This contribution gives a brief introduction to general aspects of “Industrie 4.0”. Besides basic strategies to
improve the added value and flexibility of a production, challenges of the transformation, which have to be
overcome by the companies, are shown. The commissioning of production machines gains more significance in a
dynamic production of a smart factory, so that in consequence the automation of the commissioning would bring
significant advantages. Current fluid power systems are not excluded, since most steps of the commissioning are
still done manually by the technician. By analysing the integration of a linear electro-hydraulic actuator into a
production machine, limitations and problems of current systems are identified and related to the field of fluid
power. The analysis of possible solutions is leading to methods and modern information and communication
technology, introduced by the “Industrie 4.0”.

We present a service for Predictive Maintenance in which existing machine data from control units or data from
retrofitted sensors can be acquired from industrial machines by various gateway solutions. These gateways
preprocess the data onsite and transmit it securely to a cloud-based Big Data system without impacting the
production process of the industrial machine. Additional servers run Machine Learning algorithms to analyze the
incoming data and generate data-based models representing the machine behavior. Results from existing
applications show that significant benefits can be created for our customers and that Machine Learning
algorithms demonstrate superhuman performance in detecting anomalous machine behavior.

Industrial Internet of Things (IIoT) and Industry 4.0 are very popular buzz words today. The „me too” factor is
pretty high and attracted companies are faced with an overwhelming market of data management solutions. But
despite the large amount of data that can be collected from industrial facilities, the real benefit is behind
colourful graphics and charts. To get there, the data provided by the connected components of an IIoT capable
system has to be analysed and put into context. So, the question is not what can be done with all the collected
data but how to generate useful information.

Today buzzwords like “smart machine” and “intelligent component” dominate the discussion about digitalization in the fluid power domain. However, the engineering fundamentals behind the words “smart” and “intelligent” often remain unclear. A common and target-oriented discussion needs transparent approaches including the applied technical system understanding. Therefore, this paper presents new concepts of soft sensor networks which allow the aggregation of information about fluid systems from heterogeneous sources. Soft sensors presented in this paper are physical models of system components that ensure transparency. Soft sensors and soft sensor networks are applied on exemplary hydraulic systems on three different levels: (i) the sensor level, (ii) the component level and (iii) the system level.

This study comprises testing of RoHS-compliant axial sliding bearing materials, including bronzes, brasses,
thermally sprayed coatings and PVD coatings, in a pin-on-disc tribometer and bench testing in an axial piston
pump. The aim was to compare and benchmark these materials against commonly utilized leaded bronze with
respect to durability and tribological mechanisms and to derive principles for axial sliding bearing material
suitability in hydrostatic components. By evaluating the test results, some fundamental understanding was gained
about characteristics which materials must exhibit to achieve sufficient tribological performance and durability in
hydrostatic components including, but not limited to resistance against friction-induced material transformation
and sufficient ductility to withstand pressure-induced part deflection.

Axial piston pumps are universal displacement machines that are used in a vast variety of applications. Their
high pressure resistance and ease of operation make them very popular, especially in mobile applications and
aerospace. The lifetime of axial piston pumps is depending on the design of the rotating kit, the application and
its overall robustness to external loads. The fluid film between the moving parts is responsible for bearing the
loads and sealing the displacement chambers. Its design is the most complicated part for a pump designer. All
pumps to this date have been designed in a trial and error process, which is not only costly, but doesn’t yield an
optimum in terms of efficiency and robustness. This paper aims to investigate the influence the fluid film has on
the lifetime of the pump. From the three main lubricating interfaces of an axial piston pump, two - cylinder block
/ valve plate and slipper / swash plate - were analysed in terms of temperature for both interfaces and gap height
for slipper only by means of measurements and simulation. The simulation tool that was used for the analysis is
called Caspar FSTI, developed by Purdue University. It is capable of calculating the resulting gap height
between all three main interfaces resulting from force balance calculations between external and fluid film forces
due to the pressure distribution in the gap and taking both deformation due to temperature and pressure into
account. The simulation will be used to understand the behaviour of the pump while the measurements will give
a deeper look into the actual steady state conditions as well as transient behaviour of the parts including wear in.

