Abstract:In order to accommodate the rapid development of hose reel irrigators in China, enhance the overall awareness of key techniques for the hose reel irrigator and find the gap with the rest of the world, the development history in the world and the main types of hose reel irrigators were reviewed. Key influential factors and research status of the hose reel irrigator were described. The matching relationship among the uniformity of the traveling speed of the sprinkler cart, the traveling speed of the sprinkler cart, the rotating fan angle of the spray nozzle, and the rotating speed of the spray nozzle were concluded. And it was summarized that the running stability of the sprinkler cart, the stability of the nozzle inlet pressure, the attitude and topography of the nozzle were critical factors affecting the irrigation uniformity. Energy conversion efficiency and optimized matching of each component were the key factors affecting the energy consumption of the whole machine. From the scientific and technical point of view, the research progress and existing problems of key technologies such as drive power, transmission system, speed control, energy conversion of the key link and the sprayer cart stability were analyzed, the application basis and key techniques for the development of the hose reel irrigator in China were presented. The development trend of multifunctional and intelligentized hose reel irrigator was expected, and the idea of intelligent irrigation of hose reel irrigator based on Internet of things was proposed.

Abstract:Aiming to the control of a tilt tri-rotor vertical take-off and landing (VTOL) aircraft, and the flight control system based on STM32 microprocessor was designed. Ten axes inertial navigation module was used to collect the real time position data and satellite navigation data of the carrier, and the attitude and location information was calculated by using fusion algorithm based on quaternion. Cascade PID control system was adopted, aiming at the real-time and high-accuracy feature of attitude control of UAV. Aiming at the unstable problem in the tilt tri-rotor VTOL aircraft, a PID controller with incomplete derivative was proposed. The controller adding a first-order inertial link in the derivative can reduce the negative effect of external interference on the system. Finally, the verify flight was carried out to test the pitch, yaw and roll motions of the aircraft. The results demonstrated that cascade PID controller with incomplete derivative can control the attitude of the tilt tri-rotor VTOL aircraft quickly, stably and accurately in helicopter mode, which had good robustness. In addition, cascade PID controller with incomplete derivative can reduce the difficulty of parameter tuning. The control system had a good performance with the setting of roll angle (inner ring Kp was 8.371, Kd was 3.015 and outer ring Kp was 5.1, Kd was 1.15), pitch angle (inner ring Kp was 3.137, Kd was 1.6 and outer ring Kp was 3.43, Ki was 0.003, Kd was 3.97), yaw angle (Kp was 9.30 and Ki was 0.11). And the controller designed could meet the performance requirements of the control system. It provided guidance for the follow-up study on flight control of the tilt tri-rotor VTOL aircraft. 

Abstract:An ultra wide band indoor positioning platform was developed to improve the positioning accuracy of agricultural vehicle in a greenhouse environment. Firstly, based on Ubisense radio frequency chip, a positioning platform tag and a base station were designed. The position data were obtained by location ranging method named time difference of arrival (TDOA). Then, in order to get accurate positioning information and meet the needs of precise positioning for agricultural vehicle in greenhouse, K-means clustering and segmentation processing method were applied for the optimization calculation of static and dynamic positioning data respectively. In this procedure, the measurement errors, which were caused by propagation characteristics of pulse signal and the single ranging method, were decreased. Finally, static and dynamic positioning tests were conducted under the greenhouse environment respectively. The experimental results showed that the optimized static positioning accuracy was 0.0634m. Meanwhile, the probability of the dynamic positioning accuracy, which was no more than 8cm gotten by virtue of the dynamic precision positioning algorithm can be increased by 3.7 times than that of the original Ubisense positioning platform. Hence, the platform built can meet the practical application requirements. The research provided a reference for the positioning, navigation and intelligent refinement operation of agricultural vehicle in the greenhouse.

Abstract:In order to improve the performance of autonomous navigation system of direct seeding machine in paddy field and other harsh environments, an optimal control method was proposed. It can adaptively adjust PD control parameters based on fuzzy logic. According to the kinematic model of chain system, the state space model was established. Then, according to the optimal control theory, the PD controller was designed. The range of parameters of Kp was from 0.8 to 2.1 and Kd was from 1.0 to 3.5, which were determined by the field experiment. Finally, the fuzzy adaptive optimal control method was put forward. Simulation result showed that the fuzzy adaptive optimal control method can improve the stability and rapidity compared with the PD controller. The experiment results showed that the mean absolute lateral deviation of the method was less than 0.021m on the cement pavement. And the mean absolute lateral deviation of the method in paddy field was less than 0.040m. The method can effectively improve the stability and rapidity of the autonomous navigation control system compared with PD controller and pure pursuit controller.

Abstract:In view of the problems of low accuracy and poor real-time in the research of visual simultaneous localization and mapping, a RGB-D vision SLAM algorithm for indoor mobile robots was proposed. Firstly, feature points of RGB image were extracted by using oriented fast and rotated brief (ORB) algorithm, and matching point pair set was obtained by the bidirectional K-nearest neighbor (KNN) feature matching method based on fast library for approximate nearest neighbors (FLANN). The improved random sampling consistency algorithm (RE-RANSAC) was used to eliminate false matching points and estimate the 6D motion transformation model between two adjacent images, as the initial transformation model of GICP algorithm. The generalized iterative closest point algorithm (GICP) was used to obtain the optimized motion transformation model, and then the pose diagram was obtained. In order to improve the positioning accuracy, a random closed-loop detection link was introduced to reduce the cumulative error in the robot positioning process, and the pose diagram was optimized by using the general graph optimization (G2O) method to obtain the global optimal pose diagram and camera motion trajectory, and the global color dense point cloud map was finally generated. For the tested FR1 data sets, the minimum positioning error of the algorithm was 0.011m, the average positioning error was 0.0245m, and the average processing time of each frame was 0.032s, which can meet the requirement of rapid positioning and mapping of mobile robots.

Abstract:In order to identify and locate the maize rhizomes accurately, a maize rhizome detection network based on the migration learning method was established. The function of human eye recognition to identify and locate the rhizomes of the corn from a complex field environment was simulated, which achieved the function of crawler heat fog machine walking along the corn line. Field image of corn was collected by crawler self-propelled hot fogging machine, construction of a precise identification and location model of corn rhizome based on convolutional neural network, and the “DOG Pyramid” algorithm was used to extract maize rhizome as the target from the images, which constituted the training sample database. Through training network, the single maize rhizome was precisely identified firstly, and then were accurately identified and located in the environment of corn crop. The path tracking was obtained by east square fitting algorithm based on the identified maize rhizome location, and the sliding mode track tracking algorithm was used to control the double differential drive motor of the caterpillar chassis to realize the path tracking. The test result showed that the corn root recognition method can identify and locate the maize rhizomes more accurately, the correct rate of identification and location of corn rhizome reached 91.4%, but the traditional image processing method can only reach 67.3%. It can be seen that the method of identifying maize rhizomes proposed had better positioning accuracy, which can better plan the corn field path accurately. The research results provided the key technical support for the crawler self-propelled hot fogging machine self walking along the intercropping of corn.

Abstract:Aiming to improve the picking ability of the harvesting robot, a bite-model end-effector for citrus was designed. The design requirements of the end-effector were obtained by first investigation of the growth of citrus stem, the inclination of the stem and doing statistics was defined, and the shearing requirements of the stem extreme position was lastly analyzed. That the design of the bite-model end-effector can meet the design requirements by simulating the snake mouth structure which followed the snake’s biting action and the special structure of the snake’s mouth bones. Two design ideas were proposed by simplifying the structure of the snakehead skeleton. Based on this, the initial model of the two kinds of mechanism was designed respectively. After the preliminary kinematics analysis, the optimal scheme was determined and the initial model was optimized, and the three-dimensional model of the end-effector was determined. According to the three-dimensional model, the kinematics model of the end-effector was established, and the kinematics analysis and simulation were carried out to ensure the reasonable design of the mechanism. A bite-model end-effector prototype was manufactured, and then it was verified by the citrus harvesting robot developed by the research group in laboratory and outdoor environment. In laboratory environment, the experimental results showed that the cutting success rate was not less than 95% under the condition that the air pressure was 0.6MPa, the inclination of the stem was 0°, the stem diameter was no more than 4.0mm, and the overall cutting success rate for different stem inclinations was 97.5%. The total success rate of harvesting citrus in the outdoor environment was 87.5%.

