Protecting Pedestrians Using Ultrasound Techniques

With vehicular traffic increasing on the roads, pedestrians are shifting to the status of endangered species. Frequent news reports of pedestrians falling victims to collisions with motor vehicles bear testimony to the statement. Now, researchers want to provide a remedy. At the Frankfurt University of Applied Sciences or FRA-UAS, researchers have developed a pedestrian detection sensor that can differentiate a human being from among inanimate matter.

At FRA-UAS, Professors Andreas Pech and Peter Nauth have developed the pedestrian detection system utilizing highly sensitive and efficient ultrasonic sensors. It can discriminate a human being from an object in areas where a collision is likely. Typically, vehicles use such highly cost-effective ultrasonic sensors at their rear to help in parking. The researchers have added an algorithm for recognizing patterns from the signals coming from these sensors. The algorithm, the actual innovation from the researchers, generates a situational analysis within half of a second. This is then used to activate specific protection systems.

In a collision situation, there can be two possibilities. The first could be a vehicle-to-vehicle collision, where the system activates airbags and belt pre-tensioners as it detects an imminent collision with another vehicle. However, if the system determines that the collision situation involves a pedestrian and not a vehicle, it initiates measures that will reduce the impact. These measures could vary, such as, heightening the bonnet to mitigate the impact, providing an exterior airbag to be deployed prior to collision or even reducing the rigidity of the body of the vehicle.

According to the researchers, this pedestrian detection system is relatively more cost-effective in comparison to other systems available in the market. It is possible to retrofit this system even in lower priced vehicles. Moreover, such a pedestrian detection system is also useful in other areas of application. For example, in case of a building fire, where smoke detectors trigger fire alarms, the pedestrian detection system from FRA-UAS can help to locate human beings trapped inside the burning house or apartment.

Application of such a pedestrian detection system can be seen in the crosswalk flasher system installed at the Weaver Lake Elementary School in Maple Grove, Minnesota. The school added the automatic detection system to increase the safety of children who occasionally forget to push the button to activate a flashing beacon before starting to cross the road. The pedestrian detection system uses ultrasonic sensors for detecting the presence of pedestrians waiting at the curb and automatically activates a flashing beacon to alert the approaching vehicles to the presence of the pedestrian.

Ultrasonic detectors emit sound waves of frequency ranging beyond the hearing capabilities of humans. In the presence of moving pedestrians or vehicles, part of the transmitted sound waves reflects back to the receiver. The associated electronics computes the distance and speed of the object from the time and strength of the reflected signal. Ultrasonic detectors detect objects as far away as 30 feet.

The amount of sound energy reflected from the pedestrian depends on the nature of clothes the person is wearing. It also depends on the temperature, pressure, humidity and wind speed at the location.