Study on modeling and control strategy of hybrid system in hydraulic excavator

To achieve energy saving for hydraulic excavator,a control strategy applied in parallel hybrid hydraulic excavator system was developed.Structure of the parallel hybrid hydraulic excavator system was analyzed.After the system simulation model was built and its characteristic of work condition was concluded,a control strategy using engine fuel economy and battery state of charge(SOC) as optimization variables was proposed.Multi engine work points and SOC upper and low limits were set in the control strategy.Work points or work ranges of the engine were automatically switched according to the comparison between current SOC and SOC limit during the work.Simulation results indicate that the control strategy can keep good fuel economy of the engine,and maintain SOC of the battery stable in set range 72.5%～88% both in digging operation and leveling operation.The control strategy can benefit the efficient and steady operation of the system.