Capacitive sensing is the dominant technology used for steering wheel touch detection due to its cost and functional performance. The ECU uses data obtained via a special-purpose capacitive sensor, wrapped around the steering wheel, to determine if the driver is touching it and conveys the assessment to an advanced driver assistance system (ADAS). Whereas existing hands-off detection systems are mono-zone setups, with a single electrode, Alps Alpine has developed a multi-zone configuration with four electrodes (see Fig. 1). Dividing the steering wheel and grip patterns into smaller sections enables efficient system switching and enhanced touch assessment reliability.
The sensor electrode is divided into four sections to enable identification of various grip states. This allows a more detailed assessment of driving status than a basic touching/not touching determination reached using an existing single-electrode sensor. This sensor’s data are processed in a capacitive control ASIC also developed by Alps Alpine.
Steering wheel design, sensor material, electromagnetic compatibility conditions vary from model to model, leading to variance in data obtained via the capacitive sensor. To accommodate the separate circumstances, Alps Alpine can supply an originally developed algorithm that seeks individual optimization, for example with parameter changes.
Reliability is enhanced by an original failure determination feature and the product conforms to ISO 26262, the international standard on the functional safety of electrical and electronic systems in automobiles.