| With the continuous advancement of agricultural modernization,agricultural machinery is developing in the direction of heavy and intelligent.As an essential power machinery in agricultural production,heavy tractors play a vital role in the process of agricultural modernization.This paper has carried out research on the vehicle control unit of heavy tractors,aiming to improve the intelligence degree of heavy tractors and reduce the driver’s working intensity.Firstly,according to the functions and operating conditions of the heavy tractor components,the topology of the CAN network is determined,and the communication protocol of the CAN network communication protocol based on SAE J1939 is established,and the performance simulation of CAN network is completed by CANoe software.Secondly,based on the analysis of the resource requirements of the heavy tractor control system,the hardware design of the heavy tractor controller is completed,including the design and development of the vehicle control unit schematic diagram and printed circuit board.Then,through the functional analysis of the vehicle control unit of heavy tractor,the software design of the vehicle control unit is completed from the underlying layer and the application layer.In the aspect of underlying layer program,the microprocessor driver program,CCP calibration program,fault diagnosis program and Boot Loader program are programmed for the heavy tractor controller by handwritten code.In the aspect of application layer program,the model-based design method is used to establish a tractor control strategy model based on Simulink,which includes engine starting model,electronic throttle processing model,differential lock model,four-wheel drive model and fault diagnosis model.After completing the integration and fixed-point processing of the control strategy model,the application layer embedded C code is generated by the code automatic generation technology,and the underlying layer code and application layer code are integrated in the Code Warrior software.Finally,the validity of the application layer model of the vehicle control unit is verified by simulation and software-in-loop test.The vehicle control unit is tested in the laboratory and in the real tractor,and the test results show that the designed controller can meet the basic functional requirements of the heavy tractor and achieve the expected goal. |
