Optimal design of a compound hybrid system consisting of torque coupling and energy regeneration for hydraulic hybrid excavator

For hydraulic hybrid excavators (HEEs), two recoverable energy sources for power hybridization are from engine optimization and actuator energy regeneration. This paper presents a hydraulic hybrid system that integrates with these two sources using engine torque coupling and boom energy regeneration, thus to further explore the fuel economy potential of HHE. Their different characteristics are analyzed first to perform specialized system design. Then an optimal control problem is formulated and solved for system sizing. The effectiveness of the proposed system and its energy saving performance will be assessed, as well as the contributions of engine torque coupling and boom ERS, respectively.