EXTERNAL SENSING SYSTEM FOR AGRICULTURAL ROBOT

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An external sensing system for human cooperative agricultural robots was developed and tested. The sensing system consisted of a laser scanner and infrared sensors. The laser scanner was mounted on a lift moved up and down at a distance of 300 mm to capture a three-dimensional distance data. The infrared sensors were used to detect the existence of human. From the experimental results, not only the distance to an object but also the shape of the object was detected by moving the laser scanner up and down. The human motions including location, speed and direction were detected based on the information obtained from the laser scanner and the infrared sensors. An algorithm for discriminating human bodies was also investigated. From the result, the discrimination was achieved even if human bodies overlapped each other crosswise when there was some distance between them.Furthermore, manipulator control experiments for obstacle avoidance were carried out to confirm effectiveness of the sensing system. First, the distances and the shapes of objects around a robot were measured by the laser scanner, and an avoidance motion of manipulator was decided. Secondly, the manipulator moved while avoiding the object. The degree of danger was calculated when infrared sensors detected a human body around the robot, then a speed of manipulator tip was controlled. From the experimental results, the manipulator avoided obstacles within its operating area and changed its speed in proportion to the value of degree of danger.