Recently agricultural tractors developed themselves to a central and very complex unit. By connecting the various control units
via CAN-Bus-technology the whole control system of the driveline-magement and the effectivity and quality of operation can be
improved further. The main task of the paper was find and to compare different simulation methods for various driveline strategies
and to varify these on a teststand and during real field operations with a tractor and a plough. A simulation model was investigated,
that uses a delayed neural net to cover the nonlinear dynamic connections of the engine and an existing model of the hydromechanic-
split CVT-gearbox. Two different strategies are examined, to optimize the operation, when the full power is not needed.
Depending on the chosen speed and the actual done job the optimal operating settings in combination of the engine and the CVT will
be examined. To be comparable the classic control technique will be set first. As next a Fuzzy-logic control setting is realized. The
assessment of both systems with data measured directly during a field test is based on the quality of control and the actual fuel consumption
for these controls.
As a result was examined that a Fuzzy-logic control for this situation can improve the operation but the justification for this
ependiture needs to be prooved.
On the basis of the introduction of theoretical fundamentals, dynamic interactions in hydraulic pipeline systems are studied using
different simplified simulation methods. Simulation results of the concentrated parameter method, the distributed parameter method
and the transfer matrix method are represented and compared with each other as well with the help of Bode analyses of magnitude
and phase in the frequency domain.
By flow simulation, the internal flow processes in a hydraulic pressure relief valve and a servo valve are investigated under different calculation conditions with the aid of CFD. The analyses of turbulent flow, the cavitation phenomenon under steady and unsteady condition and dynamic opening and closing process of the pressure relief valve are carried out using the corresponding turbulent-, multiphase- and dynamic meshing model provided in the CFD commercial code – FLUENT. Studies of the distributions of
various parameters, e.g., static pressure, velocity magnitude, velocity vector and volume fraction of vapor especially for the evaluation of the cavitation are carried out under the corresponding computing conditions.
Furthermore, the offline and online coupled simulations of simple hydraulic systems are implemented with the interfaces of 2- Level-S-Function in Matlab/Simulink and UDF (User-Defined-Function) in FLUENT. The principle of the coupled simulation using the model of the distributed parameter-characteristic method and CFD is briefly introduced. In the case of online coupling, the dynamic velocity profile at the inlet of the pressure relief valve, which is obtained by the simulation with the characteristic method, is
used as boundary condition for the internal flow analysis with CFD. The online coupled simulation is realized by the assignment of two parallel-working personal computers, which respectively implement CFD calculation and the computation with the characteristic method. The necessary transfer of the signal files is accomplished per TCP/IP to bring the coupled simulation to success. Hereafter, some simulation results are represented to validate the validity of the coupling principle.
During the past decades many efforts have been made to apply numerical techniques to the study of the flows inside hydraulic
valves with particular attention paid to the analysis of the flow forces: this thesis presents innovative contributions to the CFD (Computational
Fluid Dynamics) analysis of hydraulic directional control valves.
After a theoretical description of the flow conditions inside a generic proportional or traditional valve with an in-depth study of
the three dimensional effects on the discharge coefficient and flow force parameter values, a complete CFD analysis of the flow
conditions in a middle size ON-OFF closed center hydraulic directional control valve is presented.
In particular, the three-dimensional analysis points out that the circumferential flows and the consequent pressure losses are not
negligible so that the computation of the flow rate and of the axial flow force by means of a purely axis-symmetric model determines
an unacceptable global parameters estimation.
A new non-dimensional coefficient that connects directly the flow force to the square of the flow rate has been proposed and this
coefficient shows a limited dependence on the circumferential pressure losses effects.
A test rig has been properly realized in the Fluid Power Laboratory of the Polytechnics of Bari and experimental results confirm
perfectly the numerical results.
The thesis presents, moreover, an experimental and numerical analysis of the flow forces acting on the spool of an ON-OFF open
center hydraulic directional control valve.
