hand, for keys operated by the left
|
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|
|
We simply mirrored the results of the right hand for keys operated by the left
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|
|
hand and copied the values to keys which are out of reach without lifting the
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|
|
hand. Finally, we created the adjusted keyboard layout that can be examined in
|
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|
|
Figure \ref{fig:adjusted_layout}. This layout was used in our main experiment
|
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|
@ -313,25 +315,26 @@ measured via \gls{EMG}, post experiment semi structured interview and ux-curves)
|
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|
|
\subsubsection{Participants}
|
|
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|
|
\label{sec:main_participants}
|
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|
|
There were no specific eligibility criteria for participants (n=24) of this
|
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|
|
study beside the ability to type on a keyboard for longer durations and with all
|
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|
|
ten fingers. The style used to type was explicitly not restricted to schoolbook
|
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|
|
touch typing to also evaluate possible effects of the adjusted keyboard on
|
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|
|
|
untrained typists. All participants recruited were personal contacts. 54\,\% of
|
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|
|
subjects were females. Participant's ages ranged from 20 to 58 years with a mean
|
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|
|
age of 29. Sixteen out of the twenty-four subjects (67\,\%) reported that they
|
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|
|
|
were touch typists. Subjects reported the following keyboard types as their
|
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|
|
daily driver, notebook keyboard (12, 50\,\%), external keyboard (11, 46\,\%) and
|
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|
|
split keyboard (1, 4\,\%). The keyswitch types of those keyboards were distributed
|
|
|
|
|
as follows: scissor-switch (13, 54\,\%), rubber dome (8, 33\,\%) and mechanical
|
|
|
|
|
keyswitches (3, 13\,\%). We measured the actuation force of each participants own
|
|
|
|
|
keyboard and the resulting distribution of actuation forces can be observed in
|
|
|
|
|
Figure \ref{fig:main_actuation_force}. The self-reported average daily usage of
|
|
|
|
|
a keyboard ranged from 1 hour to 13 hours, with a mean of 6.69 hours. As already
|
|
|
|
|
mentioned in Section \ref{sec:telephone_interview} it is important to note, that
|
|
|
|
|
a study by Mikkelsen et al. found, that self-reported durations related to
|
|
|
|
|
computer work can be inaccurate \cite{mikkelsen_duration}. All participants used
|
|
|
|
|
the \gls{QWERTZ} layout and therefore were already used to the layout used
|
|
|
|
|
throughout the experiment.
|
|
|
|
|
study besides the ability to type on a keyboard for longer durations and with
|
|
|
|
|
all ten fingers. The style used to type was explicitly not restricted to
|
|
|
|
|
schoolbook touch typing to also evaluate possible effects of the adjusted
|
|
|
|
|
keyboard on untrained typists. All participants recruited were personal
|
|
|
|
|
contacts. 54\,\% of subjects were females. Participant's ages ranged from 20 to
|
|
|
|
|
58 years with a mean age of 29. Sixteen out of the twenty-four subjects (67\,\%)
|
|
|
|
|
reported that they were touch typists. Subjects reported the following keyboard
|
|
|
|
|
types as their daily driver, notebook keyboard (12, 50\,\%), external keyboard
|
|
|
|
|
(11, 46\,\%) and split keyboard (1, 4\,\%). The keyswitch types of those
|
|
|
|
|
keyboards were distributed as follows: scissor-switch (13, 54\,\%), rubber dome
|
|
|
|
|
(8, 33\,\%) and mechanical keyswitches (3, 13\,\%). We measured the actuation
|
|
|
|
|
force of each participants own keyboard. The resulting distribution of actuation
|
|
|
|
|
forces can be observed in Figure \ref{fig:main_actuation_force}. The
|
|
|
|
|
self-reported average daily usage of a keyboard ranged from 1 hour to 13 hours,
|
|
|
|
|
with a mean of 6.69 hours. As already mentioned in Section
|
|
|
|
|
\ref{sec:telephone_interview} it is important to note, that a study by Mikkelsen
|
|
|
|
|
et al. found, that self-reported durations related to computer work can be
|
|
|
|
|
inaccurate \cite{mikkelsen_duration}. All participants used the \gls{QWERTZ}
|
|
|
|
|
layout and therefore were already used to the layout used throughout the
|
|
|
|
|
experiment.
|
|
|
|
|
|
|
|
|
|
\begin{figure}[H]
|
|
|
|
|
\centering
|
|
|
|
|
@ -344,12 +347,12 @@ throughout the experiment.
