| CAN(Controller Area Network) is one of the most popular field bus, the net built on the microcontroller, which has so many advantages as multi-master mode, high transmission speed, long distance, automatic solving bus competition, automatic retransmission, strong correcting ability and so on. It has already been put in wide use in fields like automobile industry, automatic control, aeronautics and astronautics, process control, machine industry, textile machinery, robot, agricultural machinery, medical equipment.This article advances a tractor electronic hydraulic hitch system based on the CAN bus on the ground of the characteristics of the hitch system, in reference to the latest literature of theory and application.Firstly, this treatise illustrates the content and significance of this topic by a brief introduction of a tractor electronic hydraulic hitch system and CAN bus. Furthermore, focuses on the technology criterion, message transmission, frame structure, physical layer and error handling.Moreover, the reasonability of substituting the electronic hydraulic hitch system for the traditional is looked through and a mathematical model is developed to simulate PID by MATLAB.Finally, with the core of PIC16F877A single-chip, single-chip controller of electronic hydraulic hitch system is established, in which the primary control board acts as sampling, PID controlling, CAN communication, PWM and switch signal outputting, while operating screen board works as sampling, CAN communication, 4-digit LED screening, scanning key-board and processing. Within this system, the hardware is designed in accordance with the electrical circuit principle of PROTEL 99SE and PCB board; the software is, by means of the integrated development environment MPLAB software assembling program and off-circuit simulation can be made. The controlling system has been tested partially in the lab, and the result implies that the system can meet the requirements and can be prosperous in practice. |
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