Buenestado, P.; Acho, L. Entropy: international and interdisciplinary journal of entropy and information studies Vol. 20, num. 46, p. 1-12 DOI: 10.3390/e20010046 Data de publicació: 2018-01-11 Article en revista
Image segmentation is defined as a partition realized to an image into homogeneous regions to modify it into something that is more meaningful and softer to examine. Although several segmentation approaches have been proposed recently, in this paper, we develop a new image segmentation method based on the statistical confidence interval tool along with the well-known Otsu algorithm. According to our numerical experiments, our method has a dissimilar performance in comparison to the standard Otsu algorithm to specially process images with speckle noise perturbation. Actually, the effect of the speckle noise entropy is almost filtered out by our algorithm. Furthermore, our approach is validated by employing some image samples.
This paper presents results to assure the almost sure
stability of switching stochastic nonlinear systems. The switching
rule governing the parameters of the system is driven by
independent and identically distributed random variables. In this
scenario, we prove that the switching nonlinear system is almost
surely stable when appropriate matrices have spectral radius
less than one. The result is particularly useful for applications,
as shown in the paper by the application for an automotive
electronic throttle device. The stability result was used to design
a real-time controller for the automotive throttle device, and the
experimental data confirm the usefulness of our approach.
This paper presents a vibration control design to
the string-tip-mass system by using a non-symmetric peakdetector
mechanism. Previously, this peak-detector system was
used as an easy algorithm to mitigate vibration on a real flexible
structure. Moreover, its mathematical representation is simple
and it just has two parameters to tune. Following this former
experience, we adequate this strategy to the vibration control
of the string-tip-mass system. Finally, and according to our
numerical experiments, our control performance is better than
the boundary damper control here programmed for comparison
This article proposes an adaptive predictive control
design technique to mitigate the displacement in a hysteretical
base-isolated system seismically perturbed. The obtained predictive
control law is based on the measurable linear part of the
base-isolated model, and programmed over a prediction-time of
one-sampling-discrete-time period. Two main contributions are
highlighted. First, we use a delta-modulator with hysteresis to
avoid the zero-crossing in the control law caused by one estimated
parameters. Second, we implement a dynamic hysteretic model
based on relays as a command governor able to create new
hysteretic reference trajectories. This is realized to robustly
compensate the hysteretic behavior of the structure under control.
Finally, and according to numerical experiments, our control
design presents a good performance from the displacement
control point of view in comparison to the open-loop system
response, where the El Centro earthquake is invoked.
An active control strategy for base-isolated structures is proposed in this work. The key idea comes from the observation that
passive base isolation systems are hysteretic. Thus, an hysteresis based vibration control is designed in a way that the control force
is smooth and limited by a prescribed bound. A model of a three-story building is used to study and compare the efficacy of a
passive pure friction damper alone, with the addition of the proposed active control. We introduce a rate limiter to the actuator
to simulate its limited speed capacity, present in every physical actuator. Simulations demonstrate that our active control strategy
significantly reduces base displacements and shears without an increase in drift or accelerations.
This paper deals with a recent design of event-driven observer-based smart sensors for output feedback control of linear systems. We re-design the triggering mechanism proposed in a previously reported system with the implementation of self-sampling data smart sensors; as a result, we improve its performance. Our approach is theoretically supported by using Lyapunov theory and numerically evidenced by controlling the inverted pendulum on the cart mechanism.
This paper presents a recent self-sampled-data control algorithm applied to nonlinear systems with actuator failures. Our approach uses the linear model of a given nonlinear system, and based on a granted actuator fault observer method, an asynchronous sampled-data fault compensator controller is then formulated. The proposed sampling rule is realized by using an event-detector monitoring signal invention. On this way, the sampled rate is self governed and asynchronous by nature. Hence, our contribution is twofold. Fist, a new auto-generated non-uniform sampled-data mechanism is stated. Second, we grant an event-triggered control law with actuator failure observation and compensation. Our findings are completely supported by employing Lyapunov’s theory. Finally, according to our numerical experiments applied to an undamped torsional pendulum, our design is able to detect a failure in the actuator device and it can stabilize the undamped torsional pendulum system presenting better performance in comparison to its open-loop deployment.
