Even though ultrasound has been studied by scientists for many years, its capabilities in practical applications are yet to be fully harnessed.

Bats have been nature’s prototypes for sound-based navigation. They rely on echolocation to detect obstacles in flight, forage for food, and see in dark caves. By mimicking the bat’s technique, an ultrasonic solution was developed that provides echolocation and enables the detection of multiple objects in three-dimensional space.

Close-Range Perception

How can it be possible that a staggering one out of five motor vehicle accidents takes place in a parking lot? Even at the slow speeds usually found in parking scenarios, the driver cannot perceive his environment flawlessly, despite parking assistance functions like cameras and PDCs. Tight parking spots in car parks or crowded parking areas in front of shopping malls maximize everyday driving challenges. Car manufacturers are beginning to support their cars with the latest sensor technologies so that multiple tons of moving metal are not left without eyes.

The principle of echolocation.

Sensors are currently used to help drivers steer more safely and guide them into a parking spot via sound and light signals. In order to advance in areas like autonomous driving, mapping, and collision avoidance, sensors now need to detect more complex environmental scenarios like steering a car through a construction site or reliably detecting people in a crowded parking area. As every ride starts and ends in a parking position involving some kind of parking maneuver, it is crucial to safely perceive a car’s immediate environment.

While existing sensor technologies mostly focus on covering long distances, the immediate environment around a car (0 to 5 m) is often left out of the discussion. This is where advanced ultrasonic sensor systems come into play. In addition to measuring the distance to an object, advanced ultrasonic sensors can also calculate the horizontal and vertical position of an object relative to the sensor itself (i.e. providing 3D coordinates for detected objects).

In general, ultrasonic sensors make use of high-frequency sound waves for a range of applications. For distance measurement, a typical ultrasonic sensor uses a transducer to periodically send out ultrasonic pulses in the air. These pulses get reflected from objects in the detection area of the sensor and are received back by the sensor. By measuring the time it takes an ultrasonic pulse to travel to the object and get captured by the sensor, the distance to the object can be calculated. This principle is called time-of-flight measurement.

Conventional ultrasonic sensors used for parking assistance only record one-dimensional data, which is the distance to the closest object. Azimuth and elevation angles of objects are not calculated with this method and vertical opening angles are severely limited. Thus, many objects, such as the curb and low-lying obstacles, are not picked up by 1D sensors.

The localization of objects in 3D space allows ultrasonic sensors to detect and distinguish among multiple objects in a single scan. In that sense, the principle of ultrasonic sensors is similar to echolocation, as used by bats. In comparison, a typical ultrasonic sensor will usually only measure the distance to the nearest object. Because of this, a limited opening angle is usually applied for this type of sensor.

In contrast, advanced ultrasonic sensors allow for opening angles of up to 160°. The sensors provide reliable, rich, 3D data for the close-range environment around a vehicle. The sensors are therefore well-suited for applications in the automotive field and add yet another level of safety and redundancy to conventional radar, LiDAR, and camera technologies. The sensors can replace or complement existing optical sensing systems, providing both redundancy and an improved level of accuracy compared to standard ultrasonic sensors in various autonomous navigation applications.

The sensor data can also be used for additional comfort features, e.g. gesture control to open doors and trunks, positioning the vehicle for automated charging (for EVs), and collision avoidance for automatically opening doors.

Point cloud example recorded by automotive kit (real data recorded by sensor).

Passenger Monitoring in the Car Interior

With further improvements in the autonomous driving space, the behavior of the driver is also likely to change. While drivers today must be completely focused on the road — ready to react at a moment’s notice — this is likely to change once cars are able to drive and steer fully automatically. Drivers would then be able to lean back and relax, work on their computers, turn to their children in the back seats, or temporarily enjoy an expanded infotainment program.

Such an eventuality puts new demands on assistance systems. Just like the numerous sensors available for analyzing a car’s external environment, similar knowledge is needed for the interior in order to realize a more secure and intuitive interaction experience. In this context, the use of 3D ultrasound again provides interesting advantages. Data gained from an ultrasound sensor can be used to identify the number of people sitting in the car, their size, and their posture. Based on the information regarding where people are sitting and their physical characteristics, airbags could be adjusted to individual body sizes and further improve safety.

The technology does not collect any personal data since ultrasound cannot evaluate visual input and instead only records anonymous point-cloud data. This is an especially important consideration in terms of privacy and data protection. Furthermore, gesture simulation in the interior of the car can be used for information and entertainment purposes, like controlling the car’s infotainment systems with simple pre-configured actions.

There is no doubt that autonomous vehicles of the future will need more assistance from sensors to safely operate in populated places. Whether you are living in a big city where detecting people and accurate parking plays a major role, or in the countryside where automated charging is indispensable, 3D ultrasonic will provide many benefits to the everyday life of future drivers.

This article was written by Andreas Just, Head of Marketing for Toposens, Munich, Germany. For more information, visit here .

Tech Briefs Magazine

This article first appeared in the April, 2020 issue of Tech Briefs Magazine.

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