The Research Of Hydraulic Hybrid Excavator Power Train System

The current hybrid system researched is electric hybrid system which consists a electric motor as subsidiary power source and batteries as energy storage unit(ESU). This kind of hybrid system has the disadvantage of low power density and high cost. Another hybrid system is hydraulic hybrid in which a pump/motor acts as subsidiary power source and accumulator as ESU. It boasts of the advantage of high power density, high energy economy and low cost which leads to a bright market prospects. This paper research on the hydraulic hybrid excavator and is divided into following sections:(1) Introduction. The principle of electric hybrid system and its flaw is presented. Based on this, hydraulic hybrid system is introduced. The traditional application of hydraulic hybrid, the secondary hydrostatic transmission is not suitable to the excavator and the current application of of hydraulic hybrid, the hydraulic assistant system, is only applied on vehicles, thus the research of hydraulic hybrid excavator is necessary.(2) Section II analyzes and concludes the characteristic of different hydraulic hybrid power trains on excavators and then determines the hydraulic assist power train as the target for deep research. The load model is built as well. All these models are the basis for the control strategy analysis. The mathematic model of engine, accumulator and hydraulic pump/motor and the MATLAB/SIMULINK simulation models are built respectively(3) Section III researches on the parameter optimization of the power train components. According to the actual heavy load condition of excavator, the parameters of engine, accumulator and hydraulic pump/motor is optimized so that the system can fulfill the power requirement and the system efficiency is improved. (4)Section IV researches on the control strategy. The control strategy applied on vehicles can not be applied on excavator due to their different load condition and energy regeneration mode. The control strategy applied on electric hybrid excavator can not be applied directly either due to the different characteristic of ESU. The one-point and two-point strategy will be tested on the hydraulic hybrid simulation model and based on the result a new, suitable control strategy will be presented.