Spy in the cabin

Autonomous driving will provide a mass of external sensors, but manufacturers will not neglect the interior of the vehicle.

When Panasonic unveiled its concept for the cabin of an autonomous car earlier this year at the Consumer Electronics Show (CES), thermal imaging cameras were used to draw a picture of the body heat of the occupants of a flat screen. Display. Although future travelers like to look at thermal images of themselves during their journey, thermal sensors already play a role in the design of the vehicle and other sensors follow them.

Melexis marketing manager for temperature sensors, Joris Roels, explains that its use is currently limited to high-end vehicles, but that infrared (IR) sensors have advantages over traditional thermal sensors. Comfort is one of the reasons. The air conditioning system can adapt its performance to what the occupants feel rather than striving for a specific temperature.

IR sensors can also complement simple designs already in use, such as front-seat strain gauges. They inform both the safety belt warning and the airbag ignition control. But these sensors are easily deceived by a heavy suitcase sitting on the seat. Body heat sensors help solve the problem of confusing a bag with a body, especially when combined with other sensor and camera technologies.

Another imaging technology that may be required is the time-of-flight (ToF) camera, which measures the time it takes for reflections from light pulses sent from one laser or near LED to each pixel reach in the camera. Image sensor. For use in motor vehicles, the cameras are designed so that they can accurately measure distances of up to two or three meters in the vehicle interior.

Handling the speed of light in confined spaces is a challenge, says Norbert Bieler, senior marketing director for emerging automotive technologies at Analog Devices. However, the information obtained is a high resolution VGA image and an accurate depth map indicating the distance of an object to the camera. This facilitates the distinction between vehicle parts and persons and objects sitting or moving in the cabin.

ToF cameras in vehicles typically use IR technology for illumination rather than visible light so as not to distract the driver. Dealing with the distraction of the driver is an important part of the first wave of camera applications. Bieler emphasizes the increasing complexity of embedded controls as drivers for the transition to user interfaces that allow the driver to change the air conditioning or entertainment without forcing them to leave the road. A single hand movement can quickly move in a song instead of forcing the driver to search for the corresponding dial on a dashboard touchscreen or center column.

The camera allows the vehicle to check the driver in situations that are more likely to occur as the vehicle provides a higher autonomous control. Analog Devices has demonstrated at CES a combination of touch sensors in the steering wheel with a ToF camera to determine whether the driver can take control of an autonomous driving mode or whether the driver is sending SMS.

In a similar demonstration at CES, Infineon Technologies showed how a ToF camera can respond to the driver’s and passenger’s behavior on the car’s behavior. “The camera can be used in many applications, such as adjusting the airbag,” says Martin Lass, ToF Marketing Director at Infineon. For example, the driver can sit in his seat while the car is driving. “You want to adjust the pressure of the airbag in case of a collision.You can also adjust the mirror depending on the current position of the head.If I move to the right side, the mirror will follow my position.

Bieler says, “In the future, these cameras can be used with other sensors for applications such as driver monitoring, with the goal being a range of modular and scalable indoor sensors with different sensor technologies, and cooperating with vehicle manufacturers, third parties and strategic partners to understand the technology requirements.

Work together

For a supplier like Analog Devices, this means bringing together the work of several groups, such as health, consumers and industry. Other technologies include sensors to monitor the driver’s vital signs such as heart rate and skin conductance, which may indicate stress and body fluid. Bieler says: “Dehydration helps to detect drowsiness, but our vital signs monitoring technology could provide even more innovative features in the future that go beyond recognizing health and well-being parameters.

“The overriding goal is to get an overview of who or what is in the cabin and what’s going on there,” says Bieler.

Although ToF imagers and thermal imagers both use IRs, they can not be integrated into a single sensor technology. Thermal sensors must operate at a lower resolution when working in the remote IR range and use different sensor elements for imagers used in ToF applications.

Gualtiero Bagnuoli, Marketing Manager for Optical Sensors at Melexis, says, “The IR combination can be useful in distinguishing a living human from an object of the apparent human form, a combination of which may or may not be necessary for safety reasons Ensure reliability.

One application for a combination of IR technologies is to determine if a child has been left in the vehicle. The system may activate air conditioning to prevent overheating when sending a message to the driver’s telephone.

“IR in combination can be useful to distinguish between a living person and an object with the apparent shape of a human being.”
Gualtiero Bagnuoli, optical sensors, marketing manager
Last year, Guardian Optical Technologies, based in Israel, received $ 5 million in A-Series conveyors to develop its own sensor technology. A sensor mounted on the roof can detect movements up to a resolution of 1 μm and thus locate the number of people in the car at any time. Like ToF, Guardian expects to use sensor technology for a variety of gesture recognition tasks.

In the short term, manufacturers like Kia use simpler proximity sensors that can be based on IR or capacitive techniques, depending on their usable range, to detect simple gestures. The K900 luxury car, due out later this year, will dynamically adjust the light around the dashboard as an inmate’s hand reaches it.

The interior of the Kia K900 with a series of simple proximity sensors
Other sensors are less focused on the occupants than the environment in which they are located. Air quality can be a major goal, even if its introduction is likely to be regional, depending on local concerns. Pollution and legislation. The air recirculation can lead to the formation of undesirable gases such as volatile organic compounds (VOCs) and engine exhaust gases, which are captured by the circulation and recycled by the air conditioning system. If the system detects concentrations near a limit, it can trigger fresh air intakes.

Basically, the detection of air quality is another good application for IR sensors. However, metal oxide semiconductor sensors have advantages for automotive constructions. IR chemical sensors must be focused on specific wavelengths that are absorbed by a target molecule. Semiconductor sensors detect a wide range of gases because they focus on the changes in resistance that occur when the molecules are absorbed on the surface.

Although the rise of autonomous driving leads to a forest of sensors deployed outside the car, the builders of course do not neglect the interior. It will use different sensors to more closely observe what is happening in the vehicle.

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