Research On Key Technologies Of 3D Ice Shape Measurement In Wind Tunnel Icing Model

During the flight test,the icing wind tunnel can simulate the icing conditions of the aircraft under different meteorological conditions.Ground simulation experiments are often conducted in the icing wind tunnel.Howeve r,in the measurement of ice formation,the existing technologies are mostly contact-type measurement methods,and there are problems such as damage to the ice shape and low measurement efficiency.In this paper,an optical non-contact measurement method is proposed for the measurement of an ice-breaking ice tunnel model to realize the contour measurement of the ice model.This article describes commonly used measurement techniques for wind tunnel icing models and techniques for visual three-dimensional measurement methods.Through the analysis of different ice-shape transmittances,two complete implementations of ice-profile measurements are proposed: For ice with low surface transmittance,the principle of visible line structured light triangulation is applied;for ice with high surface transmittance using infrared laser radiation imaging and laser triangulation technology to measure.Hardware setup and software algorithm design for the two sets of systems.The hardware platform is used to collect laser images on the surface of the ice.The software algorithm design mainly includes the processing of the light strip image,the extraction of the center line,the calibration of the measurement system,and the acquisition of the 3D point cloud.The key technolog ies and difficulties that exist in the two methods are analyzed in detail.In the acquisition of light-band images,the characteristics of light-band images are analyzed to select an appropriate image pre-processing method.Considering the presence of ice fog in the icing wind tunnel,an image enhancement algorithm based on dark channels is used;in order to obtain higher measurement accuracy.Firstly,the threshold banding method was used to extract the light bands.The Hessian matrix and gradient barycentric method were used to extract the centerline of the optical band and a good extraction effect was obtained.On the calibration of the measurement system,a sufficient number of structured light plane calibration points are obtained based on the double cross ratio invariance.In the infrared laser measurement method,we designed a dedicated high-precision planar target for the infrared camera,and the experimental verification has a good calibration effect.Finally,the visible light system was used to rec onstruct and compare the spray model and the same ice structure,and a good reconstruction effect was obtained.