bluuebunny/crossref_metadata_2025 huggingface dataset:
FUZZY SLIDING MODE CONTROL WITH PIECEWISE LINEAR SWITCHING MANIFOLD
Authors: Dotoli Mariagrazia
Published: September 2010

Variable Structure Control (VSC) has been successfully established in control systems engineering in the past two decades. Recently, Fuzzy Sliding Mode Control (FSMC) techniques have drawn the attention of the scientific community, due to their effectiveness in reducing the typical chattering phenomenon arising in VSC. In this paper we present a novel FSMC technique for a class of second order dynamical systems based on a piecewise linear sliding manifold. The proposed approach enhances the effectiveness of VSC in the presence of a saturated control input. In addition, employing the proposed VSC with fuzzy rule based algorithms results in smooth dynamics when the trajectory is in the vicinity of the switching manifold, as opposed to the typical chattering arising under classical VSC. After illustrating the proposed strategy on a simple design example, the approach is applied to an inverted pendulum, a well‐known benchmark for automatic control techniques. The effectiveness of the technique is shown both by means of simulation tests and experiments on a lab equipment. Future research directions include the extension of the technique in the presence of uncertainties in the plant model.
MODEL‐REFERENCE OUTPUT‐FEEDBACK SLIDING MODE CONTROLLER FOR A CLASS OF MULTIVARIABLE NONLINEAR SYSTEMS
Authors: Hsu Liu , Costa Ramon R. , da Cunha José Paulo Vilela Soares
Published: September 2010

This paper proposes an output‐feedback sliding mode control design for a class of uncertain multivariable plants with nonlinear disturbances. The approach used here is based on the control parameterization employed in model‐reference adaptive control. The disturbances are allowed to be unmatched and to depend not only on the plant output but also on its unmeas‐urable state. A less restrictive condition on the uncertainty of the high frequency gain matrix is also obtained.
SLIDING MODE CONTROL SYNTHESIS OF UNCERTAIN TIME‐DELAY SYSTEMS
Authors: Orlov Y. , Perruquetti W. , Richard J.P.
Published: September 2010

Sliding mode control synthesis is developed for a class of uncertain time‐delay systems with nonlinear disturbances and unknown delay values whose unperturbed dynamics is linear. The synthesis is based on a new delay‐dependent stability criterion. The controller constructed proves to be robust against sufficiently small delay variations and external disturbances. An admissible upperbound such that the corresponding closedloop system remains globally asymptotically stable for each delay value less than this up‐perbound is derived. Performance issues of the controller are illustrated in a simulation study.
ROBUSTNESS ANALYSIS ON SLIDING MODE CONTROL OF INDUCTION MOTOR
Authors: Chekireb H. , Tadjine M. , Djemaï M.
Published: September 2010

The aim of this paper is to establish that flux‐speed sliding mode control of induction machine is robust in the presence of saturation of magnetic core and rising resistance effects. Further, we show how to select the free control design parameters in order to maintain sliding mode regime. Simulation results are given to point out the good performances and the robustness of the studied control system. These simulations results are performed in the presence of hard disturbances represented by increasing of rotor resistances (by an amount 100%), and by decreasing stator and rotor inductance (respectively by an amount 25% and 50%)
SECOND ORDER SLIDING MODE CONTROL OF A DIESEL ENGINE
Authors: Khan M. Khalid , Goh Keng Boon , Spurgeon Sarah K.
Published: September 2010

A 2nd order sliding mode algorithm is applied to control the speed of a diesel power generator set. Tuning guidelines are given. The robustness of the controller is investigated and the performance of the 2nd order sliding mode controller is compared with that obtained by a commercial diesel engine controller and a classical proportional‐integral (PI) controller. Robustness to unmodelled dynamics is discussed and implementation results presented.
A COMBINED SLIDING MODE‐GENERALIZED PI CONTROL SCHEME FOR SWINGING UP AND BALANCING THE INERTIA WHEEL PENDULUM
Authors: Hernández Victor M.
Published: September 2010

In this note we propose a control strategy which combines sliding modes and generalized PI (GPI) control for the swinging up, and stabilization around its unstable vertical position of the inertia wheel pendulum. Both tasks are achieved using a single controller. The pendulum angular position is assumed to be the only measured output variable. We show that this control scheme is robust with respect to constant torque disturbances. The proposed controller is used in an actual experimental setup.
TRADE‐OFF BETWEEN APPROXIMATION ACCURACY AND COMPLEXITY FOR TS FUZZY MODELS
Authors: Baranyi Péter , Korondi Péter , Patton Ron J. , Hashimoto Hideki
Published: September 2010

This paper proposes a transformation method that serves the trade‐off between the modelling complexity and accuracy of multi‐variable Takagi‐Sugeno fuzzy inference operator‐based modelling (TS fuzzy modelling). The relation between the number of fuzzy rules and the modelling accuracy is defined in the paper. The proposed transformation method is capable of finding the minimal number of fuzzy rules for a given accuracy of a given TS fuzzy model. A case study, focusing on a benchmark problem of fault diagnosis, developed in the framework of EC‐founded Research Training Network DAMADICS, of an actuator in a sugar factory, is presented to provide feasibility of the proposed method.
ROBUST ADAPTIVE CONTROL WITH MULTIPLE ESTIMATION MODELS FOR STABILIZATION OF A CLASS OF NON‐INVERSELY STABLE TIME‐VARYING PLANTS
Authors: Alonso‐Quesada S. , de la Sen M.
Published: September 2010

