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2-related-work/1-haptic-hand.tex

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 \section{Perception and Interaction with the Hand}
 \label{haptic_hand}
 
-% describe how the hand senses and acts on its environment to perceive the haptic properties of real everyday objects.
-
 The haptic sense has specific characteristics that make it unique in regard to other senses.
 It enables us to perceive a large diversity of properties of everyday objects, up to a complex combination of sensations produced by numerous sensory receptors distributed throughout the body, but especially in the hand \cite{johansson2009coding}.
-It also allows us to act on these objects, to come into contact with them, to grasp them and to actively explore them. % , and to manipulate them.
-%This implies that the haptic perception is localized at the points of contact between the hand and the environment, \ie we cannot haptically perceive an object without actively touching it.
+It also allows us to act on these objects, to come into contact with them, to grasp them and to actively explore them.
 These two mechanisms, \emph{action} and \emph{perception}, are closely associated and both are essential to form a complete haptic experience of interacting with the environment using the hand \cite{lederman2009haptic}.
 
 \subsection{The Haptic Sense}
@@ -188,8 +185,7 @@ But when running the finger over the surface with a lateral movement (\secref{ex
 In particular, when the asperities are smaller than \qty{0.1}{mm}, such as paper fibers, the pressure cues are no longer captured and only the movement, \ie the vibrations, can be used to detect the roughness \cite{hollins2000evidence}.
 This limit distinguishes \emph{macro-roughness} from \emph{micro-roughness}.
 
-%The physical properties of the surface determine the haptic perception of roughness.
-The perception of roughness can be characterized by the density of the surface elements: the perceived (subjective) intensity of roughness increases with the spacing between the elements. %, for macro-roughness \cite{klatzky2003feeling,lawrence2007haptic} and micro-roughness \cite{bensmaia2003vibrations}.
+The perception of roughness can be characterized by the density of the surface elements: the perceived (subjective) intensity of roughness increases with the spacing between the elements.
 For macro-textures, the size of the elements, the force applied and the speed of exploration have limited effects on the intensity perceived \cite{klatzky2010multisensory}: macro-roughness is a \emph{spatial perception}.
 This allows us to read Braille \cite{lederman2009haptic}.
 However, the speed of exploration affects the perceived intensity of micro-roughness \cite{bensmaia2003vibrations}.
@@ -279,99 +275,10 @@ Stiffness depends on the structure of the object: a thick object can be more com
   \subfig[.45]{bergmanntiest2009cues}
 \end{subfigs}
 
