US-12624951-B1 - Underwater point source polarized light detection device and heading angle measurement method

US12624951B1US 12624951 B1US12624951 B1US 12624951B1US-12624951-B1

Abstract

The present disclosure provides an underwater point source polarized light detection device and a heading angle measurement method, which are applied to the field of polarization navigation technologies. The polarized light detection device includes a base, a rotating detection platform provided on the base, and three sets of polarized light detection modules provided on top of the rotating detection platform. The three sets of polarized light detection modules are of the same structure, each set of detection module consists of a pair of polarization analyzing channels with transmission directions perpendicular to each other, the other two sets of detection modules are positioned such that polarized light detection directions thereof are bilaterally symmetric in the same plane about a zenith polarized light detection direction and that an included angle between each of the polarized light detection directions and the zenith polarized light detection direction does not exceed 5°, and the rotating detection platform is configured to be rotatable for 360° about an axis of the zenith polarized light detection direction. The heading angle measurement method using the detection device has advantages of good adaptability to underwater environments and requiring a reduced number and types of polarization analyzing channels.

Inventors

Daqi ZHU
Mingzhi CHEN
Yuan Liu
Weifeng Chen
Hongfei Li
Jibo Bo
Wen Pang
Jianmin Zhu

Assignees

UNIVERSITY OF SHANGHAI FOR SCIENCE AND TECHNOLOGY

Dates

Publication Date: 20260512
Application Date: 20250505
Priority Date: 20241220

Claims (9)

1 . An underwater point source polarized light detection device, comprising a base, a rotating detection platform provided on the base, and a first detection module, a second detection module, and a third detection module provided on top of the rotating detection platform, wherein: the first detection module is configured to receive and detect zenith polarized light, the second detection module is configured to receive and detect zenith right-side polarized light, and the third detection module is configured to receive and detect zenith left-side polarized light, each of the first, the second, and the third detection modules comprises a pair of polarization analyzing channels with transmission axes thereof perpendicular to each other, the second and the third detection modules are positioned such that polarized light detection directions thereof are bilaterally symmetric in the same plane about a zenith polarized light detection direction and that an included angle between each of the polarized light detection directions and the zenith polarized light detection direction does not exceed 5°, and the rotating detection platform is configured to be rotatable for 360° about an axis of the zenith polarized light detection direction, and each polarization analyzing channel comprises a polarization analyzer, and a light intensity detector, and a voltage detector that is electrically connected to the light intensity detector.
2 . A heading angle measurement method for measuring a heading angle of an underwater vehicle, comprising the following steps: S0: mounting the underwater point source polarized light detection device according to claim 1 on the underwater vehicle; S1: determining a reference direction for resolving a heading angle of the underwater vehicle, selecting a reference polarization analyzing channel in each of the first, the second, and the third detection modules, and arranging the transmission directions of all the selected reference polarization analyzing channels to be parallel to the reference direction in an initial state; S2: continuously rotating the rotating detection platform in a horizontal direction, collecting a detection voltage corresponding to each polarization analyzing channel on the rotating detection platform in real time until a difference between the detection voltages of each pair of polarization analyzing channels is maximized, and recording a rotation angle of the rotating detection platform relative to the reference direction at this time as θ a ; and S3: calculating, using in combination with the rotation angle θ a , an included angle θ s between the reference direction and projection lines of a solar meridian and an anti-solar meridian on corresponding detection points, and correcting the included angle θ s in combination with polarization information of the detected zenith right-side polarized light and zenith left-side polarized light to obtain an included angle between the reference direction and the solar meridian that is the heading angle β.
3 . The underwater point source polarized light detection device according to claim 1 , wherein a reference plane, a left mounting surface, and a right mounting surface are disposed on top of the rotating detection platform, wherein the reference plane, the left mounting surface, and the right mounting surface form a top base, a left leg, and a right leg of an imaginary isosceles trapezoid, respectively, and the first, the second, and the third detection modules are disposed on the reference plane, the left mounting surface, and the right mounting surface, respectively.
4 . The heading angle measurement method according to claim 2 , wherein in the S2, the detection voltage corresponding to the reference polarization analyzing channel in each pair of polarization analyzing channels is maximized while the difference between the corresponding detection voltages of each pair of polarization analyzing channels is maximized.
5 . The heading angle measurement method according to claim 2 , wherein in the S3, a specific azimuth of the solar meridian is determined by using the collected detection voltages of the reference polarization analyzing channels in the second detection module and the third detection module in combination with a Rayleigh scattering model and a corresponding relationship between a polarization degree of the polarized light and the detection voltage in the polarization analyzing channel, so as to correct the included angle θ s and obtain the heading angle β, wherein a range of the included angle θ s is [0°, 180°], and a range of the heading angle β is [0°, 360°].
6 . The heading angle measurement method according to claim 2 , wherein in the S1-S2, the transmission directions of the paired polarization analyzing channels are θ 1 and θ 2 , respectively, θ 2 =90°+θ 1 , the polarization analyzing channel with the transmission direction θ 1 in an initial state is used as the reference polarization analyzing channel, and the detection voltage corresponding to the reference polarization analyzing channel in each pair of polarization analyzing channels is at a minimum when the difference between the detection voltages of each pair of polarization analyzing channels is maximized.
7 . The heading angle measurement method according to claim 6 , wherein in the S2, the difference between the detection voltages of each pair of polarization analyzing channels is determined to be maximized and the rotation angle θ a at this time is recorded according to the following formula: θ a = { log [ U θ 1 U θ 2 ] Middle + log [ U θ 1 U θ 2 ] Right + log [ U θ 1 U θ 2 ] Left } wherein log [ U θ 1 U θ 2 ] Middle , log [ U θ 1 U θ 2 ] Right , and ⁢ log [ U θ 1 U θ 2 ] Left are respectively logarithms of ratios of the detection voltage U θ 1 corresponding to the polarization analyzing channel with the transmission direction θ 1 to the detection voltage U θ 2 corresponding to the polarization analyzing channel with the transmission direction θ 2 in the first detection module, the second detection module, and the third detection module.
8 . The heading angle measurement method according to claim 5 , wherein when θ 1 =0°, and then θ 2 =90°, the heading angle β is calculated according to the following relation: β = { θ s , U L < U R θ s + 180 ⁢ ° , U L > U R wherein U R is the detection voltage corresponding to the polarization analyzing channel with the transmission direction of 0° in the second detection module, and U L is the detection voltage corresponding to the polarization analyzing channel with the transmission direction of 0° in the third detection module.
9 . The heading angle measurement method according to claim 6 , wherein in the S2, the difference between the corresponding detection voltages of each pair of polarization analyzing channels is determined to be maximized and the rotation angle θ a at this time is recorded according to the following formula: θ a = arg ⁢ max ⁢ { log [ U θ 2 U θ 1 ] Middle + log [ U θ 2 U θ 1 ] Right + log [ U θ 2 U θ 1 ] Left } wherein log [ U θ 2 U θ 1 ] Middle , log [ U θ 2 U θ 1 ] Right , and ⁢ log [ U θ 2 U θ 1 ] Left are separately logarithms of ratios of the detection voltage U θ 2 corresponding to the polarization analyzing channel with the transmission direction θ 2 to the detection voltage U θ 1 corresponding to the polarization analyzing channel with the transmission direction θ 1 in the first detection module, the second detection module, and the third light detection module.

