Abstract
In this study, a miniature artificial compound eye (15 mm in diameter) called the curved artificial compound eye (CurvACE) was endowed for the first time with hyperacuity, using similar micro-movements to those occurring in the fly’s compound eye. A periodic micro-scanning movement of only a few degrees enables the vibrating compound eye to locate contrasting objects with a 40-fold greater resolution than that imposed by the interommatidial angle. In this study, we developed a new algorithm merging the output of 35 local processing units consisting of adjacent pairs of artificial ommatidia. The local measurements performed by each pair are processed in parallel with very few computational resources, which makes it possible to reach a high refresh rate of 500 Hz. An aerial robotic platform with two degrees of freedom equipped with the active CurvACE placed over naturally textured panels was able to assess its linear position accurately with respect to the environment thanks to its efficient gaze stabilization system. The algorithm was found to perform robustly at different light conditions as well as distance variations relative to the ground and featured small closed-loop positioning errors of the robot in the range of 45 mm. In addition, three tasks of interest were performed without having to change the algorithm: short-range odometry, visual stabilization, and tracking contrasting objects (hands) moving over a textured background.
Highlights
According to the definition originally proposed by Westheimer in 1975 [1] and recently reformulated in 2009 [2]: ‘Hyperacuity refers to sensory capabilities in which the visual sensor transcends the grain imposed by its anatomical structure’
We describe the development and the performances of a vibrating small-scale cylindrical curved compound eye, named active curved artificial compound eye (CurvACE)
The active process referred to here means that miniature periodic movements have been added in order to improve CurvACE’s spatial resolution in terms of the localization of visual objects encountered in the surroundings
Summary
According to the definition originally proposed by Westheimer in 1975 [1] and recently reformulated in 2009 [2]: ‘Hyperacuity refers to sensory capabilities in which the visual sensor transcends the grain imposed by its anatomical structure’. We established here that an artificial compound eye performing active periodic micro-scanning movements combined with appropriate visual processing algorithms can be endowed with angular position sensing capabilities. With this visual sensing method, an aerial robot equipped with active CurvACE was able to perform short-range visual odometry and track a target moving over textured ground. In this respect, this method differs completely from those used in previous studies based on the use of the OF, which are similar to speed estimation methods. A complete description of the implementation of this sensor on a tethered robot named HyperRob is given in section 4, and the robots capability to assess its own linear position relative to the environment and track a target thanks to the active CurvACE, based on the novel sensory fusion algorithm developed here, is established in section 5 (see section 3.3)
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