Mobile robot sonar for target localization and classification
International Journal of Robotics Research
High-Resolution Ultrasonic Environment Imaging
IEEE Transactions on Robotics
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Advanced sonar systems produce both accurate range and bearing measurements rather than just range alone as in conventional systems. Previous advanced sonar rings do not process incoming echo data as it arrives, but only after a completed measurement cycle and only on limited data samples that are above a noise floor threshold. The system described in this paper can process all echo data, as it is produced, with full matched filtering tuned to each receiver on all echo samples directly implemented in hardware. This minimises measurement latency, important for real time robotics applications and also provides optimal arrival time estimates due to the matched filters. Previous systems have used sequential firing of many transmitters around the ring to prevent interference between transmitters or used different pulses fired simultaneously. This paper presents a single transmitter solution where a reflector disperses a single ultrasonic pulse evenly around the sonar ring. Processing is performed with a dedicated hardware data processing architecture implemented with a Field Programmable Gate Array to achieve the desired real time performance. The system reports range and bearing results at a rate of 30 measurement cycles a second in a full 360 degree coverage to ranges up to 4 metres with the prototype processing over 4.9 Giga-arithmetic operations per second. Experimental results are presented that show the performance of the system is suitable for high speed mapping and localisation applications.