Ultrasonic Source Localization

An important component of robot navigation is location awareness. In order to navigate through its surroundings a robot must be aware of nearby obstacles. When multiple robots must operate in the same area it is especially important for each robot to be cognizant of the location of the other robots. There are many different techniques that can be employed to enable robots to locate each other. We use ultrasonic transducers to accomplish this task. On one robot we mounted an ultrasonic transmitter and on another robot we mounted two ultrasonic sensors with narrow beams onto a rotating servo motor. The two receiving sensors form our receiver array. We placed the two ultrasonic receivers close to each other so that they are present at the same phase center. Also, we fixed them at a thirty degree angle relative to each other. As a result of this configuration, the signals picked up by these two receivers are in phase but differ in amplitude. We use the difference in the amplitudes of these two signals to infer about the direction of arrival of the signal coming from the robot with the ultrasonic transmitter. Finally, we rotate the servo motor to align the axis of the receiver array with the location of the ultrasonic transmitter. In this manner we track the angular position of the ultrasonic transmitter in real-time.