Research On 3D Modeling Of Rosa Roxburghii Fruit Based On Point Cloud And Biomechanical Properties Of Fruit

The rosa roxburghii fruit is rich in a variety of active nutrients such as vitamin C,amino acids,superoxide dismutase,and has huge nutritional value and medical value.The rosa roxburghii industry has become one of the characteristic agricultural industries in Guizhou Province.At present,the process of picking rosa roxburghii fruit and producing preserved fruit heavily relies on manual operation,which has the problems of low production efficiency and high production cost;To design equipment related to mechanized picking,processing,and transportation of rosa roxburghii,it is necessary to master the biomechanical characteristics of rosa roxburghii fruit.Therefore,this paper establishes the geometric model of the rosa roxburghii fruit based on the point cloud algorithm,and conducts an in-depth study on the biomechanical characteristics of the rosa roxburghii fruit by using the mechanical test and finite element simulation method.It can provide a theoretical basis for the design and improvement of mechanical equipment related to rosa roxburghii fruit and the mechanized fruit picking.The main research contents and conclusions of this paper are as follows:（1）The physical parameters of rosa roxburghii fruit,such as density,weight,three-dimensional size,sphericity index and fruit firmness,were determined by physical tests.Mechanical parameters such as elastic modulus and Poisson’s ratio of the fruit were measured by compressive mechanical test.（2）A point cloud denoising and segmentation method that combines statistical filtering and radius filtering algorithms was proposed,and the results of other denoising algorithms were compared to analyze the effectiveness of this method in removing noise and fruit spikes;The simplification effect of five point cloud sampling methods was compared,and the difference of simplification effect between different methods was analyzed;Four different point cloud reconstruction algorithms were used to reconstruct the fruit geometric model,the model reconstruction effects of different algorithms were analyzed,and the accuracy of the reconstructed fruit model was evaluated.The results show that the algorithm proposed in this paper has the best denoising effect,and the spikes and noise in the point cloud data of rosa roxburghii fruit can be effectively removed;Using 3D voxel down-sampling for point cloud reduction,the feature point cloud was obviously retained,the standard deviation is the smallest,and it has the best reduction effect;The screened Poisson reconstruction algorithm has the highest volume accuracy of 1.05%,and the reconstruction model feature retention is also better than the other three algorithms.（3）The finite element simulation software ANSYS Workbench was used to simulate the separation mechanical properties of fruit and stalk,and obtained the variation law of stress and strain and the separation strain energy in the process of fruit-stalk separation;The finite element simulation results were verified by the force and displacement curves obtained from the fruit-stalk separation mechanical test.The results show that the force-displacement curve of the separation finite element simulation basically coincides with the force-displacement curve of the separation mechanics test,and the average relative error of the two curves was12.35%,the relative error of the strain energy between the test and the simulation was 6.85%.The mechanical behavior during separation is approximated as a linear elastic change.（4）The finite element simulation software ANSYS Workbench was used to simulate the mechanical properties of rosa roxburghii fruit under compressive load,and the influence of load size and compression direction on the compressive mechanical properties of rosa roxburghii fruit was explored,and the variation law of stress and strain and the compressive strain energy of the fruit were analyzed;The finite element simulation results were verified by obtaining force and displacement curves from compression mechanical tests.The results show that the force and displacement curves of the finite element simulation and the compression mechanics test show nonlinear changes,and the compression resistance in the horizontal direction of the fruit is greater than that in the vertical direction;The correlation coefficient between the force-displacement curve obtained by the finite element simulation and the curve obtained by the mechanical test reached 0.988（vertical direction）and 0.996（horizontal direction）respectively under the two compression methods,and the relative errors of the experimental and simulated compressive strain energy were 9.20%（vertical direction）and 2.09%（horizontal direction）,respectively.