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The cost-effectiveness of interconnected microgrid systems with combined heat and power is examined for 36 cases involving six microgrid applications in six different U.S. locations. In the baseline analysis, microgrids are found to be good investments in areas with relatively high 'spark spreads' (electricity/natural gas price differentials). Customers with a higher value for electric reliability realize greater benefits. Results become more favorable over time if the rate of increase of electricity prices is at least 60% of the rate of increase of natural gas prices--a plausible scenario in states with substantial natural-gas fired capacity. Sensitivity analyses reveal that the choice of microgrid customer mix has a much greater impact on system economics than climate. Economies of scale are shown to be fairly modest for the systems considered here, but microgrids do show clear benefits over traditional single customer distributed generation. If performance goals of current U.S. Department of Energy research programs for 1C engines and microturbines are met, rates of return for microgrid investments increase 10-20%. DOI: 10.1061/(ASCE)0733-9402(2007)133:3(150) CE Database subject headings: Grid systems; Powerplants; Electric power supply; Sensitivity analysis.

In this paper, we are concerned with the analysis of linear infinite-dimensional control systems that should be able to compensate and/or track signals that are periodic. Adopting the name given in the seminal paper by Hara et al., we call them repetitive controllers. We analyze the asymptotic stability in the Lyapunov sense of finite-dimensional positive real plants coupled with pure delays. For this class of systems, we initially prove convergence in the weak topology to later deduce convergence in the strong one. Index Terms--Control systems, delay systems, linear systems, Lyapunov methods.

In this note, Lyapunov-based methods are used to design a class of energy-based nonlinear controllers to globally asymptotically stabilize/regulate an underactuated mechanical system subject to an impact collision. The impact model is considered as an elastic contact with finite stiffness. One of the difficulties in controlling impact is that the equations of motion are quite different when the system status changes from a noncontact condition to a contact condition. Another difficulty arises when an impact occurs with an underactuated system because the impact may lead to instabilities or excessive transients. An energy coupling approach is developed in this paper that is motivated by the desire to improve the transient response of the system. A Lyapunov stability analysis and numerical simulations are provided to demonstrate the stability and performance of the developed controllers. Index Terms--Impact, Lyapunov methods, nonlinear systems.

In this note, the dynamical behaviors of Euler's discretization of the equivalent control based sliding-mode control (SMC) systems are studied. We show that if the discretized SMC system is asymptotically stable, then every trajectory converges to a period-2 cycle. Bounds for the steady states are derived, which allow one to estimate the maximum chattering amplitude for a given value of the time step. The analysis and results are verified with several computer simulations. Index Terms--Discretization, dynamical behaviors, equivalent control, sliding-mode control.

This paper investigates the stabilizability of uncertain linear time-invariant (LTI) systems via structurally constrained controllers. First, an LTI uncertain system is considered whose state-space matrices depend polynomially on the uncertainty vector, defined over some region. It is shown that if the system is stabilizable by a structurally constrained controller in one point belonging to the region, then it is stabilizable by a controller with the same structure in all points belonging to the region, except for those located on an algebraic variety. Thus, if a system is stabilizable via a constrained controller at the nominal point, then it is almost always stabilizable at any operating point around the nominal model. It is also shown how this algebraic variety (or the dominant subvariety of it) can be computed efficiently. The results obtained in this paper encompass a broad range of the existing results in the literature on robust stability of the LTI systems, in addition to new ones. Index Terms--Algebraic variety, decentralized control, robust control, stabilizability, uncertain systems.

This paper provides a general framework for analyzing the stability of general nonlinear networked control systems (NCS) with disturbances in the setting of [L.sub.p] stability. Our presentation provides sharper results for both [L.sub.p] gain and maximum allowable transfer interval (MATI) than previously obtainable and details the property of uniformly persistently exciting scheduling protocols. This class of protocols was shown to lead to [L.sub.p] stability for high enough transmission rates and were a natural property to demand, especially in the design of wireless scheduling protocols. The property is used directly in a novel proof technique based on the notions of vector comparison and (quasi)-monotone systems. We explore these results through analytical comparisons to those in the literature, as well as through simulations and numerical comparisons that verify that the uniform persistence of excitation property of protocols is, in some sense, the "finest" property that can be extracted from wireless scheduling protocols. Index Terms--Networked control, scheduling, stabilization, wireless networks.

