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Wu W.,South China Agricultural University | Wu W.,Mechanical Laboratory of China Agriculture Research System | Hong T.,South China Agricultural University | Hong T.,Mechanical Laboratory of China Agriculture Research System | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

To solve the shortcomings of indirect LAI measurement methods which seldom considered the factors of single isolated canopy, leaves overlapping each other and the image processing speed slowly, the intermittent model avoiding leaves overlapping was established based on the main influential factor of single isolated citrus fruiter LAI'S measuring system (α<0.05) by orthogonal experiment . Then automatic acquisition possible was realized by adopting three dimensional walking mechanisms, and an automatic measuring system of citrus LAI was developed based on infrared transmission using the LabVIEW platform. The hardware system was composed of control module, running gear, signal conditioning model, data acquisition card and PC, of which the demarcated average absolute relative error was 11.11%. With the running gear scan, locate and collect automatically in S shape, 45 citrus trees in the citrus garden of the College of Engineering of South China Agricultural University were tested. With the LAI value computed from direct method and sampling method as true values, the average absolute relative error was 31.4%. Compared with true values, average absolute relative error of the measured value from plant canopy analysis's professional version was 29.8%. Since the errors of the two systems were similar, the system proposed could meet the requirement of LAI test. Source


Wu W.,South China Agricultural University | Wu W.,Mechanical Laboratory of China Agriculture Research System | Zhao B.,South China Agricultural University | Hong T.,South China Agricultural University | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

The axle is one of the most important components directly relating the safety operation of vehicles. However, the testing method of axle on site used in China is backward and inefficient, while checking failures occur now and then. But the theory of reliability design of fatigue, which has been well developed, is difficult to be applied to the test of axle on site. In recent years, the computing automotive technology is advocated at abroad to solve the complicated problem of how to put the reliability analysis of fatigue into practice. This paper realized the 3D simulation of testing system through the Pro/E software as well as constructed the system, which was based on the trailer axle testing system prototype. The system hardware was comprised of support, guide, sensors, AC servo motor and servo driver; meanwhile, the system software adapted the modularized idea in order to divide the monolithic construction into five parts, including main operation control module and 4 testing modules. Every testing module was constituted by 5 submodules. The system software program was written by LabVIEW. It drove the linkage device by controlling the rotation of the servo motor and loaded the simulated axle through two pressure heads, then the displacement and pressure were collected as feedback through the data acquisition card. The displacement-voltage linear relationship of A/B pressure head was obtained through experiments on displacement sensors before system test. By calibrating the straight-line equation, the result was that the maximum locating relative error is 5.207%, and the absolute value of average relative error was 1.4%. The voltage-load linear relationship of A/B pressure head was obtained by accurate positioning of load. Analyzed by software SPSS, in the equation of the load stress and voltage linear regression, the result was that R > 0.994, Sig. < 0.05, thus regression was significant. According the constructed testing system, the performance of fatigue, stiffness, strength, and stress of the simulated axle were tested and analyzed. In fatigue test, flaw occurred after 821 times vibration and efficacy was lost after 1067 times vibration; in stiffness test, spot D almost stayed unchanged and the displacements of spot C and E ranged from 60 to 63 mm; in strength test, the maximum displacement of sensor E was 66.622 mm; in stress test, the maximum displacement of spot E was 66.751 mm, and the maximum stress was 259.444 MPa. The system was steady. The simulated test had been lasting for one month and no bug was found. Therefore, the result generally meets the project requirement. Source


Wu W.,South China Agricultural University | Wu W.,Mechanical Laboratory of China Agriculture Research System | Hong T.,South China Agricultural University | Hong T.,Mechanical Laboratory of China Agriculture Research System | And 7 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

The precision agriculture has become a research hotspot of agricultural science nowadays. How to acquire information of the plants is one of the key points and problems in precision agricultural research. This paper identified the relationships between leaf area index and spectrum data by spectral analysis, thereby achieving fast and accurate LAI measurement. The measurement system for citrus LAI based on spectrum information was divided into two main parts. One was the data acquisition device, with FieldSpec-FR and computers as its key components to collect spectral data of leaves. Another was the inversion platform, with computers, ViewSpecPro, Excel, SPSS and other software as its core to calculate the LAI of citrus leaves. Researching the features of LAI can provide crop biomass status information for precision agriculture. And the exact total leaf area and the nominal LAI values of citrus leaves can be calculated after a scanning calibration experiment. The regression results showed that the system could meet the LAI test requirement. Source


Wu W.,South China Agricultural University | Wu W.,Mechanical Laboratory of China Agriculture Research System | Hong T.,South China Agricultural University | Hong T.,Mechanical Laboratory of China Agriculture Research System | And 8 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

At present, distinguishing overlapped leaves is the difficulty of measuring LAI (leaf area index). In this paper, a new method for the detection of LAI of overlapped leaves was proposed. The citrus leaves were put under the direct parallel light and the photoelectric sensor was used to measure the transmitted light energy. The output voltage signal of the sensor was sent into the computer through the data acquisition card. Then, the amount of overlapped layers was determined automatically by LabVIEW software programming. The amount of overlapped layers multiplied by the area of the sensor receiver was the area of the leaves. The total area of the leaves was the cumulative leaf area in the whole testing process and the LAI could be calculated. According to the experimental results, near-infrared was chosen as the photosource and a near-infrared photoelectric sensor was designed. The short circuit current I 1 and I 2 had a good linear relationship with the preamplifiers output voltage U 1 and the main output voltage U 2. The significant level of R 2 was p < 0.05. The data acquisition experimental results showed that the absolute value of the maximum relative error between the value of LAI calculated by this platform and the real value of LAI obtained by grid method was 14.8%, in the mode of manual scanning. Moreover, the LAI with distant leaves was tested in preliminary stage showing a power function with the leaf distance significantly. Source

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