A novel MP-LSTM method for ship trajectory prediction based on AIS data

Path, feedrate and trajectory planning for free-from surface machining: A state-of-the-art review

Planar and nonplanar slicing algorithms for fused deposition modeling technology: a critical review

For the curved layer deposition with wire and arc additive manufacturing on complex surface, the molten pool behavior and bead geometry are variant at different welding positions for the dragging effect of gravity, which lead to inconsistent layer appearance. A region-based path planning method for robotic curved layer wire and arc additive manufacturing (CL-WAAM) is developed, with which all horizontal welding position can be maintained at arbitrary region of the complex surface. The adverse effect of gravity is minimized and uniform bead appearance can be guaranteed. Firstly, with a two-stage clustering method, the complex surface was divided into a certain number of simple subregions. Then, the contour line across cluster centroid of each subregion was employed as initial path, and an adaptive bead overlapping model changed with local inclined angle was used to generate the offset curved path covering the subregion. Therefore, the overall welding paths were approximate to the contour line on the surface, and the horizontal welding position and consistent forming appearance can be achieved. Finally, three surface parts were designed to validate feasibility of the method, and the forming appearance was compared with traditional iso-parametric method and flat layer WAAM (FL-WAAM). The results suggested that the surface waviness and thickness were relatively consistent at arbitrary region of complex surface with the region-based method, and the stair-step effect appeared in FL-WAAM was significantly alleviated with the CL-WAAM. The proposed method helps achieve the uniform layer appearance deposited on complex surface, which could be widely used in the manufacturing or repairing of wear-resistant surface parts, such as the hot forging die and hydraulic turbine blade.

Region-based path planning method with all horizontal welding position for robotic curved layer wire and arc additive manufacturing

Path, feedrate and trajectory planning for free-form surface machining: A state-of-the-art review

This paper presents a novel method to generate three-axis CNC tool paths for machining freeform surfaces based on a preferred feed direction field. This research was initiated from a fluid dynamics behavior that the energy loss can be reduced when the streamlines of fluid and the small grooves on a surface are in the same directions. In this research, the fluid streamlines above the surface are defined by a collection of vectors. These vectors are regularized into a grid of vectors, and these regularized vectors are further projected onto the tangent planes of a grid of points on the surface to create the preferred feed direction field. Based on the parametric model of the surface, the vectors on the tangent planes of the surface are mapped into vectors in the parametric domain. A scalar function is constructed such that the isolines of this scalar function and the preferred feed direction vectors in the parametric domain are in the same directions. A group of isolines of the scalar function are identified and these isolines are mapped back onto the 3-D surface as the created tool paths considering the tolerance requirement. The developed method has been applied to generate the tool paths for machining surfaces of a compressor blade.

CNC Tool Path Generation for Freeform Surface Machining Based on Preferred Feed Direction Field

T-spline has been recently developed to represent objects of arbitrary shapes in computer-aided design, computer graphics, and reverse engineering. In fact, fitting a T-spline over a point cloud is usually ineffective by using traditional iterative fit-and-refine paradigm. In traditional T-spline least-square fitting method, all control points are recomputed in each iteration, which costs large amount of calculations. In this paper, we propose a fast T-spline fitting method based on T-mesh segmentation. The segmentation technology is introduced to identify the inactive and active region of T-mesh. Computational costs can be largely reduced since only the control points in the active part need to be recalculated in the upcoming process, while those in inactive part are kept invariant once the fitting accuracy is achieved. Classical datasets are used to validate the proposed fast fitting method, and the experimental results yield that a total running time is reduced to $$34\%$$
 of the traditional T-spline fitting method. We argue this method is particularly useful in the reconstruction of scanned scatter data of which the parameter distribution is not uniform.

A fast T-spline fitting method based on efficient region segmentation

The invention provides a point cloud registration method. The method comprises the following steps of: obtaining four test feature points, satisfying a preset position, in a test point set and a reference feature point, corresponding to each test feature point, in a reference point set, wherein a test values is determined via Gaussian curvature and average curvature of the test feature points, and a reference value is determined via Gaussian curvature and average curvature of the reference feature points; obtaining a coarse registration matrix which enables distances from the four test feature points in the test point set to the four reference feature points in the reference point set to be minimum; obtaining a coarse registration point set according to the coarse registration matrix and the test point set; and obtaining a precise registration matrix which enables the sum of distances from coarse registration points in the coarse registration point set to a first reference point in the reference point set to be minimum, wherein the distance between the reference point and each coarse registration point in the coarse registration point set is minimum. According to the method, the problems of long time consumption and low precision caused by estimating features of all the data points in existing cloud point registration method are solved, and the calculation efficiency and precision are effectively improved.

Point cloud registration method

Virtual edge method for point cloud slicing in 3D printing is a very common algorithm due to the advantage of low computational complexity. However, this approach is not robust to density variations. To overcome this shortcoming, in this paper, a concept of column neighborhood is introduced to estimate whether the virtual edge model should be used in certain situations. Concretely, based on the technic of generating a set of multiple contours, we present an improved algorithm for high resolution point cloud slicing. To deal with multiple contours, a classify method based on convex hull is proposed, which reduces considerable calculations and separates each module from the others. At the last step, a method based on minimum angle is proposed to generate a single contour for each class. This algorithm is verified to be efficient by testing on kinds of typical benchmarks. Keywords—virtual edge; convex hull; classify

/pdf/a-slicing-algorithm-based-on-virtual-edge-for-3d-printing-2kuidsb3yb.pdf

A Slicing Algorithm Based on Virtual Edge for 3D Printing

Airborne light detection and ranging (LiDAR) technology is becoming the primary method for generating high-resolution digital terrain models (DTMs), which is essential for commercial and scientific uses. In order to generate DTMs, non-ground features as buildings, vehicles, and vegetation must be recognized and distinguished from the LiDAR point cloud. However, various degrees of errors may accumulate in the separated filtering and modeling processes. In this paper, a novel physical process driven DTM generating method for airborne LiDAR measurement is proposed, which combines the point cloud classification and surface fitting process simultaneously. Actually, the physical dynamic process is integrated with the common non-uniform rational b-splines (NURBS) model under the corresponding parameter mediation. The experimental results show that the proposed method is efficacious in reducing errors and have a nice performance in terrain fitting.

/pdf/a-physical-process-driven-digital-terrain-model-generating-3n74otc92p.pdf

A Physical Process Driven Digital Terrain Model Generating Method Based on D-NURBS

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