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Indexed by:Journal Papers

Date of Publication:2019-08-20

Journal:SENSORS

Included Journals:PubMed、SCIE、EI

Volume:19

Issue:16

Key Words:navigation sensor; scattered polarization skylight; calibration; outdoor accuracy; integrating sphere

Abstract:A bio-inspired polarization sensor with lenses for navigation was evaluated in this study. Two new calibration methods are introduced, referred to as central-symmetry calibration (with an integrating sphere) and noncontinuous calibration. A comparison between the indoor calibration results obtained from different calibration methods shows that the two proposed calibration methods are more effective. The central-symmetry calibration method optimized the nonconstant calibration voltage deviations, caused by the off-axis feature of the integrating sphere, to be constant values which can be calibrated easily. The section algorithm proposed previously showed no experimental advantages until the central-symmetry calibration method was proposed. The outdoor experimental results indicated that the indoor calibration parameters did not perform very well in practice outdoor conditions. To establish the reason, four types of calibration parameters were analyzed using the replacement method. It can be concluded that three types can be easily calibrated or affect the sensor accuracy slightly. However, before the sensor is used outdoors every time, the last type must be replaced with the corresponding outdoor parameter, and the calculation needs a precise rotary table. This parameter, which is mainly affected by the spectrum of incident light, is the main factor determining the sensor accuracy. After calibration, the sensor reaches an indoor accuracy of +/- 0.009 degrees and a static outdoor accuracy of +/- 0.05 degrees under clear sky conditions. The dynamic outdoor experiment shows a +/- 0.5 degrees heading deviation between the polarization sensor and the inertial navigation system with a +/- 0.06 degrees angular accuracy.