Abstract: In this paper, we show that the association of the PI
regulators for the speed and stator currents with a control strategy
using the linearization by state feedback for an induction machine
without speed sensor, and with an adaptation of the rotor resistance.
The rotor speed is estimated by using the model reference adaptive
system approach (MRAS). This method consists of using two
models: The first is the reference model and the second is an
adjustable one in which two components of the stator flux, obtained
from the measurement of the currents and stator voltages are
estimated. The estimated rotor speed is then obtained by canceling
the difference between stator-flux of the reference model and those
of the adjustable one. Satisfactory results of simulation are obtained
and discussed in this paper to highlight the proposed approach.
Abstract: A cart-ball system is a challenging system from the
control engineering point of view. This is due to the nonlinearities,
multivariable, and non-minimum phase behavior present in this
system. This paper is concerned with the problem of modeling and
control of such system. The objective of control strategy is to place
the cart at a desired position while balancing the ball on the top of the
arc-shaped track fixed on the cart. A State-Feedback Controller
(SFC) with a pole-placement method will be designed in order to
control the system. At first, the mathematical model of a cart-ball
system in the state-space form is developed. Then, the linearization of
a model will be established in order to design a SFC. The integral
control strategy will be performed as to control the cart position of a
system. Simulation work is then performed using
MATLAB/SIMULINK software in order to study the performance of
SFC when applied to the system.
Abstract: Semisolid metal processing uses solid–liquid slurries
containing fine and globular solid particles uniformly distributed in a
liquid matrix, which can be handled as a solid and flow like a liquid.
In the recent years, many methods have been introduced for the
production of semisolid slurries since it is scientifically sound and
industrially viable with such preferred microstructures called
thixotropic microstructures as feedstock materials. One such process
that needs very low equipment investment and running costs is the
cooling slope. In this research by using a mechanical stirrer slurry
maker constructed by the authors, the effects of mechanical stirring
parameters such as: stirring time, stirring temperature and stirring
Speed on micro-structure and mechanical properties of A360
aluminum alloy in semi-solid forming, are investigated. It is
determined that mold temperature and holding time of part in
temperature of 580ºC have a great effect on micro-structure and
mechanical properties(stirring temperature of 585ºC, stirring time of
20 minutes and stirring speed of 425 RPM). By optimizing the
forming parameters, dendrite microstructure changes to globular and
mechanical properties improves. This is because of breaking and
globularzing dendrites of primary α-AL.
Abstract: Monitoring the tool flank wear without affecting the
throughput is considered as the prudent method in production
technology. The examination has to be done without affecting the
machining process. In this paper we proposed a novel work that is
used to determine tool flank wear by observing the sound signals
emitted during the turning process. The work-piece material we used
here is steel and aluminum and the cutting insert was carbide
material. Two different cutting speeds were used in this work. The
feed rate and the cutting depth were constant whereas the flank wear
was a variable. The emitted sound signal of a fresh tool (0 mm flank
wear) a slightly worn tool (0.2 -0.25 mm flank wear) and a severely
worn tool (0.4mm and above flank wear) during turning process were
recorded separately using a high sensitive microphone. Analysis
using Singular Value Decomposition was done on these sound
signals to extract the feature sound components. Observation of the
results showed that an increase in tool flank wear correlates with an
increase in the values of SVD features produced out of the sound
signals for both the materials. Hence it can be concluded that wear
monitoring of tool flank during turning process using SVD features
with the Fuzzy C means classification on the emitted sound signal is
a potential and relatively simple method.
Abstract: This paper aims at to develop a robust optimization methodology for the mechatronic modules of machine tools by considering all important characteristics from all structural and control domains in one single process. The relationship between these two domains is strongly coupled. In order to reduce the disturbance caused by parameters in either one, the mechanical and controller design domains need to be integrated. Therefore, the concurrent integrated design method Design For Control (DFC), will be employed in this paper. In this connect, it is not only applied to achieve minimal power consumption but also enhance structural performance and system response at same time. To investigate the method for integrated optimization, a mechatronic feed drive system of the machine tools is used as a design platform. Pro/Engineer and AnSys are first used to build the 3D model to analyze and design structure parameters such as elastic deformation, nature frequency and component size, based on their effects and sensitivities to the structure. In addition, the robust controller,based on Quantitative Feedback Theory (QFT), will be applied to determine proper control parameters for the controller. Therefore, overall physical properties of the machine tool will be obtained in the initial stage. Finally, the technology of design for control will be carried out to modify the structural and control parameters to achieve overall system performance. Hence, the corresponding productivity is expected to be greatly improved.
