The setup of a suspension always leads to a compromise between comfort and safety. In order to counteract this
in a passive approach, one could attach a structural extension in the form of a dynamic vibration absorber to the
axle. Thus, energy of the wheel vibrations is diverted into the vibration absorber instead of the body. In comparison
to a classic dynamic vibration absorber, which is not in the sense of lightweight construction due to the additional
mass, our Fluid Dynamic Vibration Absorber (FDVA) reduces the dynamic mass by using a hydrostatic
transmission.

Mobile hydraulic linear actuators are a fixed part of many applications. Especially in mobile cranes, they are
used for the movement of the booms and are characterized with a light power to weight ratio. The kinematics can
be seen as a restriction of linear motor in mobile cranes. On one side the possible range of the motion and on the
other side the unfavourable constellations of the triangle of force are essentially restrictions in the construction of
mobile cranes. For the avoidance of these restrictions exists approaches by in the joints arranged hydrostatic
rotational motors. At present these solutions fails by a to high weight to force ratio, or they give no benefit in the
kinematics. In this article, a new approach of a hydrostatic rotational motor will be presented, which is
characterized by low weight and high torque. By the possibility to rotate endless these rotation hydrostatic
motors are predestined as a direct drive in the joints of mobile cranes, to get new possibilities in the kinematics
and the construction of the booms.

The performance characteristics of a hydro-pneumatic type accumulator on the responses of the hydrostatic drive
system are studied in this article. The physical system considered for the analysis consists of fixed displacement
pump, hydro-motor coupled with a loading unit and an accumulator. By varying the capacity and precharge
pressure of the hydraulic accumulator and load torque on the hydro-motor, the performance behaviour of the
accumulator is determined. In MATLAB/Simulink® environment, the simulation studies are made. By
comparing the simulation results with the test data, the model is validated. The studies made in this article may
be useful for the proper selection of accumulators in typical mining equipment.

Low damping property of hydraulic systems has been a remarkably troublesome issue for a few decades. The poor damping with two actuators or more is still intractable and pendent due to the complex coupling effect of different loads. A decoupling compensator based on pump/valve combined control is proposed for the system with dual actuators for mobile machinery. Using decoupling control of different load branches, the coupling hydraulic circuit with dual cylinders is transformed into two separate single-cylinder circuits with dynamic compensation. Compound motion tests on a 2-ton hydraulic excavator were carried out. The results indicated that the proposed compensator reduced velocity and pressure oscillations under different working conditions.

In this paper, an active yaw system with valve-controlled hydraulic motor is designed. Correspondingly,
the accurate control method of vane direction based on pressure difference feedback is presented. Then
the simulation analysis is conducted in AMESim. The simulation results show that the control method
presented in this paper is efficient. Moreover, the control accuracy can be improved by decreasing the
friction torque or adding a friction compensation link into the controller. At last, an experimental
platform is built to verify the feasibility of the control method presented. The achievements provide
theoretical and practical guidance for the design of wind turbine active hydraulic yaw systems.

This article presents an innovative technology of energy management for a conventional hydrostatic-split power
transmission (CH-SPT) system used in front end loader (FEL). A fuel efficient controller and a DC generator
are additionally connected in parallel with the load shaft of the drive to prevent the engine and the major
hydraulic components from over-loading or under-loading conditions. Detailed simulation model of the system,
so called Regenerative Hydrostatic-Split Power Transmission (RH-SPT) system is made in the
MATLAB®/Simscape environment. The performance analysis and the fuel consumption of the RH-SPT drive is
compared with that of the CH-SPT drive through simulation. It is observed that with increase in 10% fuel
consumption, the electric power regeneration through the DC generator increases by 21% of maximum power
generated in CH-SPT drive.

In the current cooling system structure of machine tools is a central fixed pump provides a constant cooling volume flow to cool all the components of the machine tool. The provided cooling volume flow does not match the temperature development of each component. This may lead to some of the components heating up while the other components are simultaneously being cooled. Due to these temperature differences, a thermo-elastic deformation of the machine structure occurs. This deformation is responsible for the displacement of the Tool Centre Point (TCP) of the machine tools. Consequently, the machine’s accuracy during the production process is reduced.
The main goal of this paper is to analyse the thermal behaviour of the current cooling system structure of two demonstration machines and to present a simulative study of new cooling system structures under consideration. The investigation of this research will examine the effectivity as well as the temperature characteristics of the components of the new structures under consideration comparing them to the current cooling system structure in order to ensure a uniform temperature distribution of the machine tool at minimal energy consumption.
The results show that the new concepts have great potential in respect to better thermal behaviour and lower hydraulic power compared to the current cooling system structure. The simulation results show a more stable temperature profile of the components as well as a lower energy consumption of the cooling system.

A new energy efficiency evaluation method, based on least squares combination weight (LSCW), is proposed in this paper. Furthermore, the method is based on the thorough analysis of Fuzzy Analytic Hierarchy Process (FAHP) and Information Entropy (IE). Because of the multi-parameter characteristic of the ammonia refrigeration system, some critical parameters are firstly selected with the help of detailed simulation. Subsequently, a new two-dimension matrix constructed by these parameters is designed. According to the actual working system, compared with the FAHP and IE, results show that the new method has better precision, smaller relative error and greater consistence with actual energy efficiency change.