-%\textcite{bergmanntiest2009cues} showed how  of these two physical measures in the perception of hardness.
 An object with low stiffness, but high Young's modulus can be perceived as hard, and vice versa, as shown in \figref{bergmanntiest2009cues}.
 With finger pressure, a relative difference (the \emph{Weber fraction}) of \percent{\sim 15} is required to discriminate between two objects of different stiffness or elasticity.
 However, in the absence of pressure sensations (by placing a thin disc between the finger and the object), the necessary relative difference becomes much larger (Weber fraction of \percent{\sim 50}).
 That is, \textcite{bergmanntiest2009cues} showed the perception of hardness relies on \percent{90} on surface deformation cues and \percent{10} on displacement cues.
-%Finally, when pressing with the finger, the perceived hardness intensity $h$ follows a power law with the stiffness $k$ \cite{harper1964subjective}:
-%\begin{equation}{hardness_intensity}
-%    h = k^{0.8}
-%\end{equation}
-
-%En pressant du doigt, l'intensité perçue (subjective) de dureté suit avec la raideur une relation selon une loi de puissance avec un exposant de \num{0.8} \cite{harper1964subjective}, \ie quand la raideur double, la dureté perçue augmente de \num{1.7}.
-%\textcite{bergmanntiest2009cues} ont ainsi observé une relation quadratique d'égale intensité perçue de dureté, comme illustré sur la \figref{bergmanntiest2009cues}.
-
-%\subsubsection{Friction}
-%\label{friction}
-%
-%Friction (or slipperiness) is the perception of \emph{resistance to movement} on a surface \cite{bergmanntiest2010tactual}.
-%Sandpaper is typically perceived as sticky because it has a strong resistance to sliding on its surface, while glass is perceived as more slippery.
-%This perceptual property is closely related to the perception of roughness \cite{hollins1993perceptual,baumgartner2013visual}.
-%
-%When running the finger on a surface with a lateral movement (\secref{exploratory_procedures}), the skin-surface contacts generate frictional forces in the opposite direction to the finger movement, giving kinesthetic cues, and also stretch the skin, giving cutaneous cues.
-%As illustrated in \figref{smith1996subjective_1}, a stick-slip phenomenon can also occur, where the finger is intermittently slowed by friction before continuing to move, on both rough and smooth surfaces \cite{derler2013stick}.
-%The amplitude of the frictional force $F_s$ is proportional to the normal force of the finger $F_n$, \ie the force perpendicular to the surface, according to a coefficient of friction $\mu$:
-%\begin{equation}{friction}
-%    F_s = \mu \, F_n
-%\end{equation}
-%The perceived intensity of friction is thus roughly related to the friction coefficient $\mu$ \cite{smith1996subjective}.
-%However, it is a complex perception because it is more determined by the micro-scale interactions between the surface and the skin: It depends on many factors such as the normal force applied, the speed of movement, the contact area and the moisture of the skin and the surface \cite{adams2013finger,messaoud2016relation}.
-%In this sense, the perception of friction is still poorly understood \cite{okamoto2013psychophysical}.
-%
-%\begin{subfigs}{smith1996subjective}{Perceived intensity of friction of different materials by active exploration with the finger \cite{smith1996subjective}. }[
-%        \item Measurements of normal $F_n$ and tangential $F_t$ forces when exploring two surfaces: one smooth (glass) and one rough (nyloprint). The fluctuations in the tangential force are due to the stick-slip phenomenon. The coefficient of friction $\mu$ can be estimated as the slope of the relationship between the normal and tangential forces.
-%        \item Perceived friction intensity (vertical axis) as a function of the estimated friction coefficient $\mu$ of the exploration (horizontal axis) for four materials (shapes and colors).
-%    ]
-%    \subfigsheight{55mm}
-%    \subfig{smith1996subjective_1}
-%    \subfig{smith1996subjective_2}
-%\end{subfigs}
-%
-%Yet, it is a fundamental perception for grasping and manipulating objects.
-%The forces of friction make it indeed possible to hold the object firmly in the hand and prevent it from slipping
-%The perception of friction also allows us to automatically and very quickly adjust the force we apply to the object in order to grasp it \cite{johansson1984roles}.
-%If the finger is anaesthetized, the lack of cutaneous sensation prevents effective adjustment of the gripping force: the forces of the object on the finger are no longer correctly perceived, and the fingers then press harder on the object in compensation, but without achieving good opposition of the fingers \cite{witney2004cutaneous}.
-
-%\subsubsection{Temperature}
-%\label{temperature}
-%
-%Temperature (or coldness/warmness) is the perception of the \emph{transfer of heat} between the touched surface and the skin \cite{bergmanntiest2010tactual}:
-%When heat is removed from (added to) the skin, the surface is perceived as cold (hot).