This paper presents an indirect adaptive control scheme for nominally stabilizable non‐necessarily inversely stable continuous‐time systems with unmodelled dynamics. The control objective is the adaptive stabilization of the closed‐loop system with the achievement of a bounded tracking‐error between the system output and a reference signal given by a stable filter. The adaptive control scheme includes several estimation algorithms and a supervisor which selects the appropriate estimator at every certain time and keeping it operating for at least a minimum period of residence time. This selection is based on a performance criterion related to a measure of the estimation errors obtained with each estimator. In this way, the performance of the output signal is improved with regard to the performance achieved with a unique estimation algorithm. All the estimators are either of the least‐squares type or gradient type. However, any well‐posed estimation algorithm is potentially valid for application. These estimators include relative dead‐zones for robustness purposes and parameter ‘a posteriori’ modifications to ensure the controllability of the estimated models of the plant, which is crucial for proving the stabilizability of the plant via adaptive pole‐placement designs.
ROBUST EIGENVALUE ASSIGNMENT IN DESCRIPTOR SYSTEMS VIA OUTPUT FEEDBACK
Authors: Duan Guang‐Ren , Lamy James , Liu Guo‐Ping
Published: September 2010

Based on a recently proposed parametric approach for eigenstructure assignment in descriptor linear systems via output feedback, the robust eigenvalue assignment problem in descriptor linear systems via output feedback is solved. The problem aims to assign a set of finite closed‐loop eigenvalues which have minimum sensitivities with respect to perturbations in the closed‐loop coefficient matrices, while at the same time, guarantee the closed‐loop regularity. The approach optimizes the design parameters existing in the closed‐loop eigenvectors to achieve the minimum eigenvalue sensitivities, and use the extra degree of freedom existing in the solution of the gain matrix to further minimize the magnitude of the gain matrix and enhance the robustness of the closed‐loop regularity. The approach allows the finite closed‐loop eigenvalues to be optimized within desired regions, and is demonstrated to be simple and effective.
ACTIVE VIBRATION ISOLATION FOR A LONG RANGE SCANNING TUNNELING MICROSCOPE
Authors: Lan Kuo‐Jung , Yen Jia‐Yush , Kramar John A.
Published: September 2010

Vibration isolation or control is critical for the optimum operation of the Molecular Measuring Machine (M3), a high‐resolution, length‐metrology instrument at the National Institute of Standards and Technology. This paper describes the extension of the M3 Mallock isolation suspension from passive to six degrees‐of‐freedom (DOF) active vibration isolation. System modeling is presented, and experimental system identification is carried out for the purpose of model verification. The paper then compares the vibration isolation performance achieved using a classical proportional‐integral‐derivative (PID) controller versus that achieved using a modified, model‐based, Linear‐Quadratic‐Gaussian (LQG) controller. Attenuation of 3 dB to 15 dB is achieved within the active vibration isolation control bandwidth, and images taken with the M3 scanning tunneling microscope (STM) probe show improved performance.
A PNEUMATIC POSITIONING DEVICE COUPLED WITH PIEZOELECTRIC SELF‐MOVING MECHANISM
Authors: Liu Yung‐Tien , Lee Chen‐Hao , Fung Rong‐Fong
Published: September 2010

This paper reports a new pneumatic positioning device coupled with a piezoelectric self‐moving mechanism to overcome the main disadvantages of the inherent poor positioning accuracy obtained by traditional pneumatic cylinder. The new driving mechanism is to mount a piezoelectric Impact Drive Mechanism (IDM) to the controlled sliding table driven by the pneumatic cylinder. Based on the configuration, the first step of positioning process is to actuate the sliding table with rough position accuracy but with the benefits of high‐speed and large‐range due to the pneumatic cylinder. The second step is to drive the sliding table with high position accuracy by utilizing the impact force of IDM. The experimental results show that the controlled sliding table is successfully positioned in 0.236 s with rough accuracy of 10 μm and with the stroke of 100 mm by utilizing the pneumatic cylinder, and the final positioning accuracy of 10 nm with respect to the terminated position of the first‐stage control is obtained in 1.479 s due to the actuations of IDM. It is shown that the pneumatic positioning device coupled with IDM has attractive practical applications in the field of precision industry.
ULTRA‐FINE TRACKING CONTROL ON PIEZOELECTRIC ACTUATED MOTION STAGE USING PIEZOELECTRIC HYSTERETIC MODEL
Authors: Huang Yi‐Cheng , Lin De‐Yao
Published: September 2010

The tracking control accuracy of the piezoelectric actuator (PEA) is limited due to its inherent hysteresis nonlinearity. A new piezoelectric‐actuator model is synthesized based on two first‐order transfer systems in parallel with two tuned parameters determined from one experiment. Two open‐loop tracking controllers are implemented with the proposed model to compensate the hysteresis of linear positioning. Numerical simulations and experimental tests on the tracking of sinusoidal and triangular waveforms with signal frequencies ranging from 1Hz to 30 Hz are revisited and compared with the conventional Bouc‐Wen and Duhem models. Experimental results reveal that the RMS tracking error can be reduced to less than 2% of the maximum traveling distance without any feedback sensor. When a piezoelectric actuated on a two Degree‐Of‐Freedom (DOF) monolithic motion stage was employed, the RMS tracking error was 50 nm within the measured sensor accuracy.
NECESSARY AND SUFFICIENT CONDITIONS FOR DEADLOCKS IN FLEXIBLE MANUFACTURING SYSTEMS BASED ON A DIGRAPH MODEL
Authors: Zhang Wenle , Judd Robert P. , Deering Paul
Published: September 2010

