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Zhou Z.,South China Agricultural University | Zhou Z.,Collaborative Innovation Center for Grain and Oil Crops in South China | Yan M.,South China Agricultural University | Chen S.,South China Agricultural University | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Automation of images registration and stitching is one of the most important key technologies to the wide use of the low-altitude remote sensing by Micro-UAVs (unmanned aerial vehicles) in rice growing. In order to overcome the limitations, i.e. the thresholds need to be artificially determined for the traditional Harris corner detection algorithm, this paper proposed a self-adaptive algorithm for Harris corner detection, which was used in image registration and stitching of the rice low-altitude remote sensing. The algorithm was improved based on the traditional Harris corner detection algorithm by using a self-adaptive threshold determination method, which calculated from the standard deviation of image pixel gray-scale value. And then the characteristics of image were described by corners, and the images were registered by using the Euclidean distance among descriptors. In order to verify the effectiveness of the algorithm and optimize the relevant parameters, a verification test was conducted based on low-altitude remote sensing images, which were gained by a multispectral camera mounted on a multi-rotor unmanned helicopter during rice tillering stage. Four indices, the repetition rate (a measure of the stability of corner detection), the recognition rate (a measure of corner recognizable description operator), the registration rate (a measure of the accuracy of image registration and stitching) and running time of algorithm (a measure of computing speed of the algorithm), were proposed to evaluate the results of registration and stitching. Sixty images were randomly divided into 3 groups for verification test. Test results showed that the average registration rate reached 98.95%, and also the average repetition rate reached 96%, which indicated that the proposed algorithm had high accuracy. The repetition rate and the difference in image registration rates among the groups were not significant (at 0.05 significance level), which indicated that the proposed algorithm was stable and reliable. And the recognition rate among the groups was significant, and it indicated that the proposed algorithm had higher distinguishability to the remote sensing images, which was conducive to the precision of the automation of images registration and stitching. Threshold value of the proposed algorithm, which is the standard deviation of the image pixel gray values after standardization, here is set to 1 and 2 for optimization test. Test results showed that the registration rate was not significant, namely there was no significant difference (at 0.05 significance level) when the threshold value was equal to 1 or 2. However, comparing the average running time of the proposed algorithm, it showed that the running time when the threshold value was 1, is 2.5 times that when the threshold value was 2. Based on comprehensive consideration of the registration rate, the running time and the efficiency, the threshold value of 2 can be set as the optimum parameter of the proposed algorithm. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Xing H.,South China Agricultural University | Zang Y.,South China Agricultural University | Zang Y.,Collaborative Innovation Center for Grain and Oil Crops in South China | Cao X.,South China Agricultural University | And 4 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Compared to rice mechanistic metering device, rice pneumatic metering device has advantages of low number of sowing seeds, high precision of seed metering and low seed-injuring rate. Because the precision of seed metering is difficult to control and the performance of hill sowing is poor, rice pneumatic metering device is difficult to be widely used in field direct-seeding. The control of the precision of seed metering is the key to design metering device. Analysis of the process of dropping seeds helps improve the precision of seed metering and the performance of hill sowing, providing a basis for the design of metering device. Seeds were taken away from sowing disc under positive pressure for blowing seeds. The dropping trajectories and hill sowing performance of rice seeds were studied in this article. A high-speed photography technology was introduced to investigate how the dropping trajectories of rice seeds varied and what influenced the dropping trajectories, on which the equations of the rice's movement were formed. The theory equations were optimized through the average horizontal displacements of actual dropping trajectories and the optimization equations under the different conditions were obtained. The diameter of hill sowing was also measured. As seeds were taken away from sowing disc under positive pressure, seeds gained an initial velocity, which was called Vz and was vertical to the sowing disc. Because seeds moved along with sowing disc rotating before seeds were blown away, the seeds gained the other initial velocity, which was called Vr and was parallel to the disc. Seeds also gained acceleration of gravity under the gravity. In the above factors, the dropping trajectories were spatial parabolic, which was more complicated than the plane parabolic trajectories of rice mechanistic metering device. In order to investigate and count the dropping trajectories of rice pneumatic metering device, a coordinate system was established. Indic hybrid Peizataifeng was taken as research subject in this article, of which water content and average length, width and thickness were 20.5% and 8.97, 2.34 and 1.90 mm respectively. There were 2 dropping trajectories, the trajectory of frontal dropping seed and the trajectory