This thesis shows the design of a robust, time-discrete controller for the application of variable displacement hydraulic motors
in flight control actuation systems using the parameter space approach. The linear controller design models and non-linear simulation
models are verified and validated with the experiment and show feasibility of the digital controller concept.
The thesis provides a method for enhancing the current design process of mechanisms in high-lift systems in transport category
aircraft. An analysis evaluates the technical properties of an investigated mechanism for subsequent multi-criteria assessment.
Quality measures are obtained by cost functions for aerodynamic efficiency, mass and power properties as well as kinematic
applicability of a certain mechanism. From these measures a utility function derives a scalar quality value. Applying this value a
genetic algorithm bears the heuristic part of the design process for purposeful altering the geometry of the mechanism. Finally, a
hierarchic method assists the selection of the best found solution.
© 2006 TuTech 79
While sampling the gas hydrate and the upper sediment with the traditional deep-sea sediment sample equipment, the firedamp
and other gas phase dissolved components will be lost due to the variation of the ambient conditions. This will lead to difficulties in
drawing a correct conclusion of the original components and phases of the sediments. Besides, the problem exists in the sampling
process of the sediments including plenty of live micro-organism addicted to the high-pressure and gas effusion around the
hydrothermal-fluid vents. So it is necessary to study the truth-preserving sampling technique for the deep-sea surface layer
sediments.
In this paper, in depth study of the truth-preserving sampling technique of seabed sediments and a complete set of design rules
for seabed sediment truth-preserving sampling corer have been presented. The contents includes: the deduction of the sphere cavity
expansion theory adapt to the seabed sediments sampling; the design rules for the pressure hull, the retaining ring and the connect
screw thread of the truth-preserving canister; the design rules for the pressure tight and compensation of the truth-preserving
PhDs, Habilitations, Awards and Books
structure, the rule of the transfer of the sampler, the rule of the auto-tight seal and the rule of the half-auto pressure tight; the spring
principles of two types deep-sea sediments truth-preserving sampling systems; the structure and the working principle of the gas
hydrate temperature-hold and pressure-tight sampling corer.
Noise reduction in hydraulic systems has been an important research topic for several decades. In recent years, industry’s interest
in the area has grown dramatically. The reason is new national and international legislation governing working conditions. As a
consequence of this, considerable reduction of noise from machinery in general has been achieved. The reduction of noise in
hydraulic systems, however, has not gained from the same considerable progress, which implies that hydraulic noise has become
perceptible through the surrounding machinery noise. Not only has noise reduction of hydraulic systems become increasingly
important, it has also become more difficult because of the ever-increasing working pressure level, which is highly correlated to
noise and vibration.
Noise in hydraulic systems is created mainly by the hydrostatic pump and motor, working with large pressure differences in the
suction and delivery ports. Being exclusively of displacement type, the hydrostatic machine creates substantial flow pulsations in
both the discharge and suction ports. The flow pulsations give rise to system pressure pulsations, which in turn transform into
vibration and audible noise. Excessive pulsating piston forces and bending moments due to the large pressure difference between the
machine’s discharge and suction ports also contribute to noise and vibration.
To obtain satisfactory noise reduction, there is a need for effective and reliable design tools and design methods. This thesis
concerns simulation, optimisation and experimental verification of axial piston pump design for noise reduction. Much of the work
relates to the different origins of noise and how to formulate objective functions that simultaneously reflects different aspects of noise
reduction. New and conventional design features are examined both theoretically and experimentally. One novel and promising
design feature thoroughly investigated in this thesis is the so-called cross-angle that aims to provide low noise in variable
displacement machines. Different measurement approaches are employed for experimental verification. It is shown that conventional
methods are often inadequate for measuring source flow in variable displacement units due to the complex outlet channel. A new
method, referred to as the Source admittance method, is proposed.
This thesis addresses modelling of high angle of attack aerodynamic characteristics and weight estimation for highly
maneuverable aircraft during conceptual design. In order to allow configuration selection with sufficient confidence, especially with
unconventional configurations, high angle of attack aerodynamic prediction and weight estimations methods need to be improved. In
this thesis, a state-space variable approach is proposed for modelling high angle of attack aerodynamics including large angular rates.