As typical discrete event systems, flexible manufacturing systems have been extensively studied in such aspects as modeling, control and performance analysis. One important topic in the study of such systems is the deadlock detection, prevention and avoidance. In the past decade, two major modeling formalisms, i.e., Petri nets and digraphs, have been adopted for developing deadlock control policies for flexible manufacturing systems. In this paper, the concepts of slack, knot, order and effective free space of circuits in the digraph are established and used to concisely and precisely quantify the sufficient conditions for a system state to be live. Necessary conditions for this liveness is quantified for a special class of system states ‐ called evaluation states. The significance of the result is that the conditions are true for avoiding both primary deadlocks and impending deadlocks that are arbitrary steps away from a primary one, whereas only second level deadlocks have been studied in the literature. Examples are provided to illustrate the method.
DYNAMIC SCHEDULING FOR A SINGLE MACHINE SYSTEM UNDER DIFFERENT SETUP AND BUFFER CAPACITY SCENARIOS
Authors: Martinelli Francesco , Valigi Paolo
Published: September 2010

The problem of dynamic scheduling for single machine manufacturing systems has been extensively studied in the past under different setup scenarios, mainly for systems with infinite buffer capacity. This paper addresses a general framework and investigates similarities and differences between policies optimal if setup times and costs are or are not negligible, if buffers have a finite or an infinite capacity. The cost function takes into account of backlog and surplus, but also includes a demand loss component if buffers have a finite capacity and a setup cost if not negligible. Both a steady state and a transient optimization problem are considered and already known results are compared and extended to complete the analysis.
MINIMAL VALID AUTOMATA OF SAMPLE SEQUENCES FOR DISCRETE EVENT SYSTEMS
Authors: Chung Sheng‐Luen , Li Chung‐Lun
Published: September 2010

Minimal valid automata (MVA) refer to valid automata models that fit a given input‐output sequence sample from a Mealy machine model. They are minimal in the sense that the number of states in these automata is minimal. Critical to system identification problems of discrete event systems, MVA can be considered as a special case of the minimization problem for incompletely specified sequential machine (ISSM). While the minimization of ISSM in general is an NP‐complete problem, various approaches have been proposed to alleviate computational requirement by taking special structural properties of the ISSM at hand. In essence, MVA is to find the minimal realization of an ISSM where each state only has one subsequent state transition defined. This paper presents an algorithm that divides the minimization process into two phases: first to give a reduced machine for the equivalent sequential machine, and then to minimize the reduced machine into minimal realization solutions. An example with comprehensive coverage on how the associated minimal valid automata are derived is also included.
OPTIMAL SWITCHING CONTROL VIA DIRECT SEARCH OPTIMIZATION
Authors: Luus Rein , Chen Yang Quan
Published: September 2010

We demonstrate in this paper that for switched systems the optimal switching time instants and the optimal control policy can be solved readily by direct search optimization. General problem formulation and numerical procedures are presented together with two demonstrative examples previously considered in the literature using other numerical solution methods.
A CLOSED‐LOOP SUBSPACE IDENTIFICATION METHOD FOR CONTINUOUS‐TIME SYSTEMS BASED ON δ‐OPERATOR MODEL
Authors: Huang Dongliang , Katayama Tohru
Published: September 2010

This paper is concerned with a subspace identification of a continuous‐time plant operating in closed‐loop in the framework of the joint input‐output approach. The main procedure consists of two steps. Firstly, the dual‐Youla parametrization of the plant is used for obtaining an equivalent open‐loop problem to the original closed‐loop identification problem. Then, a δ‐operator based IV‐MOESP type subspace identification algorithm is developed to estimate the state space model for the joint input‐output process, whereby a higher‐order state space model of the plant is obtained by an algebraic operation. Subsequently, a model reduction procedure is employed to derive a lower‐order plant model removing irrelevant modes from the higher order model. Simulation results by using numerical and chemical plant models demonstrate the feasibility of the proposed method.
DYNAMIC POSITIONING CONTROL OF SHIPS VIA RELAY OBSERVER DESIGN
Authors: Moreno‐Valenzuela Javier , Acho‐Zuppa Leonardo
Published: September 2010

A dynamically positioned ship maintains its position (fixed location or predetermined track) exclusively by means of active thrusters. In this paper, a control scheme for dynamic positioning control of ships using a relay observer design is presented. Our analysis relies on nonsmooth strict Lyapunov functions to demonstrate global asymptotic stability of the closed‐loop system equilibrium. Using simulation results we illustrate the good performance of the proposed scheme under noisy ship position measurements.
NETWORK‐INDUCED DELAY‐DEPENDENT H∞ CONTROLLER DESIGN FOR A CLASS OF NETWORKED CONTROL SYSTEMS
Authors: Jiang Xiefu , Han Qing‐Long
Published: September 2010

