A method for underwater vehicle attitude measurement based on Snell's window and its polarization mode
This paper proposed a method to observe the celestial polarization pattern and the coordinate of zenith through Snell's window,which consequently yields the navigation information of the carrier,i. e.,yaw angle,roll angle,and pitch angle. A fish-eye lens and an imaging polarimeter were installed on the carrier to capture the sky and obtain the celestial polarization pattern. First,a pinhole imaging model was established to obtain both the internal and external parameter matrices of the camera and the distortion coef-ficients of the lens. A distortion correction was applied to the polarization pattern to obtain the solar meridi-an characteristic region. A Canny operator was used to detect the edge of the characteristic region,after which a Hough line detection algorithm was used to calculate the angle between the solar meridian and the carrier's axis,yielding the Yaw angle. Second,the relationship between incidence angles and the error of polarization angle was abstracted as a function through experiments. Error compensation based on the func-tion was performed to reduce the measurement error of the polarization angle caused by changes in the inci-dent light polarization state of the fish-eye lens,hence improving the accuracy of measuring the angle be-tween the solar meridian and the carrier axis. Third,the grayscale threshold detection algorithm was used to calculate the coordinates of the zenith in the image,and therefore the roll and pitch angles of the carrier. The accuracy of the algorithm was verified through experiments. Lastly,an experimental platform was constructed to simulate an underwater environment. Results show that the mean absolute error of the yaw angle calculated by this method is 0.5303°. Within the range of[-50°,50°],the mean absolute error of the roll angle and pitch angle are 0.7544° and 0.6213°,respectively,which meets the accuracy require-ments of underwater navigation.
万方数据
维普
