Abstract: Grid connection of a large-scale wind farm affects power system small-signal angular stability in two aspects. Firstly, connection of the wind farm brings about the change of load flow and configuration of a power system. Secondly, the dynamic interaction is introduced by the wind farm with the synchronous generators (SGs) in the power system. This paper proposes a method to assess the two aspects of the effect of the wind farm on power system small-signal angular stability. The effect of the change of load flow/system configuration brought about by the wind farm can be examined separately by displacing wind farms with constant power sources, then the effect of the dynamic interaction of the wind farm with the SGs can be also computed individually. Thus, a clearer picture and better understanding on the power system small-signal angular stability as affected by grid connection of the large-scale wind farm are provided. In the paper, an example power system with grid connection of a wind farm is presented to demonstrate the proposed approach.
Abstract: This paper presents a design of a wireless read out system for tracking the frequency shift of the polymer coated piezoelectric micro electromechanical resonator due to gas absorption. The measure of this frequency shift indicates the percentage of a particular gas the sensor is exposed to. It is measured using an oscillator and an FPGA based frequency counter by employing the resonator as a frequency determining element in the oscillator. This system consists of a Gas Sensing Wireless Readout (GSWR) and an USB Wireless Transceiver (UWT). GSWR consists of an oscillator based on a trans-impedance sustaining amplifier, an FPGA based frequency readout, a sub 1GHz wireless transceiver and a micro controller. UWT can be plugged into the computer via USB port and function as a wireless module to transfer gas sensor data from GSWR to the computer through its USB port. GUI program running on the computer periodically polls for sensor data through UWT - GSWR wireless link, the response from GSWR is logged in a file for post processing as well as displayed on screen.
Abstract: In this current contribution, authors are dedicated to
investigate influence of the crystal lamellae orientation on
electromechanical behaviors of relaxor ferroelectric Poly
(vinylidene fluoride –trifluoroethylene -chlorotrifluoroethylene)
(P(VDF-TrFE-CTFE)) films by control of polymer microstructure,
aiming to picture the full map of structure-property relationship. In
order to define their crystal orientation films, terpolymer films were
fabricated by solution-casting, stretching and hot-pressing process.
Differential scanning calorimetry, impedance analyzer, and tensile
strength techniques were employed to characterize crystallographic
parameters, dielectric permittivity, and elastic Young’s modulus
respectively. In addition, large electrical induced out-of-plane
electrostrictive strain was obtained by cantilever beam mode.
Consequently, as-casted pristine films exhibited surprisingly high
electrostrictive strain 0.1774% due to considerably small value of
elastic Young’s modulus although relatively low dielectric
permittivity. Such reasons contributed to large mechanical elastic
energy density. Instead, due to 2 folds increase of elastic Young’s
modulus and less than 50% augmentation of dielectric constant, fullycrystallized
film showed weak electrostrictive behavior and
mechanical energy density as well. And subjected to mechanical
stretching process, Film C exhibited stronger dielectric constant and
out-performed electrostrictive strain over Film B because edge-on
crystal lamellae orientation induced by uniaxially mechanical stretch.
Hot-press films were compared in term of cooling rate. Rather large
electrostrictive strain of 0.2788% for hot-pressed Film D in
quenching process was observed although its dielectric permittivity
equivalent to that of pristine as-casted Film A, showing highest
mechanical elastic energy density value of 359.5 J/m3. In hot-press
cooling process, dielectric permittivity of Film E saw values at 48.8
concomitant with ca.100% increase of Young’s modulus. Films with
intermediate mechanical energy density were obtained.
Abstract: Holistic methods covering the development process as
a whole – e.g. systems engineering – have established themselves in
product design. However, technical product optimization,
representing improvements in efficiency and/or minimization of loss,
usually applies to single components of a system. A holistic approach
is being defined based on a hierarchical point of view of systems
engineering. This is subsequently presented using the example of an
electromechanical flywheel energy storage system for automotive
applications.
Abstract: Increasingly complex modern power systems require
stability, especially for transient and small disturbances. Transient
stability plays a major role in stability during fault and large
disturbance. This paper compares a power system stabilizer (PSS)
and static Var compensator (SVC) to improve damping oscillation
and enhance transient stability. The effectiveness of a PSS connected
to the exciter and/or governor in damping electromechanical
oscillations of isolated synchronous generator was tested. The SVC
device is a member of the shunt FACTS (flexible alternating current
transmission system) family, utilized in power transmission systems.
