【作者】 黄胜；

【导师】 朱瑞祥；

【作者基本信息】 西北农林科技大学 ， 农业机械化工程， 2011， 硕士

【摘要】 实行变量施药是保证单位面积施药量符合农艺要求、减少农药使用量以及降低化学污染的一项重要措施。针对目前部分施药机变量施药控制性能较差、无法进行施药过程在线监测、无法进行施药参数存储和独立喷头控制等问题,本文设计了一套车载式施药机变量监控系统。该系统能够依据施药机的行走速度,通过喷药量和压力控制,实现单位面积施药量不变;同时可实现施药过程的在线监控以及喷头的独立开闭控制等。(1)明确系统总体设计要求,即能够实现喷药量的变量控制、在线监测和喷头独立控制等三个方面的功能。通过方案比较分析,确定了系统整体方案,即系统依据施药机行走速度的变化和设定的单位面积施药量,实时调整喷药量;依据设定压力值调整实际压力值;通过LCD和PC机实时监测施药情况,并对施药参量进行存储;通过软键盘实现喷头的独立开闭控制。(2)建立了系统压力和喷药量控制模型,并进行了压力和施药量PID和模糊控制算法仿真分析。结果表明:在单位阶跃信号输入下,压力和施药量PID控制系统的响应时间分别为0.4s和0.18s;压力和施药量模糊控制系统的响应时间分别为40ms和55ms。同时提出了采用跳变步长法对施药量滞环控制算法进行优化的方法。(3)根据系统方案,对系统执行、检测部件和其它硬件设备进行了选择;设计了电源、键盘、液晶显示、通信、SD卡存储、电动球阀控制、电磁阀控制等模块电路,绘制了PCB板并制作了控制器。设计并实现了系统上位机软件和下位机软件。其中上位机软件程序包括数据库构建、系统注册、系统登录、系统设置、数据接收显示存储和数据处理等模块的程序;下位机软件程序系统初始化、液晶显示、键盘处理、数据采集处理、SD卡存储、串口通信、电动球阀控制和电磁阀控制等模块的程序。(4)进行了系统调试及验证试验,结果表明:系统上位机能够正常接收存储下位机传送的施药参量数据,并可以进行数字和图形化实时显示;下位机可以显示施药参量并将数据打包存储于SD卡中;系统对速度、压力和流量的测量精度分别达到97.7%、98.5%和99.3%;系统可以实现采用软键盘对20个喷头进行独立开闭控制。(5)进行了滞环控制算法优化试验,结果表明:在设定喷药量为200ml/s时,采用等步长和跳变步长滞环控制算法控制喷药量的平均恢复时间分别为12s和7s、恢复时间段内的平均误差分别为27.19%和13.24%、整个控制过程的平均误差分别为12.68%和7.55%;在压力为0.75MPa时,采用跳变步长滞环控制算法控制施药压力的平均恢复时间为13.4s、恢复时间段内和整个控制过程中的平均误差分别为25.49%和14.42%。更多还原

【Abstract】 Variable pesticide application is one of the most important measures for spray value of per unit area to meet the agricultural requirements, reducing the use of pesticide and chemical pollution. Some of the pesticide application machines can not spray pesticide variably, monitor on line, store the pesticide application parameter data and control nozzles independently at present. On the basis of such situations, a variable pesticide application monitoring and control system of pesticide application machine hauled by tractor was designed. The system can store and display the pesticide application parameter data while monitoring and control the spraying volume according to the speed of the tractor to stabilize pesticide application volume on per unit area and control the pressure based on the setting data, besides that it could also control nozzles independently by using soft keyboard.(1) The overall requirements of the system, which included that the system could spay pesticide variably, monitor on line and control nozzles independently, were determined. After comparision and analysis of different schemes, the system’s scheme was determined, which was that the system can change the spray volume based on the speed of the tractor and the setting spray volume, change the pressure based on the setting data, monitoring the spray situation by LCD and PC, and control the nozzles by soft keyboard, was ensured through the compare and analysis of schemes.(2) The pressure and spray volume control models were established and the PID and fuzzy control algorithm were designed and simulated. The results showed that the response time of pesticide pressure and spraying volume control were 0.85s and 1.04s respectively under the PID control, and were 40ms and 55ms respectively under the fuzzy control. Hysteresis control algorithm was optimized by jumping control step size.(3) The executive components, testing components and the other equipment were chosen according to the system’s scheme. And circuit modules including power supply, keyboard, LCD displayer, communication, storage of SD card, control circuit of electronic ball valve and solenid valve, and so on were designed, meanwhile the PCB board and the system’s controller was made. The system’s master computer software and lower computer software were designed. Among them, the master computer software’s program included construction of database, system registration, system login, system settings and reception, display, storage and analysis of data, etc. While the lower computer software’s program conained system initialization module program, LCD display, keyboard scanning, data sampling, storage of SD card, serial communication and control modules programs, etc.(4) The system debugging and verification experiments were finished, which showed that the system’s master computer can receive, store and display the pesticide application parameter data, while the lower computer can display and store the data. The average measuring accuracy of speed, pressure and spray volume was 97.7%, 98.5%and 99.3% respectively. The system can control twenty nozzles independently by using soft keyboard.(5) The optimization experiment of hysteresis control algorithm was done and the results showed that the average recovery time was twelve seconds and seven seconds respectively at the spray volume being 200ml/s while control the spray volume by hysteresis control algorithm with the same control step and jumping control step, and the average error was 27.19% and 13.24% respectively in the recovery time, while the average error was 12.68% and 7.55% respectively in the whole control process. The average recovery time was 13.4 seconds at the pressure being 0.75MPa, when controlled the pressure, and the average error was 25.49% and 14.42% respectively during the recovery time and the whole control process.更多还原