Design of Can-based Variable Rate Fertilizer Control System

A novel control system for variable rate fertilizer application based on CAN bus is presented. The system consists of variable rate controller based on DSP, ground speed sampling unit and light-bar guidance unit. These units form a control area network based on CAN bus. The variable rate controller collects signals of GPS position and ground speed, and calculates the conveyor feed shaft rotate speed according to the prescription map stored in local memory. Then the variable rate application can be realized through PID control of the shaft rotate speed. Light-bar guidance unit helps the operator to steer the machine moving by equal spacing parallel passes for less overlap and missing in operation. The effectiveness of the developed system is confirmed by the experiments using the communication protocol special for the application based on CAN bus.