Observer Research Papers - Academia.edu (original) (raw)

We survey and extend the work on the paradigm called "computing by observing". Its central feature is that one considers the behavior of an evolving system as the result of a computation. To this purpose an external observer records this behavior. In this way, several computational trade-offs between the observer and the observed system can be determined. It has turned out that the observed behavior of computationally simple systems can be very complex, when an appropriate observer is used. For example, a restricted version of context-free grammars with regular observers suffices to obtain computational completeness. As a second instantiation presented here, we apply an observer to sticker systems, an abstract model of DNA computing. Finally, we introduce and investigate the case where the observers can read only one measure of the observed system (e.g., mass or temperature) modeling in this way, limitations in the observation of real physical systems. Finally a research perspective on the topic is presented.

- by
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- Behavior, Modeling, Complexity, Natural Computing

Information analysts must rapidly assess information to determine its usefulness in supporting and informing decision makers. In addition to assessing the content, the analyst must be confident about the quality and veracity of the information. Visualizations can concisely represent vast quantities of information, thus aiding the analyst to examine larger quantities of material; however, visualization programs are challenged to incorporate

- by Judi McCuaig
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- Information Visualization, Data Analysis, Scientific Computing, Law Enforcement

A very common approach in chemistry and biology is to observe the progress of an experiment, and take the result of this observation as the final output. Inspired by this, a new approach to computing, called system/observer, was introduced in [3]. In this paper we apply this strategy to sticker systems, . In particular we use finite automata (playing the role of observer) watching the "evolution" of a sticker system and translating such "evolution" into a readable output. We show that this way of "computing by observing" brings us results quite different from the ones obtained when considering sticker systems in the standard manner. Even regular simple sticker systems (whose generative power is subregular) become universal when considered in this new framework. The significance of these results for DNA computing (by sticker systems) is briefly discussed.

- by Artiom Alhazov
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- Software Maintenance, Systems Theory, Biology, DNA computing

This paper presents state observer designs for quarter-car passive suspension. Proposed designs correspond to two theories, full-order state observer and observer on closed-loop system. Those observers are used for states and estimation errors observation. Simulation is done using MATLAB and SIMULINK. MATLAB is used to calculate both feedback gain matrix and observer gain matrix whereas SIMULINK is applied to build state space block. Results show that those observers work effectively and fit observer theories. This work may motivate to continue to other steps of observer designs, observer designs for half car and full car passive suspension.

Fault detection and isolation (FDI) of a class of networked control systems (NCS), applied for telerobotics system is studied in this paper. The considered NCS application is related to telerobotics system, where it is modelled with a hybrid manner, by including the continuous, discrete, uncertain, and stochastic aspects of all the system components. The main considered components of the NCS namely the network system and controlled system are completely decoupled according to their operation characteristics. The network part is taken as a discrete and stochastic system in presence of non-structured uncertainties and external faults, while the controlled part is considered as a continuous system in presence of input and output faults. Two model based fault diagnosis approaches are proposed in this paper. The first concerns a discrete and stochastic observer applied to the network system in order to detect and isolate system faults in presence of induced delay on the network part. The second is based on the analytical redundancy relations (ARR) allows detecting and isolating the input and output system' faults. Experimental results applied on telerobotics system, show the performance and the limit of the proposed fault diagnosis approach.

- by Rochdi Merzouki
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- Mechanical Engineering, System Identification, Mechatronics, Teleoperation
- by Hatice Gunes
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- Plastic Surgery, Image Processing, Image Analysis, User Interface

An integral terminal sliding mode-based control design is proposed in this paper to enhance the power quality of wind turbines under unbalanced voltage conditions. The design combines the robustness, fast response, and high quality transient characteristics of the integral terminal sliding mode control with the estimation properties of disturbance observers. The controller gains were auto-tuned using a fuzzy logic approach. The effectiveness of the proposed design was assessed under deep voltage sag conditions and parameter variations. Its dynamic response was also compared to that of a standard SMC approach. The performance analysis and simulation results confirmed the ability of the proposed approach to maintain the active power, currents, DC-link voltage and electromagnetic torque within their acceptable ranges even under the most severe unbalanced voltage conditions. It was also shown to be robust to uncertainties and parameter variations, while effectively mitigating chattering in comparison with the standard SMC.

