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Chen M.,Nanjing Agricultural University | Shi Y.,Nanjing Agricultural University | Wang X.,Nanjing Agricultural University | Wang X.,Jiangsu Province Engineering Laboratory for Modern Facilities Agricultural Technology and Equipment | And 3 more authors.
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2015

In order to achieve real-time variable dressing in wheat jointing stage, spectral data processing strategy and expected fertilizer quantity calculation model were studied. The variable rate fertilization expert decision system was developed based on crop canopy real-time spectral information (Normalized differential vegetation index, NDVI). Combined with NDVI information, actual traveling speed of dressing machine and feedback amount of fertilizer, the dual-channel independently controlled the speed and the opening of institutions to real-time adjust the amount of fertilization. The comparative experiments of ratio fertilization and traditional fertilization for winter wheat with different base fertilizer rates in Jiangsu Huanghai Farm were carried out. In order to improve the efficiency of expert decision system, the optimal data processing strategy was analyzed. Results showed that the best data processing frequency of the expert decision system was 1 Hz. Using more fertilizers was beneficial to promote the winter wheat individual growth, but it was not conducive to the structure of the group. The variation coefficient of NDVI in control area was the largest, as high as 11.32%. Variable fertilizer could effectively reduce the variation coefficient of NDVI, decreased by up to 3.57% and the average of 1.46%. The fertilization precision can reach above 90%. Variable rate fertilizer applied more nitrogen (28 kg/hm2) than quantitative fertilization. Variable rate fertilization would help to improve wheat population structure and reduce the yield differences. Therefore, the expert decision system was favorable, and could achieve precise fertilization in the precision agriculture. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved. Source


Zhang Y.,Nanjing Agricultural University | Wang X.,Nanjing Agricultural University | Sun G.,Jiangsu Province Engineering Laboratory for Modern Facilities Agricultural Technology and Equipment | Li Y.,Jiangsu Province Engineering Laboratory for Modern Facilities Agricultural Technology and Equipment | Sun X.,Nanjing Agricultural University
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2014

A laser vision-based measurement system consisting of a camera and a laser sheet that scanned the plant vertically was developed to measure the stem diameters and leaf lengths automatically. The 3D point cloud was obtained with the laser sheet scanning the plant vertically, while the camera videoed the process of laser scanning. Laser line centers were extracted by improved centroid method. The 3D point cloud structure of the sample plant was obtained. For leaf length measurement, iteration method for point clouds was used to extract the axis of the leaf point cloud set. The centroid of the subset of points was calculated and taken as the next axis point. Leaf length was calculated by curve fitting on these axis points. In order to increase the accuracy of curve fitting, bi-directional starting point selection was used. To evaluate the method in a sample of 8 water spinaches, the lengths of leaves and diameters of stems were measured manually and plotted versus their automatically measured counterparts. The accuracy of leaf lengths and stem diameters are 95.39% and 94.55% respectively. The tests proved that laser vision-based method could be used on plant geometries measurement in greenhouses costly and portably. Source


Chen M.,Nanjing Agricultural University | Lu W.,Nanjing Agricultural University | Wang X.,Nanjing Agricultural University | Wang X.,Jiangsu Province Engineering Laboratory for Modern Facilities Agricultural Technology and Equipment | And 4 more authors.
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2016

In order to achieve real-time variable dressing at winter wheat jointing stage, the fertilizer quantity real-time adjustment algorithm based on fuzzy PID control was studied. To achieve the optimal control of fertilizer, the rotation speed and opening of fertilizer apparatus were real-timely adjusted online. With ITAE criterion as the fitness function, the initial values of PID controller parameters were determined based on particle swarm optimization algorithm (PSO). The algorithm combined the traditional PID control with fuzzy algorithm by acquiring the real-time parameters, such as the crop canopy real-time spectral information (Normalized differential vegetation index, NDVI), rotation speed and opening. The parameters of PID were set online and the rotation speed and opening of fertilizer apparatus were real-timely adjusted to achieve optimal control of variable dressing. Results showed that the fuzzy PID had good dynamic stability and tracking performance. A fluctuation existed on fertilizing amount during the process of fertilization. But the variation coefficient of fertilizing amount was small with the maximum value of 3.22% and average value of 2.09%, which met the requirements of field variable fertilization. In the laboratory tests, the maximum overshoot of rotation speed was about 11.96%, the maximum overshoot of opening did not exceed 14.94%, and the system precision could reach above 87%. In the field experiments, the maximum overshoot of rotation speed was about 12.80%, the maximum overshoot of opening did not exceed 14.79%, and the system precision could reach above 86%. The system had good stability, accuracy and rapidity and it was able to satisfy the agriculture technical requirements. © 2016, Chinese Society of Agricultural Machinery. All right reserved. Source


Wang X.,Nanjing Agricultural University | Wang X.,Jiangsu Province Engineering Laboratory for Modern Facilities Agricultural Technology and Equipment | Chen M.,Nanjing Agricultural University | Sun G.,Nanjing Agricultural University | And 3 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

This variable rate fertilizer applicator based on crop canopy real-time spectral information (normalized differential vegetation index, NDVI) was designed to applicate real-time variable fertilization for the winter wheat. By realtime spectral information of crop canopy via six spectrum sensors, and speed of the tractor via velocity-measuring system, the expert system of the applicator could adjust the rate of the fertilizer according to the feedback fertilizer flow under fuzzy PID (proportion integration differentiation) controller. The experimental results indicated that the fuzzy PID had the good tracking performance and dynamic stability. The system precision could reach above 90%, and the measuring absolute error of the traveling speed was within 0.25 km/h. © 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Chen M.,Nanjing Agricultural University | Shi Y.,Nanjing Agricultural University | Wang X.,Nanjing Agricultural University | Wang X.,Jiangsu Province Engineering Laboratory for Modern Facilities Agricultural Technology and Equipment | And 4 more authors.
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2015

This variable rate fertilizer applicator based on crop canopy real-time spectral information (normalized differential vegetation index) was designed to realize real-time variable fertilization in the field. By accessing the real-time normalized differential vegetation index via six spectrum sensors, and the speed of the tractor via velocity-measuring system, the expert system of applicator could ascertain the rate of fertilizer based on the fertilization algorithm. The expert system of applicator adjusted fertilizing to attain precision fertilization according to the feedback fertilizer flow. The system design, working principle and experiments of the applicator were explained. The experimental results indicated that the inherent spatial variability of wheat growth within a field was considerable, and wheat canopy normalized differential vegetation index could resolve this difference. The fertilization precision could reach above 90%, and variable rate fertilizer applied more nitrogen (28 kg/hm2) than quantitative fertilization. Therefore, the control system of the rate fertilizer applicator was favorable, and the applicator could achieve precise fertilization in the precision agriculture. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved. Source

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