|
|
|
|
|
|
|
|
|
|
\subsubsection{Experimental Environment}
|
|
|
|
|
\label{sec:main_environment}
|
|
|
|
|
The whole experiments took place in a room normally used as an office. Chair,
|
|
|
|
|
and table were both height adjustable. The armrests of the chair were also
|
|
|
|
|
All the experiments took place in a room normally used as an office. Chair, and
|
|
|
|
|
table were both height adjustable. The armrests of the chair were also
|
|
|
|
|
adjustable in height and horizontal position. The computer used for all
|
|
|
|
|
measurements featured an Intel i7-5820K (12) @ 3.600\,GHz processor, 16\,gB RAM and
|
|
|
|
|
a NVIDIA GeForce GTX 980 Ti graphics card. The operating system on test machine
|
|
|
|
|
was running \textit{Arch Linux}\footnote{\url{https://archlinux.org/}}
|
|
|
|
|
measurements featured an Intel i7-5820K (12) @ 3.600\,GHz processor, 16\,gB RAM
|
|
|
|
|
and a NVIDIA GeForce GTX 980 Ti graphics card. The operating system on test
|
|
|
|
|
machine was running \textit{Arch Linux}\footnote{\url{https://archlinux.org/}}
|
|
|
|
|
(GNU/Linux, Linux kernel version: 5.11.16). The setup utilized two 1080p (Full
|
|
|
|
|
HD, Resolution: 1920x1080, Refresh-rate: 144Hz) monitors were participants were
|
|
|
|
|
allowed to adjust the angle, height and brightness prior to the start of the
|
|
|
|
|
@ -368,10 +371,10 @@ researchers were tested with antigen tests prior to every appointment.
|
|
|
|
|
|
|
|
|
|
\subsubsection{Independent Variable: Keyboards}
|
|
|
|
|
\label{sec:main_keyboards}
|
|
|
|
|
Additionally to the reference tests conducted with the participant's own
|
|
|
|
|
keyboards, we provided four keyboards which only differed in terms of actuation
|
|
|
|
|
force (Appendix \ref{app:equipment}). We decided to assign pseudonyms in the
|
|
|
|
|
form of Greek goddesses to the keyboards to make fast differentiation during the
|
|
|
|
|
Alongside the reference tests conducted with the participant's own keyboards, we
|
|
|
|
|
provided four keyboards which only differed in terms of actuation force
|
|
|
|
|
(Appendix \ref{app:equipment}). We decided to assign pseudonyms in the form of
|
|
|
|
|
Greek goddesses to the keyboards to make fast differentiation during the
|
|
|
|
|
sessions easier and reduce ambiguity. The pseudonyms for each keyboard and the
|
|
|
|
|
corresponding actuation force can be found in Table \ref{tbl:kb_pseudo}.
|
|
|
|
|
|
|
|
|
|
@ -424,12 +427,12 @@ follows:
|
|
|
|
|
\label{sec:main_design}
|
|
|
|
|
\textbf{Preparation and Demographics}
|
|
|
|
|
|
|
|
|
|
The whole laboratory experiment was conducted over a total time span of 3
|
|
|
|
|
weeks. Participants were tested one at a time in sessions that in total took
|
|
|
|
|
The whole laboratory experiment was conducted over a total time span of three
|
|
|
|
|
weeks. Participants were tested one at a time in sessions that took in total
|
|
|
|
|
$\approx$ 120 minutes. Prior to the evaluation of the different keyboards, the
|
|
|
|
|
participant was instructed to read the terms of participation which included
|
|
|
|
|
information about privacy, the \gls{EMG} measurements and questionnaires used
|
|
|
|
|
during the experiment. Next, participants filled out a pre-experiment
|
|
|
|
|
during the experiment. Next, the participants filled out a pre-experiment
|
|
|
|
|
questionnaire to gather demographic and other relevant information e.g., touch
|
|
|
|
|
typist, average \gls{KB} usage per day, predominantly used keyboard type,
|
|
|
|
|
previous medical conditions affecting the result of the study e.g.,
|
|
|
|
|
@ -459,19 +462,19 @@ was then confirmed, by observing the data received by the \textit{FlexVolt
|
|
|
|
|
the participant performed flexion and extension of the wrist. The
|
|
|
|
|
\textit{FlexVolt 8-Channel Bluetooth Sensor} used following hardware settings to
|
|
|
|
|
record the data: 8-Bit sensor resolution, 32ms \gls{RMS} window size and
|
|
|
|
|
Hardware smoothing filter turned off. To gather reference values (100\,\%\gls{MVC}
|
|
|
|
|
and 0\,\%\gls{MVC}), which are used later to calculate the percentage of muscle
|
|
|
|
|
activity for each test, we performed three measurements. First, participants
|
|
|
|
|
were instructed to fully relax the \gls{FDS}, \gls{FDP} and \gls{ED} by
|
|
|
|
|
completely resting their forearms on the table. Second, participants exerted
|
|
|
|
|
maximum possible force with their fingers (volar) against the top of the table
|
|
|
|
|
(\gls{MVC} - flexion) and lastly, participants applied maximum possible force
|
|
|
|
|
with their fingers (dorsal) to the bottom of the table while resting their
|
|
|
|
|
forearms on their thighs (\gls{MVC} - extension). We decided to also measure
|
|
|
|
|
0\,\%\gls{MVC} before and after each typing test and used these values to
|
|
|
|
|
normalize the final data instead of the 0\,\%\gls{MVC} we retrieved from the
|
|
|
|
|
initial \gls{MVC} measurements. A picture of all participants with the attached
|
|
|
|
|
electrodes can be observed in Appendix \ref{app:emg}.
