Abstract
Animals, such as Savannah sparrows and North American monarch butterflies, are able to obtain compass information from skylight polarization patterns to help them navigate effectively and robustly. Inspired by excellent navigation ability of animals, this paper proposes a novel image-based polarized light compass, which has the advantages of having a small size and being light weight. Firstly, the polarized light compass, which is composed of a Charge Coupled Device (CCD) camera, a pixelated polarizer array and a wide-angle lens, is introduced. Secondly, the measurement method of a skylight polarization pattern and the orientation method based on a single scattering Rayleigh model are presented. Thirdly, the error model of the sensor, mainly including the response error of CCD pixels and the installation error of the pixelated polarizer, is established. A calibration method based on iterative least squares estimation is proposed. In the outdoor environment, the skylight polarization pattern can be measured in real time by our sensor. The orientation accuracy of the sensor increases with the decrease of the solar elevation angle, and the standard deviation of orientation error is at sunset. Results of outdoor experiments show that the proposed polarization navigation sensor can be used for outdoor autonomous navigation.
Highlights
Navigational ability is essential for a variety of human activities, and it is an important guarantee for unmanned platforms to autonomously accomplish their tasks
The same experimental process was carried out three times, and similar results were obtained. These results show that our error model is accurate and the proposed calibration method is effective
A novel bio-inspired polarization sensor that mainly consists of a Charge Coupled Device (CCD) camera, a pixelated polarizer array and a wide-angle lens is proposed
Summary
Navigational ability is essential for a variety of human activities, and it is an important guarantee for unmanned platforms to autonomously accomplish their tasks. Current navigation approaches are mostly dependent on global navigation satellite systems (GNSS) and inertial navigation systems (INS). The error of INS will increase rapidly with time, so the accuracy of inertial navigation system cannot meet the long-term navigation needs (several hours or even several days) in terms of current technical levels. The remarkable navigation ability that many animals possess provides a good reference for us. Many animals can derive compass information from the skylight polarization pattern that appears due to the scattering of sunlight in the sky. Homberg et al [2] analyzed the polarization-vision pathways in locusts and crickets and found that the detection of sky polarized light depends on the special photoreceptor cells in the Sensors 2017, 17, 2623; doi:10.3390/s17112623 www.mdpi.com/journal/sensors
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