Research On A Variable Rate Control System Of Irrigation Machines Based On GIS And GPS

Precision Agriculture (PA) is a very important direction for agricultural development in 21st century. The study and implement of Precision Agriculture have vital meaning to change extensive agriculture, promote skill level and sustainable agriculture of China.In this study, a variable rate irrigation system, which was more practical and economical according to the actual conditions in rural areas of China, was developed using advanced electronic and computer technology. This system applied single-chip computer technology, GPS (Global Positioning System) and GIS (Geographic Information System) technology to a current dry-farming irrigation machine for precise water application at right time and right position to meet the specific needs, thus greatly improving water use efficiency, increasing yield production and saving energy. The main hardware and software components of the system included an AT89C51 single-chip unit of ATMEL Corporation as the microprocessor, an IC (Integrated Circuit) card used to transfer GIS information in the unit, and a GPS receiver based on GPS OEM. Meanwhile, a data-querying algorithm based on the vector method was used in the system. When the irrigation machine worked in the field, the system received position information from the GPS OEM, recognized the site and determined the vehicle position in the field based on the distance of point out of the line. Then, the GIS data in the IC card were queried based on information contained in electronic maps of field properties, and the amount of water needed per unit area was calculated based on vehicle speed and the spray width. Finally, after a decision was made, the control instruction was sent to adjust flow rate to accomplish variable rate irrigation. The paper focuses on the following contents:1. Hardware Section1). Use HY1602 of HY series LCM, SK5278 Keyboard Controller and 4×4 matrix and encode Keyboard, design the interface of people and computer.2). Design GPS receiver based on Jupiter GPS OEM.3)．Extend communication channels of serial interface use INS8250.4)．Realize date transmission in AT24xx IC Card Offline.5)．Accomplish controlling output include DAC0832 with drive circuit as interface circuit and ZDY small- electric-single- seat-Adjust Valve as execute unit. 6)．Achieve inspecting leavings of water and giving an alarm in the water tank by checking level in it using floater switch.7)．Realize reset, monitoring of power and Watchdog reliably with MAX706.2.Software Section1)．The PC program of navigation and monitoring, with which can Finish date sending, receiving and display in the Electronic Map, was developed and Designed with Mscomm ActiveX control and MapX4.5 ActiveX Control of MapInfo Company's product 2)．Develop mcs-51 program of decode GPS MESSAGE according to NMEA-0183 protocol.3)．Design program of calculating and output, According to the algorithm of recognizing plot, estimating location and inquiring prescription.4)．Communication protocol is Workouted, according to witch design program that can communicate with PC.Through experimentation and test, the system can realize automatic control according to prescription map and handle control, also can work online or offline. It can Guidance Variable Rate Fertilizing and Variable Rate seeding. Just systematic on-line working and the offline working design provide one kind of feasible scheme for a now available big-and-middle-sized as well as small-size agricultural machinery intelligentization of implementation of Variable Rate Control .