The Design And Realization Of Performance Testing Platform For Variable Rate Fertilization

The agriculture in China is developing from traditional rough agriculture to modern precision agriculture. And precision agriculture is a new model of agriculture which combines information technology, biotechnology and agriculture production. The application of precision agriculture is the basis of high-efficiency agriculture, and variable rate technology is an important method of precision agriculture. Variable rate fertilization can efficiently reduce the environment pollution, raise the quality and crop yield, reduce the dosage of the chemical fertilizer, cut down the cost, bringing about huge social economy benefit and good ecological effect, and making a great contribution to the modernization of agriculture.The ultimate goal of variable rate fertilization is to achieve precision fertilization in term of soil fertility and crop nutrition, which needs to precisely control Fertilizing amount per unit area based on the actual needs of the field. That requires real-time adjustment of fertilization mass flow rate based on the current velocity of fertilizer applicator and target fertilization amount. Currently, the fertilization flow rate is the average rate calculated from total fertilization over a period of time, not the real-time rate. So there is a lack of effective evaluation method for real-time performance of fertilization flow rate. At the same time, there is no effective means to detect real-time Fertilizing amount per unit area in field, or to give a reasonable performance evaluation for variable rate fertilization implementation. In these situations, the variable rate fertilization performance testing platform based on belt weigher was designed to detect real-time fertilization rate. Furthermore this platform can realize the goal of detecting the real-time Fertilizing amount per unit area indoors by using the speed of belt to simulate the velocity of fertilizer applicator in the field, which provides a scientific basis for reasonable controlling operation of fertilization apparatus and precision fertilization.In this paper, some relevant performance testing experiments have been done for outer fluted-wheel variable rate fertilization apparatus based on the platform. The detailed research and conclusions are as follows:(1) Based on electronic belt weigher, the variable rate fertilization performance testing platform was set up. This platform was made up of the host computer with embedded WinCE system and the slaver based on microcontroller system. Touch operation and data storage were implemented in the host computer MFC program. Choosing Freescale MC9S12XS128 as the main controller of the slaver realized the real-time detection of fertilization flow rate.(2) CAN bus was Designed with MCP2515 CAN controller chip as the core. All modules, including speed detection, the controller of variable rate fertilization and the target fertilization amount decision module, within the system implemented fast, reliable and stable data communication after the bus communication protocol configured by software.(3) Applied stepping motor as driving source, the MC9S12xs128 was chosen as main controller to design an outer fluted-wheel variable rate fertilization apparatus which achieved precise control of fertilization.(4) The real-time fertilization mass flow detection experiment for outer fluted-wheel variable rate fertilization apparatus was carried out by using the variable rate fertilization performance testing platform based on belt weigher. The experiment results showed that the platform had high measurement accuracy. The maximum relative error was 4.90% and the average relative error was 2.38% in the whole process. Those data were retrieved from the fertilization mass flow real-time detection Meanwhile, research indicated that in the same opening length of fertilization apparatus, the fertilization mass flow and the rotational speed of outer fluted-wheel had the linear relationship, when outer Fluted-wheel rotational speed was constant. Furthermore, the fertilization mass flow and opening length of fertilization apparatus were not linearly related.(5) The relational model was derived for Fertilizing amount per unit area with outer fluted-wheel rotation speed and the velocity of fertilizer applicator. The detection experiment of real-time Fertilizing amount per unit area was carried out. Meanwhile, when the target fertilization amount was set constant, the control experiment of real-time Fertilizing amount per unit area was conducted. During the experiment, when the velocity of fertilizer applicator (speed of belt)was changed, in terms of the established control model, the variable rate fertilization controller can regulate the outer fluted-wheel rotation speed, and keep the real-time amount of fertilization per unit area stability. The relative error between the average of real-time fertilization amount and the target fertilization amount was 3.36%. The maximum value of relative volatility was 11.29% with standard deviation 4.02% in the measurement of real-time fertilization amount.The results showed that the platform can effectively realize fertilization mass flow real-time detection of variable rate fertilizer applicator and Fertilizing amount per unit area real-time detection, and effectively measure the stability and accuracy of actual fertilization amount for variable rate fertilizer applicator.