Research on the design and control strategy for a flow-coupling-based hydraulic hybrid excavator

This paper presents a hybridization structure for the flow coupling of a hydraulic hybrid excavator. Multiple energy regeneration systems are used as the energy source for the hydraulic hybrid excavator. The flow-coupling structure is designed on the basis of practical working conditions and then integrated into a 23 ton excavator as the experimental platform to facilitate power system design and control studies. The initial constant-hybrid-ratio control is first examined using a simulation model to obtain the control performances of the main power source and the assistant power source, and the problems are then analysed to derive a two-step optimization. Prototype experiments demonstrate the effectiveness and feasibility of the flow-coupling-based hybridization structure of the hydraulic hybrid excavator. Test results indicate that flow coupling with an optimal control strategy results in an improved control performance and energy efficiency and can eventually increase the overall energy- saving effect to 10.1%.