The realization of adaptive-based controllers in many industrial control applications may exhibit the parametric drift behavior acquiring the well known bursting phenomenon. In this work, an original and novel technique is proposed to eliminate this phenomenon. It is based on a modification of the discrete-time delta modulator into its continuous-time domain and then by adding hysteresis. To verify our proposed method, numerical simulations are conducted to the Van der Pol oscillator control regulation problem solved by using a predictive adaptive-based control technique, where a small output time-delay is added to evidence the bursting phenomenon. Moreover, the realization of our hysteric delta modulator does not alter the original adaptive parametric process, this is an important contribution with respect to the existent algorithms on this topic.
Reset controllers are commonly used to smooth the transient response of systems. We use this technique to improve a standard baseline pitch controller for offshore wind turbines (WTs). The introduction of this strategy enhances the overall performance of the WT. In particular, the fore-aft and side-to-side accelerations of the WT tower are significantly reduced, whilst a steadier power output is obtained, in comparison to the standard baseline pitch controller. Furthermore, our designed pitch control’s main advantage, with respect to the baseline, is its ease of implementation and reduced complexity as it does not require a gain-scheduling technique, nor pitch position measurement (thus, it is insensitive to pitch sensor faults). The proposed approach has been simulated on the NREL 5-MW prototype offshore turbine model, mounted on a jacket support. The simulations are carried out using the aero-hydro-servo-elastic simulator FAST, and key observations are thoroughly discussed.
The main objective of this paper is to design a dynamic reference trajectory based on hysteresis to avoid saturation in controlled wind turbines. Basically, the torque controller and pitch controller set-points are hysteretically manipulated to avoid saturation and drive the system with smooth dynamic changes. Simulation results obtained from a 5MW wind turbine benchmark model show that our proposed strategy has a clear added value with respect to the baseline controller (a well-known and accepted industrial wind turbine controller). Moreover, the proposed strategy has been tested in healthy conditions but also in the presence of a realistic fault where the baseline controller caused saturation to nally conduct to instability.
This paper presents a procedure to transform a chaotic logistic map into a continuous-time delay chaotic system by using sampled-data representation of continuous-time models. Because of this, the chaotic behavior of the resultant scheme is easy to proofread. A numerical illustration is also realized by utilizing Matlab/Simulink, where the new resultant chaotic attractor is shown
This paper presents an Iterative Learning Control design applied to homing guidance of missiles against maneuvering targets. According to numerical experiments, although an increase of the control energies is appreciated with respect to a previous published base controller for comparison, this strategy, which is simple to realize, is able to reduce the time to reach the head-on condition to target destruction. This fact is important to minimize the missile lateral force-level to fulfill engaging in hypersonic target persecutions.
The paper presents results for the second moment stability of continuous-time Markov jump systems with quadratic terms, aiming for engineering applications. Quadratic terms stem from physical constraints in applications, as in electronic circuits based on resistor (R), inductor (L), and capacitor (C). In the paper, an RLC circuit supplied a load driven by jumps produced by a Markov chain—the RLC circuit used sensors that measured the quadratic of electrical currents and voltages. Our result was then used to design a stabilizing controller for the RLC circuit with measurements based on that quadratic terms. The experimental data confirm the usefulness of our approach.
This paper presents an application of Iterative Learning Control (ILC) theory to secure communication system design by using chaotic signals, where the logistic-map is employed as a source of chaos. Meanwhile, the ILC scheme is employed as a tool to encrypt and decrypt a message. A set of numerical experiments is realized to evidence the performance of our system, including the noisy case on the channels of communication of the proposed scheme.
The paper presents conditions to assure stochastic stability for a nonlinear model. The proposed model is used to represent the input-output dynamics of the angle of aperture of the throttle valve (input) and the manifold absolute pressure (output) in an automotive spark-ignition engine. The automotive model is second moment stable, as stated by the theoretical result—data collected from real-time experiments supports this finding.