|
|
|
|
|
Hardware smoothing filter turned off. To gather reference values
|
|
|
|
|
(100\,\%\gls{MVC} and 0\,\%\gls{MVC}), which are used later to calculate the
|
|
|
|
|
percentage of muscle activity for each test, we performed three
|
|
|
|
|
measurements. First, participants were instructed to fully relax the \gls{FDS},
|
|
|
|
|
\gls{FDP} and \gls{ED} by completely resting their forearms on the
|
|
|
|
|
table. Second, participants exerted maximum possible force with their fingers
|
|
|
|
|
(volar) against the top of the table (\gls{MVC} - flexion). Lastly, participants
|
|
|
|
|
applied maximum possible force with their fingers (dorsal) to the bottom of the
|
|
|
|
|
table while resting their forearms on their thighs (\gls{MVC} - extension). We
|
|
|
|
|
decided to also measure 0\,\%\gls{MVC} before and after each typing test and
|
|
|
|
|
used these values to normalize the final data instead of the 0\,\%\gls{MVC} we
|
|
|
|
|
retrieved from the initial \gls{MVC} measurements. A picture of all participants
|
|
|
|
|
with the attached electrodes can be observed in Appendix \ref{app:emg}.
|
|
|
|
|
|
|
|
|
|
\textbf{Familiarization with \glsfirst{GoTT} and the Keyboards}
|
|
|
|
|
|
|
|
|
|
@ -484,8 +487,9 @@ Aphrodite (50\,g). Additionally, because of a possible height difference between
|
|
|
|
|
choice to use wrist rests of adequate height in combination with all four
|
|
|
|
|
keyboards during the experiment. If during this process participants reported
|
|
|
|
|
that an electrode is uncomfortable and that it would influence the following
|
|
|
|
|
typing test, this electrode was relocated and the procedure in the last section
|
|
|
|
|
was repeated\footnote{Happened one time during the whole experiment}.
|
|
|
|
|
typing test, this electrode was relocated and the procedure in the last
|
|
|
|
|
paragraph\footnote{\gls{EMG} Measurements} was repeated\footnote{Happened one
|
|
|
|
|
time during the whole experiment}.
|
|
|
|
|
|
|
|
|
|
\textbf{Texts Used for Typing Tests}
|
|
|
|
|
|
|
|
|
|
@ -501,14 +505,14 @@ To receive feedback about several aspects that define a satisfactory user
|
|
|
|
|
experience while using a keyboard, we decided to incorporate two questionnaires
|
|
|
|
|
into our experiment. The first questionnaire was the \glsfirst{KCQ} provided by
|
|
|
|
|
\cite[56]{iso9241-411} and was filled out after each individual typing test
|
|
|
|
|
(\glsfirst{PTTQ}). The second survey, that was filled out every time the keyboard
|
|
|
|
|
was changed, was the \glsfirst{UEQ-S} \cite{schrepp_ueq_handbook} with an
|
|
|
|
|
additional question―``How satisfied have you been with this keyboard?''―that
|
|
|
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could be answered with the help of an \gls{VAS} ranging from 0 to 100
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(\glsfirst{PKQ})\cite{lewis_vas}. The short version of the \gls{UEQ} was selected, because of
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the limited time participants had to fill out the questionnaires in between
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typing tests (2 - 3 minutes) and also because participants had to rate multiple
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keyboards in one session \cite{schrepp_ueq_handbook}.
