温室自动施肥机的设计与仿真

Design and simulation of automatic fertilizing machine for greenhouse

精密施肥是精确农业作业体系中的重要环节之一,近年来人们对设施温室精密施肥的要求愈加迫切。该文主要设计一款小型、精准、实用的设施温室自动施肥机。该施肥机采用ARM9 S3C2440微处理器作为电路控制模块的核心,配备料位监测预警装置;采用槽轮式施肥装置,槽轮选择对颗粒肥料具有良好填充和排出效果的锥形圆弧凹槽断面,通过控制步进电动机的脉冲频率控制槽轮转动的圈数,进而控制施肥装置的施肥量。该文利用Solid Works完成施肥机的结构建模,用Simulation对其主要受力部位进行强度校核,验证其结构的可行性;采用EDEM软件对施肥机构的排肥效果进行仿真模拟,验证该施肥装置可以均匀、稳定、连续地将肥料排出施肥装置;建立施肥装置实体模型进行施肥量验证试验,试验结果表明,在5、10、15、20 r/min 4种转速下,试验得到的排肥量实际值与理论值的最大误差为2.42%,小于3%,这说明所设计的施肥装置在不同的转速下仍可以达到较高的排肥精度,可以实现精确施肥的目标。

As a large agricultural country, there are still more than 40% of people in China engaging in agricultural production activities. In recent years, the soil erosion and desertification have been in serious state, and the arable land has decreased year by year, which means that it is very necessary to develop agricultural technology to improve crop yield per unit area. Therefore, in recent years, China has vigorously developed agricultural greenhouse cultivation which has characteristics of high input, high technology and high yield. Agricultural greenhouse cultivation is an important part of China's agricultural production. In 2014, the area of greenhouse in China was up to 4.109 million hm2. With the promotion of precision agriculture, the technology of modern agricultural greenhouse cultivation is developing towards precision. Precision fertilization is one of the important parts of precision agriculture operation system. Due to that the structure of modern agricultural greenhouse is closed, and the planting area is limited in China, the large agricultural machinery cannot be applied to greenhouse operations, leading to that the mechanization level in greenhouse production is lower than other developed countries in the world. At present, the fertilization in greenhouse in China is still mainly relying on manpower. Because of the increasing labor cost and decreasing yield in greenhouse production, the profits of greenhouse is reduced. In the pursuit of more profit, people's requirements of precision fertilization in greenhouse are increasingly urgent. This paper mainly introduced a small, precise and practical fertilizing machine. This machine was mainly used in greenhouse and it was intelligent and automatic. The fertilization machine used ARM9 S3C2440 microprocessor as the core of circuit control module. It was equipped with a fertilizer level monitoring alarm device, and would alarm automatically when the fertilizer level was less than 15 cm, so that the staff could add fertilizer in time. The machine used the Geneva mechanism as fertilizer metering mechanism. By controlling the pulse frequency of the stepping motor, the amount of fertilization could be controlled so as to achieve quantitative precision fertilization. The three-dimensional model of the fertilization machine was built by the Solid Works. The intensity check was performed for its main parts of the force with simulation. All those verified that the structure could meet the requirements of hardness and intensity. The fertilization effect was simulated by the EDEM(enhanced discrete element method), a general CAE(computer-aided engineering) software applied to the discrete element method. In the simulation, the speed of the sheave was set to 10 r/min, the output time step was 0.05 s, and the total simulation time was 5 s. It was found that there weren't flying particles during the process of simulation, which showed that the selected rotational speed of the sheave and the parameter of the simulation time step were reasonable. The sheave grooves in the process of simulation were almost filled with the fertilizer particles, which proved that the device could get a good effect of fertilization and the parameter of the sheave was reasonable. The brush structure in the fertilization device could effectively get rid of the extra fertilizer particles and supplement fertilizer particles for other incompletely filled groove in order to make sure every groove could discharge a certain amount of fertilizer. The simulation results showed that the fertilization device could discharge the fertilizer particles evenly, stably and continuously. By properly controlling the rotation speed of the drive shaft, the fertilization machine could achieve the goal of precise fertilization. The results show that maximum error of fertilizer test actual value and the theoretical value is 2.42%, less than 3% under four kinds rotational speed(5, 10, 15, 20 r/min). Therefore, the machine designed in this paper could greatly improve the automation level for greenhouse production and reduce the labor intensity of fertilization in greenhouse. It has broad applicability and popularity in our facility greenhouse production.