This paper is concerned with the problem of robust H∞ controller design for a class of uncertain networked control systems (NCSs). The network‐induced delay is of an interval‐like time‐varying type integer, which means that both lower and upper bounds for such a kind of delay are available. The parameter uncertainties are assumed to be normbounded and possibly time‐varying. Based on Lyapunov‐Krasovskii functional approach, a robust H∞ controller for uncertain NCSs is designed by using a sum inequality which is first introduced and plays an important role in deriving the controller. A delay‐dependent condition for the existence of a state feedback controller, which ensures internal asymptotic stability and a prescribed H∞ performance level of the closed‐loop system for all admissible uncertainties, is proposed in terms of a nonlinear matrix inequality which can be solved by a linearization algorithm, and no parameters need to be adjusted. A numerical example about a balancing problem of an inverted pendulum on a cart is given to show the effectiveness of the proposed design method.
H2‐OPTIMAL SAMPLED‐DATA CONTROL FOR PLANTS WITH MULTIPLE INPUT AND OUTPUT DELAYS
Authors: Polyakov Konstantin Yu.
Published: September 2010

The sampled‐data H2‐optimization problem for plants with multiple input and output delays is considered. An equivalent discrete‐time system is constructed and numerical algorithm for computing matrices of its state‐space realization is presented. It is proved that stability of this system is equivalent to stability of original sampled‐data system. The proposed method can be applied to a wide class of digital control problems for continuous‐time plants with multiple input and output delays.
SCHEDULING AND CONTROL CO‐DESIGN FOR DELAY COMPENSATION IN THE NETWORKED CONTROL SYSTEM
Authors: Chen Liang , Zhang Jianming , Wang Shuqing
Published: September 2010

The networked control system (NCS) is currently receiving increasing attention from researchers. Researches on this subject, however, have not considered the co‐design of network quality of service (QoS) and control quality of performance (QoP). This paper proposes a novel NCS design framework based on scheduling and control co‐design to compensate for random network‐induced delays. In the framework, a scheduling algorithm used to find the optimal sampling regions of control loops performs rough adjustment and guarantees the network QoS, while a novel adaptive fuzzy PID controller is designed to perform accurate adjustment to guarantee the control QoP. Practical application results obtained with a multi‐loop NCS show that the framework can ensure satisfactory performance due to its robustness against network uncertainty.
STATE‐SPACE DIGITAL PID CONTROLLER DESIGN FOR MULTIVARIABLE ANALOG SYSTEMS WITH MULTIPLE TIME DELAYS
Authors: Madsen Jennifer M. , Shieh Leang‐San , Guo Shu‐Mei
Published: September 2010

This paper presents a discrete‐time state‐space methodology for optimal design of digital PID controllers for multivariable analog systems with multiple time delays. The multiple time‐delayed multivariable analog systems are formulated in a state‐space generic form so that the exact discrete‐time state‐space model can be constructed. Then, the optimal digital PID controller is designed via a state‐feedback and state‐feedforward LQR approach. The developed PID controller can be applied to a general time‐delayed multivariable analog system represented by a semi‐proper or strictly proper transfer function matrix. Illustrative examples are given to compare the performance of the proposed approach with alternative techniques.
DELAY‐DEPENDENT ROBUST CONTROL FOR UNCERTAIN SINGULAR TIME‐DELAY SYSTEMS
Authors: Su Hongye , Ji Xiaofu , Chu Jian
Published: September 2010

The problem of delay‐dependent robust stabilization for uncertain singular time‐delay systems is investigated in this paper. The parameter uncertainty is assumed to be norm‐bounded and possibly time‐varying, while the time delay considered here is assumed to be constant but unknown. A delay‐dependent condition is presented for a singular time‐delay system to be regular, impulse free, and stable, based on which robust stability analysis and the robust stabilization problem are studied. An explicit expression for the desired state‐feedback control law is also given. The obtained results are formulated in terms of linear matrix inequalities (LMIs), which involve no decomposition of the system matrices. Some numerical examples are given to show the efficiency of the theoretical conditions.
LMI OPTIMIZATION APPROACH FOR DELAY‐DEPENDENT H∞ CONTROL OF TIME‐VARYING DELAY SYSTEMS
Authors: Lien Chang‐Hua , Yu Ker‐Wei
Published: September 2010

In this paper, the robust delay‐dependent H∞ control for a class of uncertain systems with time‐varying delay is considered. An improved state feedback H∞ control is proposed to minimize the H∞‐norm bound via the LMI optimization approach. Based on the proposed result, delay‐dependent criteria are obtained without using the model transformation technique or bounded inequalities on cross product terms. The linear matrix inequality (LMI) optimization approach is used to design the robust H∞ state feedback control. Some numerical examples are given to illustrate the effectiveness of the approach.
A SURVEY ON THE CONTROL OF FLEXIBLE JOINT ROBOTS
Authors: Ozgoli S. , Taghirad H. D.
Published: September 2010

The robotics literature of the last two decades contains many important advances in the control of flexible joint robots. This is a survey of these advances and an assessment for future developments, concentrated mostly on the control issues of flexible joint robots.
ADAPTIVE COORDINATED DECENTRALIZED CONTROL OF STATE DELAYED SYSTEMS WITH ACTUATOR FAILURES
Authors: Mirkin Boris M. , Gutman Per‐Olof
Published: September 2010

