Mechanical-Hydraulic Co-Simulation And Experimental Research On Loader Full Hydraulic Steering System

As a widely used construction machinery, the loader plays an important role inthe engineering and construction projects. The steering system is one of the importantsubsystems of loader, and its performance directly relates to the safety and reliabilityof the entire machine. Therefore, the research of the steering system is of greatsignificance. The previous research on the steering system was mostly based on themathematical model, which took a variety of simplification and equivalence to thecomponents and the load, and couldn’t build the load model accurately. Consideringthis matter, this thesis combines with the project of “Research on Loader hydraulicand transmission system dynamic simulation and comparative tests”, takes the loadsensing hydraulic steering system of articulated loaders as studying object, and adoptsmechanical-hydraulic co-simulation method to analyze and study the dynamiccharacteristics of the steering system.According to the actual structure of the priority valve and the steering unit, thethesis analyzes the working principle of two key components detailedly. Throughbuilding the static mathematical model of the priority valve and the steering unit,analyze the static characteristics of them. Meanwhile, analyze the related theory of thetire. Then build the simulation model of the priority valve and the steering unit basedon AMESim, and put forward a new modeling approach of the steering unit, whichcan reflect its actual structure fully and ensure the displacement control servo function,thus reflect the principle and performance well. According to different workingconditions, simulate and analyze the dynamic performance of the steering system, andthe results show that the two steering cylinders’ displacement and speed are notexactly the same when turning. The cylinder, at the turning side, has faster velocityand larger displacement than the other’s, which was thought to be the same previously.So the simulation provides a reference for future design work. The experiments of thesteering system of articulated loader verified the correctness of the simulation model,and analyzed the dynamic performance of the system.In view of the difficulties of being equivalent about the steering system load,through using the multi-body dynamics simulation software LMS Virtual.Lab Motionthe thesis builds the dynamics simulation model of the articulated loader, and takes into account the impact of the steering mechanism and the tires with the groundeffects on the steering system, then carries out the mechanical-hydraulicco-simulation with AMESim. The comparison with the experiments proves that theresults between co-simulation and experiments are closed well, and the co-simulationresults reflect the actual situation better than the single simulation. Therefore, themechanical-hydraulic co-simulation has opened a new way of simulating about thesteering system load. Then, co-simulate in different working conditions and analyzethe tire force in turning and its effect on the system pressure, and find out thatreducing the tire cornering stiffness is beneficial to reduce the pressure vibrationpendulum phenomena of the system, which provides a reference for future researchwork.