| Wave-transmitting components are widely used in satellite communications and aerospace as a structure to protect internal components from external extreme environments.They not only need to have a certain mechanical strength but also need to meet the electromagnetic properties.The most important electromagnetic property is the Insert Phase Delay(IPD).In order to correct the electromagnetic performance of the wave-transmitting component,it is necessary to measure the IPD of each point.The measurement of IPD has strict requirements on the position and orientation.In order to achieve accurate,reliable,and efficient point-by-point measurement of IPD on a specific machine tool structure,surface reconstruction,path planning and collision detection were studied in this paper.Firstly,according to the characteristics of the wave-transmitting components and the sampled point cloud,the Non-Uniform Rational B-Spline(NURBS)surface is selected as the reconstruction model.Its mathematical model and supporting algorithms are introduced.The data points parameters,knot vector,and weights are optimized to improve the accuracy of fitting curve.And the optimization of curve fitting is extended to surface fitting by using skinned surface fitting.A local iterative optimization method for surfaces fitting is proposed.The effectiveness of the optimization is verified by numerical experiments.The experimental results show that the root means square error and the maximum error of each fitting surface are reduced by 52.8% and 43.9% on average without increasing the control points.The root means square error and maximum error of the normal vector are reduced by 43.9% and 37.8%on average.Then,using the D-H method to analyze the kinematics of the specific measuring machine tool.The transformation relationship between the machine tool coordinate system and the workpiece coordinate system is obtained,and the kinematic inverse solution of the measuring pose is obtained through the transformation matrix calculation.The measurement pose of the point on NURBS surface is obtained by using the measurement azimuth parameters of the wave-transmitting component.According to the size of the measurement area and the parameters of the machine tool,the most efficient movement trajectory of pointby-point IPD measurement is confirmed.Then,collision detection is introduced to avoid interference between machine tool components during the measurement process.According to the shape of the components and the structure of the machine tool,the oriented bounding box is confirmed as the basic model for collision detection.The bounding volume hierarchy is proposed to achieve the accurate collision detection of outer profile of the component.Its generation method is optimized making the model storage more concise and detection more efficient.A method based on the internal maximum box is proposed to realize the internal collision detection of components,and the generation and detection methods of corresponding models are discussed.The accuracy of collision detection is verified by using Lab View real-time display program and mixed programming method.The efficiency of the proposed algorithm is verified by timeconsuming experiment.Finally,the experimental verification is carried out on the actual measurement device.The sampling method of the outer profile of the wave-transmitting component is designed.The experimental sample’s outer profile is sampled and the surface is reconstructed.The collision scenes are built for the parts that may collide in the device.And the motion position of each axis when measuring the points on the component is obtained by using the fitting surface.Combined with coordinate transformation and collision detection,the range that can be used to measure IPD by transmission method is confirmed,and the accuracy of the range is verified by the actual movement of the measuring device. |
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