The designed model was tested with a multi-machine system
consisting of four machines six bus, using MATLAB/SIMULINK
software. The results obtained indicate that SVC solutions are better
than PSS.
Abstract: Graphene, a single-atom sheet, has been considered as
the most promising material for making future nanoelectromechanical
systems as well as purely electrical switching with graphene
transistors. Graphene-based devices have advantages in scaled-up
device fabrication due to the recent progress in large area graphene
growth and lithographic patterning of graphene nanostructures. Here
we investigated its mechanical responses of circular graphene
nanoflake under the nanoindentation using classical molecular
dynamics simulations. A correlation between the load and the
indentation depth was constructed. The nanoindented force in this
work was applied to the center point of the circular graphene nanoflake
and then, the resonance frequency could be tuned by a nanoindented
depth. We found the hardening or the softening of the graphene
nanoflake during its nanoindented-deflections, and such properties
were recognized by the shift of the resonance frequency. The
calculated mechanical parameters in the force-vs-deflection plot were
in good agreement with previous experimental and theoretical works.
This proposed schematics can detect the pressure via the deflection
change or/and the resonance frequency shift, and also have great
potential for versatile applications in nanoelectromechanical systems.
Abstract: Polymeric micro-cantilevers (Cs) are rapidly
becoming popular for MEMS applications such as chemo- and biosensing
as well as purely electromechanical applications such as
microrelays. Polymer materials present suitable physical and
chemical properties combined with low-cost mass production. Hence,
micro-cantilevers made of polymers indicate much more
biocompatibility and adaptability of rapid prototyping along with
mechanical properties. This research studies the effects of three
process and one size factors on the filling behaviour in micro cavity,
and the role of each in the replication of micro parts using different
polymer materials i.e. polypropylene (PP) SABIC 56M10 and
acrylonitrile butadiene styrene (ABS) Magnum 8434 . In particular,
the following factors are considered: barrel temperature, mould
temperature, injection speed and the thickness of micro features. The
study revealed that the barrel temperature and the injection speed are
the key factors affecting the flow length of micro features replicated
in PP and ABS. For both materials, an increase of feature sizes
improves the melt flow. However, the melt fill of micro features does
not increase linearly with the increase of their thickness.
Abstract: Micro-electromechanical system (MEMS)
accelerometers and gyroscopes are suitable for the inertial navigation
system (INS) of many applications due to low price, small
dimensions and light weight. The main disadvantage in a comparison
with classic sensors is a worse long term stability. The estimation
accuracy is mostly affected by the time-dependent growth of inertial
sensor errors, especially the stochastic errors. In order to eliminate
negative effects of these random errors, they must be accurately
modeled. In this paper, the Allan variance technique will be used in
modeling the stochastic errors of the inertial sensors. By performing
a simple operation on the entire length of data, a characteristic curve
is obtained whose inspection provides a systematic characterization
of various random errors contained in the inertial-sensor output data.
Abstract: In this paper we propose a discrete tracking control of
nonholonomic mobile robots with two degrees of freedom. The
electromechanical model of a mobile robot moving on a horizontal
surface without slipping, with two rear wheels controlled by two
independent DC electric, and one front roal wheel is considered. We
present backstepping design based on the Euler approximate discretetime
model of a continuous-time plant. Theoretical considerations are
verified by numerical simulation.
Abstract: This work deals with parameter identification of
permanent magnet motors, a class of ac motor which is particularly
important in industrial automation due to characteristics like
applications high performance, are very attractive for applications
with limited space and reducing the need to eliminate because they
have reduced size and volume and can operate in a wide speed range,
without independent ventilation. By using experimental data and
genetic algorithm we have been able to extract values for both the
motor inductance and the electromechanical coupling constant, which
are then compared to measured and/or expected values.
Abstract: Elastomeric dielectric material has recently become a
new alternative for actuator technology. The characteristics of
dielectric elastomers placed between two electrodes to withstand
large strain when electrodes are charged has attracted the attention of
many researcher to study this material for actuator technology. Thus,
in the past few years Danfoss Ventures A/S has established their own
dielectric electro-active polymer (DEAP), which was called
PolyPower.