Description

TECHNICAL FIELD The present disclosure relates to the field of polarized light navigation technologies, and in particular to an underwater point source polarized light detection device and a heading angle measurement method. BACKGROUND Sunlight is a natural resource, and contains abundant physical information that can be used to guide practical activities, such as atmospheric information for analyzing atmospheric composition, temperature, and pressure distribution, or polarized light information for navigation and positioning. It has been known that some aerosol particles in the atmosphere scatter sunlight, and the vibration direction of part of light waves is limited to a specific direction, thereby forming the polarized light. In order to effectively capture useful polarized light information in the atmosphere, a number of devices have been provided for detecting the polarized light in the prior art. For example, Chinese Patent Publication No. CN101694456A discloses a sensor for detecting an all-sky atmospheric polarization mode and a relevant method for processing detection signals, and Chinese Patent Publication No. CN101441171A discloses a signal processing and compensating method of four-channel atmosphere polarization information detection sensor, both of which are intended to realize related technical purposes, such as navigation and positioning of a bionic robot or an underwater vehicle, by means of detecting and analyzing atmospheric polarized light information in a target area. In underwater environments, GPS signals are denied, and inertial navigation suffers from cumulative errors. In order to improve the heading angle accuracy of underwater robots during long-range navigation, biomimetic polarized light navigation methods have become a research hotspot. The so-called biomimetic polarized light navigation method refers to a method that mimics the navigation methods of creatures like Cataglyphis and bees, which use the regular distribution of atmospheric polarized light for navigation. It has been known that the distribution of atmospheric polarized light follows at least the following laws: under a Rayleigh scattering model, the direction of polarized light at the solar meridian and the anti-solar meridian is perpendicular to the solar meridian and the anti-solar meridian, the polarization direction at any observation point in the atmosphere is perpendicular to a line connecting the observation point and the sun, the atmospheric polarized light exhibits the symmetric characteristic with respect to the solar meridian and the anti-solar meridian, and the polarization degree on the anti-solar meridian side is greater than that on the solar meridian side. The point source-type polarized light navigation method based on local polarized light areas in the sky is one of the common biomimetic polarized light navigation methods in the prior art. The method typically adopts the following steps to measure the heading angle. Firstly, a polarized light image in the zenith direction is collected through a polarization detection sensor with four channels (i.e., four polarization analyzing channels). Next, the collected polarized light image is processed, and polarization degree information and polarization angle information relative to the reference direction at an observation point is resolved by using methods such as light intensity variation curve analysis or Stokes vector analysis. Then, an included angle between the heading direction of the vehicle and the solar meridian, i.e., the heading angle of the vehicle, is calculated according to the obtained polarization angle information. In the process, due to the 180-degree periodicity of the polarization state as it varies with the polarization angle, there is a problem that two polarization angles can lead to the same polarization state, i.e., the 180-degree ambiguity problem. In order to solve the problem, existing technologies, such as heading angle measurement methods based on the PFAC model or the K-means clustering algorithm, require the detection of atmospheric polarization information from different sky areas deviating from the zenith direction, to estimate the specific azimuth of the sun by using the atmospheric polarization information. The existing point source-type polarized light navigation method has at least the following potential problems in application. First, refraction effects generated when light enters different media lead to a difference between an atmospheric polarization mode detected at an atmospheric detection point in a direction deviating from the zenith and a polarization mode detected at a corresponding underwater detection point, such that the above heading angle measurement method requiring the detection of the atmospheric polarization information deviating from the zenith direction cannot be applied to underwater environments, failing to solve the 180-degree ambiguity problem. Second, the polarized light detection sensor bas