The analysis has been realized at different flow rate values. The results highlight that the maximum flow force value occurs when
the recirculation flow rate vanishes while in the first opening phase the flow force acts in the opening direction. The peak value of the
flow force increases with the increasing flow rate but its position remains fixed. The numerical results are very reliable and are confirmed
by the experimental measurements.
A section of the thesis is dedicated to the complete analysis of the flow conditions determined by a variable slope chamfer on the
spool of a directional traditional valve. The analysis has considered both flow directions and the contribution of the different effects
is presented. The obtained results show remarkable differences between direct and inverse flows.
A complete CFD unsteady analysis shows that the usual hypothesis of pseudo steadiness of the efflux conditions for spool velocity
around 0.1 m/s is absolutely valid, thus proving that the steady numerical simulations can offer a good estimation of the flow
force trend during the spool opening. In fact, the fluid dynamic phenomena develop with time scales that are always much lower than
the spool displacement ones. The last conclusions are valid in the case of commercial traditional valves, while ON-OFF or proportional
valves with higher dynamics require, surely, a complete numerical analysis.
The thesis presents also a numerical analysis of the flow inside a proportional directional valve with tetrahedral notches. The numerical
results show that, in this kind of valves, the circumferential flows inside the chambers downstream and upstream of the
notches do not significantly influence the efflux conditions.
Virtual Prototyping has been generally adopted in product development in order to minimise the traditional reliance on testing of
physical prototypes. It thus constitutes a major step towards solving the conflict of actual increasing development cost and time due
to increasing customer demands on one side, and the need to decrease development cost and time due to increasing competition on
the other. Particularly challenging for the off-road equipment industry is that its products, working machines, are complex in architecture.
Tightly coupled, non-linear sub-systems of different technical domains make prediction and optimisation of the complete
system’s dynamic behaviour difficult.
Furthermore, in working machines the human operator is essential for the performance of the total system. Properties such as
productivity, fuel efficiency, and operability are all not only dependent on inherent machine properties and working place conditions,
but also on how the operator uses the machine. This is an aspect that is traditionally neglected in dynamic simulations, because the
modelling needs to be extended beyond the technical system.
The research presented in this thesis focuses on wheel loaders, which are representative for working machines. The technical system
and the influence of the human operator is analysed, and so-called short loading cycles are described in depth. Two approaches
to rule-based simulation models of a wheel loader operator are presented and used in simulations. Both operator models control the
machine model by means of engine throttle, lift and tilt lever, steering wheel, and brake only – just as a human operator does. Also,
only signals that a human operator can sense are used in the models. It is demonstrated that both operator models are able to adapt to
basic variations in workplace setup and machine capability. Thus, a “human element” can be introduced into dynamic simulation of
working machines, giving more relevant answers with respect to operator-influenced complete-machine properties such as productivity,
fuel efficiency, and operability already in the concept phase of the product development process.
Hydraulic elevator is one of elevators and it has become increasingly popular in Europe. However, considering environmental
protection and energy-saving, the hydraulic elevator with large installed power and high energy consumption can not be widely applied
at present. Therefore, the key interest of the hydraulic elevator is aimed at the reduction of its energy consumption and the
realization of its high efficiency.
In this paper, the hydraulic elevator of energy-saving with closed circuits is proposed using hydraulic counterweight, VVVF control
and cylinder lifting technology. The paper contents include the enhancement of system efficiency, the reduction of energy consumption
and oil quantity, the realization of pumping station miniaturization and the assurance of speed control performance and so
on. Not only the proposed method of energy-saving can be applied to the hydraulic elevator, but also to the other mechatronic system.
Furthermore the article is of great value academically and practically.
In recent years, electronically controlled automotive transmission systems, where wet clutches are used as intelligent differentials,
have appeared in the market. These applications impose great demands on the transmission fluids and friction materials used as
well as on controllability and vibration preventive (anti-shudder) properties of the clutch systems.
This thesis focuses on transmission fluids used in wet clutches in all-wheel drive systems. The investigated all-wheel drive system,
featuring a hydraulically actuated wet multi-plate clutch with a sintered brass based friction material, is described.
The thesis give insight to;
Factors influencing torque transmission in the clutch, and what lubrication regime is predominant in the limited slip differentials
studied.