A new weight estimation based on a parametrical CAD model is also proposed. The aerodynamic model is intended for use in both
conceptual design and in later design phases. In conceptual design, the parameters are defined from geometrical data. Good results
have been obtained with slender delta wings and on in various full configurations. When test data or CFD data are available, the
parameters are obtained from identification. Various results are presented with high accuracy in the model. The developed model has
been implemented in flight simulation, and in a sizing example, where two different aerodynamic models were used in order to show
the influences of large angular rates on the geometrical layout. The presented weight estimation method is based on parametrical
CAD models, and the weight is extracted from the structure layout. This allows any type of aircraft configuration to be investigated,
without the use of empirical or statistical approaches. Comparison with known aircraft has shown good agreement. This thesis
introduces a new aerodynamic model that includes large angular rates at any angle of attack, and a new weight prediction method.
Both have shown good agreement with compared data and indicate that the models are suitable for conceptual design and that further
studies should be conducted in order to extend the possibilities demonstrated here.
The performance of mobile working machines recently increased permanently. To ensure a trouble-free operation of these
machines, which use hydraulic technology, oil changes are required after a certain number of operating hours normally. These are
adapted according to experience and a specific safety factor. Thus the oil often is in a good condition when the change takes place. In
order to reduce this disadvantage, and for a complete condition monitoring of the oil, a sensor was developed which makes a
statement on the oil condition possible. Some of the most important parameters, which are subject to change during the ageing
process, can be measured by a miniaturised sensor. The characteristic values are resonance frequency (viscosity), electric permittivity
and electric conductivity. The required electrodes are integrated on an piezoelectric quartz crystal. Beside the quartz a water sensor is installed to record the relative humidity of the oil to give a full view on the oil´s condition. The multi-sensor was tested in different
hydraulic systems. The results can be used as basic parameters for an Online Condition Monitoring System (OCM).
The resonant frequency attained is caused by the geometry of the crystal. It drops when the sensor gets in contact with other
materials. In this case the resonant frequency depends on the viscosity and the density of the oil. As this density hardly changes
during normal use operation, it depends mostly on the change of the viscosity. As the viscosity as well as the resonance frequency of
the crystal are very dependent of the oil temperature, it is necessary to detect this value directly.
To use these data for an OCM-System the control unit operates with the change of the values only in order to avoid the effort of
providing characteristic diagrams. Therefore reference values and the calculation of the temperature compensation are composed at
the beginning of the measurements. The fusion of data is essential to generate a statement on the oil condition. This process can be
done by several different methods which operate on levels of varying complexity. In principle, all methods that accomplish a
classification of data sets, are appropriate. One way is given by statistic methods like the discriminant analysis. Other possibilities are
the evaluation of the parameters in a multi-dimensional feature space and the use of expert systems like Neural Networks, Fuzzy
Logic, Cluster Analysis or Bayes Theorem. These methods will be compared in the presentation.
As the applications of electro-hydraulic systems become increasingly widespread, the demand for low cost, high-level control
performance and significant energy saving schemes gets stronger and stronger. The thesis proposes an intelligent mechatronics
approach -- the seamless integration of advanced control techniques with novel hardware reconfiguration and/or re-design -- to meet
these industrial needs. Specifically, in terms of hardware redesign, the recently developed Purdue energy-saving programmable
valves will be used to replace traditional servo or four-way proportional directional control valves when controlling a hydraulic
system. The Purdue programmable valve is a unique configuration of five independently controlled poppet type cartridge valves that
enables not only the decoupled meter-in and meter-out flow controls but also the precise control of the cross-port regeneration flow.
When properly controlled, such an increased hardware flexibility and controllability of the program valves leads to significant
energy-saving, due to the reduced working pressures of the hydraulic actuators and the full use of free regeneration cross-port flows.
In addition, compared to the spool-type traditional valves, when integrated with proper advanced controls, the fast acting
characteristics of the poppet valves due to the much less driving inertia of the poppet makes it possible to achieve a higher closedloop
bandwidth, resulting a better system level control performance.
