This paper investigates the energy efficiency of a Direct Driven Hydraulic (DDH) system and a proportional electrohydraulic system. A detailed analysis of their energy efficiency is carried out based on experimental results obtained in laboratory conditions using a fully loaded cylinder and sine wave reference trajectory. To ensure fairness in the testing process, the same cylinder with the same initial conditions is used for both systems. The cylinder velocity is estimated online using a novel algebraic differentiator approach based on measured cylinder position. The power of each component is calculated from the obtained measurements, and the energy efficiency of the system is given, along with the losses for each component. Based on the obtained results, it is concluded that the efficiency of the DDH system with a fully loaded cylinder is 28%, while that of the proportional electrohydraulic system is 4%. The significantly higher energy efficiency of the DDH system is attributed to its use of a power-on-demand approach, in contrast to the proportional electrohydraulic system.
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