Methods suitable to measure and compare friction characteristics.
How fluids can be formulated to give good friction characteristics for the clutch, whilst at the same time be able to lubricate other
machine elements in the transmission such as hydraulic components and hypoid gears.
How the torque transmission of the differential can be predicted using simulation models.
The research on lubrication of port plate/cylinder block friction pair is the main objective of the thesis. The main achievements
include the contents as follow. The mathematic model of lubrication of port plate/cylinder block frictional pair was established. The
formation of the lubricating film thickness is described through the theory models. The formation of the lubricating film thickness
was researched and simulated. The influence of working pressure, temperature, rotating speed and structure on the lubrication can be
researched through simulation. The lubrication test system has been designed. The performance of the lubrication test system is analyzed.
The functions, feature and principle of the lubrication test system are summarized. The mathematic model of the micron electrohydraulic
displacement feedback control system was established and simulated. The parameters of V0/âe, Kce and PID are selected
and optimized. The control system is stabilized with PID feedback control, otherwise the control system is not stabilized. The lubrication
mechanics experiment of typical port plate /cylinder block frictional pair was finished through the lubrication test system. The
relation between lubricating film thickness and force acting on port plate was described with the mathematic models and variation
regularity of the lubricating film can be acquired.
In this thesis, theoretical and experimental studies of the three kinds of water hydraulic valve were comprehensively and systemically
dealt with. The test rig of cavitation performance in water hydraulic control valve was first developed interiorly with higher
pressure and larger flow. The cavitation phenomenon at the orifice was investigated which was the base of water hydraulic control
valve structure design, and the rule was studied which different structures influence the valve characteristic and flux coefficient. At
the same time, the key problems were researched as cavitation resistance, seal technology, selected material and so on. The structural
design of the water hydraulic control valve, the fabrication and the optimization of the prototype were discussed in detail. Some newstyle
structures were designed and the water hydraulic control valve prototypes were manufactured. The test results showed the over
shoot was smaller than 30%, adjusting time was shorter than 500 ms, the control accuracy was 90.7% under 14MPa. Dynamic and
static experiments showed that the performance of the valves accomplished the expectation. The methods were put forward which
parameters were optimized from the view of flow field control.
An electro-hydraulic proportional position control system (EHPPCS) with a single-rod hydraulic actuator is a nonlinear and timevariable
system. The variations in the system’s parameters are characteristic of non-linearity and vary with the work conditions. In
the thesis, much work is carried out with the modern control strategies for the EHPPCS. Not only stability and fast dynamic response
of the position control system are studied, but also the speed of the hydraulic actuator during the process of dynamic response. The
dynamic performance of the EHPPCS is greatly improved and the purpose of the hybrid control is also achieved. Furthermore, the
speed control of VVVF hydraulic elevator is studied using PID control law and numerical simulations are carried out with the Simulink
of Matlab. The sealing performance of the reciprocating seals on an axial piston is investigated in both Navier-Stokes equations
and finite element method. The reduction of noise for hydraulic axial piston pump is studied and two invention patents have been
received.
Motivated by the desire to understand the interrelation of notch structures, flow patterns, cavitation modality and fluid noise, the
theoretical analysis, CFD, and experiments including the pressure distribution measurement, the visualization of cavitation and noise
analysis were used to investigate the flow, cavitation and noise in the spool valves. A new test rig used to measure the pressure distribution
in groove has been proposed to investigate the noise differences related to the different grooves. It was found that both the
grooves with a passage of same cross-section areas and the grooves with large sloping angel can be used to reduce effectively the
cavitation noise, because the two groove configurations increase the pressure in groove. The results show that the steady flow force
in spool valve consisting of groove changes with the shift of the flow direction on the groove pass. In the converging flow direction,
the value of the flow force is small, and its direction tends to open the valve in middle range of valve openings. An interpretation was
proposed that the bubble growth process is determined mainly by the pressure distribution in grooves and the bubble maximum size
just before collapse is the most important factor to the sound noise level.
