Convex decomposition of concave clouds for the ultra-short-term power prediction of distributed photovoltaic system

Concave clouds will cause miscalculation by the power prediction model based on cloud ieatures for distributed photovoltaic （PV） plant. The algorithm for decomposing concave cloud into convex images is proposed. Adopting minimum polygonal approximation （MPP） to demonstrate the contour of concave cloud, cloud features are described and the subdivision lines of convex decomposition for the concave clouds are determined by the centroid point scattering model and centroid angle func- tion, which realizes the convex decomposition of concave cloud. The result of MATLAB simulation indicates that the proposed algorithm can accurately detect cloud contour comers and recognize the concave points. The proposed decomposition algorithm has advantages of less time complexity and decomposition part numbers compared to traditional algorithms. So the established model can make the convex decomposition of complex concave clouds completely and quickly, which is available for the existing prediction algorithm for the ultra-short-term power output of distributed PV system based on the cloud features.

Experimental study of free abrasive wire sawing by using multi-strands wire

Grains in the slurry can be brought into cutting zone by steel wire with a certain speed to achieve the purpose of removing the workpiece material in the free abrasive wire sawing machining. Because its own of multi- strands characteristics, we use it to replace the steel wire to do slicing experiment. In this paper, multi-strands wire is made by seven metal wires and has many grooves on its surface. Compared with steel wire, it can carry more grains into cutting zone which is conducive to improving the slicing efficiency. We do some comparative slic- ing experimcnts by applying multi-strands wire （~b0.25 mm） and steel wire （~b0.25 mm） to cut optical glass （K9）. The results show that slicing efficiency and the surface roughness of the workpiece sliced by using multi-strands wire are better than that by using steel wire. but the kerf width of the former is wider than that of the latter in the same experimental conditions.

Bionic mechanical design and 3D printing of novel porous Ti6Al4V implants for biomedical applications

In maxillofacial surgery, there is a significant need for the design and fabrication of porous scaffolds with customizable bionic structures and mechanical properties suitable for bone tissue engineering. In this paper, we characterize the porous Ti6Al4V implant, which is one of the most promising and attractive biomedical applications due to the similarity of its modulus to human bones. We describe the mechanical properties of this implant, which we suggest is capable of providing important biological functions for bone tissue regeneration. We characterize a novel bionic design and fabrication process for porous implants. A design concept of “reducing dimensions and designing layer by layer” was used to construct layered slice and rod-connected mesh structure (LSRCMS) implants. Porous LSRCMS implants with different parameters and porosities were fabricated by selective laser melting (SLM). Printed samples were evaluated by microstructure characterization, specific mechanical properties were analyzed by mechanical tests, and finite element analysis was used to digitally calculate the stress characteristics of the LSRCMS under loading forces. Our results show that the samples fabricated by SLM had good structure printing quality with reasonable pore sizes. The porosity, pore size, and strut thickness of manufactured samples ranged from (60.95± 0.27)% to (81.23±0.32)%,(480±28) to (685±31)μm, and (263±28) to (265±28)μm, respectively. The compression results show that the Young’s modulus and the yield strength ranged from (2.23±0.03) to (6.36±0.06) GPa and (21.36±0.42) to (122.85±3.85) MPa, respectively. We also show that the Young’s modulus and yield strength of the LSRCMS samples can be predicted by the Gibson-Ashby model. Further, we prove the structural stability of our novel design by finite element analysis. Our results illustrate that our novel SLM-fabricated porous Ti6Al4V scaffolds based on an LSRCMS are a promising material for bone implants, and are potentially applicable to the field of bone defect repair.

Recognition and localization system of the robot for harvesting Hangzhou White Chrysanthemums

To realize the robotic harvesting of Hangzhou White Chrysanthemums,the quick recognition and 3D vision localization system for target Chrysanthemums was investigated in this study.The system was comprised of three main stages.Firstly,an end-effector and a simple freedom manipulator with three degrees were designed to meet the quality requirements of harvesting Hangzhou White Chrysanthemums.Secondly,a segmentation based on HSV color space was performed.A fast Fuzzy C-means(FCM)algorithm based on S component was proposed to extract the target image from irrelevant background.Thirdly,binocular stereo vision was used to acquire the target spatial information.According to the shape of Hangzhou White Chrysanthemums,the centroids of stamens were selected as feature points to match in the right and left images.The experimental results showed that the proposed method was able to recognize Hangzhou White Chrysanthemums with the accuracy of 85%.When the distance between target and baseline was 150-450 mm,the errors between the calculated and measured distance were less than 14 mm,which could meet the requirements of the localization accuracy of the harvesting robot.

A finite element analysis of the stress distribution to the mandible from impact forces with various orientations of third molars

Objective： To investigate the stress distribution to the mandible, with and without impacted third molars（IM3 s） at various orientations, resulting from a 2000-Newton impact force either from the anterior midline or from the body of the mandible. Materials and methods： A 3 D mandibular virtual model from a healthy dentate patient was created and the mechanical properties of the mandible were categorized to 9 levels based on the Hounsfield unit measured from computed tomography（CT） images. Von Mises stress distributions to the mandibular angle and condylar areas from static impact forces（Load I-front blow and Load II left blow） were evaluated using finite element analysis（FEA）. Six groups with IM3 were included： full horizontal bony, full vertical bony, full 450 mesioangular bony, partial horizontal bony, partial vertical, and partial 450 mesioangular bony impaction, and a baseline group with no third molars. Results： Von Mises stresses in the condyle and angle areas were higher for partially than for fully impacted third molars under both loading conditions, with partial horizontal IM3 showing the highest fracture risk. Stresses were higher on the contralateral than on the ipsilateral side. Under Load II, the angle area had the highest stress for various orientations of IM3 s. The condylar region had the highest stress when IM3 s were absent. Conclusions： High-impact forces are more likely to cause condylar rather than angular fracture when IM3 s are missing. The risk of mandibular fracture is higher for partially than fully impacted third molars, with the angulation of impaction having little effect on facture risk.

