VASC Seminar Announcement
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Date: Monday, 4/17/00
Time: 3:45-4:45
Place: NSH 3002

Speaker:  Teruko Yata
	CMU Robotics Institute

Title: Direction Measurable Ultrasonic Sensing Systems for Mobile Robots

Abstract: 

A pulse-echo method which transmit a pulse and measure distance 
using time-of-flight is often used for mobile robot ultrasonic 
sensor.  However, it is difficult to measure accurate bearing 
angle because of its wide beam width.  On the other hand, the 
reflecting objects in indoor environment can be considered as 
specular in regard to an ultrasonic wave length in the air.
When ultrasound reflect specularly, an area corresponding to a 
leading edge of an echo is assumed as a point.  Consequently, 
if it is possible to improve bearing measurement accuracy, the 
ultrasonic sensor can measure the reflecting point.  The 
reflecting point shows special feature of the environment, for 
example position of corner or bearing angle of wall, which are 
quantitative information.  It is very useful for environment 
recognition of mobile robots to detect those reflecting points 
which show such information accurately.  In a word, it is really 
important to develop accurate direction measurable ultrasonic sensor 
for mobile robots.  Moreover, simplicity and real-time operation 
are also important to use it for moving mobile robots.

Purpose of this research is the development of highly efficient 
ultrasonic sensors for indoor mobile robots environment recognition.
Especially, it emphasized to improve a weak point of ultrasonic 
sensor, bad bearing accuracy, without injuring merit, fast 
measurement speed.  For this purpose, fast and accurate reflecting 
points measurement method are proposed, and their usefulness are 
confirmed by actual proofs on mobile robots in this research.

Two fast and accurate reflecting point measurable methods are 
concretely investigated and studied: 
-- Fast and accurate bearing measurement by a single transducer 
      using frequency directional dependency.
-- Fast and accurate reflecting points measurement of all around 
      the robot based on sonar-ring by using multiple transducers 
      and time-of-flight difference.

These methods were implemented on real mobile robots, and 
investigation of fundamental efficiency are done to confirm its 
usefulness.  In applications of mobile robots motion, wall-following 
and environment map generation, it gets excellent results that mobile 
robot can earn good environment information using those direction 
measurable ultrasonic sensors.