The rotational speed of slipper type, axial piston pumps and motors is limited. One of the most important reasons
for this limitation is the barrel tipping torque, which is (amongst others) affected by the centrifugal forces of the
pistons. The force of the barrel spring is needed to overcome the tipping of the barrel, and thus preventing the
malfunction of the pump or motor. The hydrostatic pressure can create an additional hydrostatic force, pushing
the barrel to the port plate, and thereby preventing the barrel to tip. But, at low operating pressures, the
hydrostatic force is insufficient, and the tipping torque can only be counteracted by the central barrel spring. Due
to the limited strength of this spring, the barrel will tip above a certain operating speed. At that point, the face
seal of the barrel will no longer make a full contact with the port plate, and the pump or motor cannot any longer
be operated, due to excessive leakage and wear.
Floating cup (FC) pumps and motors have the advantage that the pistons are press-fitted into the central rotor.
Therefore, the pistons can’t create anymore any tipping torque load on the barrel. But, unlike in conventional
axial piston designs, in FC-machines, the cylinders are no longer integrated and machined inside the cylinder
block or barrel. Instead, they are separated and have become cup-like cylinders which are floating on, and
supported by the remaining barrel plate. Being isolated from the barrel itself, these ‘cups’ will create another
tipping torque load on the barrel. The weight of the cups is however small, much smaller than the weight of the
pistons in an equally sized slipper type machine. Furthermore, the centrifugal tipping torque is reduced by the
short cup-stroke in the floating cup machine.
Nevertheless, it is desirable to further reduce the mass of the cups, not only to increase the maximum operating
speed, but also to reduce the force of the central barrel spring, which would further increase the overall
efficiency. The best way to reduce the mass of the cups, is by means of a reduction of the wall thickness of the
cups. It needs to be considered that the cups expand when being pressurized. Therefore, in order to maintain a
tight sealing between the cups and the pistons, the piston crown needs to expand as well, thereby following the
radial expansion of the cup. Consequently, the wall thickness of the piston crown needs to be reduced as well.
The question is whether these conditions can be met when the wall thickness of the piston crown and cup wall is
reduced. In this paper, the effects of a 50% reduction of the wall thickness are investigated and described. The
deformation is calculated by means of FEM analysis of the piston and the cup.

During flight, passenger comfort is affected by noise emissions from various aircraft systems. Apart from jet engines one of the main sources of noise within the fuselage is the power control unit (PCU) for high-lift actuation. In preparation for take-off and landing this hydraulic motor is responsible for the extension and retraction of the slats and flaps. Along with the increase in operating pressure from 206bar (3,000psi) to 345bar (5,000psi) noise and vibration induced by fluid power systems became more striking. Consequently the aim of the BMWI founded research project “Move On” was to reduce the emissions of Liebherr’s power control unit. The results of these research activities are presented within this paper. It is shown how the noise emissions could be reduced in a secondary controlled hydraulic motor by means of a valve-plate and structure optimization. In addition the results of a noise measurement campaign, conducted by Airbus on an A350, are presented.

Industrial technology is confronted with the constant demands for a reduction in investment and operating costs. Especially hydraulic power units as a core element for supply of flow and pressure for hydraulic actuation systems have a big influence by minimization of the required oil quantity used as well as by optimizing the targeted fluid condition. In addition to the reduction in the required size and weight, the cost of steel fabrications can also be significantly reduced by a smaller tank and the oil quantity during initial filling and maintenance can be reduced. With the innovative engineering-package “myCro” presented here, these advantages can be exploited by the customer.

Model-based control and regulation concepts will become increasingly important due to their specific advantages, for example in respect of performance, stability, consideration of nonlinearities etc., for hydraulic drives in particular. The fundamental prerequisite for their application is sufficiently precise knowledge of the system's response characteristic. The prerequisite for their acceptance, however, is the availability of computer-supported tools, methods and algorithms, which enable a case-specific identification and controller design. This article presents a concept for achieving these goals on the basis of an innovative nonparametric identification method, which has proved to be extremely efficient in initial applications.