However, the increased hardware flexibility of the programmable valves also results in increased complexity in controlling the
overall system: for each hydraulic actuator, instead of one control input to be synthesized for the traditional valve for the sole
objective of pure control performance, five control inputs have to be simultaneously determined for all five poppet valves to achieve
the dual objectives of having both high control performance and significant energy saving. Such a multi-input-dual-objective electrohydraulic
control problem is far from trivial to solve. A two-level coordinated control scheme is proposed in the thesis: the task-level
configures the valve usage for maximal energy saving, and the valve-level utilizes Adaptive Robust Control (ARC) technique to
guarantee the closed-loop system stability and performance under various model uncertainties and disturbances. Comparative
experimental results were obtained to show the high-level control performance and significant energy saving achieved with the
proposed low cost programmable valves. Relevant control issues, such as using the manufacturer supplied flow mappings and the
deadband problem of electro-hydraulic systems, are discussed in detail in the thesis as well.
Unlike costly conventional four-way valves, the structure of cartridge valves is very simple and easy to manufacture. However,
the mathematical model of the cartridge valve flow mapping is much more complicated and cannot simply be described by some
analytical nonlinear equations, which makes the controller design and implementation rather difficult. As such, though cartridge
valves have desirable physical properties like faster response and the ability of by-passing the sandwiched deadband control problem
of conventional four-way valves, their use has been traditionally limited to low cost applications where precision motion control is
not of major concern. In principle, the flow mappings of the cartridge valves can be individually calibrated. However, in addition to
the need of a flow calibration system that increases cost, individually calibrating each of the five cartridge valves are very time
consuming tasks, which would prohibit the widespread use of the programmable valves in industry. Furthermore, valve flow
mapping needs to be updated regularly due to the system worn out, and it may not even be possible for some applications to
disassembly the valves from the systems for the time-consuming off-board calibrations. Thus, automated and yet accurate on-board
modeling of cartridge valve flow mappings without taking the cartridge valves off the system becomes the key to the widespread use
of programmable valves without having a compromised control performance, which is another focus of the thesis. The thesis
proposed an approach to decompose and approximate the unknown flow mapping with some localized orthogonal basis functions.
The weighting parameters of the basis functions as well as the unknown system parameters were then estimated simultaneously
based on the pressure dynamics of the cylinder for regions where sufficient on-board measurement data were available. Smooth
blending and extrapolation are subsequently applied to obtain the on-board estimation of the flow mapping over entire working range
of the system. Experimental studies have been obtained to demonstrate the feasibility of the proposed method for the automated onboard
modeling of the cartridge valve flow mappings and the improvement of control performance with the estimated flow
mappings.
Primary and secondary scales considerably ruin the surface quality of ingots, slabs, blooms, plate bars, sheet metals, strips,
profiles and pipes. Not only is the rolling stock surface affected but scales also cause high wear on the rolls. Elimination of scales has
increased in priority particularly as casting and rolling are integrated into a continuous process during which a consistent high quality
must be maintained. Two forms of scale exist:
Primary scales are formed in a reheating or equalising furnace and must be removed before initial rolling or forming.
Secondary scales arise during a dwell period or between stands after peeled metal has been in contact with air, calling for
descaling at each stage of the processing cycle.
The last fifty years have seen hydraulic descaling gain ascendancy as the standard method for most applications. This involves
hitting the steel surface with jets of water at high pressure, leading to the break-up and removal of the scales. A typical hydraulic
descaling system consists of a pump to deliver water at high pressure to header bars from above and below the product. The water is
sprayed through a series of nozzles. Descaling is achieved by the impact of the water on the surface of the steel combined with
thermal action caused by the difference in temperature between cold water and the hot metal.
The basic theory of fluid flow, which is presented in the first part, involves the turbulent flow and the methods of its simulation.
The nozzle, as the important part of whole system is used on a large scale, including jet parameters and arrangement of header bars.
Many common values are shown in practical connections to help users better orientate themselves and formulate their demands to
providers of descaling systems.
The experimental part of this thesis is about the wear and tear of nozzles during this process. Because the nozzles do wear-out
and are quite expensive, it’s advantageous for users and producers to know more about this process of wear and tear on nozzles.
Therefore an investigation into the change in a nozzle’s performance in terms of flow rate, spray width at a given spray height and
impact distribution at a given pressure across the width and thickness under the conditions of the primary descaling system at the
P1500 Steckel Hot Strip Mill Mittal Steel Ostrava over a period of 8 months was conducted.The hydraulic descaling process can be
researched from various points of view. Nevertheless the main goal is to bring together basic knowledge and to connect this
knowledge with practical experience.
