DP-MVS: Detail Preserving Multi-View Surface Reconstruction of Large-Scale Scenes

This paper presents an accurate and robust dense 3D reconstruction system for detail preserving surface modeling of large-scale scenes from multi-view images, which we named DP-MVS. Our system performs high-quality large-scale dense reconstruction, which preserves geometric details for thin structures, especially for linear objects. Our framework begins with a sparse reconstruction carried out by an incremental Structure-from-Motion. Based on the reconstructed sparse map, a novel detail preserving PatchMatch approach is applied for depth estimation of each image view. The estimated depth maps of multiple views are then fused to a dense point cloud in a memory-efficient way, followed by a detail-aware surface meshing method to extract the final surface mesh of the captured scene. Experiments on ETH3D benchmark show that the proposed method outperforms other state-of-the-art methods on F1-score, with the running time more than 4 times faster. More experiments on large-scale photo collections demonstrate the effectiveness of the proposed framework for large-scale scene reconstruction in terms of accuracy, completeness, memory saving, and time efficiency.

Numerical analysis of meshing heating of involute spur gear

Involute spur gears generate heat due to tooth surface meshing friction. Excessive temperature rising affects transmission accuracy and reduces work reliability.. By establishing the normalized coordinates of the meshing curve and based on the frictional heat generation theory, the mathematical analysis model of the meshing surface heating is studied, the factors affecting the average heat flux density of meshing are explored, and the distribution law of these factors along the normalized coordinate of the meshing is analysed. The analysis shows that the tangential velocity of the meshing point and the half-bandwidth of the time domain contact have the greatest influence on the average heat flow density; the average heat flow density distribution of the driving wheel and the driven wheel are similar. The heat flow density of the driving wheel is greater than that of the driven wheel. Tooth shape modification minimizes tooth surface meshing contact stress, reduces meshing heat generation, controls temperature rise and improves transmission reliability.

An Improved Dynamic Transmission Error Model Applied on Coupling Analysis of Gear Dynamics and Elastohydrodynamic Lubrication

In order to study the coupling effect of cylindrical gear dynamics and elastohydrodynamic lubrication(EHL), based on dynamic theory, a dynamic model of a six-degree-of-freedom(six-DOF) coupled system is established. Based on the numerical solution of EHL, an improved transmission error model was established, and the oil film stiffness, oil film damping and center oil film thickness obtained by the numerical solution were used in the gear dynamics analysis. The dynamics and EHL characteristics of the gear system are analyzed and compared with the general model. The results show that by using the improved transmission error model, the comprehensive stiffness and comprehensive damping of the gear increase and fluctuate slightly, and the amplitude of the tooth surface meshing force and dynamic response decreases. Under the action of tooth surface meshing force, the oil film pressure and thickness show oscillation characteristics.

An Efficient and Adaptable Path Planning Algorithm for Automated Fiber Placement Based on Meshing and Multi Guidelines

Path planning algorithms for automated fiber placement are used to determine the directions of the fiber paths and the start and end positions on the mold surfaces. The quality of the fiber paths determines largely the efficiency and quality of the automated fiber placement process. The presented work investigated an efficient path planning algorithm based on surface meshing. In addition, an update method of the datum direction vector via a guide-line update strategy was proposed to make the path planning algorithm applicable for complex surfaces. Finally, accuracy analysis was performed on the proposed algorithm and it can be adopted as the reference for the triangulation parameter selection for the path planning algorithm.