This paper develops an adaptive state feedback coordinated decentralized control scheme for a class of dynamic systems with state delay in subsystems and in the interconnections and in the presence of unknown actuator failures in each subsystem. The main contributions of this paper are the development of a new controller parametrization which attempt to anticipate the future states and failures, the introduction of an appropriate Lyapunov‐Krasovskii type functional to design the adaptation algorithms, and a stability proof.
FLEXIBLE SPACECRAFT VIBRATION SUPPRESSION USING PWPF MODULATED INPUT COMPONENT COMMAND AND SLIDING MODE CONTROL
Authors: Hu Qing‐lei , Ma Guang‐fu
Published: September 2010

This paper presents a dual‐stage control system design method for the rotational maneuver and vibration stabilization of a spacecraft with flexible appendages. In this design approach, attitude control system and vibration suppression were designed separately using lower order model. The design of attitude controller was based on sliding mode control (SMC) theory leading to a discontinuous control law. This controller accomplishes asymptotic attitude maneuvering in the closed‐loop system and is insensitive to the interaction of elastic modes and uncertainty in the system. The shaped command input controller based on component synthesis vibration suppression (CSVS) method is designed for reduction of flexible mode vibration, which only requires information about natural frequency and damping of the closed system. Additionally, to extend the CSVS method to the system with on‐off actuators, pulse‐width pulse‐frequency (PWPF) modulation is employed to control the thruster firing and integrated with the CSVS method. Simulation results have been proven the potential of this technique to control flexible spacecraft.
INTERNET‐BASED REAL‐TIME CONTROL ARCHITECTURES WITH TIME‐DELAY/PACKET‐LOSS COMPENSATION
Authors: Ji Kun , Kim Won‐jong , Srivastava Abhinav
Published: September 2010

The main objective of this paper is to demonstrate the feasibility of Internet‐based real‐time control. A novel client/server‐based architecture for Internet‐based supervisory control with a Common Gateway Interface/Hyper Text Markup Language (CGI/HTML) interface is presented. A real‐time operating environment was established for closed‐loop control over Ethernet. We conceived of an autoregressive (AR) prediction scheme and a novel compensation algorithm to compensate for network‐induced time delays and data‐packet losses simultaneously. We constructed an open‐loop unstable ball magnetic‐levitation (maglev) setup as a test bed to validate the two proposed control architectures. Experimental results proved the feasibility of Internet‐based real‐time control and verified the effectiveness of the proposed time‐delay/packet‐loss compensation algorithm in networked feedback control systems.
ROBUST FAULT‐TOLERANT CONTROL FOR A CLASS OF SWITCHED NONLINEAR SYSTEMS IN LOWER TRIANGULAR FORM
Authors: Wang Rui , Jin Gang , Zhao Jun
Published: September 2010

This paper investigates the problem of robust fault‐tolerant control for a class of uncertain switched nonlinear systems in lower triangular form. A system of this class involves parameter uncertainties and unknown nonlinear disturbances. A sufficient condition for the problem to be solvable under arbitrary switching is given in terms of linear matrix inequalities (LMIs). State feedback controllers of subsystems are designed by using the solutions to the matrix inequalities to guarantee global asymptotic stability of the closed‐loop systems in presence of actuator failures and under arbitrary switching. A practical system of hybrid haptic display is analyzed to demonstrate the proposed design method.
Robust Tracking Control For A Wheeled Mobile Manipulator With Dual Arms Using Hybrid Sliding‐Mode Neural Network
Authors: Tsai Ching‐Chih , Cheng Meng‐Bi , Lin Shui‐Chun
Published: September 2010

In this paper, a robust tracking controller is proposed for the trajectory tracking problem of a dual‐arm wheeled mobile manipulator subject to some modeling uncertainties and external disturbances. Based on backstepping techniques, the design procedure is divided into two levels. In the kinematic level, the auxiliary velocity commands for each subsystem are first presented. A sliding‐mode equivalent controller, composed of neural network control, robust scheme and proportional control, is constructed in the dynamic level to deal with the dynamic effect. To deal with inadequate modeling and parameter uncertainties, the neural network controller is used to mimic the sliding‐mode equivalent control law; the robust controller is designed to compensate for the approximation error and to incorporate the system dynamics into the sliding manifold. The proportional controller is added to improve the system's transient performance, which may be degraded by the neural network's random initialization. All the parameter adjustment rules for the proposed controller are derived from the Lyapunov stability theory and e‐modification such that uniform ultimate boundedness (UUB) can be assured. A comparative simulation study with different controllers is included to illustrate the effectiveness of the proposed method.
ON QUALITATIVE BEHAVIOR OF A CLOSED‐LOOP QUANTIZED SYSTEM
Authors: Askari J. , Lunze J. , Jabedar‐Maralani P.
Published: September 2010

This paper concerns the characterization of qualitative behavior of a closed‐loop quantized system. A quantized system is a dynamical system, which instead of knowing its state x(t) and its input u(t) precisely, their qualitative values [x(t)] and [u(t)] at a discrete time set T = {t0, t1, …, tk, …} are known. The qualitative state [x(t)] and the qualitative input [u(t)] are qualitative assessments of their precise values x(t) and u(t) respectively, and they can be related to each other via a non‐deterministic automaton description. The aim is to characterize the state behavior of a quantized system whenever its nondeterministic automaton description is given. The first result of the paper is derivation of a representation W(k + 1) = AW(k) for a nondeterministic closed‐loop automaton. The second result of the paper shows that the state‐behavior of a closed‐loop quantized system can be characterized according to the eigenvalues of matrix A in a similar manner with usual linear discrete‐time systems.
GLOBAL ROBUST SERVOMECHANISM OF A CLASS OF NONLINEAR SYSTEMS USING OUTPUT FEEDBACK
Authors: Chen Zhiyong , Huang Jie
Published: September 2010

