| The energy recovery technology of hydraulic excavator is one of the important research topic in energy conservation and emissions reduction, and it has significant benefits of economic and environmental. Due to the large inertial load of the boom of hydraulic excavator, there has large energy consumption in the process of lifting and lowering of tne boom. Hence, it is required for us to regeneration and reuse potential energy of the boom for further improvement of fuel consumption.For the characteristics of hydraulic excavator, the energy recovery style of hydraulic which not only meet the requirements of vilent fluctuation of energy recovery conditions, but also avoid the conversion between hydraulic form of energy and other forms of energy. However, when the boom comes down, the working pressure of the hydraulic accumulator will be improving in the hydraulic ERS without balance cylinder, leading the pressure differential of the control valve change. Thus,the good control performance of the boom can not easily Guaranteed. And also, the regenerated energy in hydraulic accumulator is hard to release directly via the regeneration path. Commonly, a reuse circuit should be set separately. In the hydraulic energy recovery system with balance cylinder, the original driving cylinder and balance cylinder are rigid connect, and they drive the load via power coupling.When the boom was lowering, the load distribution ratio driven by balance cylinder increased gradually, so the pressure of hydraulic accumulator increased gradually,then, the load distribution ratio driven by original cylinder decreased, so the pressure of piston chamber of original cylinder decreased gradually. The speed of lowering also can control by adjusting the flow control valve of drive unit. Hence, the apply of hydraulic accumulator between actuator and load, the most load is driven by balance cylinder can make smaller power output of driving unit, that provides a new way for the energy recovery technology.Applying the ERS in HEs, the working style the system should be considered. A1.5-ton HE is research object. The regenerated energy of the boom is calculated. The recycle characteristic of ERS is analyzed based on experimental result and simulationresult. Considering the defects of the hydraulic ERS without balance unit, an ERS that combines main cylinder and balance cylinder is proposed. In such systems, the force caused by the accumulator’s pressure acting on the balance cylinder always takes itself as a balancing weight for the boom. The pressure of the main cylinder is determined not only by the load, but also by the pressure of the accumulator. Then,the mathematical models of the conventional orifice control system and the proposed system are established. And the natural frequency and the damping ratio in the two control system are analyzed. The simulation of the proposed ERS in AMESim software is carried out and the influence on the control performance is brought forward. As the goals of the balance cylinder and hydraulic accumulator is fully balance the boom’s gravity, the parameters of balance unit based on some constraint conditions are designed and optimized. The control strategy of balance unit and the drive unit is discussed to gain the best energy saving and the boom control performance, which creates a sense of the boom cylinder moving at the same speed as in the conventional HEs for the driver. A test rig was constructed. An estimated 58.2%of the total potential energy could be regenerated in the proposed ERS In addition, the experimental results proved that it can reduce fuel consumption by more than 21%. It was also shown that the proposed ERS had good control performance. |
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