Determination of time to contact using a compound eye sensor

Abstract

Recently, many control methods for autonomous robots based on biological mechanisms have been studied. In particular, the concept of time to contact, called the tau-margin, which is studied in ecological psychology, has attracted considerable attention. In conventional studies, various approaches have been used for the determination of the tau-margin, and the tau-margin has been used for the timing control of mobile robots. However, in these studies, robots fitted with a light bulb have been used, and direct light from the bulb has been used to determine the tau-margin. It is impossible to apply conventional methods to robots that use indirect light for determining the tau-margin. Therefore, we have developed a compound eye sensor comprising photodiodes. We employ the framework of optical flow to detect objects, and determine the tau-margin from the apparent size of the detected objects and the temporal changes in size. To demonstrate the effectiveness of the developed compound eye sensor, we control a mobile robot using this sensor, and conduct experiments in which the robot has to avoid an oncoming object. The timing of the robot is controlled by using the tau-margin. We conducted experiments by using an actual robot, and found that the robot could avoid an oncoming object successfully. We concluded that it is possible to determine the tau-margin by using the compound eye sensor which we have developed.