Hazardous Material Localisation and Person Tracking
A security assistance system by data fusion of person tracks and additional (chemical) sensor attributes.
Prof. Dr. P. Kaul, Dipl.-Chem (FH) C. Becher, FH Bonn-Rhein-Sieg
Dr. Wolfgang Koch, Dr. Frank Lorenz, Dipl. Math. Konstatin Safenreiter, Dr. Monika Wieneke, Forschungsgesellschaft für Angewandte Naturwissenschaften
Prof. Sigfrid Waldvogel, Universität Bonn
Dr. Christian Michelonie, University of Udine
Asymmetric threats require a powerful surveillance technology which helps to preserve public security. New technology developments concentrate on the integration of different sensor types (video, tracking sensors, CBNRE sensors) in order to get a better and comprehensive understanding of potential threats in a defined area e.g. an area controlled by security personnel. Multidatafusion can e.g. be used to combine kinematic data of objects (where, when) with additional attribute information (what) of this object in order to identify that single object carrying the attributes. Obviously a big interest is to obtain information about a "suspicious chemical signature" which might originate from toxic, explosive or other illicit chemicals.
Such a security assistance system based on multisensor data fusion has successfully been demonstrated in an EU project HAMLeT (PASR-2006). One aim of HAMLeT was the data fusion of person tracking data (originating from laser scanner) with additional attribute information in order to identify threats coming from hazardous materials (originating from chemical gas sensors).
In the HAMLeT data fusion project several chemical sensors for hydrocarbons like fuels, alcohols or solvents were used. Sensitive devices for the detection of these analytes are e.g. metal oxide sensors. The surface resistance of a thin film of metal oxide particles is dependent on the amount of the analyte in ambient air.
The data fusion aspect combines a track of one or more persons with its or their sensor response. The sensor response yields mainly two parameters which help two identify the person carrying the hazardous material. One is the signal strengths the other is the time delay which are both dependent from the distance between the person and the sensor system. Analyte diffusion, convection and transportation by a ventilation air stream reduce the gas concentration and influence both parameters.
The detection of explosives or explosive related compounds (ERC) is a very challenging task because most explosives have a very low vapour pressure and do not evaporate enough analyte molecules into air. An exception is TATP (Triacetonetriperoxide) which is known as a "homemade explosive" often used by terrorists and which has a relative high vapour pressure. For this analyte a special multi sensor quartz microbalance sensors system was developed by the HAMLeT partner University of Bonn and tested within the HAMLeT project. Sensor systems based on QMB with chemically modified surfaces are a powerful method to detect trace amounts up to 3 ppm of TATP and other hazardous and volatile analytes. With a sensor array the TATP can be unequivocally identified in a few seconds.
In the HAMLeT concept a moving object (person) carrying an analyte source has to be detected in an open environment. Using a blower system in a defined gangway reduces the dilution of the analyte's source concentration (which itself is dependent from the source evaporation rate) on its way to the detector and increases the detection speed. Nevertheless, the sensing system must be able to detect airborne TATP concentrations in the ppb range or less within two seconds. Up to now no technology for airborne ERC detection is sufficient for the HAMLeT concept and intensive research on detector systems is absolutely necessary to meet the demands of a fast and sensitive chemical multisensorsystem with stand off properties.