Repurposing Capacitive Sensors to Distinguish Driver and Passenger Touches on In-Vehicle Screens
UIST 2017: Edward Jay Wang, Jake Garrison, Eric Whitmer, Mayank Goel, Shwetak Patel
Standard vehicle infotainment systems often include touch screens that allow the driver to control their mobile phone, navigation, audio, and vehicle configurations. For the driver’s safety, these interfaces are often disabled or simplified while the car is in motion. Although this reduced functionality aids in reducing distraction for the driver, it also disrupts the usability of infotainment systems for passengers. Current infotainment systems are unaware of the seating position of their user and hence, cannot adapt. We present Carpacio, a system that takes advantage of the capacitive coupling created between the touchscreen and the electrode present in the seat when the user touches the capacitive screen. Using this capacitive coupling phenomenon, a car infotainment system can intelligently distinguish who is interacting with the screen seamlessly, and adjust its user interface accordingly. Manufacturers can easily incorporate Carpacio into vehicles since the included seat occupancy detection sensor or seat heating coils can be used as the seat electrode. We evaluated Carpacio in eight different cars and five mobile devices and found that it correctly detected over 2600 touches with an accuracy of 99.4%.
Carpacio is a system that differentiates whether a driver or passenger touches the screen in a car by measuring the parasitically coupled signal from the screen. As a user touches the screen, a signal is coupled to the body. By using an electrode embedded in the seat, this signal can be measured using an ADC
The algorithm used in Carpacio uses a series of filtering to reduce the ambient noise. Each block shows a step in the signal processing pipeline. The blue signal is the time domain signal measured by the seat pad on the driver’s side. The orange signal is from the passenger’s side. The final output of the system is a classification of driver/passenger based on which side has the stronger signal after filtering
For our validation set, we tested 5 built-in screens in cars, 2 capacitive controllers, 4 phones, and 1 tablet. To get this dataset, we took our hardware setup all around seattle to different dealerships around town to test on a variety of makes and models. And we tested the phones and tablets in a car that did not have a built-in system.