Robot investigates suitcase bombs
Again and again, abandoned pieces of luggage are discovered. This is a case for the security forces, who have to assume that there are suspected bombs. A remote-controlled sensor system is to support the police in their operations in the future.
Anyone who forgets their luggage in public places, airports or train stations causes a major police operation. Suitcases, bags or backpacks left alone cause bomb alarms time and again. Most of the orphaned pieces of luggage turn out to be harmless. But first, the emergency services have to assume that there is a possible danger and check whether it is an unconventional explosive and incendiary device (IED) - in other words, an explosive object. In doing so, they must examine the luggage at close range. A system that enables a rapid assessment of the hazardous situation and also records the contents of the luggage, the shape of the luggage and the surroundings in three dimensions would make the specialists' work much easier, speed up the reconnaissance and minimize the risk for the emergency services.
For some time now, researchers at the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) in Wachtberg have been developing such a system, called "USBV-Inspektor", together with the North Rhine-Westphalia State Office of Criminal Investigation, Leibniz University Hannover and industrial partners.
From a safe distance
The intelligent mission assistant is a multimodal sensor suite. It consists of a millimeter-wave scanner, a high-resolution digital camera, and a 3D environmental sensing system. The components are integrated into a housing and mounted on a robotic platform. The robot is remotely controlled by the defusers from a safe distance. The swiveling 3D sensors measure the crime scene in three dimensions, and the digital camera provides high-resolution images for later visual evidence collection. The millimeter-wave sensor shines through the source of danger and images the interior. An embedded PC integrated on the robot collects the data and sends it to the investigators, where it is merged at the computer via sensor data fusion.
Contents of the suitcase bomb are measured three-dimensionally
"With previous methods, suitcase bombs cannot be visualized three-dimensionally; a spatial assignment of the contents is not possible or only possible to a limited extent. With the sensor suite, we can visualize the inside of a piece of luggage in three dimensions and determine which parts the bomb consists of and how they are arranged in the luggage," explains Stefan A. Lang, team leader at FHR and coordinator of the project. This will enable the explosives experts to quickly assess the threat situation and will also give them the opportunity in the future to obtain as many clues as possible about the bomb. Until now, the specialists were often forced to destroy the suitcase bombs, which made it difficult to identify the perpetrators. Other advantages of the non-contact detection system: It is lightweight, compact and platform-independent, so it can be mounted on any robot.
In the project, the researchers from FHR are developing the millimeter wave scanner, also known as a radar sensor, for rapid reconnaissance. It allows for very high depth resolution. "For the radar, we apply the SAR principle, short for Synthetic Aperture Radar. In this method, the sensor is moved over a trajectory, a kind of path - for example, from left to right in front of the suitcase - and the Doppler information generated in this way is used for image generation," explains Lang. In addition to the sensor, the expert and his team are also researching how to determine the optimal trajectory for measuring the object. This depends on the shape of the piece of luggage or container, its position in the environment and the position of the robot.
Jens Fiege, Fraunhofer Institute for High Frequency Physics and Radar Techniques
