Vol. 84, No. 4
Abstract
Biosensing Method of Growth Diagnosis in Forcing Culture of Strawberry
── Available Airflow Velocity for Monitoring of Young Leaves ──
[Keywords: strawberry, leaf, air velocity, load, drag coefficient, petiole, damage]
To add airflow to strawberry plants to expose young leaves, we investigated the physical characteristics of leaves associated with the air velocity that damages the leaves. First, the drag coefficient of the leaf blade gradually decreased with respect to the air velocity. Subsequently, as an indicator of petiole damage due to load, the bending stress of the petiole was as strong as 44 MPa in the third leaf and 32 MPa in the other leaves. Young's modulus was 89 MPa for new leaves and higher for older leaves, indicating higher strength against buckling. In addition, damage at the plant base was more likely to occur when petioles were narrower.
Development of Pear Cultivation Management Technology Using Information and Communications Technology for the Next Generation of Farmers (Part2)
── Development of a Water Sprout Estimation Algorithm ──
[Keywords: point cloud data, water sprout, voxelization, DBSCAN, RANSAC]
We developed “water sprout extraction” and “length estimation” methods based on 3D point cloud data. The tree extraction algorithm comprised four steps : voxelization, water sprout extraction, removal of leaf points and estimation of the length of water sprouts using Density Based Spatial Clustering of Applications with Noise (DBSCAN) and Random Sample Consensus (RANSAC). The measured point cloud data sets were used for the evaluation of the algorithm with 0.56 a as training data and 3.14 a as validation data. As a result, obtained using the proposed method demonstrated that the extraction accuracy of water sprouts was 97.3％, and the coefficient of determination (R2) between the measured and predicted data with regard to the total length of water sprout length was 0.99.
Relationship between Changes in Potato Epidermis Physical Properties due to Soil Moisture and Bruise Incidence.
[Keywords: potato, tuber skin, puncture force, bruise, moisturizing]
This study aimed to develop a technique to decrease potato bruising. The physical properties of the tuber epidermis are considered to be associated with bruise resistance. The effect of bruising on moistened tubers was investigated in volcanic ash soil. Initially, the bruising test was performed using a potato harvester. The number of bruised tubers was lower in irrigation plots that were adjusted to a soil water content of 31％ or higher. Subsequently, in a laboratory bruising test, bruising was observed under all conditions, except when the test impact strength was weak and when a variety with high bruising resistance was used. We conclude that high soil water content affected the physical properties of the tuber epidermis, reducing potato bruising.
Autonomous Navigation System in a Vineyard by Vision Sensors
[Keywords: autonomous navigation, vineyard, electric vehicle robot, vision sensor, image processing, neural network, ArUco marker, heading error, lateral error]
Autonomous navigation by vision sensors was realized in a vineyard. We used a neural network to detect vanishing points in images from two vision sensors on the front and back of an electric vehicle robot. The vehicle was steered based on the heading and lateral errors calculated geometrically. Turning was performed by detecting markers on vine hedges with a vision sensor and an IMU. When the vehicle was driven manually to evaluate the accuracy of estimation, the heading RMSE was 1.3°, and the lateral RMSE was 0.12 m. When the vehicle traveled autonomously between vine rows, the lateral RMSE was 0.06 m. When the vehicle completed turning autonomously, the heading error was 1.8° and the lateral error was 0.04 m.
Development of High-precision Heading Estimation Technology Using the Quasi-Zenith Satellite System Michibiki
[Keywords: heading estimation, Quasi-zenith satellite system, Centimeter level augmentation service, electronic compass, spin turn]