Abstract:Semi-automatic grafting machine is widely used in variety of vegetables with a low equipment price. However, its production capacity is relatively low. In order to simplify the operation and improve the efficiency of grafting, a semi-automatic grafting machine for single person to graft rootstock and scion seedlings was designed. The design of the key components of the grafting machine included stock and scion seedlings clamping and rotation mechanism, a seedling holding anti-rotation mechanism and a cutting mechanism. The seedling holding anti-rotation device adopted a double ratchet reverse stop to realize a single motor driven two axles with reverse rotation, which was used to ensure the orderly mating process for the grafting seedlings. The optimized layout design for seedling putting position, clamping, cutting, and grafting position would be convenient for single-person to put rootstock and scion seedlings at the same time. The pumpkin seedlings and loofah seedlings were used for grafting test. The different groups test of single artificial seedling was carried out to analyze the graft success rate and grafting efficiency of the model. The grafting experiments on pumpkin and loofah seedlings showed that the success rate of grafting reached 89%, which was similar to that of artificial grafting. The grafting speed reached 846.3 strains/h, which was nearly 3.3 times of artificial grafting rate. It proved that the semi-automatic grafting machine design met the requirements of factory grafting operations.

Abstract:Separating carrot tassel from fruit by pulling can meet the requirement of tassel fruit separation better. In order to provide design parameters for pull type carrot tassel fruit separation device, and obtain the best separation effect, the influence of related parameters on the pull rod kinematics characteristics should be analyzed qualitatively. To analyze the influence of relevant parameters on the kinematic characteristics of pull rod accurately, the kinematics model of pulling device type tassel fruit separation should be established. To verify the correctness of the previous theoretical analysis, the pull type carrot tassel fruit separation test device was designed. Then a series of orthogonal tests were carried out to explore the factors that affecting the effect of tassel fruit separation. In the orthogonal testing, the pull rod speed, belt line speed and the angle between pull rod and conveyer belt were test factors. The comparison between the results of test and theoretical analysis showed that the pull rod speed had the biggest influence on carrot tassel fruit separation effect, and angle between pull rod and conveyer belt also had significant effects on carrot tassel fruit separation effect. At the same time, the best combination of parameters in carrot tassel fruit separating device was obtained as follows: pull rod speed was 200r/min, belt line speed was 1.2m/s, and angle between pull rod and conveyer belt was 40°. The results showed that the concordance rate in the tassel fruit separation was 97%, the success rate was 94%, and the injury rate was 7.7%.

Abstract:In order to improve the picking fruit quality of blueberry machine, a blueberry picking machine was designed based on grooved cam transmission. The key components of the prototype were designed, including the calculation and selection of drive components, distribution of reduction ratio of drive system, and the calculation of cam motion curve. The cam profile curve was derived by the inversion method, and the end execution device of the picking system was designed by using the angle dividing line method. A picking machine model was established in ADAMS. The simulation environment was set up to analyze the dynamics of the picker. The influence of the cam design parameters, the length of each member and the speed of driving element on the picking drive was studied. The blueberry picking test was conducted in the plantation. The extraction efficiency of the slot cam picking machine was 4.6kg/min, the unripe fruit shedding rate was 3.2%, the mature fruit recovery rate was 83%, and the fruit damage rate was 3.1%. The comparison analysis showed that the quality of the groove cam picker was superior to the traction picker, and the picking efficiency was 13 times of that of manual picking.

Abstract:In order to solve the problem of high impurity rate and loss rate caused by the residual grain codes and the high moisture content in the raw material of millet after the first stripping, a roll-twist cylinder screen type of millet cleaning device was designed. The device was mainly composed of spikelet roller rubbing device, cylinder screen device, cross flow fan and centrifugal fan, which realized the function of clearing millet code first and then cleaning it. The rotating speed and angle of centrifugal fan, speed of cross flow fan, rotational speed of cylinder screen as well as the rotational speed of spikelet roller rubbing device were selected as the test factors, the impurity rate and the loss rate were taken as the test indexes for the orthogonal test. Results of orthogonal test showed that the optimal combination of the cleaning device was the rotation speed of spikelet roller rubbing device as 250r/min, the angle of centrifugal fan as 3°, the speed of small cylinder screen as 60r/min, the speed of centrifugal fan as 700r/min, the speed of medium cylinder screen as 60r/min, the speed of large cylinder screen as 70r/min, and the speed of cross flow fan as 600r/min. The combination of the parameters was tested and the cleaning performance of the device was compared, under such conditions, the impurity content was 1.64%, the loss rate was 0.86%, the impurity rate and loss rate of this device were lower than those of traditional fan cylinder screen and fan vibrating screen cleaning device.

Abstract:Corn stalks are stout and non-perishable in Northeast China, which results in the low cutting-out rate and high working resistance torque of the no-tillage planter. To improve the cutting efficiency of corn stalks and stubbles, a dynamic bionic stubble cutting device was designed, which was based on both the multistep serrated mouthpart structure and the moving mode of different-direction isokinetic occlusion. The planetary gear mechanism and bionic cutting disc were designed through bionic-construction, mechanism design, theoretical analysis and parameter optimization;the intelligent driving system was designed by using Arduino system and intelligent control method, and thus the coupling bionic of motion mode and structure was realized. Moreover, the effect of structure and operating parameters, including the number of blades, radius of gyration and forward speed,on the cutting efficiency and working torque was studied via optimization test and regression analysis. The simulation tests results showed that the dynamic bionic stubble cutting device achieved the optimal working efficiency when the machine speed was 10km/h, the radius of gyration was 250mm, the number of bionic locust mouthpart blade in positive rotation cutting disc was 9, and the number of bionic locust mouthpart blade in reverse rotation cutting disc was 18. The comparative tests showed that for the dynamic bionic stubble cutting device, the cutting rate of corn stalks and stubbles were decreased with the increase of machine speed. The cutting-out rate was the highest with a value of 97.1% when the machine speed was 6km/h, while it was the lowest with a value of 92.9% when the machine speed was 10km/h. Compared with the passive notch disc and the driving notch disc, the cutting-out rate of the dynamic bionic stubble cutting device was increased by 22.6%~27.4% and 8.6%~13.5%, respectively. Besides, the cutting torque of dynamic bionic stubble cutting device was decreased with the increase of the machine speed. When the machine speed was 6km/h, the cutting torque was the largest with value of 60.5N·m. Whereas the cutting torque reached the minimum at the machine speed of 10km/h with value of 54.1N·m. The cutting torque of dynamic bionic stubble cutting device was reduced by 19.5%~21.8% compared with the driving notch disc. After the operation, the average surface roughness and the maximum wear scar depth were decreased by 14.5% and 15.9%, respectively, compared with that of the driving notch disc.

Abstract:To reduce the loss of maize and ensure certain cleanliness of maize after screening operations, the movement of maize mixture was analyzed in the airflow field, and the stepped screen body was designed based on shell screen. The stepped buffer zone was designed by analyzing the theory of maize’s collision to temporarily retain grains in the stepper and reduce the effect on carrying maize from maize mixture and avoid maize accumulation in the ladder. However, maize debris directly went across the ladder. To make the screen amplitude as 19mm, the computational fluid dynamics and discrete element method (CFD-DEM) were coupled in the quadratic orthogonal rotational-combinational simulation tests. The factors were the inlet velocity and direction angle of airflow, height of the ladder and vibration frequency of screen. The indexes were the loss and cleanliness of maize grains collected. The test data were analyzed by the response surface method and the regression mathematical models were multi-objective optimized by using Design-Expert software. The results showed that the loss and cleanliness of maize were 1.69% and 98.8%, respectively, when the inlet velocity of airflow was 16m/s, the direction angle of airflow was 25°, the height of the ladder was 8.36mm, and the vibration frequency of screen was 4.45Hz. The performances met the requirements of corn harvest. The performance tests were done in the laboratory to verify the accuracy of the simulation results. The rate of maize loss was 2.12% and the cleanliness of maize grains collected was 99.16% after screening. Compared with the flat shell screen, the loss of maize grains across the stepped shell screen was reduced by 1.14 percentage points and the cleanliness of maize grains was increased by 1.98 percentage points. The cleaning performance of screen was improved.

Abstract:The mounting height of the wing is one of the key structural parameters of the winged subsoiler, which greatly affects disturbance behavior of subsoiling. The disturbance behavior and resistance under different heights of the wing (55mm, 75mm, 95mm, 115mm and 135mm) were compared and analyzed by the comprehensive use of EDEM and digitized soil-bin test. The results showed that with the increase of mounting height of the wing (MHW), the disturbance area of hardpan layer after subsoiling was increased first and then decreased, and it reached the maximum when MHW was 75mm;moreover, the horizontal tillage resistance was decreased gradually with the increase of MHW, and the horizontal tillage resistance of the share and arc section in the hardpan layer was the main source of horizontal tillage resistance of subsoiler (more than 90%), which was also decreased gradually with the increase of MHW;MHW directly affected the displacement of different directions of soil at different depths during tillage. When MHW was 75mm, the maximum displacement in the working direction of soil of each layer in the longitudinal center of the subsoiler was relatively small, the maximum displacement in the vertical direction of the soil in hardpan layer was relatively large, and the maximum displacement in the vertical direction of the top soil and the soil of tillage layer was relatively small;and a proper mounting height of the wing was of great importance to disturbance effectiveness, and the discrete element simulation could accurately simulate the disturbance behavior of subsoiling. The average errors of five mounting heights of the wing of soil bulkiness, soil disturbance coefficient, soil fragmentation parameter and longitudinal accumulation angle of surface soil between simulation and experiment were 11.69%, 11.54%, 14.20% and 9.64%, respectively.

