COVER STORY
Automotive sensors sharpen up for safer driving
Opportunities for more and better automotive sensors continue to expand, as carmakers, legislators, and car buyers all seek further improvement in aspects such as reliability and safety. The number of sensors fitted to an average car is set to exceed 100 devices; as we move into the era of connected cars, the depth and diversity of information captured will continue to increase. By 2025 the number of sensors used in a car is supposed to double. Sensor developers – including automotive tier-1 suppliers and specialist automotive-electronics businesses – need to continue to up their game as they develop sensors that are more highly integrated and offer higher performance with lower power consumption. Gregor Knappik and Thomas Foj, Avnet Silica explain more
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The driving forces behind new sensors
afety is a major driver for the development of new types of sensors. To reduce accidents on the
roads, vehicles are taking on responsibility not only to manage their own safety- critical systems but also to help deal with driver fatigue, aid concentration, and alleviate stress. Indeed, driver fatigue may be a factor in about 20 per cent of road accidents today, and a high proportion of these tend to be serious or fatal because fatigue is often manifested as “micro sleeps” during which the driver has little or no ability to brake or steer to lessen the impact.
Driver monitoring systems tend to
measure steering behaviour as an indicator of fatigue. Fortunately, steer-by-wire systems already capture angular position and rate information from high-resolution sensors made by companies such as
8 October 2018
Allegro Microsystems, Elmos, Infineon and NXP. A high-speed interface allows a host microcontroller to capture and process the sensor data, while some sensors feature built-in processing to reduce the load on the host.
Early signs of driver fatigue include long periods with barely any steering activity, punctuated by small but abrupt corrections. A driver-awareness algorithm may combine the steering-sensor data with other information, such as use of turn signals, the length of the journey, and time of day to calculate a level of fatigue and generate a warning if the level exceeds a pre-set threshold: some drivers may already be familiar with the coffee-cup symbol on the dashboard, as a common prompt to take a break.
Other means of detecting driver fatigue include monitoring the position and movements of the driver’s head and eyes using 3D imaging techniques. With this
Components in Electronics Gregor Knappik
technology in the cabin, combining cameras and other detectors such as time- of-flight proximity sensors marketed by suppliers like ON Semiconductor and STMicroelectronics, which measure the distance to objects more accurately than conventional contrast-based proximity sensors, other value-added features also become possible. In combination with geographical information and artificial intelligence, the vehicle can identify an object the driver may be seeing – such as an architectural site – and automatically provide information when the driver asks a question such as “What building is this?” 3D image sensors and time-of-flight proximity sensors are also important for the higher levels of autonomous driving (Level 4 and Level 5 as defined by the SAE). At the opposite end of the driver- behaviour scale, stresses such as time pressure on commercial travellers can translate into excessive speed and erratic driving. Techniques using infrared sensing to detect signs of over-stress can be linked with other vehicle systems to try to combat
Thomas Foj
these effects. With the advent of tuneable LED-based interior lighting, the vehicle can adjust the light level and spectral content autonomously towards calming blue wavelengths to encourage safer driving. Further innovations to improve comfort and aid concentration include so-called wellness seats. Sensors form the core of this type of innovation, using advanced techniques to achieve non-invasive monitoring of important vital signs such as the driver’s heart rate or respiration. Pressure sensors are already widely used to assist lumbar support, and in fact are used in many places throughout the vehicle such as airbag controls and LPG (Liquid Petroleum Gas) fuel-pressure monitoring.
Sensing for touchless HMI Safety can be further improved by enabling drivers to interact naturally with in-cabin equipment such as infotainment or lighting. The arrival of touchscreens in the centre console has enabled new and more intuitive ways of tuning the radio, selecting music or adjusting climate
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