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@@ -11,7 +11,6 @@ This second experiment aims to evaluate whether a visuo-haptic hand rendering af
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The chosen visuo-haptic hand renderings are the combination of the two most representative visual hand renderings established in the first experiment, \ie Skeleton and None, described in \secref[visual_hand]{hands}, with two contact vibration techniques provided at four delocalized positions on the hand.
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\subsection{Vibrotactile Renderings}
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\label{vibration}
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@@ -19,7 +18,6 @@ The vibrotactile hand rendering provided information about the contacts between
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We evaluated both the delocalized positioning and the contact vibration technique of the vibrotactile hand rendering.
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\subsubsection{Vibrotactile Positionings}
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\label{positioning}
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@@ -32,18 +30,17 @@ We evaluated both the delocalized positioning and the contact vibration techniqu
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}
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\begin{itemize}
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\item \textit{Fingertips (Tips):} Vibrating actuators were placed right above the nails, similarly to \cite{ando2007fingernailmounted}. This is the positioning closest to the fingertips.
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\item \textit{Proximal Phalanges (Prox):} Vibrating actuators were placed on the dorsal side of the proximal phalanges, similarly to \cite{maisto2017evaluation, meli2018combining, chinello2020modular}.
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\item \textit{Wrist (Wris):} Vibrating actuators providing contacts rendering for the index and thumb were placed on ulnar and radial sides of the wrist, similarly to \cite{pezent2019tasbi, palmer2022haptic, sarac2022perceived}.
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\item \textit{Opposite fingertips (Oppo):} Vibrating actuators were placed on the fingertips of contralateral hand, also above the nails, similarly to \cite{prattichizzo2012cutaneous, detinguy2018enhancing}.
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\item \textit{Nowhere (Nowh):} As a reference, we also considered the case where we provided no vibrotactile rendering.
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\item \textit{Fingertips (Tips):} Vibrating actuators were placed right above the nails, similarly to \cite{ando2007fingernailmounted}. This is the positioning closest to the fingertips.
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\item \textit{Proximal Phalanges (Prox):} Vibrating actuators were placed on the dorsal side of the proximal phalanges, similarly to \cite{maisto2017evaluation, meli2018combining, chinello2020modular}.
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\item \textit{Wrist (Wris):} Vibrating actuators providing contacts rendering for the index and thumb were placed on ulnar and radial sides of the wrist, similarly to \cite{pezent2019tasbi, palmer2022haptic, sarac2022perceived}.
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\item \textit{Opposite fingertips (Oppo):} Vibrating actuators were placed on the fingertips of contralateral hand, also above the nails, similarly to \cite{prattichizzo2012cutaneous, detinguy2018enhancing}.
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\item \textit{Nowhere (Nowh):} As a reference, we also considered the case where we provided no vibrotactile rendering.
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\end{itemize}
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\subsubsection{Contact Vibration Techniques}
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\label{technique}
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@@ -52,8 +49,8 @@ When a fingertip contacts the virtual cube, we activate the corresponding vibrat
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We considered two representative contact vibration techniques, \ie two ways of rendering such contacts through vibrations:
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\begin{itemize}
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\item \textit{Impact (Impa):} a \qty{200}{\ms}--long vibration burst is applied when the fingertip makes contact with the object; the amplitude of the vibration is proportional to the speed of the fingertip at the moment of the contact.
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\item \textit{Distance (Dist):} a continuous vibration is applied whenever the fingertip is in contact with the object; the amplitude of the vibration is proportional to the interpenetration between the fingertip and the virtual cube surface.
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\item \textit{Impact (Impa):} a \qty{200}{\ms}--long vibration burst is applied when the fingertip makes contact with the object; the amplitude of the vibration is proportional to the speed of the fingertip at the moment of the contact.
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\item \textit{Distance (Dist):} a continuous vibration is applied whenever the fingertip is in contact with the object; the amplitude of the vibration is proportional to the interpenetration between the fingertip and the virtual cube surface.
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\end{itemize}
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The implementation of these two techniques have been tuned according to the results of a preliminary experiment.
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@@ -68,7 +65,6 @@ For this reason, we designed the Impact vibration technique (Impa) so that conta
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Similarly, we designed the distance vibration technique (Dist) so that interpenetrations from \qtyrange{0}{2.5}{\cm} are linearly mapped into \qtyrange{15}{100}{\%} amplitude commands for the motors, recalling that the virtual cube has an edge of \qty{5}{\cm}.
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\subsection{Experimental Design}
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\label{design}
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@@ -101,10 +97,10 @@ Similarly, we designed the distance vibration technique (Dist) so that interpene
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We considered the same two tasks as in Experiment \#1, described in \secref[visual_hand]{tasks}, that we analyzed separately, considering four independent, within-subject variables:
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\begin{itemize}
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\item \emph{{Vibrotactile Positioning}:} the five positionings for providing vibrotactile hand rendering of the virtual contacts, as described in \secref{positioning}.
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\item \emph{Contact Vibration Technique}: the two contact vibration techniques, as described in \secref{technique}.
