双变量施肥机定比施肥控制系统设计与试验分析

发布时间：2018-11-19 07:18

【摘要】：精准农业是现代农业发展的必然趋势,并已在我国取得了较为显著的经济效益与社会效益。变量施肥是精准农业重点研究的领域之一,变量施肥技术是以不同空间单元的目标产量与土壤理化性质等为依据进行综合测算分析,结合营养专家系统、作物生长模型进行施肥量决策,指导变量施肥机进行田间网格差异性施肥,而变量施肥机是变量施肥技术的基础和载体,同时变量施肥机的排肥控制系统又是实现变量施肥系统的重要组成部分,是实现精准变量施肥的关键。因此,综合考虑国内外变量施肥机及施肥控制系统现状与发展趋势的基础上,提出了一种基于上位工控机下位单片机的电控液压传动闭环双变量施肥控制系统,同时考虑到系统的可靠性及信号完整性,本文将系统从硬件上划分为液压传动系统、基于工控机的上位主控系统、基于STC单片机下位控制系统以及GPS/DGPS定位系统四块相互独立的部分来设计。为了实现对排肥主轴转速的无极调节,实现精准变量施肥,设计了双变量液压无级调速变量施肥系统,以液压油路的稳定性和排肥槽轮机构驱动控制方法为研究重点,并在液压油路中设置了液压稳压环节和液压压力传感器,实现更好的控制施肥精度。基于工控机的上位主控系统是施肥决策的主控制系统,上位工控机可以提供良好的人机交互界面及高效的数据运算。研究主要内容是通过对图形化的人机交互界面进行设计,实时获取数据库中施肥处方信息和DGPS/GPS模块数据信息,并对数据进行管理与解析,实现排肥轴转速与开度闭环控制等,目的是便于控制系统进行氮肥、磷肥及钾肥(N、P、K)等营养元素的自动配比施肥,并将施肥配比与控制信号发送给下位控制系统。基于STC单片机下位控制系统重点研究利用AD转换将上位给定的施肥量信息转化为电液比例调速阀和开度电磁阀所需的控制信号,该系统的设计主要是基于PCA转速测控系统,利用PCA脉冲捕获的高速度和高可靠性,采集变量施肥机行驶速度,实时的将拖拉机的速度通过串口总线发给基于工控机的上位机主控系统,用于实时的施肥闭环控制。GPS/DGPS定位系统设计主要研究重点通过GPS/DGPS定位模块获取当前机具位置信息,利用串口将定位数据发送到上位主控制系统,使上位控制系统从数据库中获取该位置下的处方施肥信息。为了使施肥决策系统得到精确的施肥量,本文通过试验建立了排肥量与排肥轴转速、开度的函数关系,建立了外槽轮排肥器每转排肥量Q数学的模型、液压驱动马达转速与给定信号的数学模型及变量施肥机Q=F(L,N,V)数学控制模型,并得出了影响变量施肥机排肥量的主次因素。最后,为了综合验证本文所设计的变量施肥控制系统的性能,进行了动态条件下的排肥试验。试验结果表明:研制的变量施肥机工作稳定、排肥可靠、具有较高的控制精度,满足了系统的设计要求,为下一步开发大型自动变量施肥机提供了理论和技术参考。本文研制的双变量施肥机目前已通过专家组的验收。
[Abstract]:Precision agriculture is an inevitable trend of the development of modern agriculture, and has achieved remarkable economic and social benefits in our country. Variable fertilization is one of the most important fields in the research of precision agriculture, and the variable fertilization technique is based on the target yield of different space units and the physical and chemical properties of the soil, so as to combine the nutrition expert system and the crop growth model to make the fertilizer amount decision. The variable fertilizer applicator is the base and the carrier of the variable fertilization technology, and the fertilizer and fertilizer control system of the variable fertilizer applicator is an important part of the realization of the variable fertilization system, which is the key to realize the precise variable fertilization. Therefore, on the basis of considering the current situation and development trend of the variable fertilizer applicator and the fertilizer application control system at home and abroad, a closed-loop double-variable fertilization control system based on the lower computer of the upper computer is proposed, and the reliability and signal integrity of the system are also taken into account. In this paper, the system is divided into the hydraulic transmission system, the upper master control system based on the industrial personal computer, the lower control system based on the STC single chip and the four independent parts of the GPS/ DGPS positioning system. in order to realize the stepless regulation of the rotating speed of the fertilizer discharging main shaft, the precise variable fertilizer application is realized, the double-variable hydraulic stepless speed-regulating variable fertilization system is designed, the stability of the hydraulic oil path and the driving control method of the fertilizer discharging grooved pulley mechanism are taken as the research focus, and a hydraulic pressure stabilizing link and a hydraulic pressure sensor are arranged in the hydraulic oil path to achieve better control and fertilization precision. The main control system based on the industrial personal computer is the main control system of the fertilization decision, and the upper industrial personal computer can provide good man-machine interaction interface and high-efficiency data operation. The main contents of the study are to design the graphical human-computer interaction interface, to obtain the fertilizer prescription information and the DGPS/ GPS module data information in the database in real time, to manage and analyze the data, to realize the closed-loop control of the rotation speed of the fertilizer discharge shaft and the opening degree, and the like, and aims to facilitate the control system to carry out nitrogen fertilizer, the fertilizer and the potassium fertilizer (N, P, K) are used for automatic proportioning and fertilization, and the fertilization proportion and the control signal are sent to the lower control system. Based on the key research of the lower control system of the STC single-chip computer, the application of AD conversion is used to convert the information of the fertilizer amount given by the upper computer into the control signal needed by the electro-hydraulic proportional speed-regulating valve and the opening-degree electromagnetic valve, the high speed and the high reliability of the PCA pulse capture are utilized, the driving speed of the variable fertilizer applicator is acquired, and the speed of the tractor is distributed to the main control system of the upper computer based on the industrial personal computer through the serial port bus in real time, and is used for real-time fertilization closed-loop control. The main research of the design of the GPS/ DGPS positioning system is to acquire the position information of the current implement through the GPS/ DGPS positioning module, and send the position data to the upper master control system by using the serial port, so that the upper control system acquires the prescription fertilization information in the position from the database. In order to get the accurate fertilizer application of the fertilization decision-making system, this paper establishes a mathematical model of the Q-mathematical model of the amount of fertilizer per revolution of the outer-sheave fertilizer-discharging device by establishing a function relation between the quantity of the fertilizer and the rotation speed and the opening degree of the fertilizer-discharging shaft. The mathematical model of the rotational speed of the hydraulic drive motor and the given signal and the mathematical control model of the variable fertilizer applicator Q = F (L, N, V) are given, and the primary and secondary factors that affect the amount of fertilizer discharge of the variable fertilizer applicator are obtained. Finally, in order to comprehensively verify the performance of the variable fertilization control system designed in this paper, the test of the fertilizer discharge under the dynamic condition is carried out. The results of the test show that the variable fertilizer applicator is stable and reliable, has high control precision, meets the design requirement of the system, and provides the theoretical and technical reference for the next development of the large-scale automatic variable fertilizer applicator. The double-variable fertilizer applicator developed in this paper has been accepted by the expert group.
【学位授予单位】：石河子大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S224.2

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