Advanced Sonar with Velocity Compensation

Robotics research is dependent on intelligent, fast, accurate, reliable and cheap sensors. Sonar sensing can fulfil these requirements. Moreover sonar physics provides robotics researchers with a natural selection capability for landmark detection in navigation problems. This paper presents a new sonar system that produces accurate measurement and on-the-fly single cycle classification of planes, corners and edges. The paper shows how double pulse coding of the transmitted pulse can be exploited to simultaneously reject interference and perform classification. On a moving platform, the velocity of the sonar sensor affects range and bearing measurements and is dependent on the target type. These effects are analysed in the paper. Effects of rotation are also considered. The analytical results derived in the paper for velocity generated deviations in sonar range and bearing estimates are compared with experimental data. The experiments show that the deviations are evident at speeds encountered in mobile robot research. Compensation of these effects can be achieved using the analytical expressions derived in the paper, the sonar information of range, bearing and target classification, and odometry measurements.