Vargas, A.; Sampio, L.; Acho, L.; Zhang, L.; do Val, J. IEEE transactions on control systems technology Vol. 24, num. 5, p. 1820-1827 DOI: 10.1109/TCST.2015.2508959 Data de publicació: 2016-09-01 Article en revista
The note presents an algorithm for the average
cost control problem of continuous-time Markov jump linear
systems. The controller assumes a linear state-feedback form
and the corresponding control gain does not depend on the
Markov chain. In this scenario, the control problem is that of
minimizing the long-run average cost. As an attempt to solve the
problem, we derive a global convergent algorithm that generates
a gain satisfying necessary optimality conditions. Our algorithm
has practical implications, as illustrated by the experiments that
were carried out to control an electronic dc–dc buck converter.
The buck converter supplied a load that suffered abrupt changes
driven by a homogeneous Markov chain. Besides, the source of
the buck converter also suffered abrupt Markov-driven changes.
The experimental results support the usefulness of our algorithm.
In wind turbines (WTs), some faults can induce saturation of the control signal, and these saturation nonlinearities might lead to instability. Therefore, a robust system against saturation can better deal with faults. In this work, an avoid saturation strategy is proposed for the torque control of WTs. The key idea is that the reference power and generator speed set-points are hysterically manipulated. Simulation results from a 5MW benchmark model show that the proposed strategy has a clear added value with respect to the baseline controller not only in healthy condition but also in presence of a realistic fault.
Mujica, L.E.; Ruiz, M.; Acho, L.; Alferez, E.; Tutivén, C.; Vidal, Y.; Rodellar, J. European Workshop on Structural Health Monitoring p. 1-10 Data de presentació: 2016-07-06 Presentació treball a congrés
The future of wind energy industry passes through the use of larger and more flexible wind turbines in remote locations, which are increasingly offshore to benefit stronger and more uniform wind conditions. Cost of operation and maintenance of offshore wind turbines is among 15-35% of the total cost. From this, 80% comes from unplanned maintenance due to different faults in the wind turbine components. Thus, an auspicious way to contribute to the increasing demands and challenges is by applying low-cost advanced fault detection schemes. This work proposes a new method for fault detection of wind turbine actuators and sensors faults in variable-speed wind turbines. For this purpose, time domain signals acquired from the operating wind turbine are converted into two-dimensional matrices to obtain gray-scale digital images. Then, the image pattern recognition is processed getting texture features under a multichannel representation. In this work, four types of texture features are used: statistical, wavelet, granulometric and Gabor features. Then, the most significant features are selected with the conditional mutual criterion. Finally, the fault detection is performed using an automatic classification tool. In particular, a 10-fold cross validation is used to obtain a more generalized model and evaluate the classification performance. In this way, the healthy and faulty conditions of the wind turbine can be detected. Coupled non-linear aero-hydro-servo-elastic simulations of a 5MW offshore type wind turbine are carried out for several fault scenarios. The results show a promising methodology able to detect the most common wind turbine faults.
This work is concerned with active vibration mitigation in wind turbines (WT) but not through the use of specifically tailored devices. Instead, a general control scheme is designed for torque and pitch controllers based on a super-twisting algorithm, which uses additional feedback of the fore-aft and side-to-side acceleration signals at the top of the WT tower to mitigate the vibrational behavior. In general, proposed methods to improve damping through pitch and torque control suffer from increased blade pitch actuator usage. However, in this work the blade pitch angle is smoothed leading to a decrease of the pitch actuator effort, among other benefits evidenced through numerical experiments. The most frequent faults induce vibrations in the corresponding WT subsystems. In fact, vibration monitoring has been recently used for fault diagnosis Thus, by means of vibration mitigation, different faulty conditions can be alleviated leading to a passive fault tolerant control. In this work, coupled non-linear aero-hydro- servo-elastic simulations of a floating offshore wind turbine are carried out for one of the most common pitch actuator faults.
This work addresses the problem of online fault detection of an advanced wind turbine benchmark under actuators (pitch and torque) and sensors (pitch angle measurement) faults of different type: fixed value, gain factor, offset and changed dynamics. The fault detection scheme starts by computing the baseline principal component analysis (PCA) model from the healthy or undamaged wind turbine. Subsequently, when the wind turbine is inspected or supervised, new measurements are obtained and projected into the baseline PCA model. When both sets of data—the baseline and the data from the current wind turbine— are compared, a multivariate statistical hypothesis testing is used to make a decision on whether or not the wind turbine presents some damage, fault or misbehavior. The effectiveness of the proposed fault- detection scheme is illustrated by numerical simulations on a well-known large offshore wind turbine in the presence of wind turbulence and realistic fault scenarios. The obtained results demonstrate that the proposed strategy provides an early fault detection, thereby giving the operators sufficient time to make more informed decisions regarding the maintenance of their machines.
