Before the hybrid technology was adopted in the field of construction machinery, the research on energy saving of traditional hydraulic excavators mainly included the improvement of hydraulic system and the power matching between engine and load. With the development of electro-hydraulic proportional control technology and electronic control technology, the energy-saving effect of hydraulic excavator has been significantly improved. By adjusting the engine throttle and the displacement of hydraulic pump, the power matching between engine and load is realized, so as to achieve the purpose of energy saving. The traditional hydraulic excavator adopts the open volume control hydraulic system based on variable displacement pump speed control valve, which not only can not reduce the throttle loss, but also can cause the increase of average power. Because of the wide range of excavator working load, it is difficult to realize that the engine working point is often in the area of high fuel consumption, so hybrid technology appears. The engine of hydraulic excavator with hybrid technology can output average power no matter how the load changes. From the perspective of hybrid technology, the key to energy saving is the reduction of average power, the improvement of hybrid structure and hybrid control strategy. Now the research on energy saving of hybrid hydraulic excavator mainly focuses on the improvement of hybrid structure and hybrid control strategy.
