陈玲, 王浩云, 肖海鸿, 马仕航, 杨瑶, 徐焕良. 利用FL-DGCNN模型估测绿萝叶片外部表型参数[J]. 农业工程学报, 2021, 37(13): 172-179. DOI: 10.11975/j.issn.1002-6819.2021.13.020
    引用本文: 陈玲, 王浩云, 肖海鸿, 马仕航, 杨瑶, 徐焕良. 利用FL-DGCNN模型估测绿萝叶片外部表型参数[J]. 农业工程学报, 2021, 37(13): 172-179. DOI: 10.11975/j.issn.1002-6819.2021.13.020
    Chen Ling, Wang Haoyun, Xiao Haihong, Ma Shihang, Yang Yao, Xu Huanliang. Estimation of external phenotypic parameters of Bunting leaves using FL-DGCNN model[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(13): 172-179. DOI: 10.11975/j.issn.1002-6819.2021.13.020
    Citation: Chen Ling, Wang Haoyun, Xiao Haihong, Ma Shihang, Yang Yao, Xu Huanliang. Estimation of external phenotypic parameters of Bunting leaves using FL-DGCNN model[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(13): 172-179. DOI: 10.11975/j.issn.1002-6819.2021.13.020

    利用FL-DGCNN模型估测绿萝叶片外部表型参数

    Estimation of external phenotypic parameters of Bunting leaves using FL-DGCNN model

    • 摘要: 为了能够低成本、自动化批量获取植物叶片的外部表型参数,同时解决自然生长条件下的植物叶片存在遮挡而无法获取完整的外部表型数据的问题,该研究以绿萝叶片为研究对象,基于曲面参数方程建立叶片几何模型,提出一种基于特征分层的动态图(Dynamic Graph CNN based on Feature Layering,FL-DGCNN)和堆栈编码器模型的绿萝叶片外部表型参数估测算法。通过多层组合的编码-解码器模型对残缺点云进行形状补全,将不同尺度下的点云通过多层感知机提取分组点不同层的特征向量融合后获取特征信息,以决定系数和均方根误差评价模型结果。结果表明:多层组合的编码模型对残缺点云补全的鲁棒性更高,特征分层的动态图模型估测结果的叶长、叶宽、叶面积的决定系数分别为0.92、0.93和0.94,叶长、叶宽的均方根误差分别为0.37、0.34 cm,叶面积的均方根误差为3.01cm2。该方法对叶类植物叶片的外部表型参数估测效果较好,具有实用性。

       

      Abstract: Plant leaves blocked under natural growth conditions cannot fully acquire the complete external phenotypic data. Therefore, this study aims to estimate these parameters in low-cost and automated batches using Dynamic Graph CNN with Feature Layering (FL-DGCNN). A stack encoder model was also used for Bunting (Epipremnum aureum) leaves. A camera was selected to shoot at a certain angle between two images. Further, motion recovery was utilized to reconstruct the three-dimensional model of the plant after feature points matching. Straight-through filtering and clustering segmentation were used to obtain a single chip Point cloud data. Specifically, the geometric model of the blade using surface parameters was discretized into a point cloud, but the point cloud was incomplete to a certain proportion to simulate the natural growth state. An auto-encoder model was modified into a deep-structured stack encoder under a multi-layer combination, and then to reduce the distance between the input point cloud and the actual point cloud. As such, the incomplete geometric model point cloud achieved shape completion after the training. The determination coefficients of leaf length, width, and area estimated by the stack encoder decreased less, as the percentage of incomplete point clouds increased, while those estimated by the auto-encoder decreased by multiples. The robustness of stack encoder completion was better in the leaf point cloud, compared with autoencoders under the same incompleteness. The shape was also similar to the original point cloud after completion within 40% of incompleteness. There were great variations in the shape of the blade when the blade was incomplete or more than 50%. A better performance was also achieved in the occluded blades. The completed point cloud was input into the FL-DGCNN deep learning network, and the feature maps were then extracted at different scales in the image pyramid, thereby enhancing semantic and geometric information. The farthest point sampling was used to extract from the original point cloud. The extracted features were connected to obtain a vector after feature layering and fusion, particularly for point clouds with contour features at different scales. The basic neural network module of edge convolution structure was adopted to better capture the local structure. The point cloud structure was represented by the directed graph, where the edge feature was obtained from the neighbor nodes. The local features of each group were superimposed on the shallow and deep network for the multiple perceptions in the original edge convolution structure, and then the leaf length, width, and area were estimated for the external phenotypic parameters of leaves. The highest accuracy was achieved to estimate the leaf width and area, followed by that of leaf length with a relatively small error. The determination coefficient and root mean square error were better than before, indicating a relatively lower error and stronger ability of feature extraction, compared with multiple networks. Additionally, a total of 200 leaves of Epipremnum aureum were collected in the experiment to verify the model, where the estimated values were linearly fitted to the measured. The determination coefficients and root mean square errors of leaf length, width, and area were 0.92 and 0.37 cm, 0.93 and 0.34 cm, 0.94, and 3.01 cm2, respectively. The experiment demonstrated that the model is highly effective to estimate the external phenotypic parameters of plant leaves.

       

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