Modelling and energy comparison of system layouts for a hydraulic excavator

For decades the improvement of energy efficiency in mobile hydraulics has forced the research world to develop energy saving solutions and to redesign existing hydraulic circuits. This paper presents an overview about the state of the art of excavator valve systems based on open centre flow control (OFC) and a load sensing principle (LS). The purpose of this study is to compare different hydraulic systems on a middle size (9ton) excavator and to analyse the differences in term of energy saving and fuel consumption. Starting from a validate mathematical model of the considered hydraulic excavator whose functioning is in LS logic, many alternatives are proposed as flow on demand system, positive and negative flow control. Systems comparison has been done on typical excavator working cycles as trench digging and levelling referring to the JCMAS standard. An optimization tool, based on genetic algorithm, has been exploited for the definition of the optimal spool areas to reduce the pressure losses and by-pass flow rate maintaining identical controllability and performance.