Abstract: A Laboratory-scale packed bed reactor with microbial
cellulose as the biofilm carrier was used to investigate the
denitrification of high-strength nitrate wastewater with specific
emphasis on the effect the nitrogen loading rate and hydraulic
retention time. Ethanol was added as a carbon source for
denitrification. As a result of this investigation, it was found that up
to 500 mg/l feed nitrate concentration the present system is able to
produce an effluent with nitrate content below 10 ppm at 3 h
hydraulic retention time. The highest observed denitrification rate
was 4.57 kg NO3-N/ (m3 .d) at a nitrate load of 5.64 kg NO3-
N/(m3 .d), and removal efficiencies higher than 90% were obtained
for loads up to 4.2 kg NO3-N/(m3 .d). A mass relation between COD
consumed and NO3-N removed around 2.82 was observed. This
continuous-flow bioreactor proved an efficient denitrification system
with a relatively low retention time.
Abstract: One of the major disadvantages of the minimally
invasive surgery (MIS) is the lack of tactile feedback to the surgeon.
In order to identify and avoid any damage to the grasped complex
tissue by endoscopic graspers, it is important to measure the local
softness of tissue during MIS. One way to display the measured
softness to the surgeon is a graphical method. In this paper, a new
tactile sensor has been reported. The tactile sensor consists of an
array of four softness sensors, which are integrated into the jaws of a
modified commercial endoscopic grasper. Each individual softness
sensor consists of two piezoelectric polymer Polyvinylidene Fluoride
(PVDF) films, which are positioned below a rigid and a compliant
cylinder. The compliant cylinder is fabricated using a micro molding
technique. The combination of output voltages from PVDF films is
used to determine the softness of the grasped object. The theoretical
analysis of the sensor is also presented.
A method has been developed with the aim of reproducing the
tactile softness to the surgeon by using a graphical method. In this
approach, the proposed system, including the interfacing and the data
acquisition card, receives signals from the array of softness sensors.
After the signals are processed, the tactile information is displayed
by means of a color coding method. It is shown that the degrees of
softness of the grasped objects/tissues can be visually differentiated
and displayed on a monitor.
Abstract: In the gas refineries of Iran-s South Pars Gas
Complex, Sulfrex demercaptanization process is used to remove
volatile and corrosive mercaptans from liquefied petroleum gases by
caustic solution. This process consists of two steps. Removing low
molecular weight mercaptans and regeneration exhaust caustic. Some
parameters such as LPG feed temperature, caustic concentration and
feed-s mercaptan in extraction step and sodium mercaptide content in
caustic, catalyst concentration, caustic temperature, air injection rate
in regeneration step are effective factors. In this paper was focused on
temperature factor that play key role in mercaptans extraction and
caustic regeneration. The experimental results demonstrated by
optimization of temperature, sodium mercaptide content in caustic
because of good oxidation minimized and sulfur impurities in
product reduced.
Abstract: In this paper we consider a nonlinear feedback control
called augmented automatic choosing control (AACC) for nonlinear
systems with constrained input using weighted gradient optimization
automatic choosing functions. Constant term which arises from
linearization of a given nonlinear system is treated as a coefficient of
a stable zero dynamics. Parameters of the control are suboptimally
selected by maximizing the stable region in the sense of Lyapunov
with the aid of a genetic algorithm. This approach is applied to a
field excitation control problem of power system to demonstrate the
splendidness of the AACC. Simulation results show that the new
controller can improve performance remarkably well.
Abstract: This paper presents an exact pruning algorithm with
adaptive pruning interval for general dynamic neural networks
(GDNN). GDNNs are artificial neural networks with internal dynamics.
All layers have feedback connections with time delays to the
same and to all other layers. The structure of the plant is unknown, so
the identification process is started with a larger network architecture
than necessary. During parameter optimization with the Levenberg-
Marquardt (LM) algorithm irrelevant weights of the dynamic neural
network are deleted in order to find a model for the plant as
simple as possible. The weights to be pruned are found by direct
evaluation of the training data within a sliding time window. The
influence of pruning on the identification system depends on the
network architecture at pruning time and the selected weight to be
deleted. As the architecture of the model is changed drastically during
the identification and pruning process, it is suggested to adapt the
pruning interval online. Two system identification examples show
the architecture selection ability of the proposed pruning approach.