- by IEEE/CAA J. Autom. Sinica
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- Power Quality, Wind Turbines, Fuzzy Approach, Observer

Background: The observer-rated Hamilton depression scale (HamD) and the self-report Beck Depression Inventory (BDI) are among the most commonly used rating scales for depression, and both have well demonstrated reliability and validity. However, many depressed subjects have discrepant scores on these two assessment methods. The present study evaluated the ability of demographic, clinical and personality factors to account for the discrepancies observed between BDI and HamD ratings. Method: The study group consisted of 94 SCID-diagnosed outpatients with a current major depressive disorder. Subjects were rated with the 21-item HamD and completed the BDI and the NEO-Five Factor Inventory. Results: Younger age, higher educational attainment, and depressive subtype (atypical, non-melancholic) were predictive of higher BDI scores relative to HamD observer ratings. In addition, high neuroticism, low extraversion and low agreeableness were associated with higher endorsement of depressive symptoms on the BDI relative to the HamD. In general, these predictive variables showed a greater ability to explain discrepancies between self and observer ratings of psychological symptoms of depression compared to somatic symptoms of depression. Limitations: The study does not determine which aspects of neuroticism and extraversion contribute to the observed BDI / HamD discrepancies. Conclusions: Depression ratings obtained with the BDI and HamD are frequently discordant and a number of patient characteristics robustly predict the discrepancy between these two rating methods. The value of multi-modal assessment in the conduct of research on depressive disorders is re-affirmed.

- by Derrick Larsen
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- Demography, Psychometrics, Higher Education, Personality

The paper presents a comparison of methods of the back EMFs estimation for the permanent magnets synchronous motor in a case of position estimation at the low speed range. These methods are based on the following structures for back EMF estimation: observer for model of the electrical part of the motor, the observer for the modified correction function and estimation based on the simplified model. Obtained in this way the instantaneous values of the back EMFs, depending on the method of obtaining them, are characterized by different quality and accuracy of the estimated shaft position.

- by Konrad Urbanski
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- Permanent Magnet Synchronous Machines, Observer, Sensorless Control

This paper studies the detection of broken rotor bars in induction motors. The hypothesis on which detection is based is that the apparent rotor resistance of an induction motor will increase when a rotor bar breaks. Here, the apparent rotor resistance is that in the balanced steady-state single-phase electricol model of an induction motor. To detect broken rotor bars, measurements of stator voltage, stator current, stator excitation frequency, and rotor velocity are taken over a small range of velocity. These measurements are processed by a near-leastsquare-error estimator to produce estimated motor states and parameters. In particular, rotor resistance is estimated and compared with its nominal value to detect broken rotor bars. As part of this estimation process, it is necessary to compensate for the thermal variation in rotor resistance. The broken-rotor-bar detector is evaluated experimentally using one stator and three rotors from identical 3-hp induction motors. In one rotor, a bar is broken by milling into the rotor. The apparent rotor resistance, as estimated, is clearly greater for the rotor with the broken bar.

- by Aswathi Poozhikkuth
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- Engineering, Algorithms, Artificial Intelligence, System Identification

Recent academic research on mysticism is entrenched in an ideological clash between two schools of interpretation of mysticism: perennialism (essentialism, or decontextualism), on the one hand, and anti-perennialism (constructivism, intentionalism, or contextualism), on the other. The former upholds the universality of the mystical experience, while the latter takes it to be—like any other human experience, they say— completely conditional. I will begin by explaining what ‘mysticism’ means. I will then proceed to define and illustrate the two schools of interpretation— perennialism and anti-perennialism—by the arguments of their representative pupils. My point is that the two schools of interpretation commit the disjunctive fallacy, or the fallacy of exclusive alternatives. Then, assessing the relation between mystical experience in practice, and systematic metaphysical theory, I will propose process philosophy (i.e., from Heraclitus to Peirce and Whitehead) as a framework for the debate, and my theoretical solution. In the end, upon reviewing two strong alternatives called, respectively, a “Middle Way” (Jackson, 1989), and a “middle ground” (Forman, 1993), I will suggest my own metaphysical understanding which is akin to the proposed alternatives to perennialist and anti-perennialist interpretations of the purity of mystical experience.