Ford-Otosan, a producer of light and medium commercial vehicles, wanted to improve order-to-delivery times while reducing costs in the course of expanding its capacity. It started a six-sigma project to [...]

In this paper, analytical models are developed to study the performance of a transfer production line featuring Andon. In addition to providing analytical expressions to evaluate effective production rates, we investigate conditions under which Andon should be introduced and implemented. Some practical rules are derived to guide operations management on the factory floor. We show that when average repair times are short, introducing Andon to stop the line and repair all defects on the line is an effective way to achieve a high throughput of non-defective jobs., 1. Introduction Andon, derived from the Japanese word for paper lantern, is a term for a visual control system using an electric light board (or other signal device) hung in [...]

This paper presents an application of an online self-organizing fuzzy logic controller to a boiler-turbine system of fossil power plant. The control rules and the membership functions of the proposed fuzzy logic controller are generated automatically without using a plant model. A boiler-turbine system is described as a multi-input multioutput (MIMO) nonlinear system in this paper. Then, three single-loop fuzzy logic controllers are designed independently. Simulation shows robust results for various kinds of electric load demand changes and parameter variations of boiler-turbine system. Index Terms--Boilers, fuzzy control, self-organizing control.

This paper presents a novel speed control scheme of an induction motor (IM) using fuzzy-logic control. The fuzzy-logic controller (FLC) is based on the indirect vector control. The fuzzy-logic speed controller is employed in the outer loop. The complete vector control scheme of the IM drive incorporating the FLC is experimentally implemented using a digital signal processor board DS-1102 for the laboratory 1-hp squirrel-cage IM. The performances of the proposed FLC-based IM drive are investigated and compared to those obtained from the conventional proportional-integral (PI) controller-based drive both theoretically and experimentally at different dynamic operating conditions such as sudden change in command speed, step change in load, etc. The comparative experimental results show that the FLC is more robust and, hence, found to be a suitable replacement of the conventional PI controller for the high-performance industrial drive applications. Index Terms--Digital signal processor, fuzzy-logic controller, induction motor, PI controller, real-time implementation, speed control.

The development of an automatic deceleration system for a winding machine in a siderurgy factory is presented in this paper. The proposed system controls the speed of a winding machine in order to obtain the optimum stop point in terms of security and fast production. The system is based on a microcontroller and an extremely simple hardware. The system has been tested for two years and results evince a very good mean time between failures. Index Terms--Automatic deceleration, control system, fast production, microcontroller, m.t.b.f. improvement.

This paper deals with a hydraulic servo system with compliance control for the operation in an environment with frequent machine-human interaction. The compliance is mechanically adjusted in the present hydraulic system by changing the neutral position of the bridge valves between the full opening and the full closing states. The mathematical model of the system is first derived, and the static and the dynamic behavior of the system are investigated through numerical simulation. Since the present system exhibits a strong nonlinear characteristic in the operating condition of large compliance, a nonlinear controller is designed with the feedback linearization technique. In the operating condition of small compliance, on the other hand, a conventional linear control is applicable as usual hydraulic control systems. The performance of the present control system is investigated through both numerical simulation and experiment, justifying that the present hydraulic servo system continuously adapts its performance between a rigid positioning against disturbances and a compliant positioning to prevent damage to obstacles on the path. [DOI: 10.1115/1.1433803]

Wing control surfaces are used to trigger the breakup of trailing vortices behind aircraft in a flaps-down configuration. In the near field of the aircraft there are multiple pairs of vortices, which admit new instability mechanisms that do not exist on a single pair of vortices. A periodic motion of the control surfaces is used to introduce a unique form of perturbation that is amplified in the multiple vortex-pair system but conserves total circulation, lift, and rolling moment. Growth of the perturbations leads to the periodic pinching of the starboard and port vortices into a series of vortex rings. The concept is demonstrated using numerical simulations and towing-tank experiments. Results show that the system breaks up the trailing vortices more rapidly than a comparable excitation of the Crow instability on a single pair of vortices. The overall effectiveness of the system depends on the airplane configuration, namely, details of the flap system and the horizontal tail.