Energy efficient and environment conscious solutions are currently in high demand. This paper illustrates the
potential of pump-controlled actuators such as directly driven hydraulic drives (DDH) for various zonal
hydraulics applications. A novel pump-controlled actuator, powered directly by a servo motor is considered for
industrial and mobile applications replacing conventional valve-controlled hydraulics. This solution is targeting
improvements in energy efficiency, especially for continuous operation systems, however, due to the nature of
the solution, system response has high dependency on electric motor dynamics. Therefore, adaptive controller is
designed to realise benefits of the DDH. Study presents results of performance by simulation of this new
concept.

The paper presents an optimal reference tracking algorithm for electrohydraulic steering systems which is based
on multivariable system identification, linear quadratic control and Kalman filtering for state estimation. A
laboratory test-bench composed of electrohydraulic-steering unit (EHSU), steering cylinder, 32-bit
microcontroller, steering wheel and joystick supports experimental work. Traditional approach for reference
tracking in steering usually is based on classical control algorithms such digital PI regulator or non-digital hydromechanical
feedback. In contrast the control theory suggests advanced control techniques, which can take into
account multivariable nature of the process. In this way a higher closed-loop performance can be achieved.

Functionality and performance of novel hydraulic systems under real life stress can usually be examined in field tests only. In order to gather information about the behavior under stress during the development process as soon as possible, system components as well as systems get tested on test rigs. In hydraulics, applying passive loads e.g. to linear actuators can easily be done by throttling the outflow. For rotatory units, loads can either be applied with ropes and masses or other rotatory units. Especially applying active loads i.e. loads with the same orientation as the motion of the cylinder, is difficult and usually connected to a high complexity. At Karlsruhe Institute of Technology (KIT), a hydraulic load unit for hydraulic cylinders was developed to be used at various test rigs. The load units’ controller design allows for the application of either active or passive loads in variable directions and intensities. The following paper introduces the load unit, its open- and closed-loop control concept and the verification results from simulation, which show the potential of the load unit.

Fault tolerance is the most important feature in safety-critical applications, including aircraft flight controls,
nuclear systems, and medical devices, but it is a desirable property of any mechatronic system. In this paper, the
fault tolerance of a multi-outlet digital hydraulic pump-motor is studied. This machine has actively controlled
on/off valves to independently connect each piston to the tank or one of its outlets. Furthermore, the pump-motor
can control an actuator directly without having directional control valves in the system; thus, the on/off control
valves of the machine are the most vulnerable components of failure. A valve can either become jammed on (not
able to close) or off (not able to open), whether the fault is electrical or mechanical. The effect of a defective
valve is studied through simulations, and a method for fault compensation is proposed with a control algorithm
adapted for each fault case. The simulations and experimental results show that the valve faults can be
effectively compensated for by reconfiguring the software. Only slight degradation in the control performance
can be expected.

An independent metering valve control system (IMVCS) controls the meter-in and meter-out orifices of a valve independently. This innovative structure achieves a better energy saving performance, but also requires a more complex control algorithm. A flow and pressure coupling control system is proposed to control both the flow rate of the load and the pressure in each chamber. A DSP controller with TI-RTOS real-time operating system and digital driving module is adopted for fast response and accurate control. A two level fuzzy PID control algorithm and a lookup table algorithm are applied to improve the performance of the IMVCS. Experimental results show that the created control system can effectively control an IMVCS, and realize the function of flow and pressure coupling control.

This paper presents an experimentally validated semi-empirical lumped parameter model developed for analysing the dynamic stability and performance limitations of a pressure compensated vane pump system. The model calculates continuous displacement chamber pressure profiles for the determination of the internal forces acting on the vane pump’s pivoting cam. Extensive measurements conducted on a custom test stand were used to define a nonlinearly progressive bias spring model and a transfer function model of the pump control system valves for realistic system characteristics. Analysis of the complete model reveals the performance limitations imposed by the control system valves in terms of system stability and achievable controller bandwidth are the most restrictive.

Regarding the trend of optimizing energy efficiency and meeting upcoming regulations of energy consumption
there are many ways to refine existing hydraulic drive systems. To gain more knowledge about components,
combinations of those components and their interaction with the overall process, a combination of measurement,
simulation and calculation of energy consumption is used to build the foundation for finding optimization
approaches regarding the efficiency of electro-hydraulic pump drives. This is a three-step process focusing on
the following topics: increased component efficiency, matching pump drive components and adjusted process
layouts. By utilizing this strategy, a manufacturer- and customer-dedicated optimization of pump drive systems
can be realized.

This contribution presents a holistic approach to the system optimization of a highly dynamic proportional valve. The model with lumped parameters which is used for the evaluation of the closed-loop performance is parameterized based on Finite-Element-Method (FEM) data. In addition to the calculation of static characteristic curves, a suitable excitation signal is applied to the transient FEM simulation. The valve dynamics of the current geometrical valve design are identified using the transient simulation results. This new approach enables a fully automated system optimization of a proportional valve. Hence, during the optimization, human expertise is not required.

