In the field of hydraulic drive technology various power supply systems are used within different power unit set-ups. The both of two mostly used drive concepts in modern electrohydraulic systems, a variable displacement pump driven by constant speed electric motor and fixed displacement pump driven by a variable speed electric motor, have some disadvantages, especially regarding the increasing demand for maximum efficiency of the entire power unit without lowering the high dynamics. The combination of a variable pump and speed-controlled electric motor, offers the option of setting two parameters of the drive, the rotational speed of the motor and the pump flow-rate.Such a combination allows all power unit components to operate within the areas of their maximum efficiencies, the so-called maximum efficiency drive. A prerequisite for designing suitable controllers that would ensure the operations of individual components within the areas of maximum efficiency, regardless of the current operating point, is certainly knowledge about the efficiency area of the entire power unit. This paper presents a procedure for determining areas of efficiency, first on the basis of simulation and detailed models of each component, and later verification of the model using an experiment.

Hydraulic power units are one of the most commonly used power sources in industry. The progress in recent years has offered high efficiency and reliable hydraulic components, yet the hydraulic tank design is often neglected part of the development.The paper presents the development of industrial 400 litre hydraulic tank. In order to reduce oil swirling and improve stability of fluid flow, CFD simulations of oil flow inside hydraulic tank were made. Several variations of new hydraulic tank designs are compared with standard industrial tank. Furthermore, to achieve steady flow through the entire reservoir and reduce the phenomenon of oil swirling, newly-developed diffuser is used. Consequently a full scale hydraulic power unit was built according to obtained results.

Improvement in regard to machine energy efficiency is one of the more important goals throughout all fields of research. This is especially true for hydraulically driven machines with large installed power. The use of the appropriate drive concepts, along with a suitable control concept, can result in quite substantial energy savings. Equipping a hydraulic machine with a speed-variable drive and a variable displacement pump enables maximum efficiency tracking for all operating points, represents the most promising drive concept in regard to energy savings. For each operating point, there is an optimal pump setting; consequently, the hydraulic system is able to ensure hydraulic power with minimum losses if the drive components are selected thoughtfully and the system controlled properly. However, in the desire to maximise the system efficiency, the system's responsiveness is too often overlooked.The paper summarises the principle of different drive concepts, along with the drive controller, in terms of the dynamic response and the drive efficiency. Although the speed-variable drive concepts are the most efficient, they have some disadvantages, which are also presented.

The aim of this work was to identify, which of the known ionic liquids used within the technical area, primarily as a lubricant, would also be appropriate for use as a hydraulic fluid. In this context, their suitability has been proved based on experimental research with respect to the appropriate physical and chemical properties as required for mineral based hydraulic fluid. Primary aim of the research was to determine the ability of ILs to protect against corrosion, which is one of the important factors in choosing an ionic liquid. The results show that, despite excellent lubricating properties, certain ILs fail on this corrosion test. Except the corrosion protection performance of the basic hydraulic components parts, e.g. hydraulic pumps and valves, in the foreground was their compatibility with other materials used within other parts of hydraulic system, e.g. coating of the hydraulic tank and the filter material. For this purpose standard tests methods for mineral based hydraulic oils have been used, supplemented with non-standard tests, carried out at the same conditions as they occur during the operation of the hydraulic system.

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