- by Randolph T Dible
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- Philosophy, Metaphysics, Constructivism, Aldous Huxley
- by D. E. C BELKHIAT
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- Hybrid Systems, Fault Detection, Switched Systems, Fault diagnosis

In this paper, a class of nonlinear systems with faults, parametric uncertainties and without full state measurements are considered. A novel observer is designed whose estimation error is not affected by faults, and an observer-based fault tolerant tracking controller is proposed to make the outputs asymptotically track the reference signals while the states are bounded. The proposed FTC method can help to provide a switching detection scheme and a family of Lyapunov functions for a class of hybrid nonlinear systems with uncontrollable switchings, and to guarantee the global tracking performance. A three-tank system is taken as an example to show the efficiency of the proposed method.

The following research proposal is presented as a technological solution focused on the design of a current controller for a grid-connected photovoltaic (PV) inverter. In order to achieve a suitable grid-connection, it is required a filter interface between the voltage source inverter (VSI) and the electrical grid. In the earlier times, the interface was composed of a single inductor. A single inductor filter (L filter) has the disadvantage of not fully eliminating switching harmonics. To overcome this issue, LCL filters have gained preference over L filters. Systems based on LCL filters produce less switching harmonics and have reduced size inductors. However, LCL filters present an undesired resonance, and are more sensitive to electric grid harmonics. Due to these drawbacks, it is necessary to design more sophisticated controllers to guarantee stability and good performance. Generally, the knowledge of the state variables in the LCL filter is required to solve the instability problem associated to the overall system. Nevertheless, measurement of all state variables is an expensive solution because of the quantity of required sensors. In this paper it is proposed a current controller based on a reduced-order observer to reduce the number of measured state variables.

- by Josue Alonzo
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- Photovoltaics, Solar Energy, grid connected PV inverters, Solar PV

Piezoelectric actuators are popularly applied as actuators in high precision systems due to their small displacement resolution, fast response and simple construction. However, the hysteresis nonlinear behavior limits the dynamic modeling and tracking control of piezoelectric actuators. This thesis studies a dynamic model of a moving stage driven by piezoelectric stack actuator. The Bouc-Wen model is introduced and analyzed to express the nonlinear hysteresis term of the piezoelectric stack actuator, where the values of the parameters of the model have been taken from a previous work. The simulated results using MATLAB/Simulink demonstrate the existence of the hysteresis phenomenon between the input voltage and the output displacement of the piezoelectric stack actuator, and validate the correctness of the model. Moreover, a Luenberger observer is designed to estimate the hysteresis nonlinearity of the system, and then combined with the voltage input signal to form a Luenberger-based feedforward controller to control the displacement of the system. Furthermore, a Proportional-Integral-Derivative (PID) feedback controller is integrated with the feedforward controller to achieve more accurate output displacement, where the gains of the PID controller are optimized using Particle Swarm Optimization. Several performance index formulas have been studied to get the best solution of the PID’s gains. An Integral Time Squared Error plus Absolute Error performance index formula has been proposed to achieve zero overshoot and steady-state error. The simulated results accomplished using MATLAB/Simulink show the ability of the designed controllers to vastly reduce the amount of error of the output displacement and the response time of the system.

- A usual argument against GPC is its demand for processing power. In industry, however, this is not a serious argument if better control performance can be reached. As the development of new processors with increased performance takes... more

- by Ralph Kennel
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- Control Systems, Sampling methods, Error Correction, Predictive models

Singapore is expert at using education as a means of projecting soft power internationally. For years, it has offered free and subsidized education opportunities in Southeast Asia, and now, with its interests in the Arctic, it is offering... more

A sliding-mode observer is proposed in order to estimate the phase-to-phase trapezoidal back-EMF in a brushless DC motor by using only the measurements of the stator currents and voltages. The main feature of the proposed observer is that it is not sensitive to the switching noise and no filtering is required. The back-EMF estimate was then used to deduce the six rotor positions of the motor. In addition, a method to obtain an estimate of the rotor speed of the motor, by exploiting the mathematical relationship between the speed and the back-EMF, is presented. The observer of the trapezoidal back-EMF is implemented practically on a DSP board. Simulation and experimental results are given to show the performance of the observer.