The paper presents the Dana methodology to address the integrated design for winch systems. Beginning with
the analysis of the generic expected performance of the system, the main issues and tasks are evaluated;
moreover, the design workflow and the main benefits of integrated design are described with particular attention
to the strong team working required to fulfil the defined target in the most efficient way.
Different sub-systems are analysed: the hydraulic motor-winch coupling, with particular attention to clocking
speed and its relationship with motor non-uniformity grade and specific reducing gear-ratio to improve
hydraulic-mechanic coupling, the hydraulic control system with the possibility to integrate several different
functions in a compact and efficient solution, the winch torque sensor and motor angular sensor, which are
specifically designed to merge with the components, provide fundamental information for the defined control
strategy and also for safety assurance and the central control unit and its software providing an efficientintegrated
control strategy and a user-oriented capability for personalization.

The paper presents a methodology for calculating the pressure loss in unsteady flows through concentric annular
channels. The momentum equation in axial direction is solved in the Laplace domain to obtain the unsteady
radial velocity distribution. Based on the velocity profile, the relation between the Laplace transforms of pressure
loss and area-averaged flow velocity is derived. A time domain representation of this equation is provided for
oscillating flows. For arbitrary temporal distributions of the flow, the inverse Laplace transform of the relation
between pressure loss and flow velocity has to be derived. Since finding the inverse Laplace transform of the
exact weighting function for each possible radius ratio is cumbersome, the annular channel flow is approximated
by a plane channel. An error analysis shows that this approximation introduces errors less than 1 % for channel
geometries down to radius ratios of 0.45. The approximated weighting function is transformed into the time
domain by using the residue theorem from complex analysis. The resulting convolution integral can be used in
one-dimensional hydraulic system simulation software.

Water hydraulics are used for applications which require an environmental safety standard for the fluid. In comparison to oil, lubrication with water is a challenging aspect because of the fluid’s lower viscosity. Wear and leakage in water lubricated contacts require lower pressure loads. In order to estimate the possible load carrying capacity in water hydraulics, the tribological contact between the piston slipper and swash plate in axial piston machine and respectively eccentric shaft in radial piston machines is investigated. For this purpose simulations based on the Reynolds-Equation are carried out and analysed.

Digital pumps using high speed on/off valves to control fluid entering and leaving the piston cylinder displacement chamber can increase efficiency by eliminating the leakage and friction associated with the port plate. Leakage scales with the displacement because the displacement chamber is only pressurized during a portion of the piston stroke. This work investigates the modeling, prototyping, and testing of two prototype digital pumps. The first prototype actuated on/off valves using electrical solenoids; the second configuration used mechanical cams. The mechanical actuation improved the repeatability and accuracy of the valves, matching or exceeding the performance of the electrically actuated prototype while eliminating all transducers and electronics. The mechanically actuated pump operated at 86% efficiency (full displacement) and 58% efficiency (25% displacement).

A new-born design and construction of a mini gerotor metering pump with trochoidal-teeth is presented. The
technical innovation in this new-born design is to study the fluid dynamic effects of interteeth and lateral
clearances by using OpenFOAM toolbox, an open source CFD software. This work is based on two critical
aspects, the deforming of the mesh following the solid gears rotation, a complex interaction between mesh and
gear profile surface that has to maintain a moderate quality of the mesh, and the simulation by means of a new
boundary condition of the interteeth contact, reproducing actual contact points between the rotors. The posibility
of contact point simulation by means of a proper mesh motion model is also suggested.

The proportion of churning losses increases significantly with the increasing speed, thus churning losses reduction has a significant influence on the efficiency improvement in axial piston pumps. In this paper, a test pump with nano-coating is proposed, and analyzed in details. The analysis shows that the surface energy and friction coefficient on the outside surface of cylinder block are reduced due to the decrease of surface roughness and wettability on the nano-film. Experimental results indicate that energy losses of the proposed nano-coated test pump are reduced by 12~37%. Some of the conclusions in this paper may provide a suitable novel guidance for improving the friction-reducing abilities in axial piston pumps.

The objective of this work is to design and investigate the aerodynamic performance of a novel integrated motor-compressor. The integrated motor-compressor integrates the axial-flow compression into the electromagnetic function by designing the airfoil-shaped rotor of the electric machine to provide compression. Hence, the integrated motor-compressor is both an axial-flow compressor and an electric machine. It is capable of providing axial flow compression and electromagnetic torque at the same time. In this work, the aerodynamic design of the proposed machine is done and evaluated by both analytical method and computational fluid dynamics (CFD). The effect of attack angle to the blade lift and drag forces are investigated. The effect of solidity to the axial-flow compressor performance is also evaluated. The electromagnetic performance of the proposed machine is investigated by motor sizing equations and finite element analysis (FEA).

While designing an hydraulic cylinder, you may spend a long time choosing the right seals, guide rings and wipers that will fit into the application. In the case of a standard cylinder with a wide application range, the plentiful options offered in the market will make the search difficult and validating the different combinations will be costly. Based on standard applications in mobile hydraulics, Freudenberg Sealing Technologies has developed sealing systems for rod and piston taking into consideration the cylinder application and the right combination of sealing elements and guide rings. The designer can rely on expert knowledge to quickly pick up a sealing system for the cylinder instead of spending time searching for every single seal in the cylinder.
Keywords: Fluid

In this study, the efficiency of the low speed high torque gerotor hydraulic motor for mobile hydraulic was investigated. A gerotor with the floating outer ring is rarely described in literature. The purpose of this paper was to analyse the influence of the size of the holes in the valve plate on the total efficiency of the gerotor. A very high total efficiency was obtained with the hole size of Φ6,3 mm. In that case, the total efficiency was on average 5 % higher in comparison to the initial hole size of Φ5,5 mm. Some tribological tests have been performed. We investigated relationship between surface roughness, contact force and friction. The minimum friction was 0,077.