Given the equation motion of a moving charged particle in a controlled electromagnetic field, this paper proves that its velocity-trajectory motion converges to an specified velocity-surface in the 3-D Euclidean dimensional space. This is basically realized by just manipulating the electric field of an electromagnetic field. Lyapunov theory is invoked to test our statement; besides, a numerical example is provided to support our theoretical contribution. Finally, we consider that the exposition of this paper could be of interest to undergraduate students.
The main objective of this paper is to present an academic example of a PD
controller applied to teach position control design of a DC-motor to automatically adjust a
potentiometer. This adjustment is focused on to solve the maximum power transfer objective
in a linear electrical circuit. This design involves the use of the extremum seeking algorithm. To
support our proposal, numerical simulations and mathematical modelling of the main problem
statement are programmed.
This paper presents an application of unscented Kalman filters ( UKFs) to an automotive electronic throttle device. The motivation of this study is on estimating the position of the throttle device when measurements of the position are inaccessible, e. g., due to failures in the sensor of position. In this case, an external wattmeter is connected in the circuitry to measure the power consumed by the throttle, and this information feeds UKFs to produce the estimation for the position. Experimental data support the findings of this paper. Almost all of the brand-new vehicles based on spark-ignition combustion engines have an electronic throttle valve to control the power produced by the engine. The electronic throttle has a unique sensor for measuring the position of the throttle valve, and this feature can represent a serious problem when the sensor of position fails. As an attempt to prevent the effects of a failure from such a sensor, we present an algorithm ( UKF) combined with the use of an additional sensor, i. e., a wattmeter. The wattmeter is detached from the throttle's structure but is arranged to measure the electric power consumed by the throttle. Measurements of the power consumption then feed the UKF. This filter then produces an estimation of the position of the throttle valve. Experimental data illustrate the practical benefits of our approach.
The paper presents an application of unscented
Kalman filters to an automotive electronic throttle device. The
motivation of this study is on estimating the position of the
throttle device when measurements of position are inaccessible,
e.g., due to failures in the sensor of position. In this case, an
external wattmeter is connected in the circuitry to measure the
power consumed by the throttle, and this information feeds
unscented Kalman filters to produce the estimation for the
position. Experimental data support the findings of this paper.
The continuous increase in the size of wind turbines (WTs) has led to new challenges in the design of novel torque and pitch controllers. Today’s WT control design must fulfill numerous specifications to assure effective electrical energy production and to hold the tower vibrations inside acceptable levels of operation. Hence, this paper presents modern torque and pitch control developments based on the super-twisting algorithm (STA) by using feedback of the fore- aft and side-to-side acceleration signals of the WT tower. According to numerical experiments realized using FAST, these controllers mitigate vibrations in the tower without affecting the quality of electrical power production. Moreover, the proposed controllers’ performance is better than the baseline controllers used for comparison.
The main contribution of this paper is to propose new control techniques which not only provide fault tolerance capabilities to the WT system, but also improve the overall performance of the system in both fault free and faulty conditions. Coupled non-linear aero-hydro-servo-elastic simulations of an offshore wind turbine with jacket platform are carried out. The proposed controllers are based in the super-twisting algorithm (STA) by using feedback of the generator shaft speed as well as the fore-aft and side-to-side acceleration signals of the WT tower.
Every physical actuator is subject to saturation. It has been well recognized that, when the actuator saturates, the performance of the closed-loop system (designed without considering actuator saturation) may seriously deteriorate. In extreme cases, the system stability may even be lost. This paper proposes an avoid saturation strategy for the torque controller of a wind turbine benchmark model. The simulation results show that the proposed strategy has a clear added value with respect to the baseline controller (well- accepted industrial controller) in the presence of faults. Another advantage of the contributed method is that conservative bounds for the actuator torque can be fixed in order to extend the service life of the wind turbine.