In this paper, we address fault detection for networked control systems subject to random packet dropout. The packet dropout is assumed to be existing in the sensor-to-controller link and the controller-toactuator link. Both parity space and observer based residual generation and evaluation approaches are proposed. In parity space based fault detection scheme, a new optimization index is proposed to deal with stochastic system parameters caused by random packet dropout, while in observer based scheme, this is accomplished by introducing a reference model. In order to evaluate performance of the designated threshold, the corresponding false alarm rate is given. The two fault detection schemes can ensure both robustness to packet dropout as well as disturbance and sensitivity to fault. An experimental study is employed to verify that the proposed method performs better than the existing approaches.

- by Steven Ding
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- Engineering, System Identification, Fault Detection, Distributed System

The paper presents results of a research on the sensorless drive with PMSM supplied through the sinusoidal filter. The back electromotive force based observer is used to the shaft position estimation. Used in the study, the observer's correction function, contains multi integrators in the path, which improves the position estimation. Otherwise than in a typical implementation of the position observer, the presence of the filter was not taken into account in observer structure, however, it was taken into account in the observer parameters. This type of control allows the use of conventional control system and there is no need to take account the filter in the control circuit. Presented concept has been proven in laboratory.

The paper deals with the problem of speed and position estimation in SRM drive equipped with hysteresis band current controller. Instead of measured current the observer utilize reference current. The voltage is calculated from switching on-time. A speed observer structure which uses estimated back EMF and current of each phase is presented. The shaft position is integrated from estimated speed signal. Observer uses a simplified 1-dimensional nonlinear equation set instead of 2-dimensional.

- by Konrad Urbanski
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- Observer, Sensorless Control, SRM

The encountering of the experiencer or observer—transcendental subjectivity itself—at the foundation of the world leads inevitably to the recognition of pure objectivity as ultimate reality (which can be taken as its ultimate deconstruction, analogous to the apophatic or via negativa), from which objects derive their value, weight, significance, meaning or objectivity. In this way, pure objectivity can be seen as the supra-self-evident Axiological Axiom, so to speak, even Unconditional Love, in romantic terms. This axiology (value theory) has a structure inverse to the relationship between transcendental subjectivity as the radical unity of pure self-reference and on the other hand, the world of forms, as mere traces (representations, indications) of the unique, original “first distinction” Spencer-Brown speaks of at the foundation of his calculus. That is, all forms (i.e., distinctions, differences) would reduce to being the first distinction, also known as the marked state, which ...

- by Randolph T Dible
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- Philosophy, Metaphysics, Constructivism, Aldous Huxley

This paper presents a case study, where a failure detection "lter and failure diagnosis based on the generalized Luenberger observer (GLO) are implemented. It is known that these types of observers use the output and the output derivatives of the observed system as its inputs. In some cases, the derivatives can cause false failure propagation, making diagnosis impossible. This study focuses on the GLO implementation using an industry example.

- by Rocco Tarantino Alvarado
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- Mechanical Engineering, Applied Mathematics, Fault Detection, Case Study

Screen adaptations of Agatha Christie's novel Murder in Orient Express-you observe and you are being observed Agatha Christie (1890-1976), less known as lady Mallowan, an outstanding author, mainly of detective novels, published Murder in Orient Express in 1933/34. From the very beginning, the book was considered a masterpiece of this genre. The reason for that is not only brilliantly constructed plot with astonishing culminating point, but also the fact that the author of the book referred to an authentic event which evoked great emotions. The event that inspired this novel was kidnapping and murder of the little son of a known and admired American pioneer of intercontinental flights, Charles August Lindbergh, that happened in 1932. The novel was translated into almost all languages. There were also numerous stage adaptations. At least four films were based on this novel which indicates the cultural significance of the work. The subject of the considerations in the present paper is an attempt to search for the answer about the role of the so-called observer in the process of reconstruction, retransmission and assimilation of thematic threads, which can become the reference point not only for the author of the literary work. They may become an element of collective memory and, in this way, the element of culture constituting narration. However, as an object of general knowledge, they are at the same time subjected to common interpretation. The Heisenberg's uncertainty principle, referred to in its basic range in quantum mechanics, indicates the significant role of the subject observing in this process. Heisenberg proved that the presence of an observer is not neutral from the point of view of the quality of the results. Referring to these considerations on the text as a cultural object, let us analyse the ways in which the theme was modified and the significance of these changes. We consider Agatha Christie's novel and especially its screen adaptations an interesting object of research. The observer, as it turns out, is beside the researcher also the author of the literary text, screenwriter, translator…

- by Iwona Bartoszewicz
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- Adaptation, Interpretation, Agatha Christie, Observer

Nonlinear observers for estimation of lateral and longitudinal velocity of automotive vehicles are proposed, based on acceleration and yaw rate measurements in addition to wheel speed and steering angle. The observer for lateral velocity uses a tyre-road friction model. Exponential stability of the observers are shown. A structural assumption on the friction model is discussed. The observer structure is validated using experimental data from cars.

