Development and performance assessment of map-based variable rate granule application system
1. National Engineering Research Center for Information Technology in Agriculture, Beijing 100097, China; 2. Information Engineering College, Capital Normal University, Beijing 100048 ,China）
Abstract：A kind of map-based variable rate granule application system consisting of field computer, DGPS, main controller, electro-hydraulic proportional valve, hydraulic motor, ground speed measurement module and parallel guidance light bar was developed. By using PC 104 CPU module and variable rate control, guidance software was developed based on embedded COM - GIS. TI 2407 DSP was chosen as micro-controller for main controller and an improved PID control arithmetie for granule application rate control was developed. System characteristics were evaluated through infield testing. Result shows the application rates with coefficient of variation of 16.83% for the 75 kg/hm^2 and 8.08% for 225 kg/hm^2 respectively. Compared with target application rate, the average application error is 2.98% and 1.05% respectively. Test case of variable-rate application from a low rate （0 kg/hm^2） to high rate （375 kg/hm^2） has been done to test system dynamic characteristics. Result shows that lag distance is 3.57 m and system delay time is about 1.84 s.
2009, Vol. 30 