Abstract:Extensive fertilization method is one of the main reasons for the low utilization rate of fertilizer in China. Compared with the strip-type fertilization, the hole-type fertilization method can effectively improve the efficiency of fertilizer utilization, but currently there is a lack of mature hole-type fertilization equipment. In view of the above problems, a kind of notched precision hole-fertilizing apparatus was designed, which was used for granular fertilizer. The main structure and working parameters of the device were determined through theoretical analysis, and the analyzing of the shape of fertilizer cavity was focused on. The discrete element method (EDEM) was used to simulate and analyze the filling performance and fertilizer group movements under different conditions. The simulated results showed that the fertilizer cavity shape, operation speed and the fertilizing amount had significant influence on the fertilizing amount coefficient of variation between holes. With the increase of the operating speed and the reduction of fertilizing amount, the variation coefficient of fertilizing amount between holes was increased. Circular-type fertilizer cavity had the best stability in four kinds of shapes. The operating speed and fertilizer cavity shape had significant influence on the fertilizer disturbance coefficient. The time of fertilizer plate passing through the box and the form and size of disturbance on the fertilizer were main reasons affecting the stability of fertilization. Taking the qualified rate of fertilizing amount and coefficient of variation between holes as indicators, four types of fertilizer plates were arranged as verification test of at working speed of 7km/h and fertilizing amount of 300kg/hm2. The results showed that the performance of the circular-type fertilizer cavity was the best with fertilizing amount qualified rate of 94% and the variation coefficient between holes was 6.5%, which satisfied the requirements of hole-fertilizing.

Abstract:The current domestic integration of a variable rate fertilization system and a fertilizer feeder fault alarming system has a low level, and there is less research on dynamic response of a motor driving fertilization system. A variable rate fertilizing control system supporting seeding and fertilizing monitoring was designed based on a motor driving method. The system mainly included a touch screen, a central controller and a data collector. The central controller was designed based on an MCU, which monitored both the vehicle speed by using a GPS module and the fertilization motor speed in real time. The touch screen was used to set or read the operation parameters by communicating with the controller. The data collector monitored the working status of the multiple seed metering or fertilizer feeder. An experimental platform was built to evaluate the monitoring accuracy. When the sowing axle speed was 12.5~125r/min and the monitoring sensitivity was set to 3s, the accuracy of the fault alarming system was 100%. A test was conducted to find the system response time with different fertilization rates, the test results showed that the maximum system response time was 0.75s when fertilization rate was from 0g/min to 11500g/min.The prototype machine test result showed that when the fertilization rate was from 75kg/hm2 to 450kg/hm2 with an increment of 75kg/hm2, the average system response time was 1.08s. When the fertilization rates were 450kg/hm2, 600kg/hm2 and 750kg/hm2 with different vehicle speeds, the average accuracies of fertilizer ejecting were 95.92%, 95.24% and 98.26%, and the variances were 3.01%, 1.39% and 1.36%, respectively. The field test results showed that when the fertilization rates were set to 450kg/hm2, 600kg/hm2 and 750kg/hm2, the average accuracies of fertilizer ejecting was 94.69% with variance of 2.23%, and the accuracy of the fault alarm for multiple feeders was 100%.

Abstract:As we all know, China is one of the famous country for swine. with the development of pig breeding industry, it is important to improve feed-discharging uniformity and sufficient flow in unit time of feeders. A new type of feeder for nursery was designed based on characteristics of mass flow. The principal factors which affected the discharging performance of the feeder were determined through comprehensive analysis. In order to optimize the structural and operating parameters of the designed nursery pig feeder, virtual orthogonal test was carried out by discrete element method software with rotational speed, discharge opening diameter, angle of conical wall of the hopper and filling coefficient as experimental factors and coefficient of variation and flow as evaluation indexes. Based on experimental data, a mathematical model was built by using the Design-Expert 8.0.10 software, and the optimum parameters were obtained. The simulation experiment results showed when rotational speed was 45r/min, discharge opening diameter was 110mm, angle of conical wall of the hopper was 65°, and filling coefficient was 65%, coefficient of variation was 3.96% and flow was 165.93g/s. Then the feeder was designed according to above optimized parameters, and the experiment was done. The results showed that the flow pattern of pelleted feed was mass flow;the relative error of coefficient of variation and the flow was 4.14% and 3.92%, respectively. The results were basically consistent with the simulation optimization, and the designed feeder can meet the feeding needs of nursery pig, which can ensure the quality and efficiency of the operation and provide support for the research and development of pig feeders.

Abstract:During the variable rate irrigation operation of large-sized lateral moving irrigation system based on pulse width modulation (PWM) technique, it is quite difficult to solve the flow rate of each sprinkler from the designed prescriptions of management zones because the spraying areas of sprinklers will overlap with each other. At the beginning, the overlapped water distribution in lateral direction, and the two-dimensional contour plot of overlapped water distribution were gotten based on the feature of single sprinkler water distribution of Nelson R3000. Then four sprinklers were determined to control a management zone and the water distribution rate of spraying area was solved. And on this basis a weighted average method and a genetic algorithm (GA) method based on genetic algorithm were proposed to perform sprinkler flow rate distribution according to the prescription. It was found that the solution accuracy can reach 5% when the change between adjacent prescriptions was less than 33% of the maximum prescription by analyzing the irrigation error in management zone. In order to make up for the reduction of irrigation uniformity caused by GA method, a combined method of weighted average method and GA method was put forward. Related examples had showed that the irrigation error caused by the saltation of adjacent prescriptions can be reduced by the combined method effectively and the irrigation uniformity of management zones where prescriptions changed little can also be guaranteed at the same time. By changing the mapping relationship between sprinkler flow rate and actual irrigation volume in each management zone, this method can be extended to more than four sprinklers controlling a management zone.

Abstract:The high mixing uniformity for pesticides and carrier water was an important requirement in direct nozzle injection system (DNIS) used to alleviate the waste of pesticides and protect environment from being contaminated by pesticides residues. To evaluate the mixing effects of pesticides mixers, new analysis methods for mixing uniformity were presented and the swirling jet mixer was used to carry out the experiments of in-line mixing for the water and non-water soluble pesticides under variable working conditions. Quantitative descriptions for mixing uniformity of mixture inside the mixer were achieved based on calculating the coefficient of variation(α) and areaweighted uniformity index (γ) for the regions of interest（ROI） in the mixture images of the mixer. The accuracy of the analysis methods was verified by comparing the images of artificial premixed mixture and the images of unmixed mixture, as well as the images of mixture in standing state, and it proved that the indexes could be taken as criteria to judge whether the mixers could meet the requirements for in-line mixing or not. The experiments result under variable working conditions revealed that the mixing uniformity was increased with higher carrier flow rate and the flow rate of 2400mL/min gave rise to the best uniformity while the uniformity was declined heavily with lower flow rate under the conditions of settled mixing ratios. When the carrier flow rate was remained unchanged, higher mixing ratios would contribute to higher uniformity. Therefore, it was necessary to provide high flow rate to ensure good mixing uniformity when it came to lower mixing ratios. Normally, The criteria of α=0.2239 and γ=80.39% were set to be the thresholds for uniform mixtures and non-uniform mixtures as there were no non-scatted pesticides remaining in the mixer when the indexes were better than them. Moreover, the filtering results showed that the flow rate which was higher than 2000mL/min could meet the uniformity requirements at different mixing ratios while the flow rate of 800mL/min could not meet the uniformity requirements at any mixing ratios, and the mixing uniformity at part of these ratios could be satisfied when the flow rates were between 800mL/min and 2000mL/min.

Abstract:In order to improve the phenomenon of increased flow separation caused by the influence of gas viscosity on the small multi-blade centrifugal fan, the influence of gas viscous torque on volute wall distribution was studied based on the traditional volute design theory, and the momentum correction was used to modify the design. In addition, in order to truly reflect the distribution of the flow field in the fan, the viscous stress was added to the diffusion term of standard k-εcalculation model to reduce the maximum calculation error to 3%. Comparing and analyzing the fan’s numerical simulation and experimental results before and after modification, the modified k-εmodel was used to calculate, and it was found that the vortex intensity in the modified fan was reduced, and the flow separation near the volute outlet at the volute outlet was improved. The experimental results showed that the static pressure at the outlet of the modified fan was increased by about 25Pa, and the maximum full-pressure efficiency was improved by about 10% compared with the prototype. At the same time, due to the expansion of the volute expansion, flow separation can be suppressed, the vortex intensity in the vicinity of the volute tongue and its influence area were reduced, and the noise of the multi-blade centrifugal fan was effectively reduced by 2.5dB.