Pujol-Vazquez, G.; Vidal, Y.; Acho, L.; Vargas, A. International journal of numerical modeling. Electronic networks devices and fields Vol. 29, num. 2, p. 192-204 DOI: 10.1002/jnm.2063 Data de publicació: 2016-03 Article en revista
This paper presents an improved model for an automotive electronic throttle inspired on the behavior observed in real-time experiments. Due to a number of issues, particularly the return-spring, the performance
of the throttle valve depends on whether it is opening or closing. This asymmetric behavior was taken into account to design a mathematical model of the throttle body and to derive a nonlinear asymmetric PI controller. The experimental demonstration suggests that considering an asymmetric term dramatically improves the performance of the controller
This is the peer reviewed version of the following article: Pujol, G., Vidal, Y., Acho, L. and Vargas, A. N. (2015), Asymmetric modelling and control of an electronic throttle. Int. J. Numer. Model, which has been published in final form at http://dx.doi.org/10.1002/jnm.2063. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
This paper presents an improved model for an automotive electronic throttle inspired on the behavior observed in real-time experiments. Due to a number of issues, particularly the return-spring, the performance of the throttle valve depends on whether it is opening or closing. This asymmetric behavior was taken into account to design a mathematical model of the throttle body and to derive a nonlinear asymmetric
PI controller. The experimental demonstration suggests that considering an asymmetric term dramatically improves the performance of the controller
Seismic isolation systems are essentially designed to preserve structural safety, prevent occupants injury and properties damage. An active saturated LMI-based control design is proposed to attenuate seismic disturbances in base-isolated structures under saturation actuators. Using a mathematical model of an eight-storied building structure, an active control algorithm is designed. Performance evaluation of the controller is carried out in a simplified model version of a benchmark building system, which is recognized as a state-of-the-art model for numerical experiments of structures under seismic perturbations. Experimental results show that the proposed algorithm is robust with respect to model and seismic perturbations. Finally, the performance indices show that the proposed controller behaves satisfactorily and with a reasonable control effort.
Wind turbines (WTs) are basically controlled by varying the generator load torque (with the so-called torque control) and the blade pitch angles (with the so-called pitch control) based on measurement of the generator shaft speed. These two controllers unitedly work to satisfy the control objectives, and it is crucial that they are tolerant to possible faults in the WT system. Passive fault-tolerant control comprises the design of robust controllers against disturbances and uncertainties. This enables the controller to counteract the effect of a fault without requiring reconfiguration or fault detection. In this regard, the main contribution of this paper is to propose new control techniques that not only provide fault tolerance capabilities to the WT system but also improve the overall performance of the system in both fault-free and faulty conditions. Coupling nonlinear aero-hydro-servo-elastic simulations of an offshore WT with jacket platform is carried out for several pitch actuator faults. The jacket platform motions and structural loads caused by fault events with the proposed controllers are compared with loads encountered during normal operation and with respect to a well-known baseline controller in the literature. The proposed controllers are based in the super-twisting algorithm by using feedback of the generator shaft speed as well as the fore-aft and side-to-side acceleration signals of the WT tower.
Security and secrecy are some of the important concerns in the communications world. In the last years, several encryption
techniques have been proposed in order to improve the secrecy of the information transmitted. Chaos-based encryption techniques
are being widely studied as part of the problem because of the highly unpredictable and random-look nature of the chaotic signals.
In this paper we propose a digital-based communication system that uses the logistic map which is a mathematically simple model
that is chaotic under certain conditions.The input message signal is modulated using a simple Delta modulator and encrypted using
a logistic map. The key signal is also encrypted using the same logistic map with different initial conditions. In the receiver side, the
binary-coded message is decrypted using the encrypted key signal that is sent through one of the communication channels. The
proposed scheme is experimentally tested using Arduino shields which are simple yet powerful development kits that allows for
the implementation of the communication system for testing purposes.
This paper presents a modified discrete-time chaotic system obtained from the standard logistic map model. Then, a secure communication system is given and numerical experiments are carried out using the conceived discrete-time chaotic oscillator. Moreover, an experiment of our chaotic model is realized using the Arduino-UNO board. (C) 2015 The Franldin Institute. Published by Elsevier Ltd. All rights reserved.
