Three dimensional extension of Bresenham’s algorithm with Voronoi diagram

Bresenham’s algorithm for plotting a two-dimensional line segment is elegant and efficient in its deployment of mid-point comparison and integer arithmetic. It is natural to investigate its three-dimensional extensions. In so doing, this paper uncovers the reason for little prior work. The concept of the mid-point in a unit interval generalizes to that of nearest neighbours involving a Voronoi diagram. Algorithmically, there are challenges. While a unit interval in two-dimension becomes a unit square in three-dimension, “squaring” the number of choices in Bresenham’s algorithm is shown to have difficulties. In this paper, the three-dimensional extension is based on the main idea of Bresenham’s algorithm of minimum distance between the line and the grid points. The structure of the Voronoi diagram is presented for grid points to which the line may be approximated. The deployment of integer arithmetic and symmetry for the three-dimensional extension of the algorithm to raise the computation efficiency are also investigated

Triangular Bézier sub-surfaces on a triangular Bézier surface

This paper considers the problem of computing the Bézier representation for a triangular sub-patch on a triangular Bézier surface. The triangular sub-patch is defined as a composition of the triangular surface and a domain surface that is also a triangular Bézier patch. Based on de Casteljau recursions and shifting operators, previous methods express the control points of the triangular sub-patch as linear combinations of the construction points that are constructed from the control points of the triangular Bézier surface. The construction points contain too many redundancies. This paper derives a simple explicit formula that computes the composite triangular sub-patch in terms of the blossoming points that correspond to distinct construction points and then an efficient algorithm is presented to calculate the control points of the sub-patch

Workspace analysis of Cartesian robot system for kiwifruit harvesting

Purpose – This paper aims to investigate if a Cartesian robot system for kiwifruit harvesting works more effectively and efficiently than an articulated robot system. The robot is a key component in agricultural automation. For instance, multiple robot arm system has been developed for kiwifruit harvesting recently because of the significant labor shortage issue. The industrial robots for factory automation usually have articulated configuration which is suitable for the tasks in the manufacturing and production environment. However, this articulated configuration may not fit for agricultural application due to the large outdoor environment. Design/methodology/approach – The kiwifruit harvesting tasks are completed step by step so that the robot workspace covers the canopy completely. A two-arm, Cartesian kiwifruit harvesting robot system and several field experiments are developed for the investigation. The harvest cycle time of the Cartesian robot system is compared to that of an articulated robot system. The difference is analyzed based on the workspace geometries of these two robot configurations. Findings – It is found that the kiwifruit harvesting productivity is increased by using a multiple robot system with Cartesian configuration owing to its regular workspace geometry. Originality/value – An articulated robot is a common configuration for manufacturing because of its simple structure and the relatively static factory environment. Most of the agricultural robotics research studies use single articulated robot for their implementation. This paper pinpoints how the workspace of a multiple robot system affects the harvest cycle time for kiwifruit harvesting in a pergola style kiwifruit orchard

Integration of stereo vision system calibration and kinematic calibration for an autonomous kiwifruit harvesting system

Stereo vision system and manipulator are two major components of an autonomous fruit harvesting system. In order to raise the fruit-harvesting rate, stereo vision system calibration and kinematic calibration are two significant processes to improve the positional accuracy of the system. This article reviews the mathematics of these two calibration processes and presents an integrated approach for acquiring calibration data and calibrating both components of an autonomous kiwifruit harvesting system. The calibrated harvesting system yields good positional accuracy in the laboratory tests, especially in harvesting individual kiwifruit. However, the performance is not in line with the outcomes in the orchard field tests due to the cluster growing style of kiwifruit. In the orchard test, the calibrations reduce the fruit drop rate but it does not impressively raise the fruit harvesting rate. Most of the fruit in the clusters remain in the canopy due to the invisibility of the stereo vision system. After analyzing the existing stereo vision system, a future visual sensing system research direction for an autonomous fruit harvesting system is justified