This paper analyzes performance of periodically time-varying sampled data controllers for [L.sub.p] deterministic and uniform disturbance rejection. For a given linear periodic sampled data controller controlling a linear time-invariant continuous-time plant, it is shown that a linear time-invariant controller can be found to give better [L.sub.p] sampled data control than the time-varying controller. The performance analysis is in time domain using convexity properties of the [L.sub.p] signal space. Index Terms - Continuous-time systems, discrete-time systems, [L.sub.p] control, sampled data control, time-varying systems.

A study was conducted to examine the effectiveness of the use of in-vehicle route guidance and informations systems (IVRGIS) for older people and newly qualified drivers. Results show that elderly drivers responded better to less complex guidance directions, rather than full guidance directions, as the former provide them more time to make the association between the directions to be taken and the spatial location of these turns. For new drivers, however, wayfinding performance has decreased with the use of IVRGIS.

The stability, steady-state error analysis, damping factor, and setting time of discrete data drives for computer numerical control (CNC) machine tools are analyzed to obtain the necessary information for the design of a practical system. The stability of the drive is reviewed using Jury's test and the Mitrovic criterion. The variation of damping factor and settling time with respect to system parameters are presented based on the Mitrovic criterion. Index Terms - Computer numerical control-drive control, Mitrovic's criterion.

This paper proposes a simplified theory to predict and compare the seismic performance of viscoelastical (VE)- and elastoplastical (EP)- damped passive control systems, and to demonstrate their ability to protect structures during a major seismic event. Closed-form expressions for 'equivalent period' and 'equivalent damping' of these systems are proposed by idealizing them as linear single-degree-of-freedom (SDOF) systems. The expressions are used to clarify and compare the structural parameters, seismic drift, and force for the systems, based on a common high-damping linear spectrum. By extending the SDOF theory, a seismically deficient 14-story steel moment resisting frame (MRF) is upgraded by inserting VE or EP dampers. Extensive three-dimensional multi-degree-of-freedom nonlinear dynamic analyses are performed for the MRF, VE system, and EP system using earthquakes of various intensities. The 14-story VE and EP systems responded as predicted by the SDOF theory. They show much smaller drifts than the original MRF, keep frame members elastic, and protect nonstructural components, even against major earthquakes.

A Unified Power Flow Controller (UPFC) is a typical FACTS device capable of instantaneous control of three system parameters. This paper presents a basic control system which enables the UPFC to follow the changes in reference values of the active and reactive power supplied from the outer system controller. The analysis is based on the transformation of the three-phase system to the rotating reference frame. As a step closer to a practical application of the UPFC a modified control structure with a predictive control loop and precontrol signal for a dc-voltage control was designed. The new control system offers better stability and transient performance in comparison with the classical decoupled strategy, especially considering the harmonic distortion of the current being controlled. The derived basic control of the UPFC was tested with the NETOMAC program system.

Material productivity, design preciseness, and time to market are becoming critical in motor manufacturing and can be improved by detailed system design analysis and simulation within manufacturing tolerance. Design by analysis and simulation of switched reluctance motor (SRM) systems and the development method of a new design software are the subjects of this paper, with a focus on the main difficulties. The modeling of geometric, electromagnetic, control, mechanical, and thermal concerns is presented. The electromagnetic approaches include lumped-parameter analysis, finite-element analysis, and boundary-element analysis. The aspects of the study include the following: magnetization curves; controller characterization; system simulation; performance prediction; control system dynamics; vibration modes and frequencies; radial magnetic forces, stresses, and vibrations; and dynamic heat distribution and transfer. Index Terms - Design simulation, finite-element analysis, motor design software, switched reluctance motor.

