Control Optimisation of a Pump-Controlled Hydraulic System using Digital Displacement Pumps

Abstract

When dealing with electrification of working machines, energy-efficient operation is key to maximise the usage of the limited capacity of on-board batteries. Previous research indicate that plenty is gained by reducing component and system losses by means of design. In contrast, this paper focuses on how to maximise energy efficiency by means of control optimisation. Dynamic programming with backward-facing simulation is used to find the optimal electric motor speed trajectory for a scooptram machine equipped with pump control, using digital displacement pumps with dynamic flow sharing as enabling technology. The results show that low shaft speed is preferred to minimise drag losses from parasitic components, partly facilitated by the relatively high and operation point-independent efficiencies of the pumps and electric motor. The results indicate energy reduction of 5 - 9 %, where higher figures could be expected for other, more hydraulic-intense applications, such as excavators.