| Differential is an important component in vehicle's drive axle, presently, the main types used in Wheel Loader are Open Differential and Passive Limited Slip Differential(PLSD), however, Active Limited Slip Differential(ALSD), advanced type, has not been used in Wheel Loader. ALSD can adjust its limited-slip function in time according to the road condition, which keeps the vehicle in a better drive state. if used in Wheel Loader, it will improve the Loader drive performance efficiently.Compared with the development of ALSD at home and abroad, ZL50 Loader is taken as the research object, based on the analysis of the structure and the transmission process of Open Differential and friction-plate PLSD, completed the type selection, structural design, control system design and transmission analysis of electric-hydraulic ALSD according to the feature of large torque and low speed in Loader powertrain.The characteristic of engine and hydraulic converter, and the phase-matching characteristic of them have been investigated by the sequence of the power transfer in ZL50 Loader drive system, it have been built the model of transmition and drive axle, and the tire model is also determined. Integrating the dynamics of engine, hydraulic converter and other drive components, it has been derived the ZL50 Loader dynamic differential equation of four-wheel drive, and built the drive system dynamics model in straight running. On account of articulated chassis change Loader gravity center and tire load accompany with the steer angle changing in steering, which make the tire slip angle changing with steer angle too. Therefore, by analsizing the characteristics of kinematics in articulated steering and considering the influence of steer angle, the drive system dynamics model in steering has been established.Differential, separated from drive system, which works as a control model, the inner structure of the controller and its algorithm has also been put forward. Firstly, with the analysis of the running condition of Loader which need differential acted. Secondly, selectμ-split road as simulation environment. Finally, the simulation system of ZL50 Loader drive process has been established. After analyzing the characteristic of the tire properties and obtaining the initial stable dynamics parameters, the iteration cycle process of solving dynamics differential equation has been established. It has been designed some programs in Matlab, which can simulate the performance of Loader in straight front-wheel drive, steering front-wheel drive, straight four-wheel drive, steering four-wheel drive, compared the result of simulation with ALSD, PLSD and Open Differential.The simulation results verify the fact that electric-hydraulic ALSD can overcome the inherent shortcomings of PLSD, which can adjust limited-slip function as the road adhesion coefficient variety, and control the slip state of tires. So it can improve the drive force and the lateral force efficiently, which prove that electric-hydraulic ALSD, and its structure parameters, composition of system, control strategy, control method are satisfied with Wheel Loader. |
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