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Article
Publication date: 19 June 2017

Gokhan Bayar

The purpose of this paper is to develop a methodology for detecting tree trunks for autonomous agricultural applications performed using mobile robots.

Abstract

Purpose

The purpose of this paper is to develop a methodology for detecting tree trunks for autonomous agricultural applications performed using mobile robots.

Design/methodology/approach

The system is constructed by following the principles of Voronoi diagram method which is one of the machine learning algorithms used by the robotics, mechatronics and automation researchers.

Findings

To analyze the accuracy and performance and to make verification and evaluation, both simulation and experimental studies are conducted. The results indicate that the tree trunk detection system developed using Voronoi diagram method can be able to detect tree trunks with high precision.

Originality/value

A novel solution technique to detect tree trunks is proposed. The adaptation of Voronoi diagram method in an agricultural (orchard) task is presented.

Details

Industrial Robot: An International Journal, vol. 44 no. 4
Type: Research Article
ISSN: 0143-991X

Keywords

Article
Publication date: 1 August 2003

Nestor Calvo, Sergio R. Idelsohn and Eugenio Oñate

The extended Delaunay tessellation (EDT) is presented in this paper as the unique partition of a node set into polyhedral regions defined by nodes lying on the nearby…

Abstract

The extended Delaunay tessellation (EDT) is presented in this paper as the unique partition of a node set into polyhedral regions defined by nodes lying on the nearby Voronoï spheres. Until recently, all the FEM mesh generators were limited to the generation of tetrahedral or hexahedral elements (or triangular and quadrangular in 2D problems). The reason for this limitation was the lack of any acceptable shape function to be used in other kind of geometrical elements. Nowadays, there are several acceptable shape functions for a very large class of polyhedra. These new shape functions, together with the EDT, gives an optimal combination and a powerful tool to solve a large variety of physical problems by numerical methods. The domain partition into polyhedra presented here does not introduce any new node nor change any node position. This makes this process suitable for Lagrangian problems and meshless methods in which only the connectivity information is used and there is no need for any expensive smoothing process.

Details

Engineering Computations, vol. 20 no. 5/6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 13 November 2009

L.M.J.S. Dinis, R.M. Natal Jorge and J. Belinha

The purpose of this paper is to extend the natural neighbour radial point interpolation method (NNRPIM) to the dynamic analysis (free vibrations and forced vibrations) of…

Abstract

Purpose

The purpose of this paper is to extend the natural neighbour radial point interpolation method (NNRPIM) to the dynamic analysis (free vibrations and forced vibrations) of two‐dimensional, three‐dimensional and bending plate problems.

Design/methodology/approach

The NNRPIM shape‐function construction is briefly presented, as are the dynamic equations and the mode superposition method is used in the forced vibration analysis. Several benchmark examples of two‐dimensional and plate bending problems are solved and compared with the three‐dimensional NNRPIM formulation. The obtained results are compared with the available exact solutions and the finite element method (FEM) solutions.

Findings

The developed NNRPIM approach is a good alternative to the FEM for the solution of dynamic problems, once the obtained results with the EFGM shows a high similarity with the obtained FEM results and for the majority of the studied examples the NNRPIM results are more close to the exact solution results.

Research limitations/implications

Comparing the FEM and the NNRPIM, the computational cost of the NNRPIM is higher.

Originality/value

The paper demonstrates extension of the NNRPIM to the dynamic analysis of two‐dimensional, three‐dimensional and bending plate problems. The elimination of the shear‐locking phenomenon in the NNRPIM plate bending formulation. The various solved examples prove a high convergence rate and accuracy of the NNRPIM.

Details

Engineering Computations, vol. 26 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 March 2006

Mingjun Zhang, Weimin Tao, William Fisher and Tzyh‐Jong Tarn

For semiconductor and gene‐chip microarray fabrication, robots are widely used to handle workpieces. It is critical that robots can calibrate themselves regularly and…

Abstract

Purpose

For semiconductor and gene‐chip microarray fabrication, robots are widely used to handle workpieces. It is critical that robots can calibrate themselves regularly and estimate workpiece pose automatically. This paper proposes an industrial method for automatic robot calibration and workpiece pose estimation.

Design/methodology/approach

The methods have been implemented using an air‐pressure sensor and a laser sensor.

Findings

Experimental results conducted in an industrial manufacturing environment show efficiency of the methods.

