Search

CN-121994342-A - High-precision hydrophone calibration positioning mechanism and method based on vision

CN121994342ACN 121994342 ACN121994342 ACN 121994342ACN-121994342-A

Abstract

The invention discloses a high-precision hydrophone calibration positioning mechanism and method based on vision, belonging to the technical field of underwater sound measurement, which mainly solves the problems of low precision, poor repeatability and large influence by pressure deformation caused by relying on manual vision and mechanical positioning in the traditional laser method hydrophone calibration, comprises a visual imaging unit arranged outside a pressure water tank, a precise movement unit for driving the visual imaging unit to move, and an image processing and control unit, and performs strabismus imaging by a high-resolution industrial camera, the optimal visual angle is adjusted by combining a six-axis displacement platform, distortion correction, edge feature extraction and coordinate conversion are carried out by utilizing an image processing algorithm, the relative position deviation between the hydrophone and the diaphragm is calculated, an actuating mechanism is driven to realize closed-loop accurate positioning, the invention realizes non-contact and automatic alignment, overcomes the interference of pressure deformation, and particularly effectively solves the problem that the film sheet is difficult to be positioned visually through strabismus imaging, thereby improving the positioning precision of the calibrating device.

Inventors

  • CAO MENG
  • JIA GUANGHUI
  • WANG SHIQUAN

Assignees

  • 中国船舶集团有限公司第七一五研究所

Dates

Publication Date
20260508
Application Date
20260116

Claims (8)

  1. 1. The utility model provides a hydrophone calibration positioning mechanism based on vision, is applied to in the laser method hydrophone acoustic pressure calibration system, calibration system includes pressure water pitcher (1) and standard hydrophone (9) and diaphragm (11) that set up in it, and pressure water pitcher (1) have the observation window, its characterized in that, positioning mechanism includes: The visual imaging unit is arranged outside the pressure water tank (1), and the optical axis of the visual imaging unit passes through the observation window to be aligned with a target area in the tank and is used for acquiring images containing the end face of the standard hydrophone (9) and the diaphragm (11); The precise movement unit is in driving connection with the visual imaging unit and is used for adjusting the spatial position and the gesture of the visual imaging unit; the image processing and control unit is in signal connection with the visual imaging unit and the precise movement unit and is configured to correct distortion of an image acquired by the visual imaging unit, identify and extract edge profile characteristics of the end face of the standard hydrophone (9) and the diaphragm (11) from the corrected image, calculate relative position deviation between the standard hydrophone (9) and the diaphragm (11) based on the edge profile characteristics, and output a control signal based on the relative position deviation so as to drive an actuating mechanism for adjusting the position of the standard hydrophone (9) or the diaphragm (11) in the calibration system until the relative position deviation is smaller than a preset threshold.
  2. 2. The hydrophone calibration and positioning mechanism based on vision as recited in claim 1, wherein the vision imaging unit comprises a high-resolution industrial area camera (3) and an optical lens, the number of pixels of the industrial camera (3) is not less than 1 hundred million pixels, and the focal length of the optical lens is adjustable or fixed-focus.
  3. 3. The hydrophone calibration positioning mechanism based on vision as set forth in claim 2, wherein the vision imaging unit adopts a strabismus imaging layout, so that an included angle is formed between an optical axis of the industrial camera (3) and a normal line of a plane where the end face of the standard hydrophone (9) and the diaphragm (11) are located, and the included angle is an acute angle.
  4. 4. A vision-based hydrophone calibration positioning mechanism as recited in claim 3, wherein the precision motion unit comprises an electric six-axis displacement platform (4), and the industrial camera (3) is arranged at the execution end of the six-axis displacement platform (4) and is used for driving the industrial camera (3) to perform translational and rotational motions in a three-dimensional space so as to realize posture transformation from a wide-angle searching position to a high-precision strabismus imaging position and automatic focusing.
  5. 5. The hydrophone calibration positioning mechanism based on vision as recited in claim 1 wherein the image processing and control unit performs distortion correction on the image, specifically comprising: Correcting an image pixel point based on a lens distortion coefficient of the visual imaging unit obtained by pre-calibration, wherein the distortion coefficient comprises a radial distortion coefficient k 1 , k 2 , k 3 and a tangential distortion coefficient p 1 , p 2 ; for normalized image coordinates (x, y), the radial distortion correction formula is: ; the tangential distortion correction formula is: Wherein r 2 =x 2 +y 2 .
  6. 6. A vision-based hydrophone calibration positioning mechanism as recited in claim 1, wherein the image processing and control unit identifies and extracts edge profile features from the image, an edge detection algorithm combining visual profile detection with gray or color information is used, and the center position of the diaphragm (11) is determined by a linear feature extraction algorithm by utilizing the banded region features formed by strabismus imaging of the diaphragm.
  7. 7. A vision-based hydrophone calibration positioning mechanism as recited in claim 1, wherein the image processing and control unit calculates the relative positional deviation, comprising: The plane homography matrix obtained through calibration is applied to pixel coordinates (u, v) of the end face center of the standard hydrophone (9) and the center of the diaphragm (11) in an image, and the pixel coordinates are converted into physical coordinates (X w , Y w ) on a target plane in the pressure water tank (1); And calculating a physical coordinate difference value of the standard hydrophone (9) and the diaphragm (11) to obtain the relative position deviation.
  8. 8. A hydrophone calibration positioning method applied to a positioning mechanism as defined in any one of claims 1-7, characterized in that the method comprises the steps of: s1, adjusting the visual imaging unit to an initial imaging position through the precise movement unit (4); S2, controlling the visual imaging unit to acquire a target image comprising a standard hydrophone (9) and a diaphragm (11); S3, carrying out distortion correction on the target image; s4, extracting edge profile features of the standard hydrophone (9) and the diaphragm (11) from the corrected image, and calculating relative position deviation of the standard hydrophone and the diaphragm; S5, judging whether the relative position deviation is smaller than a preset threshold value or not; If not, generating a control instruction based on the deviation, driving an executing mechanism to adjust the position of the standard hydrophone (9) or the diaphragm (11), returning to the step S2, and if so, completing positioning.

