New compound energy regeneration system and control strategy for hybrid hydraulic excavators

Energy regeneration systems (ERSs) that use the same energy storage device as hybrid power systems can improve the fuel economies of hybrid hydraulic excavators (HHEs). However, conventional ERSs have worse dynamic actuator performance than traditional orifice control systems. In addition, the capacities of both the hydraulic motor and the generator should be large enough to avoid overload. Based on comprehensive considerations, a compound ERS that combines the advantages of an electric accumulator and a hydraulic accumulator was proposed. Then control strategies that guarantee the minimum and maximum recovery times and methods for controlling the boom velocity and improving the recovery efficiency were discussed. A test bench was constructed and described here. An estimated 39% of the total potential energy could be regenerated under the standard operating conditions in the proposed system, while the recovery efficiency of the conventional ERS is approximately 36%. In addition, the recovery efficiency can be improved under extreme operating conditions. It was also shown that the proposed ERS had better control performance than the conventional ERS, while the capacity of the regenerator could be reduced by more than 65%.