Originality/value

The contribution of this paper consists of an industrial solution to automatic robot calibration and workpiece pose estimation for automatic semiconductor and gene‐chip microarray fabrication.

Details

Industrial Robot: An International Journal, vol. 33 no. 2
Type: Research Article
ISSN: 0143-991X

Keywords

Article
Publication date: 13 March 2007

B. Pradhan, K. Sandeep, Shattri Mansor, Abdul Rahman Ramli and Abdul Rashid B. Mohamed Sharif

In GIS applications for a realistic representation of a terrain a great number of triangles are needed that ultimately increases the data size. For online GIS interactive…

Abstract

Purpose

In GIS applications for a realistic representation of a terrain a great number of triangles are needed that ultimately increases the data size. For online GIS interactive programs it has become highly essential to reduce the number of triangles in order to save more storing space. Therefore, there is need to visualize terrains at different levels of detail, for example, a region of high interest should be in higher resolution than a region of low or no interest. Wavelet technology provides an efficient approach to achieve this. Using this technology, one can decompose a terrain data into hierarchy. On the other hand, the reduction of the number of triangles in subsequent levels should not be too small; otherwise leading to poor representation of terrain.

Design/methodology/approach

This paper proposes a new computational code (please see Appendix for the flow chart and pseudo code) for triangulated irregular network (TIN) using Delaunay triangulation methods. The algorithms have proved to be efficient tools in numerical methods such as finite element method and image processing. Further, second generation wavelet techniques popularly known as “lifting schemes” have been applied to compress the TIN data.

Findings

A new interpolation wavelet filter for TIN has been applied in two steps, namely splitting and elevation. In the splitting step, a triangle has been divided into several sub‐triangles and the elevation step has been used to “modify” the point values (point coordinates for geometry) after the splitting. Then, this data set is compressed at the desired locations by using second generation wavelets.

Originality/value

A new algorithm for second generation wavelet compression has been proposed for TIN data compression. The quality of geographical surface representation after using proposed technique is compared with the original terrain. The results show that this method can be used for significant reduction of data set.

Details

Engineering Computations, vol. 24 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 19 June 2007

Felipe Campelo, Kota Watanabe and Hajime Igarashi

The paper introduces an evolutionary algorithm based on the artificial immune systems paradigm for topology optimization (TO) in 3D.

Abstract

Purpose

The paper introduces an evolutionary algorithm based on the artificial immune systems paradigm for topology optimization (TO) in 3D.

Design/methodology/approach

The 3D TO algorithm is described, and experimentally validated on an electromagnetic design problem.

Findings

The proposed method is capable of finding an optimal configuration for the validation problem used.

Research limitations/implications

More tests are needed in order to fully assert the capabilities of the algorithm. Moreover, further improvements are needed in order to obtain smoother topologies at the end of the optimization procedure.

Practical implications

The paper presents a novel tool for the design of electromagnetic devices, using a TO approach.

Originality/value

So far most of the TO algorithms did not tackle true 3D problems, and the ones capable of 3D optimization do it at high computational costs. The algorithm presented here is capable of true 3D design at a reasonable computational budget.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 June 2006

J. Pina‐Henriques and Paulo B. Lourenço

To contribute for a reliable estimation of the compressive strength of unreinforced masonry from the properties of the constituents (units and mortar).

1801

Abstract

Purpose

To contribute for a reliable estimation of the compressive strength of unreinforced masonry from the properties of the constituents (units and mortar).

Design/methodology/approach

Sophisticated non‐linear continuum models, based on damage, plasticity, cracking or other formulation, are today standard in several finite element programs. The adequacy of such models to provide reliable estimates of masonry compressive strength, from the properties of the constituents, remains unresolved. The authors have shown recently that continuum models might significantly overestimate the prediction of the compressive strength. Hence, an alternative phenomenological approach developed in a discrete framework is proposed, based on attributing to masonry components a fictitious micro‐structure composed of linear elastic particles separated by non‐linear interface elements. The model is discussed in detail and a comparison with experimental results and numerical results using a standard continuum model is provided.

Findings

Clear advantages in terms of compressive strength and peak strain prediction were found using the particle model when compared with standard continuum models. Moreover, compressive and tensile strength values provided by the model were found to be particle size‐ and particle distortion‐independent for practical purposes. It is also noted that size‐dependent responses were obtained and that shear parameters rather than tensile parameters were found to play a major role at the meso‐level of the phenomenological model.

