For example the resolution of commands could be too low, the mechanical response to the command can be non-linear, the quality of the contact between the haptic system and the user can be sub-optimal, the mechanical effects can be out of the perceptual range, and haptic illusions can alter the interpretation of sensations.
While the work of researchers in specialized domains mentioned in Figure~\ref{fig:hapticpath} is to avoid, or at least minimize such drifts in their part of the pipeline, my work as an HCI researcher consists in selecting, adjusting, combining, designing, implementing and evaluating such parts to build \defword{interactive systems}.
My research is therefore fundamentally interdisciplinary, and I combine, complement or replace expertise of different domains, depending of the needs of each research project, and the expertise of my collaborators.
+My objective is to make interactive systems better than the sum of their parts.
%I prefer the term “interactive system” over “interface” because it better conveys my systemic approach.
%In my opinion, sytems are not a computing core with an interface to feed inputs and display outputs.
We presented technologies for haptic devices above.
Interactive languages are systematic descriptions of the inputs and outputs of an interactive device.
Similar to programming languages, they have three levels: lexical, syntactic, and semantic.
+
The \emph{lexical level} defines the basic vocabulary of the device.
For example, we can control vibrations in frequency, amplitude, shape, and duration (Figure~\ref{fig:lexical}).
Hence the command for a vibrotactile actuator is an electrical signal made of these elements.
+The research challenge here is to bridge the knowledge gap between the engineering of actuators and human factors, and find tactile parameters that users can perceive and distinguish.
+Such research is typically useful to guide the design of tactile actuators.
+We will illustrate this kind of research in section~\ref{sec:stimtac}.
+
%For example the output vocabulary of a 3 degrees-of-freedom (DOF) force-feedback device is a force vector.
%Hence, a software controller sends three values to the electro-mechanical system, which will convert it to forces.
%Such devices also have an input vocabulary, typically 3DOF or 6DOF (translations + rotations) and sometimes one or several buttons.
The figure~\ref{fig:syntactic} shows several examples of such haptic phrases with vibrotactile feedback.
Frequency and amplitude modulation create new kinds of feedback, that Brown \etal describe as roughness \cite{brewster04}.
They also use sequences of vibrations to form rhythms.
+
%Typically, force-feedback device use force models, as described in the previous section.
%These are functions that compute forces depending on the device's position.
%For example, there are force models for springs, magnets, damping or other kinds of forces.
%Leverage the sense of touch to improve interaction.
-Potential issues at all levels: difficulties to reproduce effects in a consistent way across devices and people.
- Coding \texttt{=>} Command \texttt{=>} physical effect \texttt{=>} sensation \texttt{=>} information…
+%Potential issues at all levels: difficulties to reproduce effects in a consistent way across devices and people.
+ %Coding \texttt{=>} Command \texttt{=>} physical effect \texttt{=>} sensation \texttt{=>} information…
- Many places where information can get lost: command resolution, non-linear mechanical effect, bad contact between device and user, effect out of perceptual range, haptic illusions.
+% Many places where information can get lost: command resolution, non-linear mechanical effect, bad contact between device and user, effect out of perceptual range, haptic illusions.
Replicability
Can people notice and interpret correctly information when they do not expect the tactile cues?
\subsection{Tactile textures}
+ \label{sec:stimtac}
command/effect relation
singularity of the effects produced by research prototypes
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