The aim of this paper is to discuss the problems relating to communication in distributed process control, highlighting the limits of traditional centralized communication systems based on point-to-point connections. The paper intends to show the real advantages that can be obtained by using a distributed common-bus communication system in time-critical process control applications, highlighting its impact on the architecture of control systems from the point of view of both hardware and software. Particular reference is made to the International Electrotechnical Commission/Instrument Society of America (IEC/ISA) communication system which is close to becoming an international standard. In particular, the solution based on the use of the distributed common-bus communication protocol is applied to the control of an orange-picking robot, which had previously been implemented in a traditional way using point-to-point communications. The choice of a case study referring to a robot control system seems an appropriate benchmark for the real potential of the fieldbus because the processes involved in a robot control system have highly critical time constraints which may stress the fieldbus communication system. The paper presents a qualitative analysis of the advantages that can be obtained by introducing the fieldbus into the orange picking robot control system. The analysis gives a detailed illustration of the hardware and software modification needed to replace the traditional point-to-point control systems of the orange picking robot with the fieldbus. Then an evaluation of the performance of fieldbus system is provided. The evaluation is made by modeling and simulating the distributed communication system with transition timed Petri nets (TTPN's). The results obtained in the study as a whole confirm the authors' conviction that, by careful analysis, it is possible and advantageous even in difficult cases to replace classical centralized point-to-point control systems with distributed systems based on use of the fieldbus. Index Terms - Fieldbus, orange-picking robot, Petri nets.

Robustness of closed loop systems, subjected to unmodeled dynamics, using the Generalized Predictive Controller (GPC) is analysed. A stability bound equation for the GPC controller is derived using the small gain theorem and, from the analysis of this equation, guidelines for selecting the order of the observer polynomial T in the GPC are developed. The choice of the polynomial T order is based on the stability bound equation tendency in high frequencies and is a function of the GPC tuning knobs. Different strategies for choosing the polynomial T roots are also included. The aim is to improve robustness. Key words: GPC, robustness, unmodeled dynamics, closed loop stability.

Frequently, due to the irregularities in fuel properties of the wastes and variations in feed rates, the operation of a batch-fed incinerator may encounter pressure surges and transient flue gas leakages. A lumped model to simulate the flow, pressure, and temperature behavior of an incineration system was developed, according to the fundamental conservation laws governing the overall balances of flow and thermal-mechanical energies of the system components. The system dynamic responses to flow control and waste burning variations were analyzed numerically. Qualitatively, the results correctly reflected the observed operational characteristics of batch-fed incinerators. The lumped system model can serve as a tool to design control algorithms. The concepts and approaches adopted in this work can be used as the basis for further expansion in details toward the development of an incinerator system simulator for operator training purposes.

The structured singular value method is applied to continuous-time SISO repetitive control systems in order to determine their stability and performance robustness in the presence of structured parametric modeling error in the plant. Performance measures for repetitive control systems are introduced and the robust performance analysis using structured singular values is modified, taking the alternating magnitude behaviour of the sensitivity function of a repetitive control system into account. The analysis procedure is simplified considerably in the case of large time delay by noting that the upper and lower envelopes of the structured singular value plots are obtained from corresponding finite dimensional systems without any time delay. The analysis procedures developed are applied to an example on repetitive control of an electrohydraulic material testing machine, available in the literature, to demonstrate their usefulness.

Two methods of control of semi-active suspensions that specifically address the problem of structural vibrations of the vehicle body are considered. These control strategies are based on those developed for active suspension systems in Part I of this study and rely on either modifications of suspension control forces that account for body compliance or on the addition of a proof-mass actuator to reduce structural vibrations. A half-car model that includes body compliance is used to evaluate the effects of these control strategies on the performance of the suspensions with two-state and continuously modulated dampers. The performances of the systems are evaluated in both the time and frequency domains. The effect of time delays in the process of actuating the adjustable dampers is investigated. Significant reductions of structural vibrations are observed when the nodes of body beaming modes are a sufficient distance away from the suspension mounting points, and the time delays in the control system are negligible. The results deteriorate markedly when two-state dampers are used instead of continuously variable dampers or when a time delay in excess of 5 ms is present in the control loop. When the preference in suspension design shifts toward road holding it becomes increasingly difficult to improve the vehicle structural response without sacrificing other aspects of performance.

A novel nonlinear sliding mode controller has recently been developed for direct acting proportional solenoid valves. This paper presents a comparison between the valve performance using this controller, and that obtained using two alternative control strategies; state feedback and PID control. Each controller is described in turn, and experimental step response results are presented to demonstrate the validity of each strategy. These results are compared on the basis of response time, overshoot, and steady-state error. The time taken to design each controller, and the required level of knowledge of the valve dynamics, are also assessed. The ability of each controller to reject flow reaction forces is evaluated by observing the changes in the step response when oil is passed through the valve. The results demonstrate that the sliding mode controller results in a faster, more robust closed-loop response. In addition, only minimal knowledge of the valve dynamics is required in order to design the controller.