This paper presents a modified discrete-time chaotic system obtained from the standard logistic map model. Then, a secure communication system is given and numerical experiments are carry out using the conceived discrete-time chaotic oscillator. Moreover, an experiment of our chaotic model is realized using the Arduino-UNO board.
Vargas, A.; Acho, L.; Pujol-Vazquez, G.; Costa, E.; Ishihara, J.; João B. R. do Val, J. International journal of robust and nonlinear control DOI: 10.1002/rnc.3393 Data de publicació: 2015-07-30 Article en revista
The note presents an output feedback control strategy for Markov jump linear systems with no mode observation. Based on minimizing a finite-time quadratic cost, we derive an algorithm that generates output feedback gains that satisfy a necessary optimality condition. These gains can be computed off-line relying only on the initial condition of the system. This result expands a previous one from the literature that considered state-feedback only. To illustrate the usefulness of the approach, real-time laboratory experiments were performed to control an automotive electronic throttle valve subject to Markov-driven voltage fluctuations.
The note presents conditions to assure the stability in probability for a class of continuoustime quadratic Markov jump systems. From the viewpoint of the state-space evolution, the system has two parts: (i) a linear term, in which the matrix parameter jumps according to a Markov chain, and (ii) a quadratic term with no jumps. The stability in probability for the quadratic Markov jump system is then assured under mild conditions. A numerical example illustrates the usefulness of the derived results.
The number and complexity of control systems in wind turbines (WT) is expanding rapidly, and their design can be the difference between an immensely profitable system or a damaged system. Designing a robust control system requires to test the control algorithms in the actual controller hardware. However, WT are large and expensive, thus we would like to perform this test virtually, without using prototypes of the WT.
This work develops a fault diagnosis (FD) and fault tolerant control (FTC) of pitch actuators in wind turbines. This is accomplished by combining a disturbance compensator with a controller, both of which are formulated in the discrete-time domain. The disturbance compensator has a dual purpose: to reconstruct the actuator fault (which is used by the FD technique) and to design the discrete-time controller to obtain a FTC. That is, the actuator faults are reconstructed and then the control inputs are modified to achieve a FTC with a comparable behavior to the fault-free case.
The performance of the FD and FTC schemes is tested in a Hardware-in-the-Loop (HiL) testbed for WT controllers. The used controller hardware is an open hardware Arduino board which is connected to the virtual WT via USB. The onshore 5MW turbine is simulated on the open-source National Renewable Energy Laboratory WT simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence). The proposed HiL is used to characterize the behavior of the WT in the full load region in normal operation as well as under fault operation.
This paper develops a fault detection and isolation (FDI) and active fault tolerant control (FTC) of pitch actuators in wind turbines (WTs). This is accomplished combining a disturbance compensator with a controller, both of which are formulated in the discrete-time
domain. The disturbance compensator has a dual purpose: to reconstruct the actuator fault (which is used by the FDI technique) and to design the discrete-time controller to obtain an active FTC. That is, the actuator faults are reconstructed and then the control inputs are modified with the reconstructed fault signal to achieve a FTC in the presence of actuator faults with a comparable behavior to the fault-free case. The proposed techniques are validated using the aeroelastic wind turbine simulator FAST. This software is designed by the U.S. National Renewable Energy Laboratory and is widely used for studying wind turbine control systems.
The objective of this paper is to present a power control strategy to direct-driven permanent magnetic synchronous generator wind turbines. This strategy is composed by two parts. One part to control the magnetic ¿eld of the generator system and the other to control the collective blade pitch angle. We slightly modify the standard ¿eld-oriented controllers to smooth the reference setpoints before they are sent to the generator system. The aim of this modi¿cation is to reduce fast dynamics on the generator device. On the other hand, the proposed collective pitch angle control seems to be a novel one which only use the information of the active power generated by the wind turbine. According to numerical experiments, our power control strategy displays an acceptable performance.
This paper develops a fault diagnosis (FD) and fault-tolerant control (FTC) of pitch actuators in wind turbines. This is accomplished by combining a disturbance compensator with a controller, both of which are formulated in the discrete time domain. The disturbance compensator has a dual purpose: to estimate the actuator fault (which is used by the FD algorithm) and to design the discrete time controller to obtain a FTC. That is, the pitch actuator faults are estimated, and then, the pitch control laws are appropriately modified to achieve an FTC with a comparable behavior to the fault-free case. The performance of the FD and FTC schemes is tested in simulations with the aero-elastic code FAST.