The main objective of this work was to investigate the dynamic
characteristics for vibration control of a PolyPower actuator folded in
‘pull’ configuration. A range of experiments was carried out on the
folded actuator including passive (without electrical load) and active
(with electrical load) testing. For both categories static and dynamic
testing have been done to determine the behavior of folded DEAP
actuator.
Voltage-Strain experiments show that the DEAP folded actuator is
a non-linear system. It is also shown that the voltage supplied has no
effect on the natural frequency. Finally, varying AC voltage with
different amplitude and frequency shows the parameters that
influence the performance of DEAP folded actuator. As a result, the
actuator performance dominated by the frequency dependence of the
elastic response and was less influenced by dielectric properties.
Abstract: In this paper, design and fabrication of an actuated parallel-plate mirror based on a 3D-printer is described. The mirror and electrode layers are fabricated separately and assembled thereafter. The alignment is performed by dowel pin-hole pairs fabricated on the respective layers. The electrodes are formed on the surface of the electrode layer by Au ion sputtering using a suitable mask, which is also fabricated by a 3D-printer.For grounding the mirror layer, except the contact area with the electrode paths, all the surface is Au ion sputtered. 3D-printers are widely used for creating 3D models or mock-ups. The authors have recently proposed that these models can perform electromechanical functions such as actuators by suitably masking them followed by metallization process. Since the smallest possible fabrication size is in the order of sub-millimeters, these electromechanical devices are named by the authors as SMEMS (Sub-Milli Electro-Mechanical Systems) devices. The proposed mirror described in this paper which consists of parallel-plate electrostatic actuators is also one type of SMEMS devices. In addition, SMEMS is totally environment-clean compared to MEMS (Micro Electro-Mechanical Systems) fabrication processes because any hazardous chemicals or gases are utilized.
Abstract: Two multisensor system architectures for navigation
and guidance of small Unmanned Aircraft (UA) are presented and
compared. The main objective of our research is to design a compact,
light and relatively inexpensive system capable of providing the
required navigation performance in all phases of flight of small UA,
with a special focus on precision approach and landing, where Vision
Based Navigation (VBN) techniques can be fully exploited in a
multisensor integrated architecture. Various existing techniques for
VBN are compared and the Appearance-Based Navigation (ABN)
approach is selected for implementation. Feature extraction and
optical flow techniques are employed to estimate flight parameters
such as roll angle, pitch angle, deviation from the runway centreline
and body rates. Additionally, we address the possible synergies of
VBN, Global Navigation Satellite System (GNSS) and MEMS-IMU
(Micro-Electromechanical System Inertial Measurement Unit)
sensors, and the use of Aircraft Dynamics Model (ADM) to provide
additional information suitable to compensate for the shortcomings of
VBN and MEMS-IMU sensors in high-dynamics attitude
determination tasks. An Extended Kalman Filter (EKF) is developed
to fuse the information provided by the different sensors and to
provide estimates of position, velocity and attitude of the UA
platform in real-time. The key mathematical models describing the
two architectures i.e., VBN-IMU-GNSS (VIG) system and VIGADM
(VIGA) system are introduced. The first architecture uses VBN
and GNSS to augment the MEMS-IMU. The second mode also
includes the ADM to provide augmentation of the attitude channel.
Simulation of these two modes is carried out and the performances of
the two schemes are compared in a small UA integration scheme (i.e.,
AEROSONDE UA platform) exploring a representative cross-section
of this UA operational flight envelope, including high dynamics
manoeuvres and CAT-I to CAT-III precision approach tasks.
Simulation of the first system architecture (i.e., VIG system) shows
that the integrated system can reach position, velocity and attitude
accuracies compatible with the Required Navigation Performance
(RNP) requirements. Simulation of the VIGA system also shows
promising results since the achieved attitude accuracy is higher using
the VBN-IMU-ADM than using VBN-IMU only. A comparison of
VIG and VIGA system is also performed and it shows that the
position and attitude accuracy of the proposed VIG and VIGA
systems are both compatible with the RNP specified in the various
UA flight phases, including precision approach down to CAT-II.