Abstract: This study presents a simulation model for converting coal to methanol, based on gasification technology with the commercial chemical process simulator, Pro/II® V8.1.1. The methanol plant consists of air separation unit (ASU), gasification unit, gas clean-up unit, and methanol synthetic unit. The clean syngas is produced with the first three operating units, and the model has been verified with the reference data from United States Environment Protection Agency. The liquid phase methanol (LPMEOHTM) process is adopted in the methanol synthetic unit. Clean syngas goes through gas handing section to reach the reaction requirement, reactor loop/catalyst to generate methanol, and methanol distillation to get desired purity over 99.9 wt%. The ratio of the total energy combined with methanol and dimethyl ether to that of feed coal is 78.5% (gross efficiency). The net efficiency is 64.2% with the internal power consumption taken into account, based on the assumption that the efficiency of electricity generation is 40%.
Abstract: Scolothrips longicornis Priesner is one of the
important predators of tetranychid mites with a wide distribution
throughout Iran. Life table and population growth parameters of S.
longicornis feeding on two-spotted spider mite, Tetranychus
turkestani Ugarov & Nikolski were investigated under laboratory
condition (26±1ºC, 65±5% R.H. and 16L: 8D). To carry of these
experiments, S. longicornis collections reared on cowpea infested
with T. turkestani were prepared. The eggs with less than 24 hours
old were selected and reared. The emerged larvae feeding directly on
cowpea leaf discs which were infested with T. turkestani. Thirty
females of S. longicornis with 24 hours age were selected and
released on infested leaf discs. They replaced daily to a new leaf disc
and the laying eggs have counted. The experiment continued till the
last thrips had died. The result showed that the mean age mortality of
the adult female thrips were between 21-25 days which is nearly
equal life expectancy (ex) at the time of adult eclosion. Parameters
related to reproductive table including gross reproductive rate, net
reproductive rate, intrinsic rate of natural increase and finite rate of
increase were 48.91, 37.63, 0.26 and 2.3, respectively. Mean age per
female/day, mean fertile egg per female/day, gross hatch rate, mean
net age fertility, mean net age fecundity, net fertility rate and net
fecundity rate were 2.23, 1.76, 0.87, 13.87, 14.26, 69.1 and 78.5,
respectively. Sex ratio of offspring also recorded daily. The highest
sex ratio for females was 0.88 in first day of oviposition. The sex
ratio decreased gradually and reached under 0.46 after the day 26 and
the oviposition rate declined. Then it seems that maintenance of
rearing culture of predatory thrips for mass rearing later than 26 days
after egg-laying commence is not profitable.
Abstract: A fast adaptive Tomlinson Harashima (T-H) precoder structure is presented for indoor wireless communications, where the channel may vary due to rotation and small movement of the mobile terminal. A frequency-selective slow fading channel which is time-invariant over a frame is assumed. In this adaptive T-H precoder, feedback coefficients are updated at the end of every uplink frame by using system identification technique for channel estimation in contrary with the conventional T-H precoding concept where the channel is estimated during the starting of the uplink frame via Wiener solution. In conventional T-H precoder it is assumed the channel is time-invariant in both uplink and downlink frames. However assuming the channel is time-invariant over only one frame instead of two, the proposed adaptive T-H precoder yields better performance than conventional T-H precoder if the channel is varied in uplink after receiving the training sequence.
Abstract: This paper explores the implementation of adaptive
coding and modulation schemes for Multiple-Input Multiple-Output
Orthogonal Frequency Division Multiplexing (MIMO-OFDM) feedback
systems. Adaptive coding and modulation enables robust and
spectrally-efficient transmission over time-varying channels. The basic
premise is to estimate the channel at the receiver and feed this estimate
back to the transmitter, so that the transmission scheme can be
adapted relative to the channel characteristics. Two types of codebook
based channel feedback techniques are used in this work. The longterm
and short-term CSI at the transmitter is used for efficient channel
utilization. OFDM is a powerful technique employed in communication
systems suffering from frequency selectivity. Combined with
multiple antennas at the transmitter and receiver, OFDM proves to be
robust against delay spread. Moreover, it leads to significant data rates
with improved bit error performance over links having only a single
antenna at both the transmitter and receiver. The coded modulation
increases the effective transmit power relative to uncoded variablerate
variable-power MQAM performance for MIMO-OFDM feedback
system. Hence proposed arrangement becomes an attractive approach
to achieve enhanced spectral efficiency and improved error rate
performance for next generation high speed wireless communication
systems.