Abstract:As a basic unit to coordinate the relationship between human activities and natural resources, county is an important area to carry out afforestation project and forest landscape resources management. The case study site was Yixian County of Hebei Province, which is well known for its landscape diversity, more forestation and high forest coverage. With the support of geographic information system (GIS) and principal component analysis (PCA), and based on the date of forest resources inventory and land use, the forest landscape patterns and its hierarchical characteristics were studied at county scale. The results showed that woodland landscape accounted for more than 58% of the total area, poplar, Pinus tabulaeformis, oak trees, apricot and other economic forest were the dominant forest landscape;splitting index (SPLIT), Shannon’s diversity index (SHDI) and patch density (PD) exhibited a strong response to the changes in three levels of organizational hierarchy. With the refinement of the organization level, the degree of landscape fragmentation was increased, the area and quantity of the patch were increased gradually. The higher the organization level in the landscape level and patch type level was, the more obvious the trend of forest landscape contagion and cohesion was, in contrast, the more fine the organization level was, the more obvious the forest landscape aggregation and clumpiness was, and the more prominent the edge effect of the landscape patch was. Moreover, it proved that many factors affected forest landscape patterns and coupled with each other, such as terrain, land use type and living environment. From mountain to plain area, with the enhancement of the human activities and forest landscape, the forest landscape fragmentation, complexity of patch shape and its spatial difference were increased gradually. Therefore, the health management of forest landscape resources should be focused on the key indicators such as landscape diversity, spatial segmentation, core patch area and number, and so on

Abstract:Based on comprehensive consideration of the comprehensive quality of cultivated land, autocorrelation and landscape patterns, the demarcation of permanent basic farmland is of great significance to regional food security and ecological security. Taking Chongren County as an example, GIS platform and GeoDa software were used to evaluate the comprehensive quality of cultivated land through the construction of comprehensive quality evaluation system of cultivated land, and spatial autocorrelation analysis was carried out according to the results of comprehensive quality assessment, and then according to the results of autocorrelation analysis and the ecological security of cultivated land landscape and correspondence between patterns to describe permanent basic farmland. The soil physical and chemical properties, farming conditions were comprehensively considered into the research, and arable land conditions in the study area, and a permanent basic farmland delineation method was proposed based on the comprehensive quality of farmland, comprehensive quality cluster relationship and cultivated land landscape structure, and delineated permanent basic farmland in Chongren County as 305.94km2, the ploughed land was more in line with the requirements of the permanent basic farmland, which would contribute to the longterm management and protection of basic farmland, and also provide a reference for the comprehensive quality evaluation of farmland and the demarcation of basic farmland.

Abstract:One of the prominent problems in hyperspectral remote sensing is the existing of mixed pixel widely. How to effectively interpret mixed pixels is an important problem of hyperspectral remote sensing applications. It is not only a problem of mixed pixels effects identification and classification precision of objects, but also a major barrier for the development of remote sensing technology. Mixed pixel decomposition, which is the most effective method to solve the mixed pixel problem, can break through the limitation of spatial resolution. Aiming to the shortcoming of the traditional algorithm of mixed pixel decomposition, an improved method of mixed pixels was put forward, which can take account of the spatial correlation of spectral information and spectral information, and multi-core parallel processing method to raise its efficiency. The endmembers were automatically extracted, and the abundance charts corresponding to each endmember were obtained at the same time. The performance of the proposed algorithm was verified by using actual hyperspectral image. The experimental results on simulated and real hyperspectral image demonstrated that the proposed algorithm can overcome the shortcomings of traditional method and obtain more accurate endmembers and corresponding abundance, which can provide a strong support for urban object classification.

Abstract:Vegetation is the most important ecosystem in the earth, which plays an important regulatory role in global climate change. Research on the temporal and spatial dynamic changes of vegetation has important scientific and practical value. Based on the normalized difference vegetation index (NDVI) of Landsat satellite remote sensing imagery extracted in 2007, 2012 and 2016 and the forest inventory data of Sanming City, the spatio-temporal changes of NDVI of Minjiang River upstream area in the last 10 years and the influencing factors were studied. The results showed that the NDVI values of the study area in 2007, 2012 and 2016 were increased gradually, and their values were 0.72, 0.75 and 0.79, respectively, which indicated that the coverage of vegetation was high, and the overall ecological quality was good. The lower NDVI values were located in the urban area, the concentration points of the township residents and near the road network. The NDVI values of different vegetation types were in a descending trend as broadleaf forest, shrub forest, Masson pine forest, bamboo forest, Chinese fir forest, miscellaneous wood forest, eucalyptus forest, other wooded land, economic forest, eucalyptus forest and non-forest land. NDVI index value was gradually increased with the increase of forest age, canopy closure and slope, while it was decreased with the increase of grade of the site quality. According to variation of changing dynamics of NDVI index with age of different types of vegetation, and the vegetation was divided into the following three types: type of steadily rising, such as broad-leaved forest and Pinus massoniana forest;type of rising fast at early stage and slow at late stage, such as eucalyptus forest;type of rising first and then fall, such as Chinese fir forest and other woodland. The NDVI value of Pinus massoniana forest was increased with the increase of slope, while the NDVI value of other forest vegetation types was risen first and then decreased with the increase of slope, and reached the highest value at the slope of 30°~ 40°. The NDVI index values of different vegetation types had different responses to canopy closure.

Abstract:To provide the basis for the methods of vegetation height inversion by using single-baseline PolInSAR SAR data and explore a more effective inversion method, the European Space Agency (ESA) Toolbox PolSARPro was used to simulate L-band (L=23cm) PolInSAR SAR data with an average vegetation height of 18m. The DEM difference, RVoG, SINC, Hybrid, and Hybrid method were studied based on coherent optimization. The vegetation height ranged from 3m to 30m was analyzed with 1104 sample points in the middle region of the image. Giving a 3D image, range profile image with azimuth of 48 and statistical image of vegetation height and topographic phase were used to compare the performance of five methods. Compared with the real value of 18m, the descending order of vegetation height means was SINC, Hybrid, improved Hybrid, RVoG and DEM difference method. The difference between the improved Hybrid inversion method and the real value was the smallest as 0.12m, smaller than Hybrid of 0.31m. RMSE of the improved Hybrid, Hybrid, SINC, RVoG and DEM difference was 1.06m, 1.48m,3.49m, 7.51m and 8.04m, respectively. The vegetation height of the improved Hybrid method had the smallest difference and RMSE. The estimated topographic phase average value of the improved Hybrid, RVoG/Hybrid and DEM difference method was -0.018rad, 0.011rad and 0.1rad;RMSE was 0.045rad, 0.054rad and 0.15rad;and mean value of absolute value was 0.03rad, 0.04rad, and 0.1rad, respectively. The topographic phase of the improved Hybrid method was approximately the closest to the simulated and had the smallest RMSE and the mean of absolute value. Improved Hybrid inversion method produced the best result among the five methods, combining the merits of Hybrid with the coherent optimization, with the smallest difference between real value and RMSE of vegetation height and topographic phase. The Hybrid method was improved based on the coherent optimization and the accuracy of vegetation height was analyzed with the ground phase estimation results to compare the five methods.

Abstract:Photosynthesis plays a vital role in crop growth, dry mater accumulation and yield formation. How to monitor it quickly and widely is still a problem so far. Taking the unmanned aerial vehicle (UAV) as the remote sensing platform, and a multispectral camera with six bands was mounted. To explore the feasibility of retrieving crop canopy photosynthetic parameters by using remote sensing technology, the cotton in budding period were studied. The camera was used to capture the image of cotton canopy at different times in one day (09:00, 11:00, 13:00, 15:00 and 17:00)，of which the reflectance information was extracted. The parameters of cotton photosynthetic (net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci) and transpiration rate (Tr)) were measured at the moment when the UAV was landed. Through the correlation analysis of the four photosynthetic parameters and the six-band reflectance, the retrieving model of different photosynthetic parameters at different times was established by univariate linear regression, principal component regression (PCR), ridge regression (RR) and partial leastsquares regression (PLSR), respectively. The results showed that the best retrieving models of net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular carbon dioxide concentration (Ci) were the univariate linear model based on the reflectance of the blue light band at 13:00, the univariate linear model based on the reflectance of the red light band at 15:00, the ridge regression model at 15:00 and the univariate linear model based on the red light band at 15:00，respectively. The decision coefficients（R2） of the models were more than 0.5, and the relative errors（RE） were less than 9%. The research result can provide a certain reference for monitoring the photosynthesis of crops in a large scale.

