Outdoor Field Performances of Insect-based Visual Motion Sensors
Considerable attention has been paid during the last decade to navigation systems based on the use of visual optic flow cues. Optic flow-based visuo-motor control systems have been implemented on an increasingly large number of sighted autonomous robots designed to travel under specific lighting conditions. Many algorithms based on conventional cameras or custom-made sensors are being used nowadays to process visual motion. In this paper, we focus on the reliability of our optical sensors which can be used to measure the local 1-D angular speed of robots flying outdoors over a visual scene in terms of their accuracy, range, refresh rate and sensitivity to illuminance variations. We have designed, constructed and characterized two miniature custom-made visual motion sensors: (i) the APIS-based local motion sensor involving the use of a custom-made VLSI array (APIS stands for Adaptive Pixels for Insect-based Sensors), which is equipped with Delbrück-type auto-adaptive pixels, and (ii) the LSC-based (LSC is a component purchased from iC-Haus) local motion sensor involving the use of off-the-shelf linearly amplified photosensors, which is equipped with an on-chip pre-amplication circuit. By combining these photodetectors with a low-cost optical assembly and a bio-inspired visual processing algorithm, highly effective miniature sensors were obtained for measuring the visual angular speed in field experiments. The present study focused on the static characteristics and the dynamic responses of these local motion sensors over a wide range of illuminance values, ranging from 50lux to 10000lux both indoors and outdoors. Although outdoors experiments are of great interest to equip Micro-Air Vehicles with visual motion sensors, we also performed indoors experiments as a comparison. The LSC-based visual motion sensor was found to be more accurate in a narrow 1.5-decade illuminance range, while the APIS-based visual motion sensor is more robust to illuminance changes in a larger 3-decade range. The method presented in this study provides a new benchmark test for thoroughly characterizing visual motion and optic flow sensors designed to operate outdoors under various lighting conditions, in unknown environments where future Micro-Aerial Vehicles will be able to navigate safely.
Outdoor Field Perfomances of Insect-based Visual Motion Sensors
F. Expert, S. Viollet, Franck Ruffier (2011),
Journal of Field Robotics, Vol. 28 pp. 529-541