The Common Pressure Rail (CPR) is a new kind of hydraulic system and higher in efficiency, simpler in structure. But the CPR
has not been widely applied because of having no higher efficiency components. The Hydraulic Transformer (HT) based on CPR is a
new component, combining pump with motor, and adjusting load pressure. The HT is characteristics of higher in efficiency, simpler
in structure and control of many actuators respectively, so that it is increasing popular in engineering construction and mining machinery.
In the thesis, a new structure of the HT is proposed to expand the output pressure range. The pressure fields between the cylinder
block and the valve plate and between the valve plate and the end housing have been set up, and the HT is designed and checked. The CFD is used to simulate the fluid fields of three kinds of distribution pairs. Experimental results show the pressure regulation is realized
using the HT and the ratio of pA to pB is from 0 to 1.2. The displacement of the HT depends on the angle of the valve plate, is
not influenced by rotation speed and loads. The output pressure depends on the angle of the valve plate and is influenced by loads.
The research achievements provide the referenced basics in the future.
This thesis concentrates on the human’s eye and neck vision simulation system. It constructs the framework of the simulation
system, studies on the basic theory, technology and application. The primary work includes system model, monocular motion analysis
under complex background, objects active tracking, versatile camera calibration technology, specific face reconstruction based
stereovision and DSP technology based vision processing.
The math models, which include kinematics math model of the human’s eye and neck system and math model of the camera, are
established. With analysis of the math model of camera in detail, a new camera calibration method based on line rectification is proposed.
Motion vision analysis is studied in detail. A motion objects detection algorithm under complex background is proposed.
Theory analysis and experiment are performed to human’s specific face reconstruction based binocular vision. The principle of the
face reconstruction based on binocular vision is introduced. A new energy minimization equation is proposed in stereo matching. The
disparity is obtained by using correlation calculation with pyramid structure and active contour model. The specific face is reconstructed
successfully.
GMM (Giant Magnetostrictive Material) is a new type of function material appearing in recent years with giant strain, fast response
speed, high energy density and large output force and so on. Utilizing GMM to design new-type actuator, replacing traditional
actuator such as the torque motor or the force motor, will enhance the response speed and precision of electro-hydraulic servo valve.
In the thesis, the nozzle flapper servo valve based on GMM actuator is systematically, deep analyzed and researched by combining
theory analysis, computer simulation, finite element numerical computation and experimental study together. The scheme and
concrete structure of the GMM actuator’s nozzle flapper servo valve utilizing the pre-pressure exerted organization, dynamically
offset adjustment of the magnetic field, additional magnetic ring etc. are presented for the first time, in addition, self-adaptive thermal
compensation mechanism of GMM actuator is also brought forward. Both the simulated and experimental results on the GMMdriven
servo valve show that the GMA nozzle-flapper servo valve has wide pressure control properties which are up to 0.52MPa,
good linearity which is about 2.5%, fast response speed with rising time less than 1ms and 680 Hz frequency width (-3dB).
This work presents an optimum design of a capillary electrophoretic analysis chip with an integrated planar micro valveless
pump as a device for automatic sample exchanging and washing by using two key techniques including glass micromachining technology
and Micro DPIV. The structural design of the planar micro valveless pump, the fabrication and the optimization of the prototype,
the structural integration design of the microfluidic controlling devices and the fabrication process of the devices are discussed
in detail, and as a result, the integrated capillary electrophoretic analysis chip is realized and optimized.
The research is presented on the fabrication on a glass wafer in detail as a key technology of the microfluidic system and Micro-
DPIV technology. Microfluidic testing on the micro fastigiated tube and the stability of the prototype are carried out. The principle of
a micro valveless pump is discussed. This also presents the fabrication and performance testing of the capillary electrophoretic analysis
chip integrated with micro valveless pump. Finally, the feasibility of the integration scheme and the stability of the prototype are
validated by multiple testing on its performance.
D. N. Johnston, C. R. Burrows and K. A. Edge
Publisher: John Wiley & Sons, Ltd.
ISBN: 13 978-0-470-01677-0