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(\glsfirst{PTTQ}). The second survey, that was filled out every time the
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keyboard was changed, was the \glsfirst{UEQ-S} \cite{schrepp_ueq_handbook} with
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an additional question―``How satisfied have you been with this keyboard?''―that
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could be answered with the help of a \gls{VAS} ranging from 0 to 100
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(\glsfirst{PKQ})\cite{lewis_vas}. Due to the limited time participants had to
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fill out the questionnaires in between typing tests (2 - 3 minutes) and also
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because participants had to rate multiple keyboards in one session, the short
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version of the \gls{UEQ} was selected \cite{schrepp_ueq_handbook}.
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\textbf{Post Experiment Interview \& \Gls{UX Curve}s}
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@ -518,12 +522,12 @@ tests were completed. We recorded audio and video for the whole duration of the
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interviews and afterwards categorized common statements about each
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keyboard.
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Further, we prepared two different graphs were participants had to draw
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\Gls{UX Curve}s related to subjectively perceived typing speed and subjectively
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Further, we prepared two different graphs were participants had to draw \Gls{UX
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Curve}s related to subjectively perceived typing speed and subjectively
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perceived fatigue for every keyboard and corresponding typing test. The graphs
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always reflected the order of keyboards for the group the current participant
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was part of. Furthermore, before the interview started, participants were given
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a brief introduction on how to draw \Gls{UX Curve}s and that it is desirable to
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a brief introduction on how to draw \Gls{UX Curve}s and, that it is desirable to
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explain the thought process while drawing each curve \cite{kujala_ux_curve}. An
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example of the empty graph for perceived fatigue (group 1) can be seen in Figure
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\ref{fig:empty_ux_g1}.
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@ -538,24 +542,25 @@ example of the empty graph for perceived fatigue (group 1) can be seen in Figure
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\textbf{Main Part of the Experiment}
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Each subject had to take two, 5 minute, typing tests per keyboard, with a total
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Each subject had to take two, 5-minute-typing-tests per keyboard, with a total
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of 5 keyboards, namely \textit{Own (participant's own keyboard)}, \textit{Nyx
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(35\,g, uniform), Aphrodite (50\,g, uniform), Athena (80\,g uniform)} and
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\textit{Hera (35\,g - 60\,g, adjusted)} (Table \ref{tbl:kb_pseudo}). As described
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in Section \ref{sec:main_keyboards}, the order of the keyboards \textit{Nyx,
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Aphrodite, Athena} and \textit{Hera} was counterbalanced with the help of a
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balanced latin square to reduce order effects. The keyboard \textit{Own} was
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used to gather reference values for all measured metrics. Thus, typing tests
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with \textit{Own} were conducted before (one test) and after (one test) all
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other keyboards, to also capture possible variations in performance due to
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fatigue. Participants were allowed, but not forced to, correct mistakes during
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the typing tests. The typing test application allowed no shortcuts to delete or
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insert multiple characters and correction was only possible by hitting the
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\textit{Backspace} key on the keyboard. The \textit{Capslock} key was disable
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during all typing tests, because there was only visual feedback in form of
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coloring of correct and incorrect input and no direct representation of entered
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characters (Figure \ref{fig:gott_colorblind}), which could lead to confusion
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when the \textit{Capslock} key is activated on accident.
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\textit{Hera (35\,g - 60\,g, adjusted)} (Table \ref{tbl:kb_pseudo}). As
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described in Section \ref{sec:main_keyboards}, the order of the keyboards
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\textit{Nyx, Aphrodite, Athena} and \textit{Hera} was counterbalanced with the
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help of a balanced latin square to reduce order effects. The keyboard
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\textit{Own} was used to gather reference values for all measured metrics. Thus,
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typing tests with \textit{Own} were conducted before (one test) and after (one
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test) all other keyboards, to also capture possible variations in performance
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due to fatigue. Participants were allowed, but not obligated to, correct
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mistakes during the typing tests. The typing test application allowed no
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shortcuts to delete or insert multiple characters and correction was only
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possible by hitting the \textit{Backspace} key on the keyboard. The
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\textit{Capslock} key was disabled during all typing tests, because there was
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only visual feedback in form of coloring of correct and incorrect input and no
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direct representation of entered characters (Figure \ref{fig:gott_colorblind}),
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which could have led to confusion when the \textit{Capslock} key was activated
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by accident.
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\subsection{Summary}
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\label{sec:meth_summary}
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phga
4 years ago