Abstract:The extraction method of cotton coverage was studied based on the difference of vegetation and non-vegetation pixels of RGB images from hand-held camera and unmanned aerial vehicle (UAV) remote sensing in different color spaces. Under different lighting conditions, totally 29 high-resolution (0.4mm) RGB images of cotton in seedling and bud stage were obtained by hand-held digital camera. The recognition abilities of cotton in Lab (a), RGB (2G-R-B) and HIS (H) color spaces were compared and analyzed. Two threshold classification threshold getting methods, dynamic threshold and fixed threshold were used to extract cotton coverage. The dynamic thresholds were determined by the intersection of the Gaussian distributions of vegetation and non-vegetation pixels. The fixed thresholds were set as the mean values of dynamic thresholds in the three color spaces, respectively. The results showed that vegetation and nonvegetation pixels obeyed Gaussian distribution in a, 2G-R-B, and H color spaces, which could be fitted by using nonlinear least-squares algorithm. The distribution range of dynamic classification thresholds was relatively concentrated, and their mean values of -3.78, 0.06 and 0.13 could be set as fixed classification thresholds. Compared with 2G-R-B and H, the a color space had the best ability to identify green vegetation and was more suitable for extracting cotton vegetation coverage. Compared with dynamic threshold, the extraction accuracy based on fixed threshold was better and the average extraction error was 0.0094. It can also accurately extract fractional vegetation cover (FVC) from UAV images captured under different light conditions (sunny and cloudy) with different soil moistures. After preliminary tests and analysis, it was believed that based on the differences of vegetation and non-vegetation pixels in Lab (a) color space, combining with a fixed classification threshold of -3.78,cotton coverage in seedling and bud stage could be accurately extracted under different light conditions.

Abstract:With the rapid development of remote sensing platform of low altitude unmanned aerial vehicle (UAV), the dynamic, fast and inexpensive features, the UAV remote sensing platform has more research in various fields, especially in the precision agriculture irrigation technology. The unmanned aerial vehicle thermal infrared low altitude remote sensing technology can quickly monitor the canopy temperature information of the crop, which can further use the canopy temperature information to diagnose the water stress condition of the crop. However, the processing of high resolution thermal infrared image of UAV is the key to the diagnosis of crop moisture, eliminating the soil background of UAV thermal infrared image is an effective way to improve the accuracy of crop water diagnosis. However, it is also a difficult problem in thermal infrared image processing. Different water treatments were carried out, including I1 (50% of field holding water), I2 (65% of field holding water), I3 (80% of field holding water) and I4 (control group 95%~100% of field holding water), and each water treatment set three repeat tests, a total of 12 plots, each plot was 4m×5m）. Flower boll cotton was taken as study object at 09:00, 13:00 and 17:00 of day, respectively, and UAV high resolution thermal infrared images were obtained. Firstly, the two-valued Ostu algorithm and the Canny edge detection algorithm were used to deal with the thermal infrared image, and achieve the elimination of soil background, then, the two-valued Ostu algorithm and Canny edge detection algorithm contained soil background were used to calculate the crop water stress index, finally, the relationship models between three kinds of crop water stress index (CWSI) and cotton leaf stomatal conductance at different times was established. The researchresults showed that the application of Canny edge detection algorithm can effectively eliminate the soil background in thermal infrared image, and there was a single peak distribution of the temperature histogram after removing the soil background. Among the crop water stress index obtained from three kinds of treatment methods, the CWSI of Canny edge detection algorithm was the minimal, the CWSI of two-valued Ostu algorithm was higher, and the CWSI with soil background was the largest. The determination coefficient between CWSI and cotton leaf stomatal conductance by using Canny edge detection algorithm to remove the soil background was up to 0.84, and that by using two-valued Ostu algorithm resulted the second, and that got by containing soil background was the worst. The research result can provide a reference method for monitoring water condition of the plant by UAV thermal infrared technology.

Abstract:In the field of hyperspectral detection on heavy metal pollution levels in agricultural soils, the accuracy and stability of hyperspectral inversion model for soil cadmium were seriously affected by the high dimensional and high redundancy characteristics in visible/NIR spectra. In order to solve the above problems, Spearman’s rank correlation analysis-based genetic algorithm by using random forest (SGA-RF) was proposed to select the characteristic wavelength from hyperspectral data. On the first-layer of feature selection stage, Spearman correlation analysis-based feature selection method was applied to remove redundancy between all spectra features and retain the characteristic wavelength which was the most relevant to the cadmium content. On the second-layer of feature selection stage, a new fitness function based on random forest was proposed, which perfectly combined the strong global search ability of genetic algorithm and the high inversion ability of random forest. With the proposed fitness function to evaluate the viability of individuals, the distinguishing ability between similar individuals was improved and a subset of optimal spectra feature set with minimum redundancy and maximum differentiation were obtained. In order to verify the validity of the proposed algorithm, totally 124 representative soil samples collected from the Dagu River Basin were chosen as samples. The optimal feature subset which contained 37 sensitive wavelengths was chosen and used to build soil available cadmium content inversion model, and its performance was compared with that of current feature selection methods. Results indicated that the minimum numbers of wavelength features was selected and meanwhile the prediction performance had lower predictive root mean square error of 0.0601, higher correlation coefficient of 0.9502 and residual predictive deviation of 2.03. As an important step for the quantitative inversion of cadmium concentration by using visible/NIR spectra, the research could provide some theoretical basis for monitoring soil heavy metal pollution.

Abstract:The moving window partial least squares (mwPLS) has higher prediction accuracy in the wavelength selection of near infrared spectroscopy, but the runtime of mwPLS is very long on single core serial algorithm. In order to reduce running time for wavelength selection, the task scheduling strategies on multi core were investigated. Taking interval partial least squares (iPLS) as example on the premise of not changing the prediction accuracy of the serial algorithm, the sequential distribution algorithm (SDA), equal space allocation algorithm (ESAA) and sorting allocation algorithm (SAA) were presented to study the effect of task scheduling strategy on the performance of parallel algorithm. The SAA had the best load balance and the highest parallel efficiency among the three task scheduling strategies. Then, based on the 16 cores cloud computing platform, the SAA was applied to the parallel wavelength selection algorithm of synergy interval partial least squares (siPLS), backward interval partial least squares (biPLS) and mwPLS. Comparing with single core serial algorithm, two cores parallel wavelength selection of biPLS and mwPLS with SAA reduced the runtime from 9.22h and 55.51h to 4.98h and 29.03h, and totally 45.99% and 47.70% runtime of biPLS and mwPLS were saved, respectively. The experimental results showed that when considering the parallel efficiency and computational cost condition, the two cores parallel algorithm for the four spectral region selection algorithms had the highest parallel efficiency and cost performance among the 1~16 core parallel algorithm.

Abstract:To quantitatively analyze the relationship between plant canopy structure and light distribution and photosynthesis, simulate real time photosynthetic rate of plant canopy in actual environments, and prove a plant canopy scale photosynthetic productivity calculation method for crop yield estimation, a 3D virtual plant canopy photosynthesis simulation model was constructed based on L-system. The model was divided into three contents. The first submodel was the 3D virtual canopy based on L-iterative grammar system and 3D graphic rendering technology. The second sub-model was that the photosynthetically active radiation (PAR) transformation in the virtual canopy was simulated by using forward ray tracing and sky visibility algorithm. The third sub-model was that the real-time PAR intensity at the top of a virtual canopy based on parameters such as the sun’s geometric parameters, atmospheric influence parameters and geographic location. After the photosynthetic environmental factors were directly or through interpolated way to input to the sub-models, by using the single leaf photosynthesis model and related respiration models, the net photosynthesis rate within the canopy and the accumulation of plant biomass accumulation during the model simulation cycle can be calculated. The simulation results of Chinese fir showed that the simulation of the PAR distribution based on the virtual canopy and the canopy photosynthesis rate calculation was an effective method for estimating photosynthetic productivity of plants.

Abstract:Aiming at solving the location restrict of sensor and complicated calibration problem of traditional point cloud fusion and the problem of missing edges in Kinect outdoor work, a method of plant point cloud information fusion based on SICK and Kinect was put forward. The 3D accurate reconstruction of data acquired by 2D laser sensor, SICK LMS151, needed the cooperation of real speed sensor. Due to the short time of obtaining per frame data of SICK and low speed, X-axis data for each column was set the same and the distance between two columns was calculated according to the real speed and sensor working frequency. Original color point clouds of plant were merged by color images and depth images obtained by Kinect. Firstly, preprocessing was carried out to extract point cloud of plant from original point clouds, in which lots of point clouds of background and noise were involved. In order to minimize the amount of points and keep enough characteristics, voxel grid was executed to down sample the plant point cloud. Secondly, normal calculation was executed on each point of plant point cloud to compute feather information by making use of depth features and peripheral point, fast point feature histograms (FPFH) was performed to enrich the feather information, which contained 33 dimensions element for each point. Thirdly, sample consensus-initial alignment (SAC-IA) algorithm, an initial registration algorithm, was applied to register SICK laser point cloud and Kinect point cloud to provide a better spatial mapping relationship for accurate registration. Fourthly, on the basis of initial registration, the iterative closest point (ICP) algorithm was used to refine the initial transform matrix inferred by initial registration. Finally, the information fusion was adopted by ANN algorithm to find corresponding point in Kinect color point cloud from SICK point cloud. However, Kinect point cloud would lose lots of edge information when working under the sun, resulting in the fusion faults. Overlimit compensation would work, when ANN cannot find the corresponding point or the distance between corresponding point and searching point was beyond threshold, the searching point would be considered as corresponding point and found the color information by corresponding function provided by Kinect SDK. Experiments showed that the fusion method can effectively and accurately realize the information fusion between different point clouds and suppress the interference of the sun.