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\item \emph{visual Hand rendering}: two visual hand renderings from the first experiment, Skeleton (Skel) and None, as described in \secref[visual_hand]{hands}; we considered Skeleton as it performed the best in terms of performance and perceived effectiveness and None as reference.
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\item \emph{Target}: we considered target volumes located at NW and SW during the Push task, and at NE, NW, SW, and SE during the Grasp task (\figref{tasks}); we considered these targets because they presented different difficulties.
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\item \emph{{Vibrotactile Positioning}:} the five positionings for providing vibrotactile hand rendering of the virtual contacts, as described in \secref{positioning}.
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\item \emph{Contact Vibration Technique}: the two contact vibration techniques, as described in \secref{technique}.
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\item \emph{visual Hand rendering}: two visual hand renderings from the first experiment, Skeleton (Skel) and None, as described in \secref[visual_hand]{hands}; we considered Skeleton as it performed the best in terms of performance and perceived effectiveness and None as reference.
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\item \emph{Target}: we considered target volumes located at NW and SW during the Push task, and at NE, NW, SW, and SE during the Grasp task (\figref{tasks}); we considered these targets because they presented different difficulties.
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\end{itemize}
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To account for learning and fatigue effects, the positioning of the vibrotactile hand rendering (positioning) was counter-balanced using a balanced \numproduct{10 x 10} Latin square.
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@@ -115,7 +111,6 @@ As we did not find any relevant effect of the order in which the tasks were perf
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This design led to a total of 5 vibrotactile positionings \x 2 vibration contact techniques \x 2 visual hand rendering \x (2 targets on the Push task + 4 targets on the Grasp task) \x 3 repetitions $=$ 420 trials per participant.
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\subsection{Apparatus and Protocol}
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\label{apparatus}
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@@ -166,7 +161,6 @@ When the contact is lost, the spring is destroyed.
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Preliminary tests confirmed this approach.
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\subsection{Collected Data}
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\label{metrics}
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@@ -184,7 +178,6 @@ They then rated the ten combinations of Positioning \x Technique using a 7-item
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Finally, they rated the ten combinations of Positioning \x Hand on a 7-item Likert scale (1=Not at all, 7=Extremely): %
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\emph{(positioning \x Hand Rating)} How much do you like each combination of vibrotactile location for each visual hand rendering?
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\subsection{Participants}
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\label{participants}
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@@ -16,7 +16,6 @@ Yet, there was a tendency of faster trials with Proximal and Opposite.
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The NW target volume was also faster than the SW (\p{0.05}).
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\subsubsection{Contacts}
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\label{push_contacts_count}
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@@ -27,7 +26,6 @@ More contacts were made with Fingertips than with Opposite (\qty{+12}{\%}, \p{0.
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This could indicate more difficulties to adjust the virtual cube inside the target volume.
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\subsubsection{Time per Contact}
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\label{push_time_per_contact}
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@@ -15,7 +15,6 @@ Indeed, some participants explained that the contact cues were sufficient to ind
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Although the Distance technique provided additional feedback on the interpenetration of the finger with the cube, it was not strictly necessary to manipulate the cube quickly.
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\subsection{Questionnaire}
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\label{questions}
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@@ -30,7 +29,7 @@ Although the Distance technique provided additional feedback on the interpenetra
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\subfig[0.24]{results/Question-Workload-Positioning-Overall}
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\end{subfigs}
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\figref{questions} shows the questionnaire results for each vibrotactile positioning.
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\figref{results_questions} shows the questionnaire results for each vibrotactile positioning.
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Questionnaire results were analyzed using Aligned Rank Transform (ART) non-parametric analysis of variance (\secref{metrics}).
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@@ -40,7 +39,6 @@ Wilcoxon signed-rank tests were used for main effects and ART contrasts procedur
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Only significant results are reported.
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\subsubsection{Vibrotactile Rendering Rating}
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\label{vibration_ratings}
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@@ -52,7 +50,6 @@ Proximal more than Wrist (\p{0.007}), Opposite (\pinf{0.001}), and No Vibration
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And Wrist more than Opposite (\p{0.01}) and No Vibration (\pinf{0.001}).
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\subsubsection{Positioning \x Hand Rating}
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\label{positioning_hand}
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@@ -66,15 +63,13 @@ Wrist more than Opposite (\p{0.03}) and No Vibration (\pinf{0.001});
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And Skeleton more than No Hand (\pinf{0.001}).
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\subsubsection{Workload}
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\label{workload}
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There was a main of Positioning (\anova{4}{171}{3.9}, \p{0.004}).
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There was a main effect of Positioning (\anova{4}{171}{3.9}, \p{0.004}).
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Participants found Opposite more fatiguing than Fingertips (\p{0.01}), Proximal (\p{0.003}), and Wrist (\p{0.02}).
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\subsubsection{Usefulness}
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\label{usefulness}
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@@ -88,7 +83,6 @@ Wrist more than Opposite (\p{0.008}) and No Vibrations (\pinf{0.001});
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And Opposite more than No Vibrations (\p{0.004}).
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\subsubsection{Realism}
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\label{realism}
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