Audi MMI touch controller. Figure 3 (right). Adaptive control elements can dynamically change their shape to communicate information to the driver in an eyes-free manner [ 9].

projects that are looking into possibilities to add haptic feedback to touch interaction.

Touch Interaction and Haptic Feedback Depending on the position of the screen (e.g., in the middle of the dashboard), it can be cumbersome for the driver to reach and touch the central information display. Decoupled input devices like the multifunctional controllers mentioned before allow us to overcome this issue. Similarly, touch input decoupled from the display is used in the MMI touch interface [ 6] developed by Audi: A touchpad on the center stack close to the gearshift allows drivers to perform gestures, input characters, or execute shortcut commands (assigned to certain areas of the input device) to control the infotainment system (see Figure 2). Since this is a traditional touchpad, this device offers neither visual nor haptic feedback, which makes it difficult to implement, for example, virtual buttons.

To add vibrotactile feedback,
Richter et al. created the Hap Touch
system, which enriched a touch-
screen with force sensors and a
linear actuator able to move the
entire display in z-direction [ 7].
When the screen is touched, the
system can sense a finger position
and provide tactile information. If
the display is pressed harder, fur-
ther interaction, such as pressing
a button, can be implemented.

March + April 2013