Originality/value

This paper provides further insight into the compressive behaviour of quasi‐brittle materials, with an emphasis on the strength prediction of masonry composites. Reliable prediction of masonry strength is of great use in the civil engineering field, allowing one to reduce experimental testing in expensive wallets and to avoid the usage of conservative empirical formulae.

Details

Engineering Computations, vol. 23 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 December 2001

Vojin Jovanovic, Souran Manoochehri and Constantin Chassapis

A simplified approach for estimating weld lines, vent locations and fill times for resin transfer molding applications in non‐planar geometry is presented. The molding…

Abstract

A simplified approach for estimating weld lines, vent locations and fill times for resin transfer molding applications in non‐planar geometry is presented. The molding parts are treated as polyhedral spaces for which the concept of Voronoi diagram and shortest paths is utilized to predict the formation of weld lines, location of vents and filling times. The approach is based purely on geometrical considerations and on previously established observations that it is possible to treat the resin flow inside the mold as partly radial and partly channel‐like. The proposed procedure is geared towards software implementation, but it enables one to gain more insight into the process before detailed and time‐consuming calculations are attempted.

Details

Engineering Computations, vol. 18 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 6 November 2017

Gholamreza Shobeyri and Mohammad Yourdkhani

The purpose of this paper is to develop an efficient and accurate mesh-less method to simulate free flows with continuous deformation in boundary positions.

Abstract

Purpose

The purpose of this paper is to develop an efficient and accurate mesh-less method to simulate free flows with continuous deformation in boundary positions.

Design/methodology/approach

A two-step pressure projection method in a Lagrangian form is used to solve the governing equations of mass and momentum conservation. In the first step, velocity field is calculated in which incompressibility is not enforced. In the second step, a pressure Poisson equation is applied to satisfy incompressibility conditions. The numerical proposed method is used for spatial discretization of the governing equations. Three benchmark-free surface problems, namely, dam break, solitary wave propagation and evolution of an elliptical bubble with available experimental results and analytical solutions, are used to test the accuracy of the proposed method. The results prove the accuracy of the method in simulating free surface problems.

Findings

The Voronoi diagram instead of kernel function summation can be used to estimate the particle or nodal volume concept in particle-based (mesh-less) methods for function approximation. This idea probably works well especially for highly irregular node distributions.

Originality/value

The continuous moving least squares shape functions are applied for function approximation, and the Voronoi diagram concept is also used to estimate region influence of computational nodal points or particle volumes. Combinations of these two concepts and finite differences formulation for first derivatives gives an accurate numerical model for Laplacian operator in the proposed method.

Details

Engineering Computations, vol. 34 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 21 January 2019

Qisheng Wang, Boqing Gao and Hui Wu

Modern CAD systems facilitate the creation of any surface geometry imaginable, and complex surfaces for free-form grid shells are often represented by a set of Non-Uniform…

Abstract

Purpose

Modern CAD systems facilitate the creation of any surface geometry imaginable, and complex surfaces for free-form grid shells are often represented by a set of Non-Uniform Rational B-Splines surface patches. But it remains an intractable issue how to generate high-quality grids on complex surfaces efficiently. To solve this issue, an automatic triangular mesh generation method is presented, based on bubble dynamics simulation and a modified Delaunay method.

Design/methodology/approach

A moderate amount of points are first distributed on a given surface. Next, by regarding the points as elastic bubbles with the same size and introducing the forces acting on bubbles, the motion control equations of bubbles are established. The equilibrium state of the bubble system is found by Verlet algorithm. Then, the Voronoi diagram on the surface is obtained by calculating the intersection between the surface and the three-dimensional (3D) Voronoi diagram of the centers of bubbles. Finally, a triangular mesh, Delaunay triangulation on the surface, is determined based on the dual change of the Voronoi diagram.

Findings

This method generates meshes on the surface directly, unlike mapping-based methods, avoiding the mapping distortion. Examples are given to demonstrate the successful execution of this method. The result also illustrates that this method is applicable to various surfaces in high automation level and resultant meshes are highly uniform and well-shaped.

Originality/value

Thus, this method provides the convenience for the geometry design of complex free-form grid structure.

Details

Engineering Computations, vol. 36 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

1 – 10 of 157