Design And Implement CAN-bus Of Automatic Navigation System On The Tractor

Automatic navigation technology on tractor is one of precision agriculture technology, using the leading technology ensures accurate operation, direction and distance, improving the accuracy of a job. In addition,it can also reduce duplication of work, speed up the operation progress, reducing pilot workload. Tractor automatic navigation is commercialization now in the developed countries, but is began to strengthen the study in China in recent years.Automatic navigation system on tractor has a large number of electronic control units, every hardware circuit and the communication between each other are the subject of study focus on. A CAN bus network is designed for the navigation system on tractor, consisting three nodes——steering control node, seeding node and intelligent control Terminal. Main research work has the following sections:(1) We realized the present situation of communication bus using in automatic navigation system through the analysis of present status of agricultural vehicle automatic navigation system at home and abroad. The system CAN bus application layer protocol has been designed for the use of farmland work tractor, CAN bus network structure, as well as the implementation of features, based on agricultural and forestry machinery ISO11783standard.(2) The Cortex-M3processor chip——LM3S5749,which with CAN controller,is used to design the steering control node and the sowing node ECU based on the above protocol, as the core. GPS, electronic compass, and angle sensor are information collectors of the steering control node device. The electromagnetic valve is controlled by the seed node. In addition, the STM32experimental in laboratory is the intelligent control terminal. Those nodes are formed auto navigation system based on CAN-bus. System hardware design include CAN bus communication circuit, RS232communication circuits, A/D conversion circuit, stepper motor drive circuit and solenoid valve control circuit, as well as the necessary anti-jamming circuit design.(3) The IAR, a programming software, is used to program to complete the function of the system. These programs contain CAN communications, sensors’information collection and analysis procedures, shipping calculation and optimal control algorithms, and so on.(4) We test the circuit’s functions after the design is complete. System debugging is done on the basis that the function test can be carried out right, as well as field path tracking experiments. The results indicate that the system has good reliability and real-time, track speed I.5M/s speed of straightness error in15cm.Experimental proof that:the automatic navigation system on tractor designed in this subject can complete the expected tasks, such as receiving sensor information, decoded, controlling of steering control system, packaging and sending CAN bus messages, and receiving functions. It has a high reliability and real-time.