In the proposed cooperative sensor system, pedestrians carry a reactive transceiver which is interrogated by a localization and tracking unit in the car. The prototype system applies Round-Trip Time-of-Flight (RTOF) techniques for the determination of the distance between the transponder and the demonstrator vehicle. A smart antenna array integrated into the car is used to determine the Direction-of-Arrival (DoA) of the transponder's response signal. Knowing the distance and azimuth angle relative to the car, the pedestrian's position and movement are calculated. These data are used as input for a highly reliable collision warning and collision mitigation system. The sensor system is capable of addressing a huge number of communication partners within each measurement cycle. Additionally, secure burst identification is ensured for a robust localization and the suppression ofunwanted co-channel interference. This is achieved by using pseudo randomcoded signals with a Time Division Multiple Access (TDMA) method. The distance accuracy was improved by introducing a new mirror technique in combination with an interpolation algorithm. The prototype localization system set up at 2.4 GHz covers a range up to 200m in free field condition. With the current system a distance resolution with centimetre accuracy and an angular measurement accuracy of about 1 degree have been achieved. Based onthis low-cost transponder-based localization system, a preventive vulnerable road user (VRU) protection system was designed and integrated in a test vehicle. The system able to provide a warning to the driver if a crash is likely and to automatically brake the vehicle if the crash is unavoidable. The full text of this paper may be found at: http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0136.pdf For the covering abstract see ITRD E145407.
Abstract