Ultrasonic Sensing For A Mobile Robot To Recognize An Environment - Measuring The Normal Direction Of Walls -. - Yoshiaki Nagashima; Shin'ichi Yuta (IROS, 1992)

Exploring Unknown Environment and Map Construction Using Ultrasonic Sensing of Normal Direction of Walls. - Akihisa Ohya; Yoshiaki Nagashima; Shin'ichi Yuta (ICRA, 1994)

High-Speed Measurement of Normal Wall Direction by Ultrasonic Sensor. - Akihisa Ohya; Yoshiaki Nagashima; Shin'ichi Yuta (J. Robotics Mechatronics, 1999)