In the paper, an active-control digital hydraulic damper is designed and modelled, which is comprised of multiple digital throttle units. The digital throttle units consist of a throttle valve and high speed on/off solenoid valve which are connected in series. A mathematical model of the digital throttle unit is provided. A control algorithm based on PID is given which is used for the active control of the variable throttle area. The working process of the active damper is simulated and analyzed in AMESim with a comparison of the working process of a passive Porous Hydraulic Damper. Pressure-Time curves, Displacement-Time curves and Velocity-Time curves are given which show thet performance differences between the active-control digital hydraulic damper and the passive Porous Hydraulic Damper. According to the simulation comparison, it is clear that the buffering stroke of the active-control digital hydraulic damper is increased by 8.9% but the peak pressure of the active-control digital hydraulic damper is reduced by 20% compared with the passive Porous Hydraulic Damper. It indicates better performance of the Digital hydraulic damper which can complete the damping process more smoothly and effectively.

The resonant behaviour of voice coil actuators driven by fast changing signals limits their application in hydraulic servo valves. A very good damping, precision and the ability to dynamically overcome the effects of flow forces are some special requirements. The paper attempts to propose some control strategies and solutions to reduce the effects of raising impedance near the resonant frequency, thus improving the damping, which allows further enhancements in bandwidth. Theoretical models and simulation results are presented and discussed and some recommendations are proposed. The parameters used in simulation correspond to those of an already developed and tested voice coil prototype.

With the rapid development of industry, the dynamic performance of hydraulic components has drawn more and more attention /1/. In many hydraulic systems, it is difficult to optimize the designs of the flow components because of many complex parameters and dynamic flow field/2/. At the same time, it is necessary to find out the key structure areas that affect the relevant hydraulic performance and ensure that multi-parameters are optimized synchronously. In this study, the multi-conditions optimization design algorithm is proposed to achieve the optimization of hydraulic components (for example, the throttle valve) by combining the adjoint method and the mesh deformation technique.

In flat steel industry, a hydraulic mould oscillator (HMO) sophisticated mechanism is frequently used to provide
oscillatory motion to the steel casting mould. The HMO system is highly sensitive to oil contamination,
accordingly for the sustainability of operation, oil contamination level must be monitored and controlled to
ensure that it meets system requirements. While continuous oil filtration had been practiced in EZDK Co. factory
in past years, now a novel approach is being adopted that incorporates online monitoring of oil contamination
level and its control via an external filtration unit. This approach lowers filtration unit electric power
consumption and increases its service life-time.

Government-enforced regulations have led to increasing demands for energy efficient solutions in the industry.
To diminish the losses of hydraulic systems and to increase their energy efficiency, several pump control
methods have been developed. In this work, a new experimental direct drive actuator solution, powered directly
by a servo motor controlled hydraulic pump-motor, is evaluated. As an additional innovative feature, a load
compensating hydraulic circuit has been introduced in order to reduce power consumption even further. The
study presents results of performance measurements of this new concept.

Aiming at the disadvantage of long time and high cost in the reliability evaluation of the hydraulic pump based on the life test or accelerated life test, a reliability evaluation method for hydraulic pump based on performance degradation is proposed. The stochastic volatility, individual differences and measurement errors have been considered in the creation of the degradation model. Compared with the method based on degradation path model and Wiener process model, it is necessary to consider the stochastic volatility with time, individual differences and measurement errors of performance degradation in the reliability evaluation of hydraulic pump based on degradation.

A Matlab/Simulink model is utilised to study the total energy consumption and power distribution of a micro
excavator. The model consists of the hydraulic and mechanical systems related to actuation of the front hoe, i.e.
boom, arm, and bucket. The excavator is equipped with pressure and position sensors, from which the
measurement data is collected for parameterization and verification of the simulation model. Two different duty
cycles, named the digging and loading cycle and levelling cycle, inspired by the JCMAS standard, are utilised in
this study. The results indicate substantial room for improvement, concerning the hydraulic system, since power
loss of as much as 60% occurs in the proportional directional valve group.

This paper deals with the design, practical realization and wireless control of a prototype of an electro-hydraulic
robotic manipulator (EHROM) suitable for handling heavy weight objects in industrial environment. The
EHROM has been designed in the Laboratory for Automation and Robotics at the Faculty of Mechanical
Engineering and Naval Architecture, University of Zagreb. The prototype has been completely built in
cooperation with two Croatian companies and is fully open to implementations of various control methods. The
robotic manipulator has three-degrees-of-freedom (spherical or polar kinematic configuration) with a hydraulic
gripper at the end of the mechanical structure. The manipulator uses a load sensing hydraulic system that
provides superior controllability regardless of the load and also contributes to the energy efficiency. Originally
the manipulator had no advanced way of being operated, other than the use of joystick or levers on the hydraulic
valve block itself. The control system has been upgraded with an assembly suitable for wireless control of the
manipulator using a mobile device on iOS platform. This multidisciplinary task involved skills in mechanical
engineering, electronics and electrics, as well as computing. The paper focuses on the wireless control of the
manipulator using a low-cost microcontroller and custom made controlling interface.

