The effects of control methods on energy efficiency and position tracking of an electro-hydraulic excavator equipped with zonal hydraulics

Compared to conventional central hydraulic systems still typically used in most off-road machinery, the main advantages of zonal hydraulics are lower pressure losses, lower power demand, and thus, lower energy consumption on a system level and easy automatisation. In this case study, zonal hydraulics is realised with Direct Driven Hydraulics (DDH), and it is implemented as a replacement for the conventional centralised hydraulic system of a micro excavator. A simulation model for the front attachment of the excavator with three individual DDH units is presented. The proposed model of a single DDH unit was partially validated with a standalone test setup. Various common working cycles, such as digging and dumping with differing payloads and levelling, were adopted for this simulation study. Two controllers—a conventional proportional-integral-derivative (PID) controller and a flow-rate-matching feedforward plus PID controller—were designed for each DDH unit. Thereafter, detailed comparisons were provided, consisting of energy consumption, energy efficiency and position tracking performance between the two controllers. The results showed that the proposed feedforward plus PID controller had better performance than a conventional PID in the studied case. By adopting this controller, higher system energy efficiency (improved by 11–24% without regeneration and by 8–28% when considering regeneration) and better position tracking performance (root mean square tracking error and max errors lowered by 20–87% and 35–83%, respectively) were achieved simultaneously. Therefore, this work can be applied to zonal hydraulics to facilitate the electrification and automatisation of construction machinery.