-%Metal will be perceived as colder than wood at the same room temperature: This perception is different from the physical temperature of the material and is therefore an important property for distinguishing between materials \cite{ho2006contribution}.
-%This perception depends on the thermal conductivity and heat capacity of the material, the volume of the object, the initial temperature difference and the area of contact between the surface and the skin \cite{kappers2013haptic}.
-%For example, a larger object or a smoother surface, which increases the contact area, causes more heat circulation and a more intense temperature sensation (hot or cold) \cite{bergmanntiest2008thermosensory}.
-
-%Parce qu'elle est basée sur la circulation de la chaleur, la perception de la température est plus lente que les autres propriétés matérielles et demande un toucher statique (voir \figref{exploratory_procedures}) de plusieurs secondes pour que la température de la peau s'équilibre avec celle de l'objet.
-%La température $T(t)$ du doigt à l'instant $t$ et au contact avec une surface suit une loi décroissante exponentielle, où $T_s$ est la température initiale de la peau, $T_e$ est la température de la surface, $t$ est le temps et $\tau$ est la constante de temps:
-%\begin{equation}{temperature}
-%    T(t) = (T_s - T_e) \, e^{-t / \tau} + T_e
-%\end{equation}
-%Le taux de transfert de chaleur, décrit par $\tau$, et l'écart de température $T_s - T_e$, sont les deux indices essentiels pour la perception de la température.
-%Dans des conditions de la vie de tous les jours, avec une température de la pièce de \qty{20}{\celsius}, une différence relative du taux de transfert de chaleur de \percent{43} ou un écart de \qty{2}{\celsius} est nécessaire pour percevoir une différence de température \cite{bergmanntiest2009tactile}.
-
-%\subsubsection{Spatial Properties}
-%\label{spatial_properties}
-
-%Weight, size and shape are haptic spatial properties that are independent of the material properties described above.
-
-%Weight (or heaviness/lightness) is the perceived \emph{mass} of the object \cite{bergmanntiest2010haptic}.
-%It is typically estimated by holding the object statically in the palm of the hand to feel the gravitational force (\secref{exploratory_procedures}).
-%A relative weight difference of \percent{8} is then required to be perceptible \cite{brodie1985jiggling}.
-%By lifting the object, it is also possible to feel the object's force of inertia, \ie its resistance to velocity.
-%This provides an additional perceptual cue to its mass and slightly improves weight discrimination.
-%For both gravity and inertia, kinesthetic cues to force are much more important than cutaneous cues to pressure \cite{bergmanntiest2012investigating}.
-%Le lien entre le poids physique et l'intensité perçue est variable selon les individus \cite{kappers2013haptic}.
-
-%Size can be perceived as the object's \emph{length} (in one dimension) or its \emph{volume} (in three dimensions) \cite{kappers2013haptic}.
-%In both cases, and if the object is small enough, a precision grip (\figref{gonzalez2014analysis}) between the thumb and index finger can discriminate between sizes with an accuracy of \qty{1}{\mm}, but with an overestimation of length (power law with exponent \qty{1.3}).
-%Alternatively, it is necessary to follow the contours of the object with the fingers to estimate its length (\secref{exploratory_procedures}), but with ten times less accuracy and an underestimation of length (power law with an exponent of \qty{0.9}) \cite{bergmanntiest2011cutaneous}.
-%The perception of the volume of an object that is not small is typically done by hand enclosure, but the estimate is strongly influenced by the size, shape and mass of the object, for an identical volume \cite{kahrimanovic2010haptic}.
-
-%The shape of an object can be defined as the perception of its \emph{global geometry}, \ie its shape and contours.
-%This is the case, for example, when looking for a key in a pocket.
-%The exploration of contours and enclosure are then employed, as for the estimation of length and volume.
-%If the object is not known in advance, object identification is rather slow, taking several seconds \cite{norman2004visual}.
-%Therefore, the exploration of other properties is favoured to recognize the object more quickly, in particular marked edges \cite{klatzky1987there}, \eg a screw among nails (\figref{plaisier2009salient_2}), or certain material properties \cite{lakatos1999haptic,plaisier2009salient}, \eg a metal object among plastic objects.
-
-%\begin{subfigs}{plaisier2009salient}{Identifcation of a sphere among cubes \cite{plaisier2009salient}. }[
-%        \item The shape has a significant effect on the perception of the volume of an object, \eg a sphere is perceived smaller than a cube of the same volume.
-%        \item The absence of a marked edge on the sphere makes it easy to identify among cubes.
-%    ]
-%    \subfigsheight{40mm}
-%    \subfig{plaisier2009salient_1}
-%    \subfig{plaisier2009salient_2}
-%\end{subfigs}
 
 \subsection{Conclusion}
 \label{haptic_sense_conclusion}