- by Lars Imsland
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- Engineering, System Identification, Modeling, Vibration

A problem of rotor speed and position detection for sensorless PMSM drive was analysed in the paper. The concept based on detecting back EMF, induced in the stator windings, was developed and modified. A general structure of observer, with more complex function of corrector than traditional one was introduced. On the base of this concept the observer with proportional-integral and sliding mode correction was proposed. Simulation as well as experimental results showed good properties of proposed observer structure.

- by Konrad Urbanski
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- Permanent Magnet Synchronous Machines, Observer, Sensorless Control

Статья посвящена роли указания на наблюдателя и его значению для объяснения целого ряда языковых явлений. Выдвигается новая идея в изучении этой проблемы, связанной с масштабами явления указательности и его местом в языковой картине мира. Для решения этого вопроса предлагаются следующие теоретические позиции: наблюдатель и понятие "настоящее", наблюдатель и видовые противопоставления, наблюдатель и пассивная диатеза, человек и система пространственных отношений, предметная асимметрия и понятие нормы. Делаются выводы о том, каким образом познавательная деятельность человека, его чувственное восприятие находит свое проявление в языковой системе.

In this paper, tyres longitudinal forces, vehicle side slip angle and velocity are identified and estimated using sliding modes observers. Longitudinal forces are identified using higher order sliding mode observers. In the estimation of the vehicle side slip angle and vehicle velocity, an observer based on the broken super -twisting algorithm is proposed. Validations with the simulator VE-DYNA pointed out the good performance and the robustness of the proposed observers. After validating these observers, controller design for the braking is accomplished using a reduced state space model representing the movement of the vehicle centre of gravity in the (X, Y ) plane. Driver's reactions are taken into account. The performance of the closed loop system is carried out by means of simulation tests.

A new control structure is presented for use at the sensorless control of speed for low speed range. That method uses an observer for position estimation. Such structure does not require the calculation of the speed value from the estimated back EMF, thus such drive can work even in a case of non-sinusoidal shape of estimated back EMF. Such structure is especially recommended for speed in a range single revolutions per second (excluding standstill). Proposed structure is similar to the model following control, but the reference model is trying to track the motor operating point.

1. Das Problem 1 2. Die Schwierigkeit 1 3. Der Ausgangspunkt 2 4. Das Phänomen der Kognition 2 5. Grundbegriffe 2... more

1. Das Problem 1
2. Die Schwierigkeit 1
3. Der Ausgangspunkt 2
4. Das Phänomen der Kognition 2
5. Grundbegriffe 2
6. Das lebende System 3
7. Das Nervensystem 4
8. Das Nervensystem operiert als ein geschlossenes System 4
9. Das Medium 4
10. Kognition 4
11. Strukturelle Kopplung 5
12. Wahrnehmung 5
13. Wahrheit und Falschheit 5
14. Konsensuelle Bereiche 6
15. Der Beobachter 6
16. Kognitive Bereiche 7
17. Kreativität und Freiheit 7
18. Ethik und Liebe 8

The realization of maximum adhesive forces for a railway vehicle is a very difficult process, because it involves using tractive efforts and depends on friction characteristics in the contact zone between wheels and rails. Tractive efforts are realized by means of tractive torques of motors, and their maximum values can provide negative effects such as slip and skid. These situations usually happen when information about friction conditions is lacking. The negative processes have a major influence on wearing of contact bodies and tractive units. Therefore, many existing control systems for vehicles use an effect of a prediction of a friction coefficient between wheels and rails because measuring a friction coefficient at the moment of running vehicle movement is very difficult. One of the ways to solve this task is to use noise spectrum analysis for friction coefficient detection. This noise phenomenon has not been clearly studied and analyzed. In this paper, we propose an adhesion control system of railway vehicles based on an observer, which allows one to determine the maximum tractive torque based on the optimal adhesive force between the wheels (wheel pair) of a railway vehicle and rails (rail track) depending on weight load from a wheel to a rail, friction conditions in the contact zone, a lateral displacement of wheel set and wheel sleep. As a result, it allows a railway vehicle to be driven in a tractive mode by the maximum adhesion force for real friction conditions.