Description

High-precision hydrophone calibration positioning mechanism and method based on vision Technical Field The invention relates to the technical field of underwater sound measurement and metering, in particular to a non-contact high-precision positioning device based on machine vision, which is applicable to a laser method sound pressure calibration system, and belongs to a positioning mechanism in a hydrophone sensitivity calibration device. Background Hydrophones are key sensors in underwater acoustic measurements, and the accuracy of sensitivity calibration directly affects the accuracy and reliability of the underwater acoustic metering system. The laser interferometry is one of the main methods for calibrating the sound pressure of the current high-precision hydrophone, and the typical implementation scheme is an alternative method, namely, a standard diaphragm is adopted as a sound pressure transmission medium by exciting an auxiliary transducer in a closed pressure water tank, and a laser vibration meter is used for measuring the vibration speed of the diaphragm under the action of the sound field, so that the sound pressure acting on the surface of the hydrophone to be measured is calculated, and finally, the calibration of the sensitivity of the hydrophone is realized. In the calibration process, the standard diaphragm and the tested hydrophone need to be aligned in a precise coplanar mode so as to ensure the accuracy of sound pressure transmission and the effectiveness of measurement results, the traditional positioning mode mainly depends on the combination of a precise movement mechanism and manual visual adjustment, however, under the test condition of high hydrostatic pressure, the pressure tank body and an internal installation structure can generate micro deformation, the traditional rigid movement mechanism can generate unpredictable elastic deformation or displacement when bearing pressure load, the factors can directly lead to the drift of preset mechanical positioning coordinates so as to introduce additional alignment errors, in addition, the manual visual adjustment is obviously influenced by experience, visual fatigue and subjective judgment of operators, and the positioning requirement of stable and repeatable submillimeter level or even higher precision is difficult to realize, so that the device becomes one of the bottlenecks for restricting the further improvement of the integral uncertainty of the laser hydrophone calibration device. With the development of machine vision technology, high-resolution industrial cameras and advanced image processing algorithms have been widely used in the fields of industrial detection, precise alignment, and the like. However, in the field of underwater acoustic metering, particularly in high-pressure, underwater and non-contact specific application scenes, how to effectively integrate the visual positioning technology into the existing calibration device, overcome the influence of pressure deformation, and realize high-precision and automatic alignment of the diaphragm and the hydrophone, and the mature technical scheme disclosed yet is not seen. The prior art lacks a special visual detection method for film target features such as thin edges, low contrast and possible optical interference in hydrophone calibration, and also lacks a systematic design for cooperation with a six-degree-of-freedom precision motion platform in a pressure environment. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a vision-based hydrophone calibration positioning mechanism, which can provide a non-contact optical positioning method, thoroughly eliminate alignment errors caused by mechanical contact or mechanism pressure deformation, realize the automation, high-precision detection and positioning of the positions of a diaphragm and a hydrophone in the calibration process, reduce the influence of human factors, improve the objectivity and repeatability of the calibration process and improve the positioning precision and efficiency of the whole hydrophone laser method sound pressure calibration system. In order to achieve the purpose, the invention provides the following technical scheme that the hydrophone calibration positioning mechanism based on vision is applied to a laser method hydrophone sound pressure calibration system, the calibration system comprises a pressure water tank, a standard hydrophone and a diaphragm arranged in the pressure water tank, the pressure water tank is provided with an observation window, and the hydrophone calibration positioning mechanism is characterized in that the positioning mechanism comprises: The visual imaging unit is arranged outside the pressure water tank, and the optical axis of the visual imaging unit passes through the observation window to be aligned with a target area in the tank and is used for acquiring images containing the end face of the standard hydrophone and t