A real time advanced sonar ring with simultaneous firing

Sonar rings are widely used for indoor mobile robots. However, it is difficult to perform on-the-fly applications such as map building and localization using a conventional sonar ring due to low speed, accuracy and interference. Digital signal processing (DSP) techniques and interference rejection ideas are applied in this paper to design a new more sophisticated, fast and accurate sonar ring called an advanced sonar ring. The advanced sonar ring consists of 48 ultrasonic transducers, 24 acting as transceivers and 24 acting as receivers, seven DSP echo processor boards, twelve four-channel 12-bit 500 kHz ADCs and low noise variable gain preamplifiers. The sonar ring is able to cover 360 degrees around robot with simultaneously firing of all 24 transmitters. Transmission and echo analysis are performed at repetition rates of about 15 Hz, depending on the environment, for ranges up to six meters. Accurate distance and bearing measurements of objects are performed in the DSP system using matched filtering techniques. The paper presents new transmit coding based on pulse duration to differentiate neighbouring transmitters in the ring. Experimental data show the effectiveness of the proposed system.