Complete related work

1-introduction/related-work/2-wearable-haptics.tex

@@ -204,7 +204,7 @@ The simplest texture simulation model is a 1D sinusoidal grating $v(t)$ with spa
 \begin{equation}{grating_rendering}
     v(t) = A \sin(\frac{2 \pi \dot{x}(t)}{\lambda})
 \end{equation}
-That is, this model generates a periodic signal whose frequency is proportional to the user's velocity, implementing the speed-frequency ratio observed with real patterned textures (\eqref{grating_vibrations}).
+That is, this model generates a periodic signal whose frequency is modulated and proportional to the user's velocity, implementing the speed-frequency ratio observed with real patterned textures (\eqref{grating_vibrations}).
 It gives the user the illusion of a texture with a \emph{fixed spatial period} that approximate the real manufactured grating textures (\secref{roughness}).
 The user's position could have been used instead of the velocity, but it requires measuring the position and generating the signal at frequencies too high (\qty{10}{\kHz}) for most sensors and haptic actuators \cite{campion2005fundamental}.
 
@@ -212,6 +212,7 @@ With a voice-coil actuator attached to the middle phalanx of the finger, \textci
 Participants moved their finger over real grating textures (\qtyrange{0.15}{.29}{\mm} groove and ridge width) with a virtual sine grating (\qty{1}{\mm} spatial period) superimposed, rendered after \eqref{grating_rendering}.
 The perceived roughness increased proportionally to the virtual texture amplitude, but a high amplitude decreased it instead.
 \textcite{ujitoko2019modulating} instead used a square wave signal and a hand-held stylus with an embedded voice-coil.
+\textcite{friesen2024perceived} compared the frequency modulation of \eqref{grating_rendering} with amplitude modulation (\figref{friesen2024perceived}), and found that the frequency modulation was perceived as more similar to real sinusoidal gratings for lower spatial periods (\qty{0.5}{\mm}) but both modulations were effective for higher spatial periods (\qty{1.5}{\mm}).
 
 %\textcite{friesen2024perceived} proposed
 
@@ -239,13 +240,13 @@ When comparing real textures felt through a stylus with their virtual models ren
 
 \begin{subfigs}{textures_rendering_data}{Augmentating haptic texture perception with voice-coil actuators. }[
         \item Increasing and decreasing the perceived roughness of a real patterned texture in direct touch \cite{asano2015vibrotactile}.
-        %\item Comparing real patterned texture with virtual texture augmentation in direct touch \cite{friesen2024perceived}.
+        \item Comparing real patterned texture with virtual texture augmentation in direct touch \cite{friesen2024perceived}.
         \item Rendering virtual contacts in direct touch with the virtual texture \cite{ando2007fingernailmounted}.
         \item Rendering an isotropic virtual texture over a real surface while sliding a hand-held stylus across it \cite{culbertson2012refined}.
     ]
-    \subfigsheight{38mm}
+    \subfigsheight{36mm}
     \subfig{asano2015vibrotactile_2}
-    %\subfig{friesen2024perceived}
+    \subfig{friesen2024perceived}
     \subfig{ando2007fingernailmounted}
     \subfig{culbertson2012refined}
 \end{subfigs}
@@ -358,7 +359,8 @@ Haptic systems aim to provide virtual interactions and sensations similar to tho
 The complexity of the haptic sense has led to the design of numerous haptic devices and renderings.
 While many haptic devices can be worn on the hand, only a few can be considered wearable as they are compact and portable, but they are limited to cutaneous feedback.
 If the haptic rendering is timely associated with the user's touch actions on a real object, the perceived haptic properties of the object can be modified.
-Several rendering methods have been developed to modify the perceived roughness and hardness, but not all of them have been already transposed to wearable haptics.
+Several rendering methods have been developed to modify the perceived roughness and hardness, mostly using vibrotactile feedback and, to a lesser extent, pressure feedback.
+However, not all of these haptic augmentations have been already transposed to wearable haptics.
 
 %, unlike most previous actuators that are designed specifically for fingertips and would require mechanical adaptation to be placed on other parts of the hand.
 % thanks to the vibration propagation and the sensory capabilities distributed throughout the skin, they can be placed without adaption and on any part of the hand