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Li J.,Kunming University of Science and Technology | Li J.,South China Agricultural University | Hong T.,South China Agricultural University | Hong T.,Key Laboratory of Key Technology on Agricultural Machine and Equipment | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

The stability of micro-irrigation system inlet water pressure affects the uniformity of the micro-irrigation and the mixed fertilizer accuracy of automatic fertilizer mixing device. In order to provide a constant inlet water pressure for small and medium-sized irrigation pipe network which adopts gravity drip irrigation, a constant pressure water supply automatic control device was developed, through employing a diaphragm pump DP-60 powered by solar energy to carry water to the reservoir built in high place, and maintaining the reservoir' water level at a fixed height in the drip irrigation process. The water level was detected online by using a level sensor YZ-YO-LAG1, and the controller control DP-60 carrying water to the reservoir according to the water level detected. Due to the certain distance between reservoir water level detection terminal and DP-60 control terminal, two wireless communication modules CC1100 were installed in each terminal respectively to realize wireless data transmission and control between two terminals. To reduce power consumption of wireless communication, a regular communication strategy combining with sleeping mechanism was adopted, and a kind of time synchronization technology was employed to keep time synchronization between the communication parties, and the WOR (wake on radio) mode of CC1100 module was enabled while communicating, the communication success rate was 100% verified by practical test. Photovoltaic capacity of the system had been designed for obtaining an optimal capacity combination of solar cell array and lead-acid battery, and the solar panel power was determined to be 60 W and the battery capacity to be 60 A·h, the capacity combination could meet the electricity demand of 500L irrigation norm for each drip irrigation cycle, and ensure that the system operates normally in seven consecutive days without sunshine. In order to maximize the use of solar energy, the relationship between solar panel power and the output frequency of solar radiation sensor TSL230 was calibrated through experiment, and then the controller could select the battery or solar panel as the direct power for DP-60 automatically, based on actual output power (obtained from the output frequency of TSL230) of the solar panel and the stage of charge of battery. To guide the application and installation of DP-60 in actual engineering, the maximum pumping head, maximum suction head, current characteristics and flow characteristics of DP-60 had been determined by experiments, with its inlet and outlet connecting with a PVC pipe of DN15 diameter respectively. To avoid the large peak pulse current, a soft start-up control was applied to control DP-60 by employing PWM (pulse width modulation) technology, and the frequency of PWM was 20 kHz, and the period for accomplishing a soft start or a soft stop was 2s. Practical application experiment for the constant pressure water supply automatic control device had been taken for more than 6 months, and the results showed the device was stable and the error of the reservoir water level was less than 1 cm.

Li J.,Kunming University of Science and Technology | Li J.,South China Agricultural University | Hong T.,South China Agricultural University | Hong T.,Key Laboratory of Key Technology on Agricultural Machine and Equipment | And 4 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Fertigation is an irrigation technology of integration of water and fertilizer, and has been widely used in micro-irrigation systems, because of uniform fertilization, high utilization of water and fertilizer, and effectively reducing the pollution of soil and environment. The venturi fertilizer injector has become one of the main means and important equipment to achieve fertigation due to its simple structure, economy, and practicability, but the liquid fertilizer concentration could not be easily adjusted automatically. In order to realize variable rate fertilization with a venturi fertilizer injector, a variable fertilizer apparatus based on PWM (pulse width modulation) technology has been developed, but the apparatus belongs to open-loop control from the perspective of automatic control, and its accuracy and stability is difficult to guarantee. Therefore, a closed-loop control automatic fertilizer-mixing device was developed to improve the liquid fertilizer concentration mixing accuracy and stability, by improving the structure of the variable fertilizer apparatus and adding a conductivity meter that was employed to feedback the real-time fertilizer solution concentration indirectly. The conductivity meter was designed based on a conductivity electrode, and a square signal whose amplitude is ±3.5 V was determined as the excitation signal of the conductivity meter through experiments, to weaken or even eliminate polarization effects and capacitance effects of the conductivity electrode in the measuring process. In order to further improve measuring accuracy, temperature compensation had been applied to the conductivity meter, the measuring range had been divided into several small-scale ranges which could be switched by a multiplexer ADG1408 controlled by a microcontroller, and the corresponding divider resistor and square signal frequency of each small scale range were determined by experiments. By comparison with a standard conductivity meter, whose model is sension 156, the effective measuring range of the conductivity meter designed was 0-12.64 mS/cm, and the conductivity meter designed was calibrated according to the data measured in the effective measuring range. It was known that the conductivity of the fertilizer solution measured by the conductivity meter has a significant linear relationship (the coefficient of determination R2 is 0.997) with the fertilizer solution concentration, based on conductivity testing of a series of different concentration fertilizer solutions prepared in the range of 0.1%-1.0%. In order to improve the control performance of the automatic fertilizer mixing device, a kind of control strategy of two-step regulating with coarse adjustment and fine adjustment was employed: first, the device adjusted the duty cycle of PWM for controlling the solenoid valve to mix fertilizer automatically, by calling the corresponding function based on the detected inlet water pressure; then the device uses a fuzzy control algorithm to regulate the duty cycle of PWM finely, according to the real-time fertilizer solution concentration measured by the designed conductivity meter, in order to make the mixed fertilizer concentration get close to the target concentration as much as possible. An actual test and verification had been undertaken for the fertilizer mixing device, and the results showed that the maximum error of the mixed fertilizer concentration was 0.04% and the response time of the control device for achieving steady-state was 7.8-10.4 s, and it is now known that the device can meet the requirements of practical application in agriculture.