Abstract:The aim was to study absorption and utilization of nitrogen fertilizer of maize under different water and fertilizer conditions by using the 15N tracer technique. Three irrigation levels (200m3/hm2, 400m3/hm2 and 600m3/hm2) and five nitrogen application levels (0kg/hm2, 150kg/hm2, 200kg/hm2, 250kg/hm2 and 300kg/hm2) were set. The absorption of nitrogen from fertilizer and soil in different organs of maize was studied at maturation stage. Soil nitrogen excitation effect and nitrogen fertilizer efficiency under different water and fertilizer conditions were also studied. The results showed that the nitrogen absorbed from fertilizer by maize accounted for 33.32%~43.54% and the nitrogen absorbed from soil by maize accounted for 56.46%~66.68% under different water and fertilizer conditions. It was showed that soil was the main nitrogen source of maize growth. The different organs’ competitive ability to nitrogen from fertilizer was different, and the expression in a descending trend was grain, leaf and stem. Increasing of nitrogen application could improve the absorption ability of maize to nitrogen from soil, but it was necessary to increase the amount of water when excessive nitrogen was applied, in order to make the maize absorb more nitrogen from soil. The 15N residue in 0~60cm soil layer was increased with the increase of nitrogen application rate. With the increase of irrigation volume, the residual amount of 15N on the surface was decreased. When the amount of irrigation was 400m3/hm2 and nitrogen applied was 250kg/hm2, the yield reached 14063.04kg/hm2, and the soil nitrogen reservoir was in equilibrium state which not only achieved high production, but also met the needs of environment friendly. The conclusion can provide reference for the management of corn fertilizer and water and the sustainable development of agriculture.

Abstract:The absence of medium and high spatial resolution image data is the main limiting factor for extraction of spatial distribution of crops with high spatial resolution. A multi-source remote sensing vegetation index data fusion model based on fuzzy C-clustering algorithm was proposed to solve the problem of no satellite image data coverage in the critical growth period of crop extraction, and it was used to generate vegetation index data with high temporal and spatial resolution by combining Landsat with MODIS vegetation index data. Standard series EVI curve was obtained by ground sample, and the fuzzy C-clustering algorithm was used to classify the vegetation index data generated by the data fusion model into several classes, and series EVI curve of each classes was obtained by using the average value of each class as the class value. The spatial distribution of rice was extracted by spectral correlation similarity analysis of standard series EVI curve and class series curve. Accuracy of the method was tested by Google Earth image and ground sample, and the accuracy were 0.92 and 0.94, respectively, thus it was thought that the method can get relatively high accuracy. The method can be applied to extract the spatial distribution information of crops that had high spatial resolution in the areas of lacking high resolution remote sensing image data. And the multi-source remote sensing vegetation index data fusion models can be used to generate vegetation index data with high spatial and temporal resolution.

Abstract:In order to get fully understanding of the interior flow field of a two-stage filtration system composed of sand filter and screen filter in irrigation system, the interior flow field was analyzed and offered optimization by building 3D model using Pro/Engineer, based on computational fluid dynamics (CFD) technique, numerical simulation and using RNG k-εmodel combined with porous media model. And the new integrated filter was made and the performance test it was done. As it was shown in the result, simulation results of the RNG k-εmodel were consistent with the experimental results. Therefore, the model can be used for flow field analysis and structural optimization. When the combined filter system was set with sand filtration material and screen mesh separately installed in different shells, it would cause huge water head loss due to the influence of pipes between sand filter and screen filter and shell of screen filter. And too much circulation and whirlpool of water inside the filter due to complexity of structure led to instability of flow field, which finally caused uneven distribution of velocity during filtering. In terms of the shortcoming of traditional combination filter system based on field flow analysis, a new type of integrated layout optimization incorporating the screen into the sand filter was proposed to improve the complexity of the layout. According to the field flow analysis, integrated filter’s water head loss was decreased by 38.5%, and interior field flow was more stable because the tank space was larger and the flow disturbance was smaller. And the flow velocity distribution was more uniform during filtering, so the utilization of the screen was more reasonable, and the screen life of the filter was extended. After the comparison of two performance tests, it was known that the new integrated filter can effectively reduce the loss of water head and it can run about 20min more when the flow rate was decreased by 20% under the condition of sand water. It was showed that the new integrated filter’s hydraulic performance was better and the irrigation efficiency was improved. According to the research raised above, a kind of digital method was proposed to discuss the performance of the filter, which was used to research and design a kind of integrated filter, and finally the advantageous structure of the integrated filter was obtained, including the sand filter and the screen filter.

Abstract:Field evapotranspiration is an important parameter for crop water requirements estimation and farmland water management, which affects the distribution of soil water and heat parameters during the wintertime and potentially affects crop growth in next spring. So far, Penman-Monteith (PM) model, Priestley-Taylor (PT) model and simultaneous heat and water (SHAW) model are widely used for surface evapotranspiration estimation. However, only the SHAW model is used for the estimation of surface evapotranspiration in wintertime, and the applicability of PM and PT models in the winter still needs to be verified. The accuracy and applicability of the above three models were analyzed and evaluated for estimating surface evapotranspiration in wheat fields overwinter. Parameters in models were modified by considering the latent heat during water-ice phase change. Meteorological parameters and actual evapotranspiration during the winter of 2011—2012 and 2012—2013 were collected in an experimental field, Changping County, Beijing, China. The estimated values using the default or empirical parameters of the three models were compared with the actual measured values, showing that the accuracy of PT model for evapotranspiration was the highest (RMSE was 0.159mm for the PT model, 0.697mm for the PM model and 0.390mm for the SHAW model), but PM and PT models overestimated the evapotranspiration, which were attributed to the solid-liquid and gas-liquid phase changes of soil surface. In order to improve the accuracy of the estimation, a water stress coefficient in the PT and PM models was introduced to modify the three model parameters by using the data of the first year of winter. The results showed that the estimated accuracies of evapotranspiration were significantly improved by the modified PM model (RMSE was 0.159mm during 2011—2012) and the SHAW model (RMSE was 0.280mm during 2011—2012). The modified models were used to estimate the surface evapotranspiration in the winter of 2012—2013. The results showed that the accuracy of the three models remained high and acceptable (RMSE was 0.267mm for PT model, 0.252mm for PM model and 0.253mm for SHAW model). In comparison, the PT model had a simple form and required less parameter input. Therefore, the PT model can be preferentially chosen when estimating surface evapotranspiration during wintertime.

Abstract:Due to the importance and complexity of crop evapotranspiration estimation under drought stress, maize drought stress special experiment was conducted based on six large-scale weighing lysimeters at Xinmaqiao Irrigation Experimental Station, the empirical parameters a and b of the Angstrom formula were optimized based on the measured solar radiation data from the experimental station, and the calculation results of the reference crop evapotranspiration were optimized, and then the characteristics of maize evapotranspiration under different drought stress scenarios were analyzed, moreover the maize evapotranspiration under drought stress was estimated by using basic crop coefficients, including Kcbini，Kcbmid, and Kcbend and upper limit of crop coefficient Kcmax, which were calibrated by genetic algorithm in the process of estimating maize evapotranspiration under no drought stress based on dual crop coefficient approach. The results showed that early mild water deficit may stimulate the adaptability function of maize, and normal physiological function of that would return after re-watering;water deficit would not only decrease current evapotranspiration of maize, but also generate the cumulative effect, which transferred stress influence to later growth stages;the same drought stress intensity had a more obvious effect on the reproductive growth stage of maize, and it may cause permanent stress;the calibration results of Kcbini, Kcbmid, Kcbend and Kcmax were 0.150, 1.090, 0.152 and 1.400, respectively, and the root mean square error (RMSE) and mean absolute error (MAE) of estimated evapotranspiration results under no drought stress in whole growth period using these crop coefficients were 1.39mm and 0.97mm, respectively, which were 6.74% and 8.23% less than those of estimated results based on FAO-56 recommended approach, the means of RMSE, MAE and MRE of estimated evapotranspiration results under two different drought stress scenarios were 1.60mm, 1.18mm and 6.73%, respectively. Therefore, the estimation of maize evapotranspiration under drought stress based on dual crop coefficient approach and genetic algorithm were reasonable and reliable, and this research would provide theoretical foundation for formulating suitable irrigation system and reducing risk of agricultural drought loss.