The thesis analyzed and studied in depth the direct-drive servo valve, utilizing theoretical analysis, finite element numerical
computation and experiment. A permanent-magnet polarized, differential controlled, moving-iron, high pressure, bi-directional
electrical-mechanical converter has been put forward. The matching relation between its structure parameters was determined by
simulation, and the experimental results indicated that the converter has the linear working range of ±1mm, hysteresis lower than 2%,
and frequency response of 160Hz. A high-pressure eddy current displacement sensor is presented, and a temperature-drift
compensation method employing non-inductive coil is also brought forward through theoretical analysis on the causes of temperature
drift. Both the simulated and experimental results show that the sensor has an effective range of 8mm, precision of 0.5%, frequency
response of 500Hz. Finally, two types of direct-drive servo valve, one with and one without displacement feedback, are given, the
matching relation between the structure parameters and the performance are discussed, and the experiments carried out. Both the
simulated and experimental results prove that the valves achieve excellent characteristics, with the nominal pressure 21MPa, nominal
flow 60l/min, nominal electrical current 2A, the hysteresis lower than 7% (without position feedback) and the frequency response of
100Hz.
In this thesis, numerical and experimental studies of a passive micromixer have been comprehensively and systemically
accomplished. A novel three-dimensional micromixer is put forward which was designed according to the characteristic of mixing
liquids on microscale. The micromixer was fabricated on glass substrates using wet-etching technique. Under a steady axial pressure
gradient, staggered oriented ridges arranged periodically in a microchannel can generate considerable transverse flow, thus chaotic
advection is induced, which stretches and folds material interfaces and enhances the mixing efficiency. The computational fluid
dynamics method (CFD) was used to analyze distribution of the velocity field in the micromixer. Via computational and
experimental visualizations, the optimal structure parameters have been found and the impact of Reynolds number on the mixing
performances analyzed. Regarding the three-dimensional velocity field in the micromixer as a nonlinear dynamic system, the
characteristics of chaotic mixing in the micromixer was studied by using the Lagrangian tracer technique. The results indicate that
the staggered oriented ridges arranged periodically in the microchannel indeed cause chaotic mixing on microscale. The micromixer
possesses a compact structure, and its fabrication process is facilitated by the technology of MEMS. So a new choice of efficient
passive mixer is available.
At present there seems lack of suitable pressure compensation for external hydraulic systems on submersibles, we propose a new
method of pressure compensation for these systems and the corresponding structure unit. This method is to install an underwater
ambient pressure compensation unit on the return pipes of the system. This arrangement will elevate the return pressure slightly
higher than the underwater ambient pressure and this novel compensation unit is expected to be sensitive to the change of underwater
ambient pressure; moreover, it can automatically compensate the oil leakage and deflation. Based on these ideas, a new design
method of anti-intervening pressure compensation is proposed for the hydraulic system which consists of multi-subsystems and
single oil source. By means of isolating oil source, the compensation pressure is isolated from the main system, thus it only
compensates the returns of underwater hydraulic subsystems, not affecting the other returns. Moreover, a redundancy design and
fault-tolerance control strategy combining mechanical signals with electrical signals is put forward, which can automatically isolate
the fault and maintain the normal operation if one of the underwater ambient pressure compensation units malfunctions. For the
external hydraulic systems on submersible equipments this work has contributed a new pressure-compensation design method and a
prototype system, which has a fine tracking ability, safety and reliability.
Pitch control is the key technology for large scale wind turbines, which includes hydraulic and electromotor control modes. In
this thesis, theoretical basis of pitch-control is put forward by research on the wind turbine aerodynamic characteristics and by model
simulations. Based on the domestic technique level of processing and the relevant equipments available, a semi-physical simulation
test-bed of pitch-controlled wind turbine is established, in which the pitch-controlled actuator, load device and control are realistic
while the other parts of wind turbine are represented by mathematical models.
In order to improve the power supply quality of wind turbines, a strategy of switching between two modes with, respectively,
predictive pitch control algorithm based on the SVR and the fuzzy individual pith control algorithm according to the load number are
put forward and used in the semi-physical simulation test-bed. The results show that as the wind speed is higher than the upper limit,
the generator power is kept steady around the assigned power and the pitch load fluctuation is greatly reduced compared with the
traditional PID control.