Ma X.,South China Agricultural University | Ma X.,Key Laboratory of Key Technology on Agricultural Machine and Equipment | Qi L.,South China Agricultural University | Qi L.,Key Laboratory of Key Technology on Agricultural Machine and Equipment | And 3 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2011

The mechanical weeding technology is important in reducing the usage of herbicide and ensuring organic rice production in paddy field. The weakness of the existing paddy weeding machines was discussed and the types and characteristics of paddy weeding techniques were summarized in this study, based on reviewing the present status of paddy weeding equipment and technology at home and abroad. The paddy weeding technology should develop toward intellectualization, technicalization of mechanical biomimetics, and fusion of several weeding techniques to improve the precision weeding effects, so that weeding technology can play a more important role in rice production.

Song S.,National Citrus Industry Technology Research System Machinery Laboratory | Song S.,South China Agricultural University | Song S.,Key Laboratory of Key Technology on Agricultural Machine and Equipment | Xia H.,South China Agricultural University | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

The air field distribution and spray efficiency are influenced by the internal structure of an air-assisted sprayer. In this paper, computational simulation was applied to analyze effects of the distributor number on the internal wind flow field in an air duct. Effects of cylindrical, conical and semi-elliptical fluid director structures on the duct wind flow field outlet speed and pressure loss were simulated. The form and structure of fluid director were optimized to obtain high efficiency. A prototype machine was made and comparative analysis was conducted with the measured duct performance before and after oriented object installation. Results indicated that the proper amount of deflector was from four to five pieces. After fluid director was installed, power saving reached to 4.88% when the fan speed was at 2926.5 r/min. The installed deflectors were benefit for turning the rotating air flow to the axial air flow within the duct and generated pressure loss. The oriented object's structure had great effects on the duct pressure loss rate and outlet wind speed. A minimum pressure loss rate was obtained by using the semi-elliptical oriented object.

Xu F.,Key Laboratory of Key Technology on Agricultural Machine and Equipment | Xu Y.,Guangdong Polytechnic Institute | Li C.,Key Laboratory of Key Technology on Agricultural Machine and Equipment
Advanced Materials Research | Year: 2012

In order to high efficiently prevent and cure the diffusion of heavy metal loss in mining area, this paper investigated the main ways of heavy metal loss, built the diffusion model of its non-steady-state and uniform loss, and solved the model by integration, a time-varying function on the path of heavy metal loss which diffused into soil and runoff waters in the mine area was acquired, and a method of efficient prevention and cure was obtained. The results shows that the continuous existence of heavy metal in the mining area will aggravate and increase the regional pollution of soil and runoff waters, among them, the diffusion speed of heavy metal loss dissolved into runoff waters due to soil erosion in mining area will be faster and the hazard will be lager, there exists a high pollution concentration in the estuarine of new waters which the runoff flowed into. The effective recovery of heavy metal residue and waste liquid in mining area, and the decrease of discharge concentration is the important ways to effectively reduce the improvement costs of heavy metal pollution area and improve the harnessing effect, if further combing the restorations of engineering plants and bacteria improvement for heavy metal polluted area, which would be more efficient and rapid, and is worth studying and popularizing. © (2012) Trans Tech Publications, Switzerland.

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