The paper presents a model-based fault detection
method for pitch actuators faults using the normalized gradient
method to estimate the parameters of the pitch actuator. One major
difficulty is that the input signal to the parametric estimation method
must be a persistent excitation. To circumvent this, a chattering term
is added to the pitch control law and the usual low-pass filters
are not used for the parametrization in the normalized gradient
method (thus acceleration information is used). In order to verify the
proposed method, simulations are conducted within a Hardware in
the Loop (HiL) platform using the wind turbine simulation software
FAST (Fatigue, Aerodynamics, Structures, and Turbulence).
The paper presents a model-based fault detection method for pitch actuators faults using the normalized gradient method to estimate the parameters of the pitch actuator. One major difficulty is that the input signal to the parametric estimation method must be a persistent excitation. To circumvent this, a chattering term
is added to the pitch control law and the usual low-pass filters are not used for the parametrization in the normalized gradient
method (thus acceleration information is used). In order to verify the proposed method, simulations are conducted within a Hardware in the Loop (HiL) platform using the wind turbine simulation software
FAST (Fatigue, Aerodynamics, Structures, and Turbulence).
This paper introduces a polyhedral approximation algorithm for set-valued estimation of switching linear systems. The algorithm generates set-valued estimates for any possible sequence of switching parameters, under the
assumption that the system has unknown but bounded disturbances and measurement noises. Our algorithm has practical implications; namely, set-valued estimates were generated for the position and electrical current of a real-time automotive electronic throttle valve, and the corresponding experimental data demonstrate the practical benefits of our approach.
In this paper, a new modified Chua oscillator is introduced. The original Chua oscillator is well known for its simple implementation and mathemati- cal modeling. A modification of the oscillator is proposed in order to facilitate the synchronization and the encryption and decryption scheme. The modifi- cation consists in changing the nonlinear term of the original oscillator to a smooth and bounded nonlinear function. A bifurcation diagram, a Poincar ´e map and the Lyapunov exponents are presented as proofs of chaoticity of the newly modified oscillator. An application to secure communications is pro- posed in which two channels are used. Numerical simulations are performed in order to analyze the communication system.
This paper presents a method to manipulate the
chaotic behavior of the Duffing oscillator by employing
a modified Delta modulator based on hysteresis
modeling. Numerical experiments are given to support
our design. Chaos is evidenced by utilizing Poincar´e
This paper illustrates how to set up a Hardware-in-the-Loop (HiL) platform for the test of wind turbine (WT) controllers. The dynamics of the WT are simulated on the National Renewable Energy Laboratory WT simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code, which emulates all required input signals of the controller and reacts to the controller commands (almost) like a real turbine. The dynamic torque control system runs on an Arduino Mega microcontroller board which is connected to the virtual WT via USB. In particular, the power generation control in variable-speed variable-pitch wind turbines is considered through torque and pitch control. Two previously published torque controllers are tested under the proposed experimental HiL setup.
This paper presents an implementation of a novel semi-active controller that uses only acceleration information, via a magnetorheorological damper, on a flexible structure. This controller was motivated by the scheme of a peak-detector system used on electronics circuits. That is, given a peak-detector system, we modify it to develop a novel semi-active controller. The experimental setup consisting of a two-story flexible structure, where the magnetorheorological damper is connected in a ‘semi’-brace connection, demonstrates an acceptable performance of our semi-active controller when it is compared with classical semi-active controllers.
The paper presents a control strategy for an automotive electronic throttle body, a device largely used into vehicles to increase the efficiency of the combustion engines. The synthesis of the proposed controller is based on a linear matrix inequality (LMI) formulation, which allows us to deal with uncertainties on the measurements of the position of the throttle valve. The LMI approach generates a suboptimal solution for the robust H-2 static output feedback control problem, and the corresponding suboptimal control gain was evaluated in practice to control the valve position of the throttle. The usefulness of the approach has been verified not only by numerical simulations but also by real experiments taken in a laboratory prototype.