The automation of mobile hydraulic machinery, such as bionic robot, requires high power-to-volume ratio and
high performance control solutions, which means miniaturized, integrated, and intelligent hydraulic systems. The
purpose of the paper is to present a new type of hydraulic swing drive for narrow spaces, where the position
sensor is integrated as a part of hydraulic system. The structural characteristics of this hydraulic swing drive as
well as its functionality are presented in detail. Through the comparison with the traditional hydraulic motor,
position resolution and power-to-volume ratio have been further improved, therefore the application of hydraulic
systems has been expanded, especially in some kinds of bionic robots.

Offshore wind energy has become the most important green energy globally. Due to the wave the working point
of the vessel oscillates and cannot be kept in a fixed position so that the maritime or underwater construction
become difficult and dangerous. Therefore, an active levelling controlled multi-axial hydraulic Turbine Access
System (TAS) system for offshore wind farms is necessary for improving this problem. This study aims to
investigate a new active levelling control multi-axial hydraulic system for Taiwan offshore wind farms including
design, dynamic modelling and simulation of TAS mechanism, hydraulic driving system, control system, and test
rig set up for dynamic simulation and experiment. The vertical height, the rolling angle and the vertical acceleration
of the end effector of TAS can be effectively reduced through the active motion compensation control of TAS for
improving the access safety of the offshore wind turbine. For simulation, the dynamic modelling and co-simulation
can be implemented by software ADAMS (Automated Dynamic Analysis of Mechanical Systems) for mechanism
integrated with MATLAB/SIMULINK for the hydraulic driving system and the closed-loop control system of the
active motion compensation control in order to verify the effect of active compensation control system of TAS.
Besides, a full-scale test rig of the TAS is set up for verifying the effect of active compensation control system of
TAS experimentally.

In this paper, a rotational pneumatic muscle actuator (PMA) is applied to build a brand new pulse diagnosis system for the traditional Chinese therapy (TCT). In traditional Chinese therapy, a doctor uses his/ her fingers to press the patient’s artery on the radial bone in order to feel the pulse signal of the patient. Based on empirical judgment, the doctor can realize and point out what kind of physical condition the patient is suffering from. However, this kind of pulse-sensing diagnosis technique relies mainly on the subjective feeling from the doctor’s fingers. Therefore, it is possible that different doctor might have a different viewpoint for the same pulse signal. In this study, a well-accepted hypothesis of Organ-Resonance will be introduced to build the complete pulse diagnosis system for TCT. The rotational PMA proposed in this paper serves to imitate the finger motion of a TCT doctor. In addition, the spectrum theory and Fast Fourier Transform (FFT) are also employed to compute and acquire the biological message hidden behind the detected time-domain pulse signal. Finally, experimental results prove the validity of the presented automatic pulse diagnosis system for TCT.

Aiming at the difficult problem of obtaining typical fault samples of pneumatic actuators in engineering practice and basing on the working principles of pneumatic diaphragm actuator, a model of pneumatic diaphragm actuator system was established by using DAMADICS. Then we simulated its common and typical faults and obtained a lot of samples. In this research, using KPCA to reduce the date dimension that obtained by the established system. We use the method of fault detection and diagnosis based on artificial immune algorithm to pneumatic diaphragm actuator’s fault diagnosis. The experimental results indicate that the fault detection method based on artificial immune algorithm performs well.

This paper presents the modeling and model validation of a gas pressure control system with a two stage pressure reducing unit. Such regulator structures are in routine use if requirements of high accuracy are coupled with a large pressure drop. Dynamic behavior of such systems drastically depends on performances of the pipe section in between two control valves. In the paper, two system modifications are considered. The initial system has a heating unit installed between two control stages and connected with them by long pipe lines. The field operation of the system at low temperature requires moving the heating unit upstream the first control valve. So the section volume between two stages decreases, and the system is prone to unstable behavior. The both modifications of the system are compared, its dynamic performances are studied on the simulation model and the critical volume of the intermediate section is defined. The experimental results revile reasonable agreement with theoretical analysis.

The traditional hydraulic components reliability test method has a long test time, low test efficiency and high energy loss, and can not meet the requirements of the reliability test of the core hydraulic components in the hydraulic system. This paper designed a parallel energy-saving method and equipment to test the reliability indexes of key hydraulic components for the hydraulic actuator of FAST. The calculated results met the lifetime request of the gear pump and the relief valve for hydraulic actuator of FAST. The reliability model based on small sample test can be used to estimate the lifetime desperation of components accurately under the status of the limit for the number of sample.

A method aims at analysing the fluid-solid-thermal coupling effect of one type of mechanical seal on failure is
proposed. The method considers the coupling effects among fluid, solid and heat into one numerical simulation
procedure. The deformations of one specific seal are calculated by ANSYS. Samples collected form workshop
and field are used for validation of the analysis. Results show that excessive stress is the main reason for the
internal ring fractures of the stationary graphite ring. The method proposed in this paper can well predict the
location of the fractures. This analysis method is helpful for exploring the failure mechanism, and designing
optimization of mechanical seal with longer lifetime and higher reliability.

Aiming at the vibration produced by the hydraulic pipeline system during operation, a bionic hydraulic pipeline
with three layers of structure is developed based on the animal biological mechanism. The 14 - equation of
hydraulic pipeline is perfected and the fluid-structure interaction dynamic model suitable for the bionic hydraulic
pipeline is deduced. The two-way fluid-structure interaction analysis of the ANSYS simulation software shows
the bionic hydraulic pipeline has better effect on absorbing pulsation and suppressing vibration. The results will
provide a new technical approach for obtaining better vibration control effect.