- by Maksym Spiryagin
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- Mechanical Engineering, Civil Engineering, Signal Processing, Adhesion

This paper proposes a new controller for an underactuated quad-rotor family of small-scale unmanned aerial vehicles (UAVs) using output feedback (OFB). Specifically, an observer is designed to estimate the velocities and an output feedback controller is designed for a nonlinear UAV system in which only position and angles are measurable. The design is performed via a Lyapunov type analysis. A semi-global uniformly ultimate bounded (SGUUB) tracking result is achieved. Simulation results are shown to demonstrate the proposed approach.

- by DongBin Lee
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- Control, Vehicle Dynamics, Aerodynamics, Control Systems

The paper recalls some sceptical comments Norbert Wiener made regarding the potential use of cybernetics in social sciences. A few social scientists were seduced by cybernetics from the beginning, but cybernetics never really caught on in sociology. The paper argues that one reason for this may lie in the mathematical theory of communication entertained by early cybernetics. This theory which maintaines that there are probability distributions of possible communication is at odds with the sociological theory's idea of a communication driven by improbable understanding. Yet the move from first-order cybernetics to second-order cybernetics, by re-entering the observer into the very systems she observes, provides for a bridge between cybernetics and sociology.

- by Dirk Baecker
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- Sociology, Communication, Technology, Cybernetics

The stabilization with time delay in observation or control represents difficult mathematical challenges in the control of distributed parameter systems. It is well-known that the stability of closed-loop system achieved by some stabilizing output feedback laws may be destroyed by whatever small time delay there exists in observation. In this paper, we are concerned with a particularly interesting case: Boundary output feedback stabilization of a one-dimensional wave equation system for which the boundary observation suffers from an arbitrary long time delay. We use the observer and predictor to solve the problem: The state is estimated in the time span where the observation is available; and the state is predicted in the time interval where the observation is not available. It is shown that the estimator/predictor based state feedback law stabilizes the delay system asymptotically or exponentially, respectively, relying on the initial data being non-smooth or smooth. Numerical simulations are presented to illustrate the effect of the stabilizing controller.

- by Bao-zhu Guo
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- Applied Mathematics, Stability, Feedback Control, Wave Equation

This note is devoted to stabilizing a coupled PDE-ODE system with interaction at the interface. First, a state feedback boundary controller is designed, and the system is transformed into an exponentially stable PDE-ODE cascade with an invertible integral transformation, where PDE backstepping is employed. Moreover, the solution to the resulting closed-loop system is derived explicitly. Second, an observer is proposed, which is proved to exhibit good performance in estimating the original coupled system, and then an output feedback boundary controller is obtained. For both the state and output feedback boundary controllers, exponential stability analyses in the sense of the corresponding norms for the resulting closed-loop systems are provided. The boundary controller and observer for a scalar coupled PDE-ODE system as well as the solutions to the closed-loop systems are given explicitly.

- by Shu-Xia Tang and +1
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- Mechanical Engineering, Applied Mathematics, System Identification, PARTIAL DIFFERENTIAL EQUATION

The Foreword locates the collection of proposals for creative research in the context of the international debates about the philosophy and methodology of the social sciences and humanities which touch on such matters as interpretation, cognition, reflexivity, social construction, reconstruction, pragmatic sociology, disclosure, social criticism, critique and so forth. The piece opens with an extrapolation of the main emphases of the three parts of the collection are: Part One – taking seriously ordinary everyday people; Part Two – establishing a link between theory and practice; and Part Three – values and aesthetics playing a vital role in transformative learning. These themes are then aligned with the major dimensions of the international debates which are stylised as having passed through three phases: first, in the late 1980s and early 1990s, the ‘interpretative turn’ drastically shifted the attention to social life and practices internally or immanently; secondly, it was followed in the early 1990s by a critical analysis of the limits of this focus which was demonstrated to require the reincorporation of the excluded external perspective; since the 1990s, thirdly, awareness of the importance of the guiding ideas, images and emotions operating in social practices has begun to mature. This framework is finally employed to offer an analytical and critical contextualisation of each of the three parts of the book.

