Wall following and obstacle avoidance results from a multi-DSP sonar ring on a mobile robot

Abstract

Sensing capabilities of a multi-DSP sonar ring are demonstrated with wall following and obstacle avoidance behaviour. The autonomous mobile robot called "Sombrero" moves perpendicular to the nearest object on the left while controlling the distance to that object and generates high quality sonar maps. The wall following and obstacle avoidance behaviour is very simple due to the accurate and timely range and bearing (incidence angle) information provided by the advanced sonar ring. The advanced sonar ring consists of 48 ultrasonic transducers, 24 acting as transceivers and 24 acting as receivers, seven custom designed DSP echo processor boards and six analogue boards. 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 10 Hz, for ranges up to six metres. Accurate distance and bearing measurements of objects are performed by the DSP system using matched filtering techniques. The robot is able to follow walls of various shapes such as a square, circle, concave corner and convex corner. Sombrero controls its motion based on the range and bearing data captured from the advanced sonar ring every 100 msec while moving with a constant speed. Experimental results illustrate the effectiveness of the sonar ring and the quality of the generated local maps.