of profile dropping seed. The dropping trajectories and diameters of hill sowing were analyzed by multi-factor experiment under different rotation rates and positive pressures for blowing seeds. The experimental results showed horizontal displacements of the trajectory of frontal dropping seed increased with the increasing of rotation rate, which were less than 5 mm. The frontal trajectory had good stability under positive pressure of 0.1 kPa, and horizontal displacements were stabilized within the range of 45-65 mm. Under positive pressure of 0.2 kPa, the frontal trajectory was unevenly distributed with bad stability. Trajectory of profile dropping seed was little affected by rotation rate. Horizontal displacements of trajectory of profile dropping seed increased with the increasing of positive pressure for blowing seeds. The profile trajectories were stabilized within the range of 0-15 mm under positive pressure of 0.1 kPa. Under positive pressure of 0.2 kPa, the profile trajectories were unevenly distributed. Diameters of the hill less than 50 mm were deemed as qualified, while diameters more than 50 mm were deemed as substandard. The probability of substandard diameter increased with the increased rotation rate and positive pressure. Performance of hill sowing was best with the rotating speed of 30 r/min and positive pressure of 0.1 kPa, of which qualified rate was 96.9%. The optimum height of dropping seeds was 10 cm. This article analyzed dropping trajectories in theory and got the optimal conditions of performance of hill sowing, providing the basis for optimal conditions of hill sowing and the reference for the design of seeding tubes of rice pneumatic metering device. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Zang Y.,South China Agricultural University | Zang Y.,Collaborative Innovation Center for Grain and Oil Crops in South China | Xing H.,South China Agricultural University | Wang Z.,South China Agricultural University | And 3 more authors.
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2015

The seeds often suck on the sucking hole when the sucking plate rotates. The area between the sucked seeds and sucking hole is smaller than the area between the normal sucked seeds and sucking hole, which leaded to a shortage of suction. As the suction is less than a sum of external forces, sucked seeds will be separated from the seed sucking hole and do a parabolic movement with a particular velocity. This phenomenon is called “early dropping seeds”. To avoid this and increase the stability of seed sowing and the performance of hill formation of rice pneumatic metering device, a shield device was designed. Shield device was fixed on seed chamber shell through bolted connections. It was able to stop the seeds flying to the second half of sucking process after the parabolic movement drove by “early dropping seeds”. Indic hybrid peizataifeng was taken as research subjects, of which the water content was 21.1%. “Early dropping seeds” phenomenon was observed by means of high-speed photography technology, which enabled moving process of sucked seed to be clearly photographed. The probability of “early dropping seeds” was studied by using multi-factor experiment under different negative pressures for seeds sucked, rotation rates and shield device. Precision of seed metering was also counted, as shield devices were installed on the metering device. The experimental results showed the “early dropping seeds” phenomenon and precision of seed metering were improved with a shield device. The optimized condition was that the sucking plate rotation speeds of 25~40 r/min and the negative pressure for seeds sucked of 1.6 kPa. The probability of 1~3 seeds was 93%~97%. In the experiment, a shield device on the metering device could control the “early dropping seeds”, and improve the stability of seed sowing and the performance of hill formation. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved. Source


Li Z.,Hunan Agricultural University | Tang C.,Hunan Agricultural University | Tang C.,Hunan Provincial Engineering Technology Research Center for Modern Agricultural Equipment | Li M.,Hunan Agricultural University | And 11 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Auxiliary pollination is the most critical process during hybrid rice seed production. The uniform and sufficient pollination has significant meaning for improving seed setting rate and operating efficiency. In the process of pneumatic auxiliary pollination for hybrid rice seed production, the pollens move with airflow, the airflow fields of multiple parallel nozzles of jet pipe overlay, and the jet cone angle and nozzle air pressure are the most important characters in airflow field. Increasing jet cone angle can expand the coverage of airflow field and reduce blind area of pollination effect, and eventually improve the uniformity of auxiliary pollination. Increasing nozzle air pressure can improve the airflow speed and increase airflow penetration, which significantly influences the uniformity and sufficiency of pollen distribution and determines the propagation distance of pollens. In order to study the relationships among jet cone angle, nozzle air pressure and pipe parameters, and find the ideal combination of pipe parameters for pneumatic auxiliary pollination, the paper firstly analyzed the superposition principle of the airflow field formed by parallel multiple nozzles, and obtained the formulae of jet cone angle and nozzle air pressure. Chromatic smoke was generated by the smoke grenade and sprayed through the nozzle, and pictures of airflow field were taken by camera. Jet pipe diameter, pipe thickness, nozzle diameter of pipe were selected as 3 factors, jet cone angle and nozzle air pressure were selected as 2 evaluation indices, and the three-factor and five-level of single factor and multi-factor orthogonal tests were done. In experiment, initial