Classification of Hydraulic Drive Networks & Their Key Elements

Hydraulic drive networks enable efficient actuation of multi-actuator hy- draulic transmission systems which incorporate different coupling mecha- nisms between the actuators. So far, the topics of hydraulic drive networks have mainly been centered around the use of variable-speed electric machines combined with fixed hydraulic displacement machines for enabling actuation. However, actuation in hydraulic drive networks may be realized in multi- ple ways, including the use of variable hydraulic displacement machines in through-drive configuration with a single electric motor, hydraulically sup- plied hydraulic motor-pump configurations and so forth. This paper makes a classification of a hydraulic drive network and its different coupling layers in the form of fluid short circuit connections, flow couplings through hy- draulic displacement machines, and couplings related to the rotational speed of the hydraulic displacement machines. Requirements for the hydraulic dis- placement machines are discussed and different component configurations and their control degrees of freedom are discussed considering the different coupling mechanisms.