A simple algorithm for medial axis transform computation

Although medial axis transform is introduced as a shape description for many engineering applications, the computational algorithm is still challenging. This is especially true for the shape with free form boundary. This paper presents an algorithm for medial axis transform computation from a perspective of minimum distance between the points in a two-dimensional shape and its boundary. The minimum distance is given by a resultant distance function which is a superposition of the individual distance function between a point within a shape and each boundary point. By elaborating the resultant distance function, the medial axis transform will be obtained naturally. The distance function is modeled as a solid cone and the superposition is equivalent to the union Boolean set operation. The implementation of the approach is simplified using a solid modeling kernel. Several examples of two-dimensional shapes with free form boundaries are raised to illustrate the concept and algorithm

Garment pattern definition, development and application with associative feature approach

Garment virtual design has been evolved significantly with the rapid development of 3D CAD tools, especially with the convenient availability of NURBS surface modeling capability. Parametric development of clothes is demanded in line with the trend of mass customization according to the true measures of customers or regulated sizes of certain markets. Virtual design features with well-defined associations with the parametric mannequins are enablers. To achieve an intelligent mass customization approach, the development of surface patches from 3D clothing designs to 2D flattened patterns become essential. This article addresses the definition, development and application of garment features with an associative feature approach

Orienting a protein model by crossing number to generate the characteristic views for identification

A protein model (such as a ribbon model) can be created from the atomic coordinates in the protein data base files. These coordinates are obtained by X-ray crystallography or NMR spectroscopy with the protein arbitrarily oriented. As such, identifying or comparing a novel structure with a known item using protein model in the protein data base can be a timely process since a large number of transformations may be involved. The identification efficiency will be improved if the protein models are uniformly oriented. This paper presents an approach to orient a protein model to generate the characteristic views with minimum and maximum crossings respectively. The projection directions for these characteristic views are determined by a set of crossing maps (C-maps). Re-orientating the protein models in the protein data base to two characteristic views will facilitate the process of identification

From Social Networking Site Use to Subjective Well-Being: The Interpersonal and Intrapersonal Mediating Pathways of Prosocial Behavior among Vocational College Students in China

In view of the growing importance of social networking sites (SNS) to adolescents and the mixed and inconclusive empirical evidence on the relationships between SNS use and their well-being, the present study aimed to investigate the associations of social function use intensity (SFUI) and entertainment function use intensity (EFUI) with adolescent life satisfaction and self-esteem, and examine the mediating roles that general prosocial behavior and school volunteering may play in the links. Drawing from the findings of a self-administered online survey with a valid sample of 3452 adolescents (mean age = 18.21) from 10 vocational colleges across four regions of China, our results demonstrated that there was an indirect positive effect of SFUI on adolescent life satisfaction and self-esteem via two interpersonal pathways of general prosocial behavior and school volunteering. We also discovered that there was an indirect negative effect of EFUI on adolescent life satisfaction and self-esteem via an intrapersonal pathway of school volunteering. Our findings provided empirical support for the differential effects of SFUI and EFUI on adolescent life satisfaction and self-esteem through the interpersonal and intrapersonal pathways, and unpacked the mediating roles of general prosocial behavior and school volunteering in these mechanisms

Development and experimental analysis of a pneumatic based dibbling machine for a forestry nursery

The rejection rate of tree stock in a forestry nursery can be as high as 35%. This is attributed to plant physiology, poorly trained seasonal workers and unsophisticated equipment. It is estimated that approximately 5% of seedling rejection in the pilot nursery (approximately 220,000 per year) is due to poorly dibbled holes. These holes are typically dibbled using a spiked wheel, which produces crooked and imprecise holes. The poor-quality holes cause bends in the stems, resulting in rejection. This article presents a tractor-drawn mechatronic dibbling machine that can produce precise vertical holes of a specified depth, spacing and diameter. Both hole quality and dibbling efficiency are greatly improved. The machine was tested at a nursery and produced 98% of the holes at the desired angle and 94% at the desired depth. The unwanted stem bends were eliminated with a subsequent reduction in rejects. Furthermore, it was found that worker productivity increased, as they did not have to spend time setting seedlings vertically