Modeling and simulation of electronic control full hydraulic steering system for grain combine harvester

Abstract: In recent years, combine harvester navigation system based on machine vision had important significance in improving the harvesting efficiency of combine harvester, reducing the labor intensity of the driver and so on. In order to realize the automatic steering control of the combine operation path, it is necessary to reconstruct the original hydraulic steering system of combine harvester. To analyze the steering performance of the modified electronically controlled hydraulic steering system for combine harvester in visual navigation system, mathematical models of the electronically controlled hydraulic steering system were established after introducing the structure of combine harvester visual navigation system. The system was mainly composed of combine harvester body, full hydraulic steering, steering transmission mechanism and hybrid stepping motor. In this paper, the mathematical models of the parts were established respectively. The steering model of combine harvester was firstly simplified to linear 2-DOF rear wheel steering vehicle model, and the basic handling dynamics model of combine harvester was established. Then, the dynamic mathematical model of simplified hydraulic steering system was given in the analysis of the fully hydraulic steering work principle for combine harvester. And then, the static model of the steering transmission mechanism was established according to its geometrical structures. Finally, the stepping motor model was simplified as an inertial system according to the step response performance, and its transfer function was given. The electronically controlled hydraulic steering system was simulated through the joint simulation method of each mathematical model by Simulink software. In order to verify the correctness of simulation models, the dynamic response characteristics of steering system was tested with the steering wheel angle step input of 90° on Xinjiang 2A combine harvester. In the real vehicle test, vehicle yaw rate was obtained by the vertical gyroscope, the lateral velocity signal was calculated according to the lateral acceleration of vehicle and the steering wheel angle signal by comprehensive estimation method. The comparative analysis of the simulation and real vehicle test showed that: Combine lateral velocity and yaw rate of the steady-state value was consistent with the real vehicle tests, and the output of lateral velocity was about -0.25 m/s, the output of yaw rate was about -12.5°/s, and the steady-state error is less than 5%. In the signal transient response, the transition time of simulation and real vehicle test were the same, which was about 1.8 s. The lateral velocity and yaw angle response speed of simulation was faster than the real vehicle test results, but the overall trend was the same. Therefore, the conclusion can be drawn that the established system models are accurate and reliable; And its consider not only the static mechanical characteristics of the electronically controlled hydraulic steering system, but also the rear wheel steering handling dynamics characteristics of combine harvester, full hydraulic steering dynamic characteristics and dynamic response performance of the stepping motor. The results reflect the dynamic and static characteristics of the electronically controlled hydraulic steering system for combine harvester visual navigation system, and provide a theoretical basis for the controller design of combine harvester visual navigation system and the realization of visual navigation system.