The robust servomechanism problem (alternatively, output regulation problem) of the class of nonlinear systems in lower triangular form has been extensively studied in recent years. The semi‐global solution was first given by either state feedback or output feedback. The global solution by state feedback was given very recently. However, the global solution by output feedback has long been an open problem. In this paper, we present a set of solvability conditions of the global robust servomechanism problem for this class of nonlinear systems by output feedback.
GENERATION OF EXACT QFT BOUNDS FOR PLANTS WITH AFFINELY DEPENDENT UNCERTAINTIES
Authors: Yang Shih‐Feng
Published: September 2010

This paper presents an efficient method for the generation of exact QFT bounds for robust sensitivity reduction and gain‐phase margin specifications for plants with affinely dependent uncertainties. It is shown that, for a plant withmaffinely dependent uncertainties, the exact QFT bounds for robust sensitivity reduction and gain‐phase margin specifications at a given frequency and controller phase can be computed by solvingm2m‐1bivariate polynomial inequalities corresponding to the edges of the parameter domain box. Moreover, the solution set for each bivariate polynomial inequality can be computed by solving for the real roots of one fourth‐order and six second‐order polynomials. This avoids the unfavorable trade‐off between the computational burden and the accuracy of QFT bounds that has arisen in the application of many existing QFT bound generation algorithms. Numerical examples are given to illustrate the proposed method and its computational superiority.
Redrawing the Map of the World? Reflections on the World Development Report 2009
Authors: Hart Gillian
Published: September 2010

abstract

The World Development Report 2009 focuses on the role of markets for land, labor, and tradable goods in reshaping economic geography, but it pays little or no attention to financial markets. While analytically convenient, this abstraction from financial markets is deeply problematic. Especially since the late 1970s, the dynamics of finance capital have played a major role in redrawing the economic map of the world and will continue to do so. In addition, this review underscores the limits of the unilinear model of rural‐urban transition that underpins the report.
Developing and testing a patient information booklet for thrombolysis used in acute stroke
Authors: Knapp Peter , Wanklyn Peter , Raynor D K , Waxman Robin
Published: September 2010

Objective

Thrombolysis decreases the chance of post-stroke dependence, although its use carries significant risk, notably of intra-cerebral haemorrhage. Patients (and families) face an important risk/benefit decision before consenting. We drafted a patient information booklet for this purpose, and applied performance-based readability testing with the aim that the most important information in the booklet could be found and understood.

Methods

The booklet was developed with reference to best practice in information writing and design. We User-Tested its performance on 56 people without prior experience of stroke. After reading the booklet they were asked to find and explain 15 pieces of information. The booklet was revised according to its performance and re-tested, until each item was found and understood by at least 80% of participants.

Key findings

The four-page information booklet contained approximately 900 words, organised into six sections. A risk-palette graphic showed the chance of positive and negative outcomes. The booklet was tested on four participant cohorts and revised, including more bold text, re-wording, changing the title and changing the graphic to a coloured bar chart. Testing the final version on the fourth cohort of 20 people showed that each of the 15 tested items of information met the target of at least 80% participants being able to find and understand it.

Conclusions

The use of information design and User Testing produced a booklet that is understandable by people with no prior experience of stroke. User Testing is an inexpensive and quick method to ensure that information intended for patients is usable.
Angio‐adaptation in unloaded skeletal muscle: new insights into an early and muscle type‐specific dynamic process
Authors: Roudier Emilie , Gineste Charlotte , Wazna Alexandra , Dehghan Kooroush , Desplanches Dominique , Birot Olivier
Published: September 2010

With a remarkable plasticity, skeletal muscle adapts to an altered functional demand. Muscle angio‐adaptation can either involve the growth or the regression of capillaries as respectively observed in response to endurance training or muscle unloading. Whereas the molecular mechanisms that regulate exercise‐induced muscle angiogenesis have been extensively studied, understanding how muscle unloading can in contrast lead to capillary regression has received very little attention. Here we have investigated the consequences of a 9 day time course hindlimb unloading on both capillarization and expression of angio‐adaptive molecules in two different rat skeletal muscles. Both soleus and plantaris muscles were atrophied similarly. In contrast, our results have shown different angio‐adaptive patterns between these two muscles. Capillary regression occurred only in the soleus, a slow‐twitch and oxidative postural muscle. Conversely, the level of capillarization was preserved in the plantaris, a fast‐twitch and glycolytic muscle. We have also measured the time course protein expression of key pro‐ and anti‐angiogenic signals (VEGF‐A, VEGF‐B, VEGF‐R2, TSP‐1). Our results have revealed that the angio‐adaptive response to unloading was muscle‐type specific, and that an integrated balance between pro‐ and anti‐angiogenic signals plays a determinant role in regulating this process. In conclusion, we have brought new evidence that measuring the ratio between pro‐ and anti‐angiogenic signals in order to evaluate muscle angio‐adaptation was a more accurate approach than analysing the expression of molecular factors taken individually.
Spike‐timing‐dependent plasticity in hippocampal CA3 neurons
Authors: Astori S. , Pawlak V. , Köhr G.
Published: September 2010

