Efficient Detection of Objects Near a Robot Manipulator via Miniature Time-of-Flight Sensors

Abstract--We provide a method for detecting and localizing objects near a robot arm using arm-mounted miniature time-of-flight sensors. A key challenge when using arm-mounted sensors is differentiating between the robot itself and external objects in sensor measurements. T o address this challenge, we propose a computationally lightweight method which utilizes the raw time-of-flight information captured by many off-the-shelf, low-resolution time-of-flight sensor . We build an empirical model of expected sensor measurements in the presence of the robot alone, and use this model at runtime to detect objects in proximity to the robot. In addition to avoiding robot self-detections in common sensor configurations, the proposed method enables extra flexibility in sensor placement, unlocking configurations which achieve more efficient coverage of a radius around the robot arm. Our method can detect small objects near the arm and localize the position of objects along the length of a robot link to reasonable precision. We evaluate the performance of the method with respect to object type, location, and ambient light level, and identify limiting factors on performance inherent in the measurement principle. The proposed method has potential applications in collision avoidance and in facilitating safe human-robot interaction. ETECTION of objects near a robot arm is useful for tasks such as collision avoidance [1], [2] or to enable proximity-based human-robot interactions [3]. Externally mounted cameras are one way of detecting such objects, but they suffer from occlusion and require the robot to remain in view of the cameras, limiting their practicality when used with mobile manipulators. Therefore, we seek a solution which uses sensors mounted on the robot.