Multi-Robot Collaborative Hunting in Cluttered Environments With Obstacle-Avoiding Voronoi Cells

This work proposes an online collaborative hunting strategy for multi-robot systems based on obstacle-avoiding Voronoi cells in a complex dynamic environment. This involves firstly designing the construction method using a support vector machine(SVM) based on the definition of buffered Voronoi cells(BVCs). Based on the safe collision-free region of the robots, the boundary weights between the robots and the obstacles are dynamically updated such that the robots are tangent to the buffered Voronoi safety areas without intersecting with the obstacles. Then, the robots are controlled to move within their own buffered Voronoi safety area to achieve collision-avoidance with other robots and obstacles. The next step involves proposing a hunting method that optimizes collaboration between the pursuers and evaders. Some hunting points are generated and distributed evenly around a circle. Next, the pursuers are assigned to match the optimal points based on the Hungarian algorithm.Then, a hunting controller is designed to improve the containment capability and minimize containment time based on collision risk. Finally, simulation results have demonstrated that the proposed cooperative hunting method is more competitive in terms of time and travel distance.

Ambient noise tomography of a linear seismic array based on an improved Voronoi tessellation

Ambient noise tomography,when applied to a dense linear seismic array,has the capability to provide detailed insights into the fine velocity structures across diverse tectonic settings.The linear station arrangement naturally generates parallel and concentrated ray paths along the array trend.This unique geometry requires specific optimization of the inversion methodology and model parameterization.The Bayesian-based transdimensional inversion method,characterized by its fully non-linear nature and high degree of freedom in parameter settings,offers a powerful tool for ambient noise inversion.To effectively adapt this method to a linear array layout,we propose a modification to the Voronoi cell tessellation built in the transdimensional method.By introducing spatial priority to the Voronoi kernels,we strategically increased the density of Voronoi cells along the direction of the array.We then applied the modified approach to a linear seismic array in the North China Craton and validated its robustness through phase velocity images and resolution tests.Our improved non-uniform sampling technique in the 2-D model space accelerates convergence while simultaneously enhancing model accuracy.Compared with the conventional damped leastsquares method,the proposed algorithm revealed a shear-wave velocity map with notable low-velocity anomalies situated in the middle and lower crust beneath the borders of the Ordos block and its surrounding orogenic belt.Aligned with the crustal structures revealed by receiver function and electrical imaging,our findings indicated that the western and eastern margins of the Ordos block had experienced intensive crustal wedge deformation and re-melting,respectively.

APPROXIMATE QUERY AND CALCULATION OF RNN_k BASED ON VORONOI CELL

Reverse k nearest neighbor （RNNk） is a generalization of the reverse nearest neighbor problem and receives increasing attention recently in the spatial data index and query. RNNk query is to retrieve all the data points which use a query point as one of their k nearest neighbors. To answer the RNNk of queries efficiently, the properties of the Voronoi cell and the space-dividing regions are applied. The RNNk of the given point can be found without computing its nearest neighbors every time by using the rank Voronoi cell. With the elementary RNNk query result, the candidate data points of reverse nearest neighbors can he further limited by the approximation with sweepline and the partial extension of query region Q. The approximate minimum average distance （AMAD） can be calculated by the approximate RNNk without the restriction of k. Experimental results indicate the efficiency and the effectiveness of the algorithm and the approximate method in three varied data distribution spaces. The approximate query and the calculation method with the high precision and the accurate recall are obtained by filtrating data and pruning the search space.

Nearest Neighbor Sampling of Point Sets Using Rays

We propose a new framework for the sampling,compression,and analysis of distributions of point sets and other geometric objects embedded in Euclidean spaces.Our approach involves constructing a tensor called the RaySense sketch,which captures nearest neighbors from the underlying geometry of points along a set of rays.We explore various operations that can be performed on the RaySense sketch,leading to different properties and potential applications.Statistical information about the data set can be extracted from the sketch,independent of the ray set.Line integrals on point sets can be efficiently computed using the sketch.We also present several examples illustrating applications of the proposed strategy in practical scenarios.

MESHLESS METHOD FOR 2D MIXED-MODE CRACK PROPAGATION BASED ON VORONOI CELL

A meshless method integrated with linear elastic fracture mechanics(LEFM)is presented for 2D mixed-mode crack propagation analysis.The domain is divided automatically into sub-domains based on Voronoi cells,which are used for quadrature for the potential energy. The continuous crack propagation is simulated with an incremental crack-extension method which assumes a piecewise linear discretization of the unknown crack path.For each increment of the crack extension,the meshless method is applied to carry out a stress analysis of the cracked structure.The J-integral,which can be decomposed into mode Ⅰ and mode Ⅱ for mixed-mode crack,is used for the evaluation of the stress intensity factors(SIFs).The crack-propagation direction,predicted on an incremental basis, is computed by a criterion defined in terms of the SIFs. The flowchart of the proposed procedure is presented and two numerical problems are analyzed with this method.The meshless results agree well with the experimental ones,which validates the accuracy and efficiency of the method.

Numerical simulation of thermo-mechanical fatigue properties for particulate reinforced composites

In this paper, a two dimensional Voronoi cell element, formulated with creep, thermal and plastic strain, is applied for the numerical simulation of thermo-mechanical fatigue behavior for particulate reinforced composites. The relation between mechanical fatigue phases and thermal fatigue phases influences the thermo-mechanical fatigue behavior and cyclic creep damage. The topological features of micro-structure in particulate reinforced composites, such as the orientation, depth-width ratio, distribution and volume fraction of inclusions, have a great influence on thermo-mechanical behavior. Some related conclusions are obtained by examples of numerical simulation.

A natural neighbour method based on Fraeijs de Veubeke variational principle for materially non-linear problems

The natural neighbour method can be considered as one of many variants of the meshless methods. In the present paper, a new approach based on the Fraeijs de Veubeke （FdV） functional, which is initially developed for linear elasticity, is extended to the case of geometrically linear but materially non-linear solids. The new approach provides an original treatment to two classical problems： the numerical evaluation of the integrals over the domain A and the enforcement of boundary conditions of the type ui = hi on Su. In the absence of body forces （Fi = 0）, it will be shown that the calculation of integrals of the type fA .dA can be avoided and that boundary conditions of the type ui = hi on Su can be imposed in the average sense in general and exactly if hi is linear between two contour nodes, which is obviously the case for tTi = O.

Modeling of interphases in multiple heterogeneities reinforced composites using Voronoi cell finite elements

In this paper,a Voronoi cell finite element model is developed to study the microscopic and macroscopic mechanical behaviors of heterogenous materials,including arbitrary distributed heterogeneity(inclusions or fibers)coated with interphase layers,based on linear elasticity theory.The interphase between heterogeneity and a matrix are regarded as in the third phase(elastic layers),in contrast to the perfect interface of the spring-like Voronoi cell finite element model(VCFEM)in the literature.In this model,both stress and the displacement field are assumed to be independent in an element.Formulations of stress are derived for each of the three phases in an element,as is the type of functional.Numerical examples were used to study the microscopic and macroscopic properties,such as the effective modulus,of the composites.The results of the proposed VCFEM were compared with analytical solution and numerical results obtained from a standard finite element analysis to confirm its effectiveness.