airflow velocity of nozzle and vertical distance between airflow junction point and center line of jet pipe were measured, and 5 photos and 5 measurements were taken for each test; the range analysis and matrix analysis were carried out, the influence laws of various factors on airflow field characteristics and their weights were obtained, as well as the relationships between airflow field characteristics and jet pipe parameters. Results showed that the influences of nozzle diameter on jet cone angle and nozzle air pressure were very obvious. As the nozzle diameter of pipe increased, the nozzle air pressure and jet cone angle increased accordingly. The influence order of the 3 factors from high to low was nozzle diameter, pipe diameter and pipe thickness. The optimal combination of the factors to jet pipe was the pipe diameter of 63 mm, the pipe thickness of 5 mm, and the nozzle diameter of 12 mm. At this time, the jet cone angle was 13.38°, and the nozzle air pressure was 31.6 Pa. The optimal factors were verified by test. Pollination effects were evaluated by the selected 3 evaluation indices on effective distribution area ratio, average distribution density, nonuniformity of pollen distribution. The confirmatory test showed that the pollen distribution was more uniform, the effective distribution area ratio of pollen was obviously improved, the nonuniformity of pollen distribution (variance) dropped to 1.33, the degree of uneven distribution was significantly reduced, and the distribution images of pollen showed unimodal normal distribution. The pipe parameters can satisfy the requirements of auxiliary pollination, which provides important reference to the design of jet pipe for pneumatic auxiliary pollination in hybrid rice seed production. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Qiu J.,Hunan Agricultural University | Qiu J.,Hunan Provincial Engineering Technology Research Center for Modern Agricultural Equipment | Qiu J.,Collaborative Innovation Center for Grain and Oil Crops in South China | Wu M.,Hunan Agricultural University | And 7 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Due to long stubble remained in farmland after harvesting as well as hardened and impervious soil in southern farmland of China, the tillage and land preparation parts of multifunctional rape-planting machine tend to wind grass and obstruct with mud, which impairs the working performance of ridging equipment and reduces the percentage of rapeseed seedling germination. In order to solve these problems, a rapeseed planting method is proposed, which combines the straw mulching cultivation with the direct seeding. The method is used to collect and cut the rice stubbles, and then the chopped rice stubbles are evenly covered on the inter-row spaces without involving the tillage apparatus. A multifunctional rape-planting device is mounted to a rice combine-harvester by replacing screening device, using the original harvester header to collect the rice stubbles and replacing the threshing cylinder to chop and scatter the rice stubbles. In this paper, an air-assisted chopping mechanism was designed, in which the moving knives and the transplanting blades were coaxially installed. The performance of the air-assisted chopping mechanism was evaluated by simulating the chopping operation of "stalk-standing" and "crop residue" in farmland through a bench test driven by an electric motor. A quadratic orthogonal rotating experiment was designed by Design-Expert software. Based on the variance analysis and regression fitting, a multiple regression equation was obtained, showing the effects of the rotating speed of feeding press rolls, the rotating speed of rotation shaft of moving knives and the gaps between moving knife and stationary knife on the qualified rate of chopped stalk length and the power attenuation. It was shown that the rotating speed of rotation shaft of moving knives had the most influential effect, followed by the gaps between moving knife and stationary knife, and the rotating speed of feeding press rolls had the least effect on the qualified rate of chopped stalk length and the power attenuation. The response surface method was applied to optimize the operation conditions. The optimum factors for "stalk-standing" and "crop residue" chopping operation were as follows: The rotating speeds of feeding press rolls were 399.2 and 401.64 r/min, the rotating speeds of rotation shaft of moving knives were 968.12 and 977.23 r/min, and the gaps between moving knife and stationary knife were 0.52 and 0.49 mm, respectively. Under the optimal condition, the corresponding qualified rates of chopped stalk length for "stalk-standing" and "crop residue" were 95.89% and 97.09%, as well as the power attenuations were 3.04 and 2.6 kW, respectively. The differences between the experimental and the software analytical value of the qualified rate of chopped stalk length for "stalk-standing" and "crop residue" were both 0.11% and those of power attenuation were 0.05 and 0.08 kW, respectively, which indicated that the software analytical value was in great agreement with the experiment value. Based on the theoretical analysis, the higher qualified rate of chopped stalk length could be achieved under the faster rotating speed of rotation shaft of moving knives and the smaller gaps between moving knife and stationary knife. Taking into consideration the existing form of rice straw in farmland, the rotating speed of feeding press roll was designed to be 401.64 r/min, the rotating speed of rotation shaft of moving knife 977.23 r/min, and the gap between moving knife and stationary knife 0.49 mm. It can provide technical support for the design of rapeseed planter with the combination of straw-mulching cultivation and direct seeding. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source

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