Abstract: In this paper we present a Feed-Foward Neural
Networks Autoregressive (FFNN-AR) model with genetic algorithms
training optimization in order to predict the gross domestic product
growth of six countries. Specifically we propose a kind of weighted
regression, which can be used for econometric purposes, where the
initial inputs are multiplied by the neural networks final optimum
weights from input-hidden layer of the training process. The
forecasts are compared with those of the ordinary autoregressive
model and we conclude that the proposed regression-s forecasting
results outperform significant those of autoregressive model.
Moreover this technique can be used in Autoregressive-Moving
Average models, with and without exogenous inputs, as also the
training process with genetics algorithms optimization can be
replaced by the error back-propagation algorithm.
Abstract: loss of feedwater accident is one of the frequently sever accidents in steam boiler facilities. It threatens the system structural integrity and generates serious hazards and economic loses. The safety analysis of the thermal installations, based extensively on the numeric simulation. The simulation analysis using realistic computer codes like Relap5/Mod3.2 will help understand steam boiler thermal-hydraulic behavior during normal and abnormal conditions. In this study, we are interested on the evaluation of the radiant steam boiler assessment and response to loss-of-feedwater accident. Pressure, temperature and flow rate profiles are presented in various steam boiler system components. The obtained results demonstrate the importance and capability of the Relap5/Mod3.2 code in the thermal-hydraulic analysis of the steam boiler facilities.
Abstract: This paper describes a newly designed decentralized
nonlinear control strategy to control a robot manipulator. Based on the
concept of the nonlinear state feedback theory and decentralized
concept is developed to improve the drawbacks in previous works
concerned with complicate intelligent control and low cost effective
sensor. The control methodology is derived in the sense of Lyapunov
theorem so that the stability of the control system is guaranteed. The
decentralized algorithm does not require other joint angle and velocity
information. Individual Joint controller is implemented using a digital
processor with nearly actuator to make it possible to achieve good
dynamics and modular. Computer simulation result has been
conducted to validate the effectiveness of the proposed control scheme
under the occurrence of possible uncertainties and different reference
trajectories. The merit of the proposed control system is indicated in
comparison with a classical control system.
Abstract: In this research, a systematic investigation was carried out to determine the optimum conditions of HDS reactor. Moreover, a suitable model was developed for a rigorous RTO (real time optimization) loop of HDS (Hydro desulfurization) process. A systematic experimental series was designed based on CCD (Central Composite design) and carried out in the related pilot plant to tune the develop model. The designed variables in the experiments were Temperature, LHSV and pressure. However, the hydrogen over fresh feed ratio was remained constant. The ranges of these variables were respectively equal to 320-380ºC, 1- 21/hr and 50-55 bar. a power law kinetic model was also developed for our further research in the future .The rate order and activation energy , power of reactant concentration and frequency factor of this model was respectively equal to 1.4, 92.66 kJ/mol and k0=2.7*109 .
Abstract: Continuous pyrolysis of Cogongrass by control
temperature in the novel pyrolysis reactor were conducted at three
difference temperatures 400, 450 and 500°C. Preliminary calculate of
the product yields founded the liquid yield of Cogongrass was
highest of 41.45 %, at 500 oC. Indicated that the liquid yield from
Cogongrass had good received yields because it gave over 40 % and
its produced more liquid than that solid and gas. The compounds
detected in bio-oil from Cogongrass showed the functional group,
especially; Phenol, Phenol, 2,5-dimethyl, Phenol, 3-methyl, 2-
methyl-1,3-oxathiofane, Benzene,1-ethyl-4-methoxy, 2-Cyclopenten-
1-one,2,3-dimethyl, 2- Cyclopenten-1- one, 3-Methyl.
Abstract: This paper presents the influence of distributed generation (DG) on congestion and locational marginal price (LMP) in an optimal power flow (OPF) based wholesale electricity market. The problem of optimal placement to manage congestion and reduce LMP is formulated for the objective of social welfare maximization. From competitive electricity market standpoint, DGs have great value when they reduce load in particular locations and at particular times when feeders are heavily loaded. The paper lies on the groundwork that solution to optimal mix of generation and transmission resources can be achieved by addressing congestion and corresponding LMP. Obtained as lagrangian multiplier associated with active power flow equation for each node, LMP gives the short run marginal cost (SRMC) of electricity. Specific grid locations are examined to study the influence of DG penetration on congestion and corresponding shadow prices. The influence of DG on congestion and locational marginal prices has been demonstrated in a modified IEEE 14 bus test system.