- by Piet Strydom
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- Aesthetics, Research Methodology, Learning and Teaching, Transformation

In this article, an approach for tracking control of robot manipulators is presented. The proposed controller incorporates the approximately known inverse dynamic model output as a model-base portion of the controller; an estimated uncertainty term to compensate for the un-modeled dynamics, external disturbances, and time-varying parameters; and a decentralized PID controller as a feedback portion to enhance closed-loop stability and account for the estimation error of uncertainties. The robustness and capabilities of the proposed approach are investigated in simulation for an example robot.

- by Meysar Zeinali
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- Mechanical Engineering, Robotics, Modeling, Adaptive Control

This paper introduces an observer-based adaptive optimal control method for unknown singularly perturbed nonlinear systems with input constraints. First, a multi-time scales dynamic neural network (MTSDNN) observer with a novel updating law derived from a properly designed Lyapunov function is proposed to estimate the system states. Then, an adaptive learning rule driven by the critic NN weight error is presented for the critic NN, which is used to approximate the optimal cost function. Finally, the optimal control action is calculated by online solving the Hamilton-Jacobi-Bellman (HJB) equation associated with the MTSDNN observer and critic NN. The stability of the overall closed-loop system consisting of the MTSDNN observer, the critic NN and the optimal control action is proved. The proposed observer-based optimal control approach has an essential advantage that the system dynamics are not needed for implementation, and only the measured input/output data is needed. Moreover, the proposed optimal control design takes the input constraints into consideration and thus can overcome the restriction of actuator saturation. Simulation results are presented to confirm the validity of the investigated approach.

- by IEEE/CAA J. Autom. Sinica
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- Nonlinear Observer, Nonlinear hybrid system, Observer, Nonlinear system

This work approaches, through an image studies perspective, the technological domain of Computer Vision, typically understood by the broad spectrum of algorithmic operations by which a machine is programmed for the automatic interpretation of visual information. It aims at describing the phenomenon of emergence and dissemination of its derived machines, but not from a purely technical point of view, paying particular attention to the modes by which they agency, through their operation, the image and the observer. Supported by the theoretic framework surrounding foucaultian concept of the dispositif, the research understands the studied domain by its concrete instantiations, in forms of regulation and government of the act of seeing and of the visible, therefore deeply traversed by formations of knowledge, institutional demands, observational practices and technical, esthetical and scientific discourses – among other elements. In order to make such articulations visible, going from a technical constitution to esthetic, social and political agencies, this work’s theoretic-analytical course is elaborated through the reunion of multiple objects, selected from technical, scientific and artistic domains, according to their potential for problematizing aspects of this dispositif’s agencement. This effort is animated by the methodological gesture of the composition, proposed by Bruno Latour, by which it is sought to build, through connections and approximations, the common ground of the approached phenomenon from the multiplicity of its heterogeneous manifestations. Concerning the modes of agencement of the image and the visible, an alternating movement is described between operations of singling, locating and identifying, in one hand; and generalizing, categorizing and idealizing, on the other. Concerning the agencement of the observer – notion taken from Jonathan Crary – it is suggested that the visualities of the human and of the machine are mutually constituted through its operation, including processes of taking back to the contemporary modes of seeing the codification of the visible developed within Computer Vision. Through this course it is suggested the paradigmatic value of this dispositif for the comprehension of contemporary dynamics of the production and circulation of the visible, as well as the constitution of new conceptions and practices of observation, even those only indirectly related to its functioning.

- by Andre Mintz
- •
- Computer Vision, Media Art, Image theory, Dispositif (Apparatus-Theory)

The observer in physics makes observations and transforms them into fact and physical laws. Observations are based on perceptions and their transformations, which are influenced by biological and psychological functions. As argued by the
philosopher Peirce, one might distinguish between extra-mental reality and its mental representation. An observer creates with his mental functions a mental representation of extra-mental reality due to perception based on specific sense organs. Extra-mental reality and its mental representation exist simultaneously, but are not always in direct contact with each other and can therefore diverge. Only during the NOW, the observer is through his sense organs in direct physico-neural contact with extra-mental reality. After interruption of this contact, observations belong to the past and the observer transforms with mental functions regularities of past observations into physical laws, which can be extrapolated into the far past and future. During the NOW, observations have precise time coordinates, but after interruption of the direct contact, memorized observations undergo transformations into abstract and often timeless concepts in classical and in quantum physics. In normal life, time is the perception of duration and its boundaries. In physics, time is reduced to the relation of its boundaries between different systems or can be completely discarded in timelessness. Whereas the NOW is a direct connection between extra-mental reality and its mental representation, past and future represent pure mental representations based on memorized NOWs. After their transformation, mental representation can predict future potentiality, which does not always correspond to extra-mental reality. Due to this reality-potentiality gap, physical laws created in mental representation need verification in a new experimental NOW, which alone assures direct contact to reality.