This paper presents a Dynamic High-Torque Test Stand with hydrostatic drive technology. The topics
discussed within the scope of this paper are the mechanical design and the hydraulic characteristics as well
as, detailed solutions implemented in this test rig using innovative technology. The evaluation methods
used to determine the test specimen properties are also described in more detail.

Rising electricity costs are forcing machine builders and plant operators to find solutions for how energyintensive
machines can be operated and produce more efficiently. Large potentials lie in the drive technology
used. The example of the electro-hydrostatic drive concept for the ring rolling process demonstrates how a
higher productivity with minimized power consumption and at the same time simplified and cost-effective
installation brings competitive advantages. Together with Moog GmbH, SMS group GmbH has developed a new
generation of ring rolling machine, the RAW ecompact, with a modern electro-hydrostatic drive concept.

As part of the trend towards greater digitalization the number of sensors installed in mobile machinery is increasing each year. OEMs are consequently now capable of collecting large amounts of component measurement data, which they unfortunately do not have time to analyze or are not capable of interpreting. This is quite a pity, because when used in the right way such information can be used to develop a much better understanding of the machine and to develop new systems with lower fuel consumption and improved performance. The following paper introduces an approach used at Linde Hydraulics to analyse and assess large amounts of data with the goal of systematically identifying potential and designing new and improved hydraulic Systems.

This paper presents the experimental assessment of the very first prototype of Meter Out Sensing System architecture. The system, based on the proportional control of meter out valves, is a novel hydraulic architecture in the field of Mobile Machines. The objective of the hydraulic control is obtained firstly by a negative control of the supply system, adjusting the pressure drop on the meter out to a given value, secondly by a three way compensator able to regenerate the flow. The energy saving is then obtained because of lower throttle losses on meter in connection and the regeneration feature that is enabled hydraulically under specific operating condition.

Rocking is often observed in wheeled excavators while digging, which impacts driver comfort and precision. To
minimize rocking, wheeled excavators need special axles with brakes at the wheel-end. The paper presents a new
solution to use low cost in-board brakes achieving the same or better stability compared to wheel brakes. This is
achieved by disconnecting one axle and braking it, while torque is actively applied on the other axle with a
hydrostatic traction motor, to preload the driveline and keep the vehicle more stable. The system hydraulic
circuit and the corresponding control algorithms are presented, as well as experimental results that prove the
concept feasibility.

The paper is about to show a comprehensive evaluation of energy efficiency in the field of excavating
machinery. The results detected with 21t excavator platforms over years deal as a basis to determine the major
energy efficiency influencers in and outside the machine. Cycles are given for a state of the art hydraulic system
in Asian markets. The measurement data collected and results provided finally lead into an ABC-analysis to
show the urgent need for new approaches to really save energy in future construction processes.

Offshore wind turbines are getting larger in terms of size and power output, resulting in lower rotation speed and higher torque at the rotor. As hydraulic transmissions are generally employed in high load systems, the case for compact hydraulic drive trains is becoming ever stronger. The hydraulic Delft Offshore Turbine (DOT) concept replaces drive train components with a single sea water pump, and pressurizes sea water to a central multi-megawatt electricity generation platform. This paper presents the first steps in realizing the DOT concept, and prototype tests are conducted with a single full-scale wind turbine with a hydraulic configuration. A hydraulic torque control strategy is developed and in-field test results are presented.

A hydrostatic transmission is commonly used in off road construction equipment for its high power density. It
can also be used in wind turbines for more reliable and cost effective transmission than a conventional gearbox.
A power regenerative test platform has been built at the University of Minnesota to understand the performance
of a hydrostatic transmission in a wind turbine. In this paper the use of an advanced control valve to characterize
the components of the test bed has been demonstrated. The electrohydraulic valve has precise control on pressure
and flow and gives more flexibility to the testbed.