Abstract:The wetting pattern is difficult to observe during the vertical line source irrigation. Knowledge of the dimensions of wetted soil around the emitter under irrigation is essential to design of cost-effective and efficient vertical line source irrigation systems. Based on the HYDRUS-2D model, a mathematical model of soil water movement in vertical line source irrigation was established. And 81 scenarios were set up to simulate the changing process of wetted soil under different soil textures, initial water content, line source length, diameter and depth conditions. The dimensions of wetted soil were mainly affected by soil texture, the thicker the soil texture was, the faster the wetted front was moved, and the length, diameter and buried depth of line source had little influence on it. The migration process of soil wetting front was in accordance with the power function relationship. The power function index was changed little in the horizontal and vertical upward directions, but it was increased with the saturated hydraulic conductivity (Ks) in the vertical downward direction. The power function coefficient was increased with the increase of Ks. An empirical model for predicting the wetted soil dimensions under vertical line source irrigation containing Ks was proposed, the model reliability was verified by using experimental data. MAE and RMSE were close to 0, PBIAS was between -4% and 9%, and NSE was not less than 0.929, indicating that the prediction effect was good. The model can be estimated only by Ks, and the experimental design was simple. The possibility of predicting the soil wetting front migration distance under vertical line source irrigation by soil physical parameters was initially realized.

Abstract:Greenhouse temperature system is a typical hybrid system, and its inputs include discrete equipment control quantities and a number of outdoor environmental disturbances that can be measured and not controlled. A hybrid system was proposed for greenhouse temperature, a switching system model was established, and a multi-input predictive control was designed based on this model. A determined device state can be considered as a subsystem, and the modeling of the greenhouse system can also be transformed into the modeling of all subsystems. There were numerous greenhouse environments, so it was needed to simplify the input variables. By correlation analysis, outside temperature, outside humidity and solar radiation had obviously strong correlation with inside temperature. The ARMAX model was used to describe the model, and the augmented recursive least square method with forgetting factor was used to identify the model parameters, and the model accuracy was verified. The ARMAX model was used to design a predictive control controller to solve each device’s action sequence, which was an NP-hard problem, and it was solved by optimized pruning simplifies the calculation process. At each sampling time, the set value predictive control was determined, however, under uncontrollable external environmental factors, the output fluctuations were large. If a fixed set-point was used, the system would be switched frequently, and thus increasing equipment loss. In order to solve this problem, the dual-period accumulative temperature method was utilized to dynamically adjust the set-point of predictive control according to the long-period average value of the indoor temperature and the current value, so as to reduce the unnecessary switching of the equipment and reduce the loss.

Abstract:Based on the actual production and scientific research needs of semi-membrane-covered aerobic composting, a kind of energy-saving, environmentally friendly and intelligent semi-membrane covered aerobic composting system was designed, including a master control system, ventilation control system, sensor system and membrane sealing system. Based on the system functional requirements above, the work of designing holistic system, selection of function modules and independent design of each modules was done, specifically including: component selection and structure design of the master control system and ventilation control system, selection of sensors and establishment of monitoring methods, determination of communication methods, design of expansion module, selection of semi-membrane and an establishment of seal fixation solutions for membranes and compost pile and ventilation control program programming of membrane-covered compost system. Based on the above system modules, the device system can realize high-precision real-time monitoring and display of key parameters for composting, flexible and intelligent feedback control of ventilation and oxygen supply, and multi-device wireless communication and other functions. The China’s conventional trough composting model was selected as the composting infrastructure. The performance of aerobic composting with membrane covering was studied by using cow manure from surrounding dairy farms and corn stalks in the planting area as the main compost material. The results showed that during the entire composting process, the maximum temperature of the body exceeded 70℃ and the duration of high temperature met the requirements for the harmless treatment of manure. The oxygen concentration was maintained at a suitable level (higher than 5%), and the whole aerobic fermentation of the whole body under the film coating process was in good condition. From the actual conditions of the flow rate, frequency, temperature, pressure and oxygen concentration parameters monitored by the system and the realization effect of each functional module, each module of the system operated basically well and can basically realize the data of temperature, pressure, flow rate and frequency. The real-time acquisition, display and export functions enabled the local area network wireless communication functions of the total control system, the wind control system, and the PC, and can realize the function of intelligent feedback mode to adjust the ventilation mode. In general, the research and design of this equipment had a positive effect on the intelligence and greenness of China’s aerobic composting equipment, but the system still needed to be further upgraded to meet the actual production needs of membrane-covered aerobic compost.

Abstract:For the real-time compositional endophenotype detection of individual wheat kernel, a quantitative and non-destructive device based on near infrared diffuse reflectance was designed and developed. The hardware consisted of a novel stereoscopic light source unit, spectrum acquisition unit and control unit, also the corresponding detection software were presented. NIR miniature LED lamps were placed in six rows multiple eight columns along an aluminum cylindrical tube to provide a constant centripetal light and the 48 lamps were connected in parallel by 16 copper conductor to inform a physically stereoscopic light structure. A pair of infrared radiation sensor was adopted on the top of the cylindrical tube to trigger the NIR spectrometer for spectra collection as a seed fell through the borosilicate glass tubing inside the light source. The spectrometer of Ocean Optics was connected to a PC with its standard interface and pin definitions, which was used to collect spectrum from the top and bottom of the light source in real-time through a bifurcate structure fiber. All the soft functions were designed in C++ language of Visual Studio platform. The realtime diffuse reflectance spectrum of each seed was transferred to absorbance via PC and predicted its real protein content according to a model embedded in the program. In order to set up a reliable prediction model, totally 300 individual wheat samples were collected to acquire absorbance spectra in the range of 900~1700nm, and pretreated with standard normal variate correction (SNV) algorithm. Two calibration models were established based on full spectra (FS) and feature wavelengths optimized by successive projections algorithm (SPA) respectively. Data showed that the calibration model based on SPA had a relatively lower determination coefficient (R2) of 0.8446 in contrast to the R2 value of 0.9604 based on FS, but the validation model based on SPA had relatively equal prediction accuracy with the model based on FS. For the nine feature wavelengths selected by SPA eliminated the collinearity relationship in spectral data but preserved characteristic of protein on spectrum band with a concise model equation, it was chosen as a superior model and developed in software to predict individual seed protein content online. To verify system design and performance, a series of experiment was conducted for wavelength repeatability, absorbance repeatability and protein predictive repeatability. The results indicated that the compositional detection device based on stereoscopic light source was able to realize fast, nondestructive and real-time detection of protein content for individual seed, also had certain applications potential on other compositional endophenotype detection for wheat and other crop seeds.

Abstract:With the aim to explore the effects of AMPK activity, AMPK mRNA expression (PRKAA1, PRKAA2) in beef during the post-mortem period were measured in Yushu yak (4500m above sea level), Gannan yak (3000m above sea level) and Simmental hybrid beef (1500m above sea level) changes in glycolysis and energy metabolism. The results showed that the AMPK activities was in a ascending trend as Simmental hybrids, Gannan yak and Yushu yak;the expression of PRKAA1 in Simmental hybrid was slightly lower than that in Gannan and Yushu;the expression of PRKAA2 in Simmental hybrid was significantly lower than that in Gannan and Yushu (P<0.05). In 12~168h, lactate content and free glucose content were in a ascending trend as Simmental hybrid cattle, Gannan yak and Yushu yak;in 72~168h, pH value and muscle glycogen content were in a descending trend as Simmental hybrid cattle, Gannan yak and Yushu yak;early maturity ATP, ADP and AMP were in a descending trend as Simmental hybrid cattle, Gannan yak and Yushu yak. In summary, as PRKAA1 and PRKAA2 gene expression in high-altitude beef body was high, AMPK was activated to increase activity, ATP concentration was lower, AMP production was increased, tissue glycolysis was accelerated, muscle lactate content was increase and pH value was lowered, thus affecting the quality of meat. The activity of AMPK in beef was increased under high altitude with hypoxia adaptability, which accelerated glycolysis metabolism and more effectively regulated energy generation.

