定量施肥机控制系统研究

发布时间：2018-04-21 11:25

本文选题：施肥机 + 螺旋式排肥器　；参考：《西南大学》2017年硕士论文

【摘要】：施化肥是增加土壤养分,改善作物生长发育条件的重要措施,在我国西南山地丘陵地区,由于地理环境因素,大中型施肥机械难以使用。常用的小型施肥机排肥器有外槽轮式、水平螺旋式等;肥料的物理特性对此类排肥器的排肥性能影响较大,施肥作业时容易出现肥料架空、堵塞等引起的“断条”即漏施现象。于是,长期以来农作物的施肥仍然以人工施肥为主,存在劳动强度大、施肥量随意性大、均匀性差等问题。因此,有必要研制一种施肥均匀性好,适用于山地丘陵地区使用的定量施肥机。为了提高施肥的利用率,降低生产成本,促进农业的可持续发展,结合我国西南丘陵地区施肥作业现状,论文对定量施肥机控制系统进行了设计与研究。采用竖直螺旋式排肥器作为定量施肥机的排肥机构,利用霍尔式传感器进行施肥机的行走速度检测,将霍尔传感器的脉冲信号经过滤波整形后得到规则的矩形波信号,设计完成以单片机为主控芯片的控制系统,利用脉冲宽度调制(Pulse Width Modulation,PWM)调节排肥器驱动电机的端电压,从而实现定量施肥机精确排肥。根据施肥机性能设计要求,结合理论分析,对竖直螺旋式排肥器进行控制策略研究,通过对螺旋式排肥器的运动参数分析,建立控制系统的数学模型;经过排肥试验,初步拟合控制系统数学模型参数,得出排肥器的排肥量与转速之间的线性关系;采用直流减速电机作为排肥器的驱动机构,根据直流减速电机的外特性,对电机的输出转速采用闭环控制,通过实时采集排肥器的转速信号,对比反馈转速信号与目标转速,实时修正排肥器的转速。在硬件电路设计方面,采用PIC18F13K22作为主控芯片,采用N沟道MOSFET管FDN359AN和P沟道MOSFET管FDN360P作为电机控制的功率开关管。在Protel软件中完成控制系统的硬件电路绘制,在MPLAB集成开发环境中完成驱动程序的编写与调试。同时,为保证整个系统运行的可靠性,在硬件电路和软件程序上都进行了抗干扰设计。对定量施肥机进行了室外施肥均匀性试验和田间施肥试验。试验结果表明,所设计的定量施肥机控制系统达到设计要求。在正常作业速度为0.5-1.2m/s、施肥量为300-750kg/hm2(20-50kg/亩)的试验范围内,均匀性试验的最大变异系数为7.06%,田间试验施肥量的最大偏差为6.76%。能够满足施肥机对均匀性和施肥量偏差的质量评价技术规范(NY/T1003-2006)的要求。
[Abstract]:Fertilizer application is an important measure to increase soil nutrients and improve crop growth and development conditions. In the mountainous and hilly areas of southwest China, it is difficult to use large and medium-sized fertilization machinery due to geographical environment. The common small fertiliser has external groove wheel type, horizontal spiral type and so on, the physical characteristics of fertilizer have a great influence on the fertilizer discharge performance of this kind of fertiliser, the fertilizer overhead is easy to occur in the fertilization operation, and the "broken strip" phenomenon caused by blockage is the phenomenon of leakage. Therefore, for a long time, the fertilization of crops is still dominated by artificial fertilization, which has many problems, such as high labor intensity, large amount of random fertilization, poor uniformity and so on. Therefore, it is necessary to develop a kind of quantitative fertilization machine which has good uniformity and is suitable for use in mountainous and hilly areas. In order to improve the utilization rate of fertilizer, reduce the production cost and promote the sustainable development of agriculture, combined with the present situation of fertilization in the southwest hilly area of China, the paper designs and studies the control system of quantitative fertilization machine. The vertical spiral fertiliser is used as the fertiliser's fertiliser, and the Hall sensor is used to detect the walking speed of the fertiliser. After filtering and shaping the pulse signal of Hall sensor, the regular rectangular wave signal is obtained. The control system with single chip microcomputer as the main control chip is designed and completed. Pulse Width Modulation Modulation (PWM) is used to adjust the terminal voltage of the motor driven by the fertiliser, so as to realize the accurate fertiliser discharge. According to the performance design requirements of fertilization machine, combined with theoretical analysis, the control strategy of vertical spiral fertiliser was studied. The mathematical model of the control system was established by analyzing the motion parameters of the helical fertiliser. The mathematical model parameters of the control system are preliminarily fitted to obtain the linear relationship between the fertiliser discharge quantity and the rotational speed, the DC deceleration motor is used as the driving mechanism of the fertiliser, and according to the external characteristics of the DC deceleration motor, Closed-loop control is used to control the output speed of the motor. The speed signals of the fertiliser are collected in real time, the feedback speed signal and the target speed are compared, and the speed of the fertiliser is corrected in real time. In the aspect of hardware circuit design, PIC18F13K22 is used as main control chip, N channel MOSFET tube FDN359AN and P channel MOSFET tube FDN360P are used as motor controlled power switch. The hardware circuit of the control system is drawn in the Protel software, and the driver is written and debugged in the MPLAB integrated development environment. At the same time, in order to ensure the reliability of the whole system, the anti-interference design is carried out in the hardware circuit and software program. The field fertilization experiments and outdoor fertilization homogeneity tests were carried out on the quantitative fertilization machine. The experimental results show that the control system of the quantitative fertilization machine meets the design requirements. In the range of normal operation speed of 0.5-1.2 m / s and fertilizer amount of 300-750kg/hm2(20-50kg/ mu, the maximum coefficient of variation of uniformity test was 7.06, and the maximum deviation of fertilization amount in field experiment was 6.76%. It can meet the requirement of NYR / T1003-2006.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S224.2

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