Abstract: Damping of inter-area electromechanical oscillations is one of the major challenges to the electric power system operators. This paper presents Gravitational Search Algorithm (GSA) for tuning Static Synchronous Series Compensator (SSSC) based damping controller to improve power system oscillation stability. In the proposed algorithm, the searcher agents are a collection of masses which interact with each other based on the Newtonian gravity and the laws of motion. The effectiveness of the scheme in damping power system oscillations during system faults at different loading conditions is demonstrated through time-domain simulation.
Abstract: A general decline in the cost, size, and power requirements of electronics is accelerating the adoption of integrated GPS/INS technologies in consumer applications such Land Vehicle Navigation. Researchers have looking for ways to eliminate additional components from product designs. One possibility is to drop one or more of the relatively expensive gyroscopes from microelectromechanical system (MEMS) versions of inertial measurement units (IMUs). For land vehicular use, the most important gyroscope is the vertical gyro that senses the heading of the vehicle and two horizontal accelerometers for determining the velocity of the vehicle. This paper presents a simplified integration algorithm for strap down (ParIMU)\GPS combination, with data post processing for the determination of 2-D components of position (trajectory), velocity and heading. In the present approach we have neglected earth rotation and gravity variations, because of the poor gyroscope sensitivities of the low-cost IMU and because of the relatively small area of the trajectory.
Abstract: This work deals with parameter identification of permanent magnet motors, a class of ac motor which is particularly important in industrial automation due to characteristics like applications high performance, are very attractive for applications with limited space and reducing the need to eliminate because they have reduced size and volume and can operate in a wide speed range, without independent ventilation. By using experimental data and genetic algorithm we have been able to extract values for both the motor inductance and the electromechanical coupling constant, which are then compared to measure and/or expected values.
Abstract: An effort for the detection of damages in the
reinforcement bars of reinforced concrete members using PZTs is
presented. The damage can be the result of excessive elongation of
the steel bar due to steel yielding or due to local steel corrosion. In
both cases the damage is simulated by considering reduced diameter
of the rebar along the damaged part of its length. An integration
approach based on both electromechanical admittance methodology
and guided wave propagation technique is used to evaluate the
artificial damage on the examined longitudinal steel bar. Two
actuator PZTs and a sensor PZT are considered to be bonded on the
examined steel bar. The admittance of the Sensor PZT is calculated
using COMSOL 3.4a. Fast Furrier Transformation for a better
evaluation of the results is employed. An effort for the quantification
of the damage detection using the root mean square deviation
(RMSD) between the healthy condition and damage state of the
sensor PZT is attempted. The numerical value of the RSMD yields a
level for the difference between the healthy and the damaged
admittance computation indicating this way the presence of damage
in the structure. Experimental measurements are also presented.
Abstract: Development of microprocessor controlled sensor for measurement of wind speed and direction is the aim of this study. Electrical circuits and software were developed to the existing electromechanical part of the sensor TM-W2 becoming the properties of so-called smart sensor. The measured data about wind speed (sensitivity 0.01 m/s) and direction (0-360° by step 10°) are transmitted as 16-bit information. The connection between sensor and control unit is realized by radio communication (FM 433 MHz). Transition range is 220 m if used Quad type antenna. This concept provides substitution of actual cable systems by wireless ones.
Abstract: Continuously variable transmission (CVT) is a type of
automatic transmission that can change the gear ratio to any arbitrary
setting within the limits. The most common type of CVT operates on
a pulley system that allows an infinite variability between highest and
lowest gears with no discrete steps. However, the current CVT
system with hydraulic actuation method suffers from the power loss.
It needs continuous force for the pulley to clamp the belt and hold the
torque resulting in large amount of energy consumption. This study
focused on the development of an electromechanical actuated control
CVT to eliminate the problem that faced by the existing CVT. It is
conducted with several steps; computing and selecting the
appropriate sizing for stroke length, lead screw system and etc. From
the visual observation it was found that the CVT system of this
research is satisfactory.
Abstract: The motion planning procedure described in this paper has been developed in order to eliminate or reduce the residual vibrations of electromechanical positioning systems, without augmenting the motion time (usually imposed by production requirements), nor introducing overtime for vibration damping. The proposed technique is based on a suitable choice of the motion law assigned to the servomotor that drives the mechanism. The reference profile is defined by a Bezier curve, whose shape can be easily changed by modifying some numerical parameters. By means of an optimization technique these parameters can be modified without altering the continuity conditions imposed on the displacement and on its time derivatives at the initial and final time instants.