Based on different motivations and driving forces for the electrification of hydraulics, this paper introduces and
explains the solutions and basic principles used for increasing the energy efficiency by electrification. The
following chapters explore these solutions and principles in depth. The key success factors for the electrification
of hydraulics are intelligent energy management and appropriate energy storage type and size. Particular
attention is paid to the energy storage systems giving an overview of their optimal application fields. The „Smart
Energy Mode“ energy management solution for industrial applications is then introduced. Afterwards, the Smart
Energy System Design is explained by way of an industrial and a mobile example. The paper concludes with a
remark concerning the current needs of automatic linking of different model-based tools. This ensures the
holistic approach required in this context.

One way to increase the compactness and power density of electro hydraulic power units is to increase the
rotational speed level. Hence, a high-speed electrical drive and a high-speed gear pump are connected.
Particularly, high-speed internal gear pumps are not state of the art and increasing rotational speed entails a lot of
challenges for the hydraulic system. This paper analyses the influence of different pump parameters for the speed
limit of internal gear pumps. Furthermore, a preliminary dimensioning of drive concepts is used to identify the
best concept in terms of power density.

Proportional solenoids generate a proportional force effect from an electrical input signal. The force is created
between the movable armature and the magnetizable counter-piece. Due to this known physical effect and
inherent to the functional principle, the magnetic force can actuate in one direction only. The return movement is
made by a spring. Based on this principle the realization of well controllable hydraulic and pneumatic valves is
possible. The novel solenoid design developed at MSM enables a bi-directional force effect. For this, particularly
the armature is considerably modified and fitted with permanent magnets. In addition to the influence of the
force direction, the pre-magnetisation of materials causes a considerable improvement of dynamics.

During the last two decades the aspect of functional safety has constantly gained more importance for all
manufactures of mobile hydraulic machines or manufactures of subsystems used therein. Initiated by the IEC
61508 /1/ first issued in 1998 many divisions have deduced their own standards concerning functional safety
with the goal to build control structures that are leading to fewer occurrence of dangerous situations during
normal machine operation as well as in the case of a failing subsystem.
Looking into the failure modes assigned to a Proportional Pressure Reducing Valve (PPRV) within the ISO
standard 13849 /2/ it was possible to integrate an intrinsic safety function into various types of pressure reducing
valves. In the case of a stuck valve spool this fail safe function opens a second flow path from the control port to
tank (Figure 1) resulting in a limited output pressure (Figure 2). For applications where this limited control
pressure is in accordance with a safe situation this fail safe function is lowering the number of failure modes that
are contributing to a dangerous situation and therefore is able to increase the diagnostic coverage of a subsystem
build with such a fail safe valve. Depending on the working principle of the pressure reducing valve different
types of fail safe designs are needed in order to realize this functionality.

Pressure control valves combine both a reducing and a relieving function. Such valves typically are spool type
valves which principally suffer from leakage flow. Additionally, in case of an electrical failure, usual
proportional pressure reducing and relieving valves fully open either the supply port connection or the tank port
connection. In some applications like clamping functions in machine tools, this is a clear disadvantage. For fail
safe operation in machine tools, it is desired to hold the set pressure in case of failure. The article introduces a
new kind of proportional pressure reducing and relieving valve, which is leak-free due to seat valve technology.
Furthermore, the valve is able to keep the set pressure in case of power-off and is therefore well-qualified for
clamping applications.

The trend of intelligent components can be observed in various fields. Intelligent component means components
with highly integrated sensors and control technology. This enables the system manufacturer to design more
complex equipment, and nevertheless decrease in the required integration effort. As a customer-oriented supplier
and development partner WEBER-HYDRAULIK concern itself with the development of highly integrated,
reliable and reasonably priced sensors for hydraulic cylinders. While an optical position transducer is developed
for mass production, this article focuses on the development activities of an in-cylinder integrated force
measurement. Parallel to the further development of the application-specific force measurement system for
supporting cylinders, a universally applicable concept for contactless force measurement was investigated.