Whenever decision makers want to follow the trend towards “all-electric” machines, but still need to maintain the major advantages of hydraulic drives, electro hydrostatic actuators (EHA) have become the technology of choice for industrial applications. In an EHA, a variable speed electric motor drives a displacement pump which is directly coupled to the actuator, namely a cylinder. After proofing the functionality of this concept in many commercial applications, current developments are targeting features and levels of efficiency that will even outperform the electro mechanical state of the art. Adaptive electro hydrostatic actuators will finally be the benchmark in terms of compactness, ease of use and energy efficiency for many application classes. This paper presents two different implementations for variable pitch EHAs and a mobile device for EHA fluid management and service.

To reduce cycle times, hydraulic drives become consciously more dynamic, what consequently leads to higher fluid exchange rates. On the part of the pressure supply no effort is too big for the design engineers. The return pipe to the tank is, however, often still calculated with rough formulas. This can lead to damages to the plant by cavitation, water hammers and diesel effects and is no longer up-to-date.
On investigating water hammer events in tank-pipes it becomes obvious that an examination with simple rough calculations is not leading to the desired results. Too many factors must be considered at the calculation of water hammer. Fortunately, nowadays the numeric simulation can calculate the pressure gradient and the pressure am-plitude of a water hammer in very good approximation. Thus, by means of simulation a basic understanding of the problem in the tank pipe can be achieved.
In this contribution the boundary conditions which lead to the emergence of a water hammer after cavitation are introduced. Calculation examples explain the differences of water hammers in drives with HLP fluid and with HFC fluid. By the combination of the simulation results to nomograms, a practice-fit tool is introduced, which can be used to assess the water hammer vulnerability of a drive already during the project planning. The presentation of possible constructive remedial measures completes this contribution.

This paper presents an alternative design approach of electrohydraulic safety manifolds for use in quick-closing
actuators. Setting off from the common 2oo3 voting architecture, a separation of flow paths produces a new
solution employing six solenoid-operated 2/2-way poppet valves with electrical coupling. The technical
discussion exhibits various advantages, such as improved reliability, both from a systematic and from a
probabilistic point of view. It is shown that the new 2oo3plus system beats common other structures with regard
to the safety metrics according to IEC 61508.

During the working stroke of hydraulic cylinder drives unexpected and unwanted resonances in attached pipes are often unavoidable. A main reason is the continuous change of the system's natural frequency because of variable piston and cylinder positions. An analytical investigation of variable resonance situations is difficult since geometric boundary conditions like e.g. diameters and lengths of pipes/cylinders as well as nonlinear effects like e.g. the fluid's compressibility or a viscous-elastic tube expansion must be considered. Typically, concentrated parameter models are used for cylinder drive simulations, though such models are not capable to represent the exact influence of variable cylinder chamber volumes on the resonance situation. This publication presents a new approach that realizes a variable cylinder chamber volume or length in combination with a advanced distributed parameter approach. With theoretical fundamental investigations as well as a simplified example it is shown, that by means of the distributed parameter cylinder, it is possible for the first time to analyse the oscillation situation of a cylinder drive during the complete operating cycle.