Research On CAN Bus Design And System Application Of Combine Harvester

Combined grain harvester is a kind of complicated agricultural operation equipment,which can realize various functions such as harvesting,threshing,cleaning,storing and unloading.With the development of intelligence,informatization and comfort of agricultural machinery,a large number of electronic units are introduced continuously.In order to improve the utilization rate of signals,a large number of data are required to be Shared among different electronic units.The traditional electrical system of combine harvester mostly adopts point-to-point single communication mode,and the low signal utilization rate can not meet the informatization demand of agricultural machinery.As a very mature technology,CAN bus has been widely used in automobile and industrial field,but it has not been widely used in the field of agricultural machinery.Especially to combine harvester,which is a complex multiple operation machine,many control units are involved,especially CAN bus is needed to connect these complex functional modules.In this paper,aiming at the domestic and foreign intelligent development of agricultural machinery equipment and the demand of remote network control of equipment Internet of things,based on ISO 11783 CAN bus standard of agricultural machinery,the CAN bus solution of combine harvester is proposed and designed.The main research contents are as follows:(1)Firstly,the operation process of the combine harvester was analyzed and the disadvantages of the current harvester control system were explained.Then the demand of the combine harvester for the communication network was analyzed.For the communication network requirements of combine harvesters,the comparison between bus network and CAN bus is the most suitable communication network solution for combine harvesters.The CAN bus system network structure consisting of power CAN bus,device management CAN bus,dedicated CAN bus 1 and dedicated CAN bus 2 is designed.Finally,based on the ISO 11783 standard,the CAN bus communication protocol of the combine harvester is designed.The protocol includes data link layer,application layer and network management.(2)The real-time communication problem in the CAN bus network of the combine harvester is studied.Firstly,the reason of communication delay is theoretically analyzed and the mathematical model of communication delay is established.A dynamic scheduling algorithm based on TTCAN is proposed.Finally,the algorithm is simulated on the CANoe platform with the dedicated device bus 2 of the combine harvester CAN bus system.The results show that the algorithm effectively avoids the queue delay and makes the communication more stable,and dynamically generates the scheduling matrix to meet the communication requirements.(3)Complete the hardware design and software development of the nodes in CAN bus system.Hardware: completed the hardware design of CAN data acquisition board,remote information interaction module and gateway,printed and welded the circuit board.Software: completed the system of all functional modules of the software design,implementation and debugging.The software and hardware design of the system is the foundation of the test platform and engineering application test.(4)A test platform of a combine harvester CAN bus system consisting of 20 nodes was built,and communication performance experiments were carried out on the platform.The tests include: system reliability test,load rate test,real-time test and load versus real-time impact test.The test results show that the system communication packet loss rate is within 0.5%,the maximum CAN bus load is within 30%,and the maximum average communication delay of all buses is 1.2ms.And experiments have shown that when the bus load is below 50%,the reliability and real-time performance of the system can be satisfied.Finally,the engineering application test was carried out with the automatic navigation of the combine harvester as an application example.The test results show that the system meets the requirements of the combined harvester engineering application.