The generally accepted explanation of the Doppler effect is that in the case, when the source of waves is moving towards the observer, each successive wave crest is emitted from a position closer to the observer than the crest of the previous wave causing an increase in the frequency and, vice versa, when the source of waves is moving away from the observer, the arrival time between successive waves is increased reducing the frequency. This statement is incomplete. It cannot explain the fact of Doppler shift conservation in photons when stars having emitted them do not exist any more. The article shows the actual reason of the Doppler effect, i.e., the independency of emitted waves from their source and Energy conservation law.

- by Ilgaitis Prusis
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- Physics, Space Sciences, Cosmology (Physics), Sound

The city of Beirut has been heavily destroyed during and after the civil war. A private company, Solidere s.a.l., attempts to rebuild the City Center in a way heavily contested by observers who fear the loss of the city's memory because of Solidere's focus on luxury offices, shops, and apartments. This paper reviews some aspects of the project in the light of its attempt to both surpass the sectarian lines dividing Beirut and to reorient the City Center and the town with it towards international networks within the Arab world and the Lebanese diaspora. Using a George Spencer-Brown modeling of Solidere to reconstruct the project with respect to second-order observers getting caught up within their mutual orientation towards each other the paper asks whether there is a chance to replace the city's altogether too narrow if understandable focus on the region's conflicts, big investors' money, and a street wary of one-sided advantages with an acknowledgement of Beirut's uncertain future. Such an acknowledgement, or so it seems, would have a rather more civilizing impact on the city than its current focus on the history of Beirut and its divergent memories.

- by Dirk Baecker
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- City, Form, Observer

i n this paper, a novel discrete position estimation scheme for sensorless operation of Switched Reluctance (SRI Motor drive is proposed. The classical flux-current approach is adopted for estimating the position. In the proposed method, the required flux-linkage characteristics measurement is automated and integrated as a part of the sensorless controller. The algorithm is tested on a real motor and the relevant test results are presented. The method is suitable for low-cost mass-produced applications.

- by Ali Keyhani
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- Optimal Control, Embedded Systems, Advanced Materials, Control Systems

This paper concerns the design of a new active fault tolerant control framework for a class of switched linear systems subject to sensor faults and unknown bounded disturbances. The framework herein proposed ensures the fault tolerance capabilities by means of the interaction between three main blocks called generalized switched observer scheme, pre-designed multiple controllers and reconfiguration block. The fault detection and isolation problem has been solved by minimization of the H_inf-norm and maximization of the H_ index. Then, a suitable trade-off between the robustness to disturbances and the sensitivity to sensor faults has been obtained. The main results are reformulated by using linear matrix inequality formulation. An example is included to illustrate the design procedure.

- by D. E. C BELKHIAT
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- Hybrid Systems, Fault Tolerant Control, Switched Systems, Fault diagnosis

Piezo-actuated stages are composed of a piezoelectric actuator (PEA) and a positioning mechanism. Hysteresis behavior of PEAs limits the position accuracy of the piezo-actuated stages. This paper presents a hybrid control approach for precise positioning of a piezo-actuated stage, where Bouc-Wen hysteresis model is used to represent the hysteresis behavior of the PEA. A Luenberger observer-based feedforward controller is designed, and then integrated with a Particle Swarm Optimization (PSO)-based Proportional-Integral-Derivative (PID) controller to form a hybrid controller. Optimal PID gains are obtained based on a fitness function proposed to reduce the displacement error and achieve fast response time. The results show that using the proposed hybrid controller reduces the hysteresis effect significantly, and thus the maximum error is minimized to 0.127 11m, which is 0.17 % of the maximum displacement of 72.1 μm.

- by Marwan Nafea
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- Hysteresis, Piezoelectric ceramics, PID controller design, Feedback Control