CN113405762A

CN113405762A - Visual measurement method for deformation attitude of wind tunnel model

Info

Publication number: CN113405762A
Application number: CN202110623586.7A
Authority: CN
Inventors: 张雪; 李玉军; 赵荣奂; 王猛; 尚金奎; 衷洪杰; 叶楠; 许东洋
Original assignee: AVIC Shenyang Aerodynamics Research Institute
Current assignee: AVIC Shenyang Aerodynamics Research Institute
Priority date: 2021-06-04
Filing date: 2021-06-04
Publication date: 2021-09-17

Abstract

The invention discloses a visual measurement method for deformation postures of a wind tunnel model, which comprises a camera with a lens, an optical filter, a long-wave ultraviolet excitation light source and an image acquisition computer, wherein a marking point for representing the shape position characteristics of the model surface adopts metal ink containing fluorescence, the metal ink is irradiated by the long-wave ultraviolet excitation light source to excite a fluorescent substance to radiate emergent light with a wavelength longer than that of the excitation light source, the emergent light penetrates through the optical filter and only keeps a fluorescence waveband to enter the camera for imaging, the obtained high signal-to-noise ratio image data is transmitted to the image acquisition computer, the three-dimensional space coordinates or the space displacement of the marking point on the model surface under a camera coordinate system are obtained through the identification and matching of the marking point images, the three-dimensional space coordinates or the space displacement under the camera coordinate system are obtained through the stereoscopic vision parallax principle, and the final posture angle and the deformation of the model are obtained after the conversion to the wind tunnel coordinate system. The method and the system can effectively improve the signal-to-noise ratio of the mark point images on the surface of the model picked up by the stereoscopic vision system, and improve the speed, accuracy and reliability of the mark point image recognition.

Description

Visual measurement method for deformation attitude of wind tunnel model

Technical Field

The invention belongs to the field of aerodynamic tests, and particularly relates to a visual measurement method for a deformation attitude of a wind tunnel model.

Background

The refinement of modern aircraft design has higher and higher requirements on the accuracy of wind tunnel test data, along with the increase of the aperture of the wind tunnel, the size of a corresponding model and the aerodynamic load are synchronously increased, and the elastic deformation of the model and a supporting system thereof in the test is increasingly obvious: the elastic angle of the model can reach 2.42 degrees, and the pneumatic load borne by the model can reach several tons. Especially for an aircraft with a high aspect ratio wing, accurate test data cannot be obtained by adopting a conventional attitude measurement means and rigid body assumption, and the performance of the aircraft is reduced and the flight safety of the aircraft is even affected by applying uncorrected data to design the aircraft. For tests with severe vibration of some models such as jet flow models, CTS models and air inlet channels, conventional attack angle sensors and other measuring devices cannot work normally, and real model attack angle data in the test process cannot be obtained. Meanwhile, the sideslip angle is the model attitude of data which cannot be obtained in the test process by the conventional measurement technology. The model deformation/attitude measurement technology based on machine vision measures the related information of the wind tunnel test in a non-contact mode, has the advantages of intuition, conciseness and no interference to a wind tunnel test flow field, and overcomes the defects of the traditional measurement technology based on a strain gauge sensor and the like in the aspects of test refinement, precision, application environment development and the like.

When the model is subjected to deformation posture optical measurement by adopting stereoscopic vision in a wind tunnel, characteristic mark points are required to be arranged on a control surface of the model, three-dimensional coordinates of the mark points are obtained by calculation according to a camera imaging principle and a stereoscopic vision parallax principle, and the shape and the posture of the model are constructed. The measurement requires a high contrast between the mark point and the background of the model surface. The most applied form at present is concentric circle sticker, and the test is carried out under white light illumination, so that strong interference of illumination reflection of the metal surface of the model and the background interference of the wall surface of the test section exist in the visual image, false detection or missing detection in the image processing process is caused, and the precision of the measurement result is influenced. Meanwhile, the thickness of the paster is usually in the order of 80-100 um, and when the deformation of the wing is measured in the form, the arrangement position and the number of the paster cause corresponding interference on airflow flowing on the surface of the wing under the influence of the thickness of the paster, so that the measurement result cannot reflect an accurate test state.

Disclosure of Invention

In order to overcome the defects of the prior art, solve the problems of illumination reflection on the surface of a model and background light interference on the wall of a hole and reduce the disturbance influence of the thickness of a mark point on the airflow on the surface of the model, the invention provides a visual measurement method for the deformation posture of a wind tunnel model, which effectively improves the signal-to-noise ratio of a visual image of the wind tunnel model, improves the image recognition speed and accuracy of the mark point on the surface of the model and reduces the thickness of the mark point on the surface of the model.

In order to achieve the purpose, the invention adopts the following technical scheme: a wind tunnel model deformation attitude vision measurement method comprises the following steps: the adopted equipment comprises a camera with a lens, an optical filter, a long-wave ultraviolet excitation light source and an image acquisition computer, wherein a marking point for representing the shape position characteristics of the surface of a model adopts metal ink containing fluorescent pigment, the fluorescent marking point with controllable oil film thickness is manufactured on the surface of the model by a silk-screen method or a template spraying method, the fluorescent material in the metal ink is excited to emit emergent light with wavelength longer than that of the excitation light source by the irradiation of the long-wave ultraviolet excitation light source, the interference of the excitation light, the model reflected light and wall surface background light is filtered by the optical filter, only a fluorescent wave band is reserved to enter a camera photosensitive chip for imaging, the obtained image data with high signal-to-noise ratio is transmitted to the image acquisition computer, the three-dimensional space coordinates or space displacement under a camera coordinate system of the marking point on the surface of the model is acquired by the identification and matching of the marking point images and the stereoscopic vision parallax principle, and converting the three-dimensional space coordinate or the space displacement into a wind tunnel coordinate system for subsequent processing by calibrating a wind tunnel shafting before testing to obtain a final attitude angle and a deformation of the model.

