In the previous section we investigated the output vocabulary for a new device providing a new type of haptic feedback.
We did not explore a particular context or application, but rather studied the possibilities and limitations of the technology.
In this project we are interested in vibrotactile feedback, which is well covered in the literature.
-We are interested in a particular case: restoring haptic feedback on touchscreens.
+We are however interested in a particular case: restoring haptic feedback on touchscreens.
Indeed touchscreens have many advantages compares to physical interfaces.
They can be updated.
They have no mechanical parts that wear over time.
\centering
\includegraphics[height=5.2cm]{figures/mojave}%
\includegraphics[height=5.2cm]{figures/mojavedashboard}
- \caption[Mojave concept car.]{The Mojave concept car designed by the Esperra Sbarro school, showcased at the Geneva Motor Show 2017. We implemented the software of the dashboard.}
+ \caption[Mojave concept car.]{The Mojave concept car designed by the Esperra Sbarro school, showcased at the Geneva Motor Show 2017. We implemented the software of the dashboard and the driving electronics.}
\label{fig:mojave}
\end{figure}
%Leverage vibrotactile feedback to restore haptic properties on touchscreens
\subsubsection{Experimental platform}
+\label{sec:printgetsplatform}
The design of the actuators is a trade-off between their size and thickess, the number of layers and the signal voltage.
-Our colleagues who designed and implemented these actuators, performed FEM simulations, and measured the response to signal with laser vibrometers~\cite{poncet16,poncet17}.
+Our colleagues who designed and implemented these actuators, performed FEM simulations, and measured the response to signal with laser vibrometers~\cite{poncet17,poncet16}.
They gave us several prototypes that we could use to design vibrotactile widgets.
-The first prototype (top of~\reffig{fig:printedslider}) had six buttons embedded in amolded plastic dashboard part.
+The first prototype (top of~\reffig{fig:printedslider}) had six buttons embedded in a molded plastic dashboard part.
The clamping area was a circle around each actuator.
-A clamping area defines the area on which the vibration propagates.
+It defines the area on which the vibration propagates, therefore this vibrotactile feedback is localized.
The second prototype was a bare flexible substrate with seven actuators.
We designed a clamping frame around the actuators so that the vibration could propagate on the whole length of the slider.
-we added tension strings to tighten the frame so that the clamping area could resonate.
+We added tension strings to tighten the frame so that the clamping area could resonate.
This is the same approach than a drum head on a drum shell.
The capactitive touch sensor, printed with silver ink, is under the actuators.
The setup is depicted at the bottom of~\reffig{fig:printedslider}.
\label{fig:printedslider}
\end{figure}
-We built a custom PCB with piezo drivers\footnote{\href{http://www.ti.com/product/DRV2667.}{TI DRV2667}} (one per actuator), and the capacitive sensing chip~\footnote{\href{http://www.microchip.com/wwwproducts/en/CAP1214.}{Microchip CAP1214}}.
+We built a custom PCB with piezo drivers\footnote{\href{http://www.ti.com/product/DRV2667.}{TI DRV2667}} (one per actuator), and the capacitive sensing chip~\footnote{\href{http://www.microchip.com/wwwproducts/en/CAP1188}{Microchip CAP1188} for buttons and \href{http://www.microchip.com/wwwproducts/en/CAP1214}{Microchip CAP1214} for sliders}.
The chips communicate with the main board that runs the application\footnote{\href{https://www.raspberrypi.org/products/raspberry-pi-3-model-b/}{Raspberry Pi 3B}} through an I2C bus.
The drivers have two mode of operation. Either we play pre-recorded signals, or we provide an audio signal in the tactile frequency-range.
The pre-recorded signal solution is easier because it does not require additional hardware.
\subsubsection{Vibrotactile widgets}
-
-\cite{lylykangas11}
-
-
-\cite{schneider16,seifi17}
-
-~\cite{frisson20,frisson17}
-
-Neuromechanics button press ~\cite{oulasvirta18}
+The idea of using vibrations to simulate button clicks on touch surfaces started with vibrotactile actuators attached to PDAs~\cite{fukumoto01,nashel03,poupyrev02}, then mobile phones~\cite{brewster07,hoggan08}.
+This was before phone manufacturers included vibrotactile actuators to mobile phone.
+And even now mobile phones do have one, it is low quality (ERM or LRA) and mostly used for message or call notifications.
+They sometimes propose vibrations for button presses, but the quality of this feedback is poor.
+Indeed other actuators provide a sharper vibrotactile feedback, we discussed this at the beginning of this chapter.
+Voice coil actuators provide precise and strong vibrations~\cite{yao10}, and piezo actuators have a smaller form factors, and convenient for implementing buttons~\cite{tashiro09,lylykangas11}.
+Our challenge is that printed actuators are thin (between $4\mu m$ and $10\mu m$).
+Therefore the vibration propagation requires a careful design as discussed in the previous page.
+
+%Designing better tactile buttons requires knowing how people operate buttons, and what they perceive.
+%Neuromechanics button press ~\cite{oulasvirta18}
+Kim and Lee analyzed force-displacement curves of physical buttons and designed high quality vibrotactile feedback that emulates button presses~\cite{kim13}.
+They split force-displacement curves into two types of sections: slopes and jumps, which are delimited by tactile points (\reffig{fig:buttonfeedback}).
+Slopes are spring-like sensations that corresponds to the material resistance.
+When pressing a button we feel a first resistance before the click, then another one when the button reaches its end.
+When releasing a button we feel another resistance before the click sensation.
+The tactile points (1) and (3) represent the click sensations when the button physically switches, and the bottom-out (2) represents the end of the button.
+We adapted and simplified these curves for the design and implementation of our buttons.
+We describe further our implementation of buttons, sliders and touchpads in~\cite{frisson20,frisson17}.
\begin{figure}[htb]
\definecolor{cellred}{rgb} {0.98,0.17,0.15}
\draw[x=\scale, y=\scale, ->, -stealth', draw=cellblue, ultra thick] (three) -- (15,20) -- (threeb);
\draw[x=\scale, y=\scale, draw, ultra thick, dashed] (one) -- (oneb);
+ \draw[x=\scale, y=\scale, draw, ultra thick, dashed] (three) -- (threeb);
\draw[x=\scale, y=\scale, draw=cellred, ultra thick] (90,40) -- (98,40);
\node[x=\scale, y=\scale, anchor=west] () at (100,40){Press curve};
\label{fig:buttonfeedback}
\end{figure}
+The design of the tactile feedback for slopes and points we described in the previous paragraph requires an iterative process.
+Several tools were designed to support the design of vibrotactile animations~\cite{schneider15,schneider16}
+As we discussed in section~\ref{sec:printgetsplatform}, the haptic drivers provide an audio mode in which we can provide an audio signal to drive the actuators.
+We leveraged this feature with Purr Data, a web-based audio synthesis programming language that we used to design vibrotactile feedback~\cite{frisson16}.
+We describe the design of the vibrotactile feedback for tactile buttons in~\cite{frisson20}.
%Leverages vibrotactile feedback for touch surfaces.
\subsubsection{Discussion and conclusion}
+put together existing building blocks to design a whole system
+
+interdisciplinary skills and knowledge
+
+low vibration amplitude => clamping arrea => localized haptic feedback
\subsection{Actuated computer peripherals}
\label{sec:metamorphe-livingdesktop}
projects / hdr.git / commitdiff