| Wheel loader is a kind of machinery with high energy consumption, high emission and low efficiency. It is significant to research energy-saving technology of wheel loader, at present resource scarcity and environmental degradation confronted the globe fiercely. This research is supported by the NSFC(Natural Science Foundation of China) project—Extreme load estimation and intelligent extrapolation optimization of multi-power hybrid engineering vehicle in whole working condition,(No.51375202). The wheel loader with 1.8 ton load capacity is used as the testing machine. A problem is show that the engine in the power train is always working in the low efficiency range and the load fluctuation is large through the test and analysis on the wheel loader. To improve the working performance and the fuel efficiency, this thesis focused on the energy-saving technology of power system and driving system. The control strategy is made according to the work modes and the system structure of the 1.8 ton wheel loader. And the parameters in the driving system are matched. The whole project is also verified by simulating in the computer. The specific research work are done as follows:Firstly, the test plan is ensured according to the operating mode of the wheel loader. The applicable sensors are chosen and demarcated. The testing wheel loader is refitted and the test instrument is installed on it. The curves of four work cycles of all test data are analyzed. According to the analysis, it is obvious that the load of the wheel loader has strong regularity and cyclicity, the powers of the shaft and the pump vary frequently with major fluctuations.Secondly, the control strategy of the motor torque dynamic distribution of independent driving system of front and rear axle in series hybrid wheel loader is proposed by analyzing the hybrid system. The thermostat and power follow control method is used in the system. According to the control method, the engine is limited in a specific section to reduce the fuel consumption and increase the emissions performance. The torque of the motors in front and rear axle is dynamically distributed to further improve the economic and dynamic performance of the vehicle.Thirdly, under the precondition of satisfying the dynamic performance, proper parts are selected and parameters of the hybrid wheel loader are matched by analyzing the work load and control strategy of the traditional wheel loader. Based on the selected parts and structure, models of control system and power system of the hybrid wheel loader are established. These models are the basis to verify the control strategy.Finally, comparison and analysis of simulation data of traditional loader and hybrid loader are made. The economic and dynamic performances of the hybrid wheel loader in different working conditions are analyzed. The results show that the hybrid wheel loader reduces fuel consumption, under the condition of satisfying the dynamic performance. It is obtained that the wheel loader with the average distribution of motor torque hybrid system can save energy by 12.8% and the dynamic distribution of motor torque hybrid system can save energy by 15.3%, compared with the wheel loader without hybrid system in the ‘V’ working condition. The 10.6% and 14.4%energy saving are shown in the extreme ‘V’ working condition. Under the working condition of straight driving with full load, the hybrid system can save energy by 17.8% and 18.6% respectively.The method of research on hybrid wheel loader is proposed. The whole research programme of the hybrid structure, the control strategy and the testing method are presented after analyzing the working performance of the traditional wheel loader. These research results could be used in other relevant research on hybrid construction machinery as reference. |
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