Abstract:Whey protein concentrate (WPC) fibril was made at pH value of 2.0 and 90℃. The investigation focused on the impact of adding CaCl2 on the aggregation of WPC spontaneous, homogeneous nuclei induced WPC and secondary nuclei induced WPC. As adding CaCl2, the properties of the hardness, viscosity and amount of WPC fibril aggregates with formation spontaneous or induced homogeneous/secondary nuclei were all increased, especially for two nuclei induced whey concentrate proteins. Adding CaCl2, the hardness was increased by 1.661 (homogeneous nuclei induced WPC) and 1.821 (secondary nuclei induced WPC) times than that of whey protein concentrate spontaneous, and the viscosity was increased by 2.261 (homogeneous nuclei induced WPC) and 2.479 (secondary nuclei induced WPC) times. The micro morphology using TEM of WPC aggregates was changed from long and semi-flexible fibrils into curly and cluster polymers when mixed CaCl2. And the fluorescence intensity was all decreased by adding CaCl2. It was speculated that because the Th T dye was unable to fully bind with the assembled fibrils. For the two ways of forming fibrils: spontaneous or nuclei induced WPC, there were different results that the aggregation ability of nuclei-induced WPC was even greater than that of spontaneous WPC fibril formation as adding CaCl2.

Abstract:Investigation was made on the effects of the peppermint oil nanoemulsion on the average particle size, zeta potential, turbidity, FFA release rate and the bioavailability of menthol in vitro simulated digestion process. It was found that peppermint oil was completely packed by SPI and nanoemulsion droplet was in the spherical shape by using confocal laser scanning 3D microscopy to observe the microstructure of peppermint oil nanoemulsion, indicating that the soybean protein was completely adsorbed at the oil-water interface of the nanoemulsion and presented a core shell structure. The results indicated that the FFA release rate and menthol bioavailability of the peppermint oil nanoemulsion prepared by high-pressure-homogenization were much higher than that in the control group of peppermint oil. In the simulated gastric digestion phase, the average particle size and the zeta potential of the nanoemulsion were increased, while the turbidity was decreased and the microstructure of the digestive emulsion showed the phenomenon of droplet polymerization. After the simulated intestinal juice was digested, the interfacial protein of peppermint oil nanoemulsion was hydrolyzed, the oil droplets were digested, the average particle size of the emulsion was decreased, and the absolute value of zeta-potential was increased. The stability of the peppermint oil nanoemulsion was checked by the Turbiscan stability analyzer, and the stability index was found to be 2.8. There was no emulsion floatation and flocculation occurred during the test.

Abstract:Soybean protein-phosphatidylcholine was used as the emulsifier to prepare fish oil nano-emulsion by high pressure homogenization technology. The effect of concentrations of soybean protein, phosphatidylcholine and fish oil, and homogenous pressure on the average particle size, PDI, ζ-potential, turbidity of fish oil nano-emulsion were studied. Results with the highest desirability (the mean droplet size was (245±3.1)nm, PDI was 0.226±0.019, ζ-potential was (-30.2±0.6)mV and turbidity was (2.413±34.7)cm-1 was obtained with mass ratio of soybean protein content of 2%，phosphatidylcholine content of 0.2%, fish oil content of 1.5%, and homogenization pressure of 100MPa.Through the super high-resolution microscopy it was observed that fish oil was embedded in the composite emulsifier and evenly distributed in the emulsion system. Through the stability study of the highest desirability soybean protein-phosphatidylcholine fish oil nano-emulsion, it was found that nano-emulsion was remained stable against coalescence and phase separation for a period of 30d (storage period) at 4℃ and 25℃, respectively. The ability of the soybean protein-phosphatidylcholine fish oil nano-emulsion was stronger than that of Tween20 fish oil nano-emulsion. The highest desirability soybean protein-phosphatidylcholine fish oil nano-emulsion had good ionic resistance ability, and the influence of Ca2+ on stability of nano-emulsions was greater than Na+. In addition, the nano-emulsion was stable under all processing conditions that encountered during food processing at pH value of 7.0~10.0. The developed fish oil nano-emulsion had potential applications in the food industry.

Abstract:To solve high power consumption and problem of braking torque heat-fade of the conventional eddy current brake, a new active electromagnetic liquid-cooled retarder was proposed based on the principle of eddy current brake and motor energy regeneration brake. The new type of retarder included a liquid cooled eddy current retarder and a single-phase switched reluctance motor with an outer rotor. The mathematical model of electromagnetic field for the retarder was established. The braking performance of the retarder was predicted by numerical simulation, the opening and closing angle of the switched reluctance motor were optimized, and the energy recovery power of the the switched reluctance motor in the downhill continuous braking, the energy recovered in the emergency braking and start torque at low speed were calculated. At last, tests for the air loss moment, heat-fade of braking toque, power generation performance and power-driven performance were carried out. The test results showed that the eddy current braking torque reached 1260N·m at 1000r/min. The braking torque was declined by 15% in the continuous braking stage. The braking torque of the motor was increased at first and then decreased with the increase of speed. When the speed was 1000r/min, the braking torque of the motor reached the maximum;when the vehicle was slowed down at speed of 35km/h, the recovery power was up to 94kW.

Abstract:In order to solve the problem that the driving condition of the electric vehicle (EV) cannot be covered by the high efficiency area of traditional single motor drive system, an optimal allocation strategy for the multi-motor drive system of EV was presented based on model predictive control. Firstly, taking the whole multi-motor drive system as research object, the model of motor and longitudinal dynamic model of automobile were established. The method to improve the efficiency of the vehicle with different front and rear axle motors in the high efficiency area was discussed. Secondly, the efficiency of the motor at specific speed and torque operation points was calibrated by the bench test. It was found that the high efficiency ranges of the two motors covered the working operation points of high speed cruising and low speed startup conditions, respectively. By introducing the driving force distribution ratio of front and rear motors, the efficiency diagram of the two motors was transformed into the vehicle driving efficiency diagram. Thirdly, theoretical analysis and simulation verification of permanent magnet synchronous motor (PMSM) system with model predictive torque control were carried out, showing that the method can ensure the rapid response of torque. Finally, the validity of the range improvement and vehicle efficiency were verified by the hardware in the loop (HIL) experiments. The results showed that the driving force distribution can integrate the high efficiency range of two motors and improve the efficiency of vehicle. Moreover, the model predictive torque control (MPTC) based on the motor benchs parameters can suppress the torque ripple in the low speed range and improve the accuracy of the output torque. The results can provide theoretical basis for the design of distributed driving system.

Abstract:The position of conventional hydraulic swing system with large inertia is controlled with driver-in-loop. According to the observation, the driver adjusts the handle to control the multiway valve with single degree of freedom. Because the human reaction is slow, the production efficiency and repetitive positioning precision is low, and it is difficult to meet the requirements of engineering operations with high rotary positioning accuracy. Furthermore, the energy consumption is high. To solve the above mentioned problems, based on the separate meter-in and meter-out hydraulic swing system, a velocity and position combined control method was proposed. In this method, a precisely desired position was given as the input signal for the position closed-loop control, and the desired velocity and displacement were S-curves. In addition, the velocity feedforward control and position closed-loop control were used to reduce the tracking error, and the pressure and velocity feedback control were also applied to the swing system to improve smoothness of the working process. Firstly, a three-dimensional co-simulation simulation model was developed, which integrated the multi-body dynamics system and electro-hydraulic system for analyzing the feasibility of this swing system, and the control parameters of the hydraulic components were determined according to hardware and the control strategy developed. Then the system principle and the control strategy were verified and debugged by making a simulation. Besides, an experiment was carried out on a 6-ton hydraulic excavator. The simulation and experiment results demonstrated that high positioning accuracy can be achieved in both forward and reverse moving directions with different desired speeds. The positioning error was about 0.5°~1.5°, and the velocity and pressure fluctuation were all reduced. The maximum fluctuation pressure was decreased by 41.6%.

Abstract:The existing quantitative pump cannot meet the multi-stage flow of single pump output. In order to solve the problem of different flow levels of the traditional hydraulic system, the variable pump and control of valve and auxiliary components were used to meet the working condition requirements. The multi-output radial piston pump was a new hydraulic component designed according to the "double stator theory". It utilized its structural specificity to achieve output flow diversity. According to the principle of force balance and the principle of crank-slider mechanism, the kinematics of multi-output radial piston pump was analyzed. By analyzing the flow pulsation of the pump under different working modes, the working mode with minimum flow pulsation was determined. Theoretical analysis showed that the flow pulsation curve of the non-adjacent two columns of plungers was similar to the output flow pulsation curve of the adjacent two columns of plungers, and the curve periodicity of the different working modes was related to the periodicity of the single column plunger curve. When the pump output maximum flow, the pulsation amplitude and pulsation period of the oil flow were much smaller than the single output. Using the pump prototype, the principle experiment of the pump was carried out. The experimental results showed that the actual flow rate of the pump was continuously decreasing as the pump outlet pressure was increased. However, due to limited processing conditions, the machining accuracy of some parts cannot be guaranteed, resulting in experimental results. The theoretical analysis did not match, and the experimental data analysis verified the correctness of the principle and structural rationality of the pump, which laid a foundation for the research and development of the radial piston pump in the future.