The paper presents some results obtained in an experimental research, in order to measure the total resistant forces which appear during the switching process of directional control valves. After some theoretical considerations regarding the possibility to calculate the resistant forces, in the second part of the paper there are presented the research infrastructure, the way in which the experimental research was conducted, and also the main results obtained, as well as some conclusions drawn after analyzing the graphical evolution of the total resistant forces, results which have allowed to determine the total resistant forces, needed for dimensioning of the electric coils or the switching mechanism.

Spray characteristics during the injection process of a combustion system, bubble formation in chemical reactors or hydraulic fluids all share surface tension as a key variable regarding aforementioned behaviours. Depending on the system. Liquid-liquid or liquid-gas interphases play a defining role. In this work, the most relevant measurement methods are presented. Based on the Du-Noüy-method, the surface tension of common fuels as well as mixtures is measured and presented. The measurements do illustrate the influence of mixture components on surface tension as the behaviour can be strongly non-linear. Additionally, the applicability of the aforementioned measurement methods on high-pressure surroundings is investigated and a possible solution for measurements up to various 100 MPa is introduced. With liquid-gas interphases being quite difficult to handle at high pressures, an assessment is made for nitrogen regarding it´s properties und extreme conditions.

As a response to the strict government emissions regulations, hybridisation of non-road mobile machinery is required. In this paper, behaviour and efficiency of a hybrid mining loader is studied. The full prototype with implemented DDH (Direct Driven Hydraulics) units had been built; however, its performance was unsatisfactory – a large undershoot and steady-state error of 34 % persisted. Therefore, a new control strategy was suggested to overcome the issues. Performance of the system was enhanced by applying a fuzzy PID controller. As a result, reference tracking was significantly improved compared to the conventional PID control case and steady-state error of 1 % was achieved, while the overall efficiency was kept high in the range of above 50%.

The widespread use of electro-hydraulic (EH) technology of the last decades has led to important improvements in the control features, safety and performance of hydraulic machines. However, limited work exploited the use the EH control features for condition monitoring. This paper proposes a neural network based diagnostic algorithm, that takes advantage of the parameters of a controller developed for the case of an independent metering hydraulic system. The reference application is a truck loading crane available at the authors’ research center. The results show how the proposed methodology is effective to detect faults (the faults considered pertain to the pump, the metering valves and the cylinder), with a limited number of sensors.

This paper focuses on the faulty issues of the independent metering valve (IMV) in mobile applications. First, typical faults are studied in a 2t excavator to analyze their negative influences. The model of the abnormal system is estimated according to the results of fault detection and diagnosis. Accordingly, a fault-tolerance controller is designed to reconfigure normal controller by the coordinate control of other parallel available valves. With the presented fault operation, the dynamic characteristic under reconfigured modes can strictly match with that of faulty system. Simulations are conducted in the excavator to verify the fault-tolerance controller.

In this paper three concepts of double pump supply units are presented and compared to a conventional variable
displacement pump as reference. These supply units consist of two off-the-shelf pumps in a parallel arrangement
and they are meant to perform like a continuously variable source of flow rate. In order to evaluate possible
energy savings of the supply units, their efficiency characteristics are firstly computed in a steady-state
simulation but also examined on a test bench. By means of a semi-synthetic load profile for an exemplary
application, the annual savings of the systems are calculated in comparison to the reference pump. Moreover, a
rating system for the system’s complexity is shown and applied to the three concepts in order to judge the tradeoff
between efficiency and complexity. The studies show that the more complex concepts provide higher saving
potentials than simpler systems, but the interdependence may come unpredictably in some cases.

Hydraulic excavator is widely used in the construction field, due to their small size to power ratio and big
actuation forces. However, due to large throttling loss and gravitational potential wasting, its energy efficiency is
very low, which is even lower than 10%. This paper aims to improve the energy efficiency of the hydraulic
excavator by reducing throttling loss and regenerating potential energy directly based on a novel pump
controlled system. The system under consideration utilizes a newly designed asymmetric pump which has three
ports, the two are connected to the hydraulic cylinder, the other is connected to an accumulator. Thus, this
system can regenerate the potential energy directly and can match the unequal flow rates of the single rod
cylinder basically. Furthermore, working performances of the excavator boom system with the asymmetric pump
and independent metering circuit are studied comparatively. Results show that, compared with an independent
metering circuit, the electric power consumption during the boom going up can be reduced by 56%.

Water in oil-based hydraulic systems is a source for many machinery failures. It accounts for up to 20% of the
life expectancy failures and even before that, it impacts the expected performance negatively /1/. Water can enter
a hydraulic system in various ways. In this article, the entry through the dynamic seal of the rod is investigated.
After a brief description of the damage mechanisms of water in a hydraulic system, the theory of the entrainment
is explained. The test bench is then described to study the effect. Finally, entrainment results for two test fluids
(oil and water) are presented and compared to the theory.