Systematic study on the mechanical and electric behaviors of the nonbuckling interconnect design of stretchable electronics

Recently, we developed a nonbuckling interconnect design that provides an effective approach to simultaneously achieving high elastic stretchability, easiness for encapsulation, and high electric performance for stretchable electronics. This paper aims to systematically study its mechanical and electric behaviors, including comparisons of the nonbuckling and buckling interconnect designs on stretchability, effects of the thickness on electric performance, and modeling and experimental investigations on the finite deformation mechanics. It is found that the results on stretchability depend on the layouts. Long straight segments and small arc radii for nonbuckling interconnects yield an enhancement of stretchability, which is much better than that of buckling designs. On the other hand, shorter straight segments or thicker interconnects are better to lower the resistances of interconnects.Therefore, optimization of the designs needs to balance the requirements of both the mechanical and electric performances. The finite deformation of interconnects during stretching is analyzed. The established analytic model is well validated by both the finite element modeling and experimental investigations. This work is key for providing the design guidelines for nonbucklingbased stretchable electronics.

A biomechanical case study on the optimal orthodontic force on the maxillary canine tooth based on finite element analysis

Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament（PDL） as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g（100 g=0.98 N） were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 k Pa（capillary pressure） and 12.8 k Pa（80% of human systolic blood pressure） was considered to be optimal, whereas an absolute strain exceeding 0.24%（80% of peak strain during canine maximal moving velocity） was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces（40–44 g for distal-direction and 28–32 g for labial-direction） were smaller than the translation forces（130–137 g for distal-direction and 110–124 g for labial-direction）. In addition, the optimal forces for labialdirection motion（110–124 g for translation and 28–32 g for tipping） were smaller than those for distal-direction motion（130–137 g for translation and 40–44 g for tipping）. Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.

Segmentation algorithm for Hangzhou white chrysanthemums based on least squares support vector machine

In order to realize the visual positioning for Hangzhou white chrysanthemums harvesting robot in natural environment,a color image segmentation method for Hangzhou white chrysanthemum based on least squares support vector machine(LS-SVM)was proposed.Firstly,bilateral filter was used to filter the RGB channels image respectively to eliminate noise.Then the pixel-level color feature and texture feature of the image,which was used as input of LS-SVM model(classifier)and SVM model(classifier),were extracted via RGB value of image and gray level co-occurrence matrix.Finally,the color image was segmented with the trained LS-SVM model(classifier)and SVM model(classifier)separately.The experimental results showed that the trained LS-SVM model and SVM model could effectively segment the images of the Hangzhou white chrysanthemums from complicated background taken under three illumination conditions such as front-lighting,back-lighting and overshadow,with the accuracy of above 90%.When segmenting an image,the SVM algorithm required 1.3 s,while the LS-SVM algorithm proposed in this paper just needed 0.7 s,which was better than the SVM algorithm obviously.The picking experiment was carried out and the results showed that the implementation of the proposed segmentation algorithm on the picking robot could achieve 81%picking success rate.

Fruit harvesting continuum manipulator inspired by elephant trunk

By combining the investigation of the biomechanics and behavior of elephant trunk in the performance of a wide range of dexterous manipulations,a novel approach in the design and kinematics modeling of a fruit harvesting continuum manipulator was proposed.By comparing the structure of two different species of elephant trunk,a new continuum structure which matched the key features of elephant trunk was designed.Based on analysis of the underlying elephant trunk’s grasping mode,a novel kinematics model was proposed.Contrast to traditional robot kinematics which focused on end effector’s position and posture,the proposed continuum manipulator kinematics focus on the center of manipulator’s position and posture,which is more effective when trunk robot realizing grasp and establishes the foundation for its application.Finally,three typical grasping experiments were implemented.The experiment results showed that the manipulator could conduct wrap/pinch manipulations effectively for both small objects and bigger ones.

Method for detecting 2D grapevine winter pruning location based on thinning algorithm and Lightweight Convolutional Neural Network

In viticulture,there is an increasing demand for automatic winter grapevine pruning devices,for which detection of pruning location in vineyard images is a necessary task,susceptible to being automated through the use of computer vision methods.In this study,a novel 2D grapevine winter pruning location detection method was proposed for automatic winter pruning with a Y-shaped cultivation system.The method can be divided into the following four steps.First,the vineyard image was segmented by the threshold two times Red minus Green minus Blue(2R−G−B)channel and S channel;Second,extract the grapevine skeleton by Improved Enhanced Parallel Thinning Algorithm(IEPTA);Third,find the structure of each grapevine by judging the angle and distance relationship between branches;Fourth,obtain the bounding boxes from these grapevines,then pre-trained MobileNetV3_small×0.75 was utilized to classify each bounding box and finally find the pruning location.According to the detection experiment result,the method of this study achieved a precision of 98.8%and a recall of 92.3%for bud detection,an accuracy of 83.4%for pruning location detection,and a total time of 0.423 s.Therefore,the results indicated that the proposed 2D pruning location detection method had decent robustness as well as high precision that could guide automatic devices to winter prune efficiently.