Synaptic plasticity of different inputs converging onto CA3 pyramidal neurons is central to theories of hippocampal function. The mossy fibre (MF) input to these neurons is thought to exhibit plasticity that is in nearly all aspects fundamentally different from plasticity in other brain regions: in particular, when induced by high frequency presynaptic stimulation, plasticity at these synapses is independent of NMDA receptor (NMDAR) activation and presynaptically expressed. Here, we show that different stimulation protocols that depend on the close timing of MF activity and postsynaptic spikes induce bidirectional plasticity in CA3 neurons in 3‐week‐old rats. Long‐term potentiation (LTP) is observed when an excitatory postsynaptic potential (EPSP), evoked by MF stimulation, precedes a single postsynaptic action potential (AP) or a brief AP burst by 10 ms. Instead, timing‐dependent long‐term depression (LTD) requires the pairing of a single AP to an EPSP with a delay of 30 ms. The pairing of APs to synaptic activity is required for plasticity induction, since the application of unpaired APs or EPSPs did not alter synaptic strength. Furthermore, our results demonstrate that both timing‐dependent LTP and LTD critically depend on the activation of NMDARs. Specifically blocking postsynaptic NMDARs prevents plasticity, demonstrating that NMDARs important to spike‐timing‐dependent plasticity in CA3 neurons are required at postsynaptic sites. In summary, this study shows that the close timing of APs to MF excitatory synaptic input can alter synaptic efficacy in CA3 neurons in a bidirectional manner.
Investigation of Blade Tip Interaction With Casing Treatment in a Transonic Compressor—Part I: Particle Image Velocimetry
Authors: Voges M. , Schnell R. , Willert C. , Mönig R. , Müller M. W. , Zscherp C.
Published: September 2010

A single-stage transonic axial compressor was equipped with a casing treatment (CT), consisting of 3.5 axial slots per rotor pitch in order to investigate the predicted extension of the stall margin characteristics both numerically and experimentally. Contrary to most other studies, the CT was designed especially accounting for an optimized optical access in the immediate vicinity of the CT, rather than giving maximum benefit in terms of stall margin extension. Part I of this two-part contribution describes the experimental investigation of the blade tip interaction with casing treatment using particle image velocimetry (PIV). The nearly rectangular geometry of the CT cavities allowed a portion of it to be made of quartz glass with curvatures matching the casing. Thus, the flow phenomena could be observed with essentially no disturbance caused by the optical access. Two periscope light sheet probes were specifically designed for this application to allow for precise alignment of the laser light sheet at three different radial positions in the rotor passage (87.5%, 95%, and 99%). For the outermost radial position, the light sheet probe was placed behind the rotor and aligned to pass the light sheet through the blade tip clearance. It was demonstrated that the PIV technique is capable of providing velocity information of high quality even in the tip clearance region of the rotor blades. The chosen type of smoke-based seeding with very small particles (about 0.5 μm in diameter) supported data evaluation with high spatial resolution, resulting in a final grid size of 0.5×0.5 mm2. The PIV database established in this project forms the basis for further detailed evaluations of the flow phenomena present in the transonic compressor stage with CT and allows validation of accompanying computational fluid dynamics (CFD) calculations using the TRACE code. Based on the combined results of PIV measurements and CFD calculations of the same compressor and CT geometry, a better understanding of the complex flow characteristics can be achieved, as detailed in Part II of this paper.
Experimental Simulation of a Film Cooled Turbine Blade Leading Edge Including Thermal Barrier Coating Effects
Authors: Maikell Jonathan , Bogard David , Piggush Justin , Kohli Atul
Published: September 2010

For this study, a simulated film cooled turbine blade leading edge, constructed of a special high conductivity material, was used to determine the normalized “metal temperature” representative of actual engine conditions. The Biot number for the model was matched to that for operational engine conditions, ensuring that the normalized wall temperature, i.e., the overall effectiveness, was matched to that for the engine. Measurements of overall effectiveness were made for models with and without thermal barrier coating (TBC) at various operating conditions. This was the first study to experimentally simulate TBC and the effects on overall effectiveness. Two models were used: one with a single row of holes along the stagnation line, and the second with three rows of holes straddling the stagnation line. Film cooling was operated using a density ratio of 1.5 and for range of blowing ratios from M=0.5 to M=3.0. Both models were tested using a range of angles of attack from 0.0 deg to ±5.0 deg. As expected, the TBC coated models had significantly higher external surface temperatures, but lower metal temperatures. These experimental results provide a unique database for evaluating numerical simulations of the effects of TBC on leading edge film cooling performance.
Casing Treatment and Blade-Tip Configuration Effects on Controlled Gas Turbine Blade Tip/Shroud Rubs at Engine Conditions
Authors: Padova Corso , Dunn Michael G. , Barton Jeffery , Turner Kevin , Turner Alan , DiTommaso Darin
Published: September 2010

