Sonar or ultrasonic sensing uses the propagation of acoustic energy at higher frequencies than normal hearing to extract information from the environment. This chapter presents the fundamentals and physics of sonar sensing for object localization, landmark measurement and classification in robotics applications. The source of sonar artifacts is explained and how they can be dealt with. Different ultrasonic transducer technologies are outlined with their main characteristics highlighted.
Sonar systems are described that range in sophistication from low-cost threshold-based ranging modules to multitransducer multipulse configurations with associated signal processing requirements capable of accurate range and bearing measurement, interference rejection, motion compensation, and target classification. Continuous-transmission frequency-modulated (CTFM) systems are introduced and their ability to improve target sensitivity in the presence of noise is discussed. Various sonar ring designs that provide rapid surrounding environmental coverage are described in conjunction with mapping results. Finally the chapter ends with a discussion of biomimetic sonar, which draws inspiration from animals such as bats and dolphins.
Side-looking multipulse sonar moving down cinder-block hallway
Author Roman Kuc
Video ID : 303
Rather than producing a single TOF reading per emission, the multipulse sonar produces multiple spikes by quickly resetting the sonar-detector integrator, thereby producing a spike density related to the echo amplitude. A side-looking sonar scans a cinder-block wall containing a door and window jambs. The resulting spikes have been processed to differentiate the first cinder-block wall, the cider-block surface and localize the window and door jambs. The red circles indicate the initial TOF values and illustrate the additional echo waveform data produced by the multipulse sonar.
Reference: R. Kuc: Recognizing retro-reflectors with an obliquely-oriented multi-point sonar and acoustic flow, Int. J. Robot. Res. 22(2), 129-145, (2003); doi:10.1177/0278364903022002004.