The thickness of the fluorescent mark point is 8-25 um.

The invention has the advantages and beneficial effects that: the method can effectively improve the signal-to-noise ratio of the stereoscopic vision system to pick up the model surface mark point image, improve the speed, accuracy and reliability of the mark point image recognition, simultaneously effectively reduce the thickness of the model surface mark point, reduce the interference of the wind tunnel surface mark point to the airflow flow in the wind tunnel test process, ensure that the measurement result can reflect the real and accurate test state, and can effectively prevent the distortion and even loss of the three-dimensional characteristic information of the model surface because the solidified and blended printing ink or printing ink has strong metal adhesive force and quick drying property and the model surface mark point has the capability of no deformation and no falling in the blowing process.

Drawings

FIG. 1 is a schematic diagram of a wind tunnel model deformation attitude vision measurement method of the present invention.

Wherein, the model comprises 1-a camera, 2-a lens, 3-a light filter, 4-a long-wave ultraviolet excitation light source, 5-a model surface, 6-a fluorescent marking point, 7-fluorescent pigment in ink, 8-an image acquisition computer and 9-excitation light.

Detailed Description

The detailed description of the embodiments of the present invention is provided in conjunction with the summary of the invention and the accompanying drawings.

Example 1

As shown in figure 1, a wind tunnel model deformation attitude vision measurement method adopts equipment comprising a camera with a lens, an optical filter, a long-wave ultraviolet excitation light source and an image acquisition computer, wherein a marking point for representing the shape and position characteristics of the model surface adopts metal ink containing fluorescent pigment, after blending through a curing agent, a fluorescent marking point with controllable oil film thickness is manufactured and formed on the model surface through a silk-screen method or a template spraying method, through the irradiation of the long-wave ultraviolet excitation light source, a fluorescent substance in the metal ink is excited to emit emergent light with the wavelength longer than that of the excitation light source, the interference of excitation light, model reflected light and wall surface background light is filtered through the optical filter, only a fluorescent wave band is reserved to enter a camera photosensitive chip for imaging, a model surface marking point image with extremely high signal-to-noise ratio is obtained, and the obtained high signal-to-noise ratio image data is transmitted to the image acquisition computer, and identifying and matching the marked point images, acquiring the three-dimensional space coordinates or the space displacement of the marked points on the surface of the model under the camera coordinate system through a stereoscopic vision parallax principle, calibrating the wind tunnel shafting before testing, converting the three-dimensional space coordinates or the space displacement of the marked points on the surface of the model under the camera coordinate system into the wind tunnel coordinate system, and performing subsequent processing to obtain the final attitude angle and the deformation of the model.

The fluorescent mark points made on the surface of the model have strong metal adhesive force and quick drying property, have the capability of no deformation and no falling off in the blowing process, can effectively prevent the distortion and even loss of the three-dimensional characteristic information of the surface of the model, and can flexibly match and select the optical filter and the fluorescent component according to the test requirements. The thickness of the fluorescent mark point is 8-25um, so that the interference of the thickness of the conventional sticker or paint on the airflow flow on the surface of the model (wing) can be effectively reduced.

In the embodiment, a long-wave ultraviolet band LED lamp or laser is used as an excitation light source. Before the test, an optical standard component is needed to calibrate the wind tunnel shafting to obtain the shafting conversion relation between the system and the wind tunnel, and then the obtained three-dimensional space coordinates or space displacement of the model surface mark points under the camera coordinate system are converted into the wind tunnel coordinate system for subsequent processing to obtain the posture and the deformation of the model.

Claims

1. A wind tunnel model deformation attitude vision measurement method is characterized by comprising the following steps: the adopted equipment comprises a camera with a lens, an optical filter, a long-wave ultraviolet excitation light source and an image acquisition computer, wherein a marking point for representing the shape position characteristics of the surface of a model adopts metal ink containing fluorescent pigment, the fluorescent marking point with controllable oil film thickness is manufactured on the surface of the model by a silk-screen method or a template spraying method, the fluorescent material in the metal ink is excited to emit emergent light with wavelength longer than that of the excitation light source by the irradiation of the long-wave ultraviolet excitation light source, the interference of the excitation light, the model reflected light and wall surface background light is filtered by the optical filter, only a fluorescent wave band is reserved to enter a camera photosensitive chip for imaging, the obtained image data with high signal-to-noise ratio is transmitted to the image acquisition computer, the three-dimensional space coordinates or space displacement under a camera coordinate system of the marking point on the surface of the model is acquired by the identification and matching of the marking point images and the stereoscopic vision parallax principle, and converting the three-dimensional space coordinate or the space displacement into a wind tunnel coordinate system for subsequent processing by calibrating a wind tunnel shafting before testing to obtain a final attitude angle and a deformation of the model.

2. The wind tunnel model deformation attitude vision measurement method according to claim 1, characterized in that: the thickness of the fluorescent mark point is 8-25 um.