| Most wheel loaders adopt rigid suspensions,and the working device is also rigidly connected to the front frame.During operation,the vibration from traveling is transmitted to the driver’s cab and the working device through the vehicle body,leading to material spillage,reduced work efficiency,increased structural friction,decreased mechanical service life,and potential health effects on the driver.This study aims to improve the driving smoothness of wheel loaders and develops a fully differential connected travel stability system with dual oil dampers.The main research work of this study is as follows:Based on the existing stability system for wheel loaders,improvements and innovations have been made,and a fully differential connected travel stability system scheme is proposed.Depending on the number and position of oil dampers in the system,single oil damper and dual oil damper fully differential connected travel stability systems are introduced.The developed dual oil damper fully differential connected travel stability system is chosen as the research object for mathematical modeling,analyzing the system’s stiffness and damping characteristics.Through analysis,the nonlinear stiffness and damping characteristics of the system are obtained,and the practical significance of the developed system is discussed.Based on the passive control hydraulic suspension system,the overall dynamic modeling of the wheel loader is conducted,taking into account the pitch motion of the vehicle body.Three-degree-of-freedom dynamic models of the whole vehicle are established for the cases without the travel stability system,with the original travel stability system,and with the fully differential connected travel stability system using dual oil dampers.Simulation models are built using the Matlab/Simulink module and subjected to excitation from a filtered white noise E-level road surface model.The models are then simulated and compared.The results show that after incorporating the travel stability system,the vertical acceleration of the loader’s body,body angular acceleration,and working device angular acceleration are significantly reduced.Furthermore,with the improvement of the original travel stability system to the fully differential connected travel stability system using dual oil dampers,the three evaluation indicators are further reduced.Based on the semi-active controlled hydraulic gas suspension system,the fuzzy control and sliding mode variable structure control theories are introduced.Two different control strategies for the semi-active controller of the travel stability system are designed,and the working principles of the controllers are defined.The semi-active control models are established using Matlab/Simulink for passive control,fuzzy control,and sliding mode variable structure control.The vehicle body acceleration and suspension deflection are taken as evaluation indicators,and comparative simulation analysis is conducted under the excitation of D-class and E-class road surfaces.The results show that the introduction of semi-active control technology further reduces the traveling vibrations of the wheel loader,particularly the sliding mode variable structure control exhibits more significant effects on vibration control. |
