Sonar ranging/light detection system for use in a robot

Abstract

A sonar ranging/light detection system provides information regarding the surrounding environment to a robot. The sonar portion of the system includes an upper rotating detector which provides 360.degree. coverage as well as a lower, fixed detector located on the front of the robot which provides sensory information in the direction of robot movement. A light detector similarly provides a 360.degree. light sensing capability. The upper sonar and light detectors utilize a common rotating mirror driven by a stepper motor and include a slotted shaft encoder in combination with an optopair semiconductor detector. The shaft encoder provides angular information to a microcomputer controller which is also responsive to sonar ranging information in exercising control of the stepper motor. The transmitted sonar signal is comprised of a pulse train of four different frequencies to ensure that simultaneous echoes from more than one surface do not cancel each other out and provide false ranging information. As the time for echo return increases for greater distances, the gain of the sonar receiver is increased by the controller in anticipation of receipt of a weaker echo. The rotating detector is capable of continuous 360.degree. rotation, sector scanning, or pointing in a designated direction in obtaining ranging information and employs a retro-torque damping technique to provide faster angular stabilization of the mirror prior to making range measurements. The upper and lower sonar detectors are utilized in an alternating manner in the various modes of operation.