The DOT concept for offshore wind energy is a seawater hydraulic network where turbines are directly
coupled to a centralized hydro-power platform. The essential missing component is a low-speed hydraulic
pump that uses seawater as its hydraulic medium. This low speed hydraulic pump is currently being
designed and tested by DOT, where novel machine components have been developed. This paper describes
the development of an interface between an oval running track which is used as eccentricity to actuate a
hydraulic piston. Several approaches have been performed as well as prototyping and validation steps.
These steps as well as the design approach are presented in this work.

Free gas in a hydraulic system is usually accompanied by negative aspects. Currently available models usually underestimate degassing at liquid-gas interfaces that are exposed to fluid flows, which is the most relevant degassing mechanism in hydraulic systems. Therefore, a new approach for physical modelling of bubble formation at liquid-gas interfaces is presented. Based on recent findings on diffusion-driven nucleation a simple model to calculate the mass fraction of gas being set free in a hydraulic fluid is derived. This approach is experimentally validated and could be implemented in available calculation tools.

Wear in swashplate type axial piston pumps mainly occurs in three tribological contact pairs. These are
swashplate-slipper, piston-cylinder and cylinderblock-valveplate. This article focuses on a simulation model,
based on the approach of Archard and Fleischer, to predict the wear in the piston-cylinder contact. Besides
general geometric data, the exact piston and cylinder contours and the wear-induced material removal over time
are taken into account. A special focus in the simulation is on the investigation of the dependency of the
viscosity of the hydraulic fluid on the wear. First results from test runs demonstrate a good correspondence
between the simulation and measured wear on a test bench.

An integrated retainer which wraps the slippers and rotates with them is assembled in an Electro-hydrostatic actuator (EHA) pump, to eliminate the high linear velocity at slipper bottoms and to diminish the PV (pressure×velocity) value of the contact area. The impacts of laser surface texturing on the performances of the high-speed rotating retainer are investigated by conducting the CFD simulation of the flow inside several micro-dimples and the experiments on an EHA pump prototype. Wear marks are observed and the dimples with an area ratio of 16.4% are found to improve the volumetric and mechanical efficiencies of the prototype by up to 7.4% at the speeds of 6000~10000 rpm.

Pneumatic drives are widely used in industrial applications. As the energy demand of production systems becomes more and more important, nowadays, many users favour a reduction of the general supply pressure to save energy. Nevertheless, some applications afford compact and powerful drives. To serve these demands, an energy efficient local pressure boosting is necessary. Today, linear pressure boosters based on double-piston cylinders are used to fulfil this task. The paper proposes a novel concept based on pneumatic radial piston motors. The new concept features a radial piston compressor, which is driven by a radial piston motor. The paper shows simulation data as well as a validation by experimental investigations of a working model of the new booster. Different configurations of the booster are examined for a range of driving pressures and pressure ratios. The experimental results are compared to a standard pneumatic booster subsequently.

It is known that the performance of a hydraulic system can be increased significantly by a combination of a
pump and a reservoir. As the electrical vacuum generation’s ability to compete compared to classical ejectors is
limited in this article the combination of pumps and reservoirs is applied to the vacuum technology used in
automated handling processes. Evacuation times and energy consumption of the electrical vacuum pumps are
measured. Two possible use case scenarios are the basis for investigations how a fluid reservoir influences
evacuation time and energy consumption. The results are then compared to a pneumatic ejector.

The increasing requirements on fast switching pneumatic valves, especially regarding the installation size, durability and high dynamics, demand for innovative systems. Magnetic shape memory (MSM) alloys are smart materials that can be activated by magnetic field to produce force and motion. Due to their high work-output and dynamics they are a promising alternative technology for a new generation of fast valves. This paper presents an investigation on the design process of a fast switching pneumatic valve based on MSM alloys. In particular, two valve concepts are described: a lever valve concept based on the magnetic elongation and mechanical resetting of the MSM element by a spring, and a seat valve consisting of an air-cored coil with a MSM element which opens the valve during its compression. The first valve concept is characterised by a lower dynamic behaviour compared to the second valve concept, but also by smaller power input required for actuation. Thus, different applications are addressed.

In this paper, a control algorithm for PWM based control of fast switching pneumatic solenoid valves is studied
on the basis of the measured fluid flow characteristics. The dynamic nonlinear behaviour of fast switching valves
is analysed using state-of-the-art mass flow sensors. The minimum PWM pulse width and nonlinear flow
characteristics depending on PWM pulse width and pressure difference are observed. On the basis of the
experiment data a new intelligent control algorithm based on the customized bilinear interpolation method is
developed and tested on pneumatic muscle.

The increase of system dynamic within the area of pneumatics requires sophisticated numerical methods to determine the systems’ performance. Cycle durations in the range of just a few milliseconds and below require the implementation of transient gas dynamic solvers to predict the systems behavior accurately and to save computational time. Yet, such solvers lack of accuracy for sharp edged elbows. This paper presents a hybrid approach using a one dimensional and a two dimensional finite volume Riemann-Solver. The results are compared to analytical acoustics theory and to a CFD approach using a turbulence model.

The paper presents possible use of Ionic Liquids as a lubricant suitable for use as a hydraulic fluid. After a short presentation of ionic liquids and their interesting properties, the paper focuses on very low compressibility (resp. very high Bulk modulus) of ILs compared to the common hydraulic mineral oils and investigates the effects of their high bulk modulus on pressure pulsation and flow ripple of hydraulic pump.
Two most adequate ionic liquids for hydraulic application with highest bulk modulus where chosen and a special test rig was built using bent axis 7-piston pump powered by a servo motor. Results show change of resonance frequencies of entire hydraulic system due to higher bulk modulus and higher density of the ionic liquids. On the other hand, there is no significant change in pump pressure pulsation in non-resonance frequency range below 2500 rpm.

