The design and selection of a hydraulic system for a particular machine is based upon a variety of factors which include: functionality, performance, safety, cost, reliability, duty cycle, component availability, and efficiency. With higher fuel costs and requirements to reduce engine exhaust emissions, new hydraulic system configurations should be considered. Traditional hydraulic systems conssume an excessive amount of energy due to metering losses. A single pump usually supplies flow to multiple functions, with differing flow and pressure requirements resulting in excessive metering losses. The energy of mass and inertial loads is usually dissipated by metering losses. Opportunities exist for reducing metering losses by the use of multiple pumps and by using hydrostatic control of individual functions. Hydrostatic control also allows for energy recovery when used in conjunction with an energy storage system. These alternative configurations have the potential of reducing engine size and reducing emissions by reduced transients and lower overall power requirement.
This paper will discuss the source of hydraulic system losses and recommend alternative configurations that can result in dramatic reductions in energy requirements. A dynamic simulation of an example machine will be presented with an improved hydraulic system, illustrating the potential for reduced losses and the ability to accomplish the same functionality and control performance. The benefits of the alternative configuration will be analyzed in comparison to the costs.