The Arc-Transversal Median Algorithm: an Approach to Increasing Ultrasonic Sensor Accuracy

Howie Choset, Keiji Nagatani, and Nicole Lazar
Proceedings of ICRA '99, May, 1999, pp. 644 - 651.


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Abstract
This paper describes a new method for determining range information about a robot's surroundings using low resolution ultrasonic sensors. These sensors emit ultrasound which bounces off of nearby objects and returns to the sensor. The time-of-flight for the sound to return to the sensor is the distance between the sensor and the object. A sonar arc represents the possible locations of the object. We model these locations with a simple uniform probability distribution on the sonar arc. We then introduce a new method to fuse sonar data to determine the actual obstacle location. This new method is termed the arc-transversal median method because the robot determines the location of an object by intersecting one arc with other arcs whose angle-of-intersection exceeds a threshold and then taking the median of the intersection. The median is a robust estimator that is insensitive to noise because a few stray readings will not affect the median. We show via some simple geometric relationships, that this method can improve the accuracy of the sonar sensor by a specified amount, when certain assumptions were in place. Finally, experimental results on a real mobile robot verify this approach.

Notes
Associated Lab(s) / Group(s): Biorobotics

Text Reference
Howie Choset, Keiji Nagatani, and Nicole Lazar, "The Arc-Transversal Median Algorithm: an Approach to Increasing Ultrasonic Sensor Accuracy," Proceedings of ICRA '99, May, 1999, pp. 644 - 651.

BibTeX Reference
@inproceedings{Choset_1999_2862,
   author = "Howie Choset and Keiji Nagatani and Nicole Lazar",
   title = "The Arc-Transversal Median Algorithm: an Approach to Increasing Ultrasonic Sensor Accuracy",
   booktitle = "Proceedings of ICRA '99",
   pages = "644 - 651",
   month = "May",
   year = "1999",
   volume = "1",
}