With pressure levels rising for applications such as compression-ignition engines and numerical design approaches are used to optimise fluid power components, rheological properties of the fluid in the according operation points gain interest. The measurement of viscosity under high-pressure has been subject to research for many years. However, to this day, it still bears uncertainty. This paper presents typical errors for high-pressure measurements and strategies to minimise uncertainty. With a focus on material combinations, geometric parameters and the measurement principle, the errors are explained, and an improvement proposal is given based on the findings.

Utilizing accumulators in hydraulic systems with the purpose of energy storage, temporal changes in state of the storage medium must be considered during design and prospectively also monitored during operation. High efficiency aside, the reduction of weight and size is of high interest, especially in mobile applications. Regarding these objectives, accumulators with sorbent material are an innovative and promising development. The herein introduced generic physical model enables the consideration of sorption processes in the description of such accumulators. The results are discussed by means of time response analysis and compared to the behaviour of conventional accumulators. Potential use cases are investigated and the model application to a practical duty cycle is shown.

High pressures and harsh working conditions in hydraulic systems has made us sceptical about suitability of
plastics for its components. Nevertheless in some cases it can become a sufficient substitute for expensive steels.
In water hydraulic components, where demanding surface contacts are slowing its development, polymers can be
a solution. Focus of our research is on implementing polymers into a moving contact in high speed water
hydraulic on/off valve where high friction and wear occur. In this article we are presenting friction coefficient
and wear rate of some engineering polymers immersed in water for different time periods. PEEK and POM
showed comparable results regardless their price difference.

To reduce turbine mass, maintenance requirements, complexity, and thus the Levelized Cost of Energy (LCOE) for offshore wind, the Delft Offshore Turbine (DOT) concept combines individual hydraulic drive train wind turbines with a centralized generator system. In 2015 DOT built and tested a large-scale prototype, by retrofitting a 600kW wind turbine with a hydraulic drive train using commercial off-the-shelf components. The goal was to showcase a proof of concept from a technological and controllability point-of-view. This paper presents the results of building and testing the DOT500. Its drive train has an oil-hydraulic stage and a water-hydraulic stage. The method of rotor torque control with spear valves is novel and proves to be a substitute for conventional implementations.

This paper deals with light-emitting phenomena in hydraulic components, which are closely linked to cavitation.
Both the micro-diesel effect and the gas discharge have been optically investigated within plane models of a
valve and a pump section, respectively. The gas discharge is caused by an electrostatic charge of the oil or of the
component. One result of the investigations is an overview of the areas of occurrence and the minimum
necessary operating conditions of the phenomena. The form of appearance of both phenomena is also shown.
Furthermore, the impact of electrically insulating materials is presented. In addition some measurements of the
temperatures in close proximity to the phenomena are presented.

In this investigation, hydraulic fluids of varying base oil and additive composition were evaluated in a dynamometer fitted with a reservoir that incorporated an aerator at the inlet, and a mass flow meter at the outlet. The effects of aeration on piston pump efficiency and air borne noise generation were evaluated. Hydraulic oils that entrained a greater volume of air demonstrated lower volumetric efficiencies and higher sound levels. The fluids differed in volumetric efficiency by as much as 8% and perceived sound level by as much as 50%. Based upon 2,500+ hours of testing in a high-intensity loader application, the performance benefits of the low aeration fluid were persistent.

In common practice a hydraulic cylinder undergoes permanent acceleration and deceleration. In general this transient behaviour is neglected in the simulation of hydraulic seals, especially regarding the fluid film where stationary conditions are assumed. In order to gain a detailed understanding of the dynamic sealing process, a finite element based, elastohydrodynamic simulation model for hydraulic seals has been developed, including transient effects /1/. In this paper the influence of these transient effects on the behaviour of a hydraulic seal is investigated. The influence is studied under different system conditions in order to examine to which extend the consideration of transient effects in a simulation of hydraulic seals is inevitable.

The presented work investigates the temperature dependence of the Navier slip boundary condition and the related reduction of load capacity of a bearing. In part (i), the Navier slip boundary condition is discussed and a modified Reynolds equation, including slip, is derived. Based on this modified Reynolds equation, the pressure distribution and the load capacity of a slider bearing are obtained. Part (ii) presents the Darmstadt Slip Length Tribometer, utilized for measuring the slip length of technical rough surfaces. Part (iii) shows the temperature dependent results of the slip length measurements and the effect on the load capacity of the slider bearing in comparison to the standard no slip boundary condition.

The piston/cylinder interface in axial piston machines requires both sealing and bearing functions. The fluid and structure coupled physical phenomena including the temperature distribution of the piston and cylinder block controls the gap fluid behavior, therefore, the dual functions of the piston/cylinder interface. Instead of addressing the heat transfer problem of the piston and the cylinder block separately as the former model, the proposed advanced heat transfer model solves the temperature distribution of both solid bodies together using the fluid domain heat transfer characteristic to assemble the two solid parts. Comparing to the former unconnected heat transfer model, the integrated model is found more robust and accurate especially at challenging operating conditions.