A multi-sensor sonar system for indoor range measurement as a navigational aid for the blind

This paper reports the methodology for the design of a sonar-based ranging and guidance system. The intended application of the system is to help a blind person avoid obstacles as he/she navigates his/her environment. Six sonar transceivers are arranged radially on a headgear worn by the user. The transceivers detect discrete range data at discrete-time sampling instances. A panoramic map of the environment is generated from the discrete-space sensory data. The paper emphasizes the challenges faced during the measurement of omnidirectional ranging information in indoor environments. Situations have been identified where erroneous range readings are generated due to channel cross talk caused by echo bouncing off multiple surfaces. Several sonar control and measurement schemes were developed and tested to avoid these situations. The results and performance of these different control schemes are compared in this paper. A microcontroller-based system commands the sonar ping sequences, acquires the echo return times and computes the ranges. The set of range data is transmitted to a PC, which utilizes the information to build a spatialized audio map of the surrounding obstacles. The hardware and software layout for the system are described in this paper.