Hybrid Hydraulic Excavator Control Strategy Design And Parameter Optimization

Hydraulic excavators(HE)have been paid much attention in the field of energy saving and environment protection,for the reason of their large application quantities,high fuel consumption and bad emission.So high efficiency and energy saving have been one of the main aims to be pursued by excavator manufactures.Ameliorating the situation of power match for engine,hydraulic system and actuators is one of the main research orientations,but the fluctuation of the engine's operating state due to load variation will result in high fuel consumption,bad emission and noise performance.This paper is mainly about the method and theory of using hybrid powered system to ameliorate the engine's operating state, the research results are verified by simulation experiments.First of all,traditional overall power match methods of HE were classified into two groups:Backward Overall Power Match and Forward Overall Power Match.Based on the study of each method's disadvantages on engineering realization,this paper put forward an improved backward overall power match method by using hybrid powered system,the principle and functions of the system were discussed subsequently.The control strategy design of the energy management between engine and electric motor is the key to realize the anticipated energy saving goal,so we made a special study focused on this core content and technical difficulty.The Electric Assist control strategy applied in parallel hybrid electric car was analyzed,and then we designed two new control strategies:Constant Work Point control strategy and Fuzzy control strategy.Subsequently,a simulation platform of hybrid system was set up. According to the simulation and comparison of traditional HE and each hybrid HE with different control strategies,hybrid HE with Electric Assist control strategy,Constant Work Point control strategy and Fuzzy control strategy reduce fuel consumption respectively by 0.48%,5.1% and 6.09%compard with traditional HE,this had not included several energy saving aspects like the cancellation of engine's idle speed,the reduction of engine's instantaneous fuel consumption and system's energy regeneration,etc. Finally,we employed genetic algorithm to do the research on single-object optimization of hybrid HE with Electric Assist control strategy,the objective function was fuel economy and the design variables were the upper and lower limit of battery SOC(state of charge). Then we also employed genetic algorithm to do the research on multi-object optimization of hybrid HE with Constant Work Point control strategy,the objective functions were fuel economy and accelerograph switching times,the design variables were the upper and lower limit of battery SOC.