Experimental results obtained for an Inconel® compressor blade rubbing bare-steel and treated casings at engine speed are described. Since 2002 a number of experiments were conducted to generate a broad database for tip rubs, the Rotor-Blade Rub database obtained using the unique experimental facility at the The Ohio State University Gas Turbine Laboratory. As of 2007, there are seven completed groups of measurements in the database. Among them a number of blade-tip geometries and casing surface treatments have been investigated. The purpose of this paper is to provide a detailed interpretation of this database. Load cell, strain, temperature, and accelerometer measurements are discussed and then applied to analyze the interactions resulting from progressive and sudden incursions of varying severity, defined by incursion depths ranging from 13 μm to 762 μm (from 0.0005 in. to 0.030 in.). The influence of blade-tip speed on these measurements is described. The results presented describe the dynamics of rotor and casing vibro-impact response at representative operational speeds similar to those experienced in flight. Force components at the blade tip in the axial and circumferential directions are presented for rub incursions ranging in depth from very light (13 μm) to severe (406 μm). Trends of variation are observed during metal-to-metal and metal-to-abradable contacts for two airfoil tip shapes and tip speeds 390 m/s (1280 ft/s) and 180 m/s (590 ft/s). The nonlinear nature of the rub phenomena reported in earlier work is confirmed. In progressing from light rubs to higher incursion, the maximum incurred circumferential load increases significantly while the maximum incurred axial load increases much less. The manner in which casing surface treatment affects the loads is presented. Concurrently, the stress magnification on the rubbing blade at root midchord, at tip leading edge, and at tip trailing edge is discussed. Computational models to analyze the nonlinear dynamic response of a rotating beam with periodic pulse loading at the free-end are currently under development and are noted.
The Effects of Intake Plenum Volume on the Performance of a Small Naturally Aspirated Restricted Engine
Authors: Hamilton Leonard J. , Cowart Jim S. , Lee Jasen E. , Amorosso Ryan E.
Published: September 2010

Intake tuning is a widely recognized method for optimizing the performance of a naturally aspirated engine for motorsports applications. Wave resonance and Helmholtz theories are useful for predicting the impact of intake runner length on engine performance. However, there is very little information in the literature regarding the effects of intake plenum volume. The goal of this study was to determine the effects of intake plenum volume on steady state and transient engine performance for a restricted naturally aspirated engine for Formula Society of Automotive Engineers (FSAE) vehicle use. Testing was conducted on a four cylinder 600 cc motorcycle engine fitted with a 20 mm restrictor in compliance with FSAE competition rules. Plenum sizes were varied from 2 to 10 times engine displacement (1.2–6.0 l) and engine speeds were varied from 3000 rpm to 12,500 rpm. Performance metrics including volumetric efficiency, torque, and power were recorded at steady state conditions. Experimental results showed that engine performance increased modestly as plenum volume was increased from 2 to 8 times engine displacement (4.8 l). Increasing plenum volume beyond 4.8 l resulted in significant improvement in performance parameters. Overall, peak power was shown to increase from 54 kW to 63 kW over the range of plenums tested. Additionally, transient engine performance was evaluated using extremely fast (60 ms) throttle opening times for the full range of plenum sizes tested. In-cylinder pressure was used to calculate cycle-resolved gross indicated mean effective pressure (IMEPg) development during these transients. Interestingly, the cases with the largest plenum sizes only took 1 to 2 extra cycles (30–60 ms) to achieve maximum IMEPg levels when compared with the smaller volumes. In fact, the differences were so minor that it would be doubtful that a driver would notice the lag. Additional metrics included time for the plenums to fill and an analysis of manifold absolute pressure and peak in-cylinder pressure development during and after the throttle transient. Plenums below 4.8 l completely filled even before the transient was completed.
Assessment of Turbulence Model Predictions for an Aero-Engine Centrifugal Compressor
Authors: Bourgeois Jason A. , Martinuzzi Robert J. , Savory Eric , Zhang Chao , Roberts Douglas A.
Published: September 2010

The accurate prediction of mean flow fields with high degrees of curvature, adverse pressure gradients, and three-dimensional turbulent boundary layers typically present in centrifugal compressor stages is a significant challenge when applying Reynolds averaged Navier–Stokes turbulence modeling techniques. The current study compares the steady-state mixing plane predictions using four turbulence models for a centrifugal compressor stage with a tandem impeller and a “fish-tail” style discrete passage diffuser. The models analyzed are the k-ε model (an industry standard for many years), the shear stress transport (SST) model, a proposed modification to the SST model denoted as the SST-reattachment modification (RM), and the Speziale, Sarkar, and Gatski Reynolds stress model (RSM-SSG). Comparisons with measured performance parameters—the stage total-to-static pressure and total-to-total temperature ratios—indicate more accurate performance predictions from the RSM-SSG and SST models as compared to the k-ε and SST-RM models. Details of the different predicted flow fields are presented. Estimates of blockage, aerodynamic slip factor, and impeller exit velocity profiles indicate significant physical differences in the predictions at the impeller-diffuser interface. Topological flow field differences are observed: the separated tip clearance flow is found to reattach with the SST, SST-RM, and RSM-SSG models, while it does not with the k-ε model, a larger shroud separation at the impeller exit seen with the SST and SST-RM models, and core flow differences are in the complex curved diffuser geometry. The results are discussed in terms of the production and dissipation of k predicted by the various models due to their intrinsic modeling assumptions. These comparisons will assist aerodynamic designers in choosing appropriate turbulence models, and may benefit future modeling research.