Boom energy recuperation system and control strategy for hydraulic hybrid excavators

In this paper, a boom potential energy recovery hydraulic system for an excavator and its controller is proposed and evaluated. It is a trend in the construction machinery sector to adopt hybrid systems to recuperate potential energy from heavy loads. Many studies have been conducted to improve the efficiency of boom potential energy recovery. However, most of the proposed solutions have limitations regarding commercialization due to low controllability and high cost. The proposed system in this paper uses only electronically controlled hydraulic components. Different operation modes are defined to increase performance, efficiency or a balance between the two. The system is mathematically analysed to derive a control strategy that is able to increase machine efficiency and control performance while maintaining its controllability. The system and control strategy are applied to a prototype machine, a Volvo 30-ton class excavator, to verify the effectiveness of the proposed approach. Experimental results demonstrate that the working cycle becomes around 3% faster, and the fuel consumption becomes around 9% lower than the operation in non-hybrid mode.