Abstract
Nowadays, due to the advantages of non-contact and high-speed, vision-based pose measurements have been widely used for aircraft performance testing in a wind tunnel. However, usually glass ports are used to protect cameras against the high-speed airflow influence, which will lead to a big measurement error. In this paper, to further improve the vision-based pose measurement accuracy, an imaging model which considers the refraction light of the observation window was proposed. In this method, a nonlinear camera calibration model considering the refraction brought by the wind tunnel observation window, was established first. What’s more, a new method for the linear calibration of the normal vector of the glass observation window was presented. Then, combining with the proposed matching method based on coplanarity constraint, the six pose parameters of the falling target could be calculated. Finally, the experimental setup was established to conduct the pose measurement study in the laboratory, and the results satisfied the application requirements. Besides, experiments for verifying the vision measurement accuracy were also performed, and the results indicated that the displacement and angle measurement accuracy approximately increased by 57% and 33.6%, respectively, which showed the high accuracy of the proposed method.
Highlights
Nowadays, the rapid development of aerospace puts high requirements on the aircraft
Aiming at further improving the vision-based measurement accuracy, we propose an improved metrology for estimating the pose information of a falling target in wind tunnel tests, considering the refraction caused by the observation window and high-speed airflow
Aimed at reducing the pinhole model-based vision measurement uncertainty caused by the glass observation window, we furthered the study, and proposed an improved vision-based pose glass observation window, we furthered the study, and proposed an improved vision-based pose measurement method, which considers the refraction of light
Summary
The rapid development of aerospace puts high requirements on the aircraft. The ability of the aircraft to accurately release the internal or external stores (e.g., weapons, auxiliary fuel tanks and bombs) in high-speed airflow directly affects the operation performance [1]. To provide a good data reference for the better layout design of the ejection system, as well as the selection of separation parameters, the study of the service performance of an aircraft under simulated airflow environment is necessary. This technology is called the wind tunnel test, among which the separation test is most critical. It allows the evaluation of the performance of the ejection mechanism through the time-varying six-degree-of-freedom parameters (i.e., three position parameters and three angle parameters) of the scaled model falling in the high-speed airflow. For the advantages of non-contact, real-time, high-precision and full-field measurement, the vision-based technique has been widely used for detecting both the geometric and motion parameters of a target in complex environments such
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