Hassane El-KhouryAs touchscreens with gesture-based interfaces have become nearly standard in the mobile phone segment, many people are waiting impatiently for the technology to make its way into the automotive market. Drivers are already familiar with getting into their car and using the touchscreen to check systems or select a music playlist to listen to. However, today’s infotainment menu structures are cumbersome and difficult to use. Drivers want to be able to flick through menus to scroll and use simple gestures such as zoom in and out, pan left, and rotate like they do with their phones.

Designing an intuitive Automotive Human Machine Interface (HMI) presents a new set of challenges compared to what is seen in the consumer segment. When adding functionality, engineers have to take into account an interface’s effect on the driver’s primary responsibility: keeping his or her eyes on the road. Gesture-based interfaces, in the case of a car, are not simply a fancy feature implemented in vehicles to make a more exciting driving experience. Although appealing to drivers, this functionality also improves safety while driving. The less time the driver spends navigating through menus, the more time that can be spent focused on the road.

First, let’s differentiate between both types of touchscreens making their way into the automotive infotainment arena:

- Resistive touchscreens are the dominant technology in automotive infotainment applications. They are the lowest cost touchscreen technology and used across many application segments. Due to their mechanical-like implementation, pressure must be applied on the panel to detect a touch. Two properties of resistive touchscreens cause it to lose traction in the automotive market: Clarity, generally between 70% and 80%, and secondly the need to regularly calibrate alignment with the LCD.

- Capacitive touchscreens offer better clarity (90%+) as well as higher accuracy across the panel without the need for regular recalibration. Where projected capacitive touchscreens truly add value, however, is their ability to detect multiple touch points simultaneously.

Gesture recognition on capacitive touchscreens is not only a new means of input but is indeed another level of input to the system. With capacitive touchscreens, one can still navigate through menu structures with a single click and increase the audio volume by sliding a finger. What is really important, however, is how easy it is for drivers to control standard functions such as navigation which are used while driving. The driver can zoom out with a simple gesture without necessarily having to look at the screen. Gestures can be introduced on any area of the screen, and therefore do not require the driver to position his fingers in a certain location prior to performing the gesture (see Figure 1). For example, the driver can slide the map left or right for better viewing with a simple finger gesture without menu navigation. 

Figure 1 - Zoom-Out Gesture on Navigation ScreenAs with any new emerging technology, customer acceptance is a critical consideration. In the automotive infotainment world, customers in general are open to technologies which are similar to those they already use every day. Touchscreens are making their way into the automotive market, and they have for years. Capacitive touchscreens are not changing the way drivers interact with their vehicle, they are enhancing it; the HMI concept with touchscreens is not about redesigning systems but rather enhancing them.

When discussing HMI concepts, voice activated systems are also emerging. However, consumers, drivers included, are not only more familiar with touch-based systems, they now have come to expect it. Voice activated systems have been implemented in vehicles, but these systems still need training, a step which consumers tend to resist. From the consumer side, voice recognition is an entirely new technology, not an incremental change. Command structures have to be learned, and these are not standard across all vehicle manufacturers. 

Introduced as an emerging technology, capacitive touchscreens with gesture recognition are not a distant reality with automotive-qualified controller ICs available to the market. With the average automotive design cycle of 2-3 years, users can expect to see next-generation infotainment systems in cars starting in 2012. With Cypress’ automotive-qualified TrueTouch controllers, for instance, automotive Tier1s and OEMs alike can start developing gesture based infotainment systems right out of the box. These controllers integrate the following system functionality highlighted in Figure 2.

- Scan the capacitive ITO (Indium Tin Oxide) panel using capacitive sensing technologies such as CSD (Sigma-Delta Modulator-based measurement). The measured signal strength is proportional to the position of the finger relative to the ITO diamond in the sensor array – the more overlap, the larger the signal strength. Note that the ITO panel is designed to allow for a finger to overlap multiple diamonds for more accurate position calculation.

- Accurately determine the position of one or multiple fingers on the panel by recognizing overlap of a touch on the diamond pattern. In the example below, the finger in the Y-axis overlaps with sensors 3 and 4 with a respective signal strength of 15 and 7.

- Decode gestures based on relative finger movement. Gestures are decoded inside the controller and transmitted to the host system as simple gesture IDs. 

Figure 2 - Capacitive Touchscreen Finger Detection

Touchscreen enhancement can be taken a step further with multi-touch all-point controllers which enable individual finger position detection for up to 10 fingers. This is useful in dual view screen applications which allow both driver and passenger to interface the infotainment unit at the same time. With dual view screens starting to see their first automotive applications, a multi-touch all-point touchscreen controller is what is needed to allow the driver to zoom in on a map while the passenger adjusts the audio volume.

Whether using gesture or all-point touchscreens, one outcome is becoming very clear. Enhancing infotainment HMI does not mean making accessing features more complex for the users. Rather, it is about relying upon familiar ways of interfacing with devices and implementing them efficiency to increase driver safety.