This paper describes the specification, development, and testing of the FT8-2 Dry Low N[O.sub.x] control system, and how the lean burn process requires an integration of the control system and combustion hardware. The FT8-2 digital fuel control system was developed to achieve the precise multizone fuel metering of both gas and liquid fuels, the calculation of combustor air flow necessary to achieve Dry Low N[O.sub.x] and the traditional governing/limiting control loops necessary for safe, stable engine operation. The system design goals were accomplished by the concurrent development of software-based fuel metering algorithms and fuel metering hardware. The fuel metering hardware utilizes an all-electronic valve positioner, employing a combination of feedback and software to achieve closed-loop control of actual fuel flow. Extensive testing under actual gas flow conditions and closed-loop bench testing using a real time engine model and fuel system model was conducted to prove system operation and develop system transient response prior to installation on the test engine. The setup and results of the flow testing and closed-loop testing are described. The paper describes the control scheme used to apportion the gas fuel between combustion zones and how external conditions such as ambient temperature and fuel gas composition affect the apportionment. The paper concludes with a description of the control system installation in the engine test cell and a review of engine test results.

In the cement industry, many optimization systems have been developed and are currently in operation to reduce total production and delivery costs or to optimize the efficiency of equipment investments. This paper deals with some of these optimization systems, which were designed with mathematical programming. Some effective usage of sensitivity analysis and a systems integration approach are also introduced.

The new coupled pickle line and cold mill (CPCM) has been processing steel since December 1991 at Dofasco Inc. in Hamilton, Ontario, Canada. This mill rolls both sheet and tin plate. The work rolls for the last stand are often textured by grit blasting to roll 'matte' finished strip. A new computer-targeted control system was developed for the roll speeds and gaps, specifically for matte rolling. The new set-up system uses Stone's model, which is more appropriate for the limited reductions evident with the rougher rolls. Conventional automatic gauge control (AGC) systems using thickness measurements after the last stand are limited in performance by the effect of long transport delays. These limitations are particularly critical during mill acceleration and deceleration. The use of a thickness gauge before the stand with matte rolls allows the development of AGC systems using shorter control loops for final gauge control. The AGC system uses a Smith predictor for transport lag, (phase shift), compensation. The combination of the shorter AGC loop and the Smith predictor allows higher gains to be used in the control system. This set-up and control system has contributed to Dofasco's position as a market leader in thickness performance.

An advanced control system for the operation of solar process heat plants and a simulation program for the design were developed. A flexible test facility was installed in order to qualify the control system and the simulation model. It consists of different small collector fields, two storage tanks, an auxiliary electric heater and an adjustable heat sink for simulating any load profile. The advanced control system provided a fast control of the necessary collector field outlet temperatures and an effective compensation for any disturbances. The simulation program based on TRNSYS was extended to meet the requirements for the design of solar process heat plants.

DART is the high speed, Unix based data acquisition system being developed by Fermilab in collaboration with seven High Energy Physics Experiments [1 - 6!. This paper describes DART run control, which has been developed over the past year and is a flexible, distributed, extensible system for the control and monitoring of the data acquisition systems. We discuss the unique and interesting concepts of the run control and some of our experiences in developing it. We also give a brief update and status of the whole DART system.

An integrated time domain state space identification technique for structural systems is presented. This technique integrates the Observability Range Space Extraction identification algorithm, Balanced Realization model reduction algorithm, and Least Square model updating algorithm to generate low order and highly accurate state space models for structural systems based upon time domain data. The algorithms are integrated in such a manner that the Observability Range Space Extraction identification algorithm is used to generate an initial overparameterized state space model and then the Balanced Realization model reduction and Least Square model updating algorithms are used to iteratively reduce and update the model to achieve minimum prediction errors in time domain. We shall present the Observability Range Space Extraction identification algorithm and the Least Square model updating algorithm and discuss the integrated identification technique. The MIT Middeck Active Control Experiment (MACE) is used as an application example. MACE is an active structure control experiment to be conducted in the Space Shuttle middeck. Results of ground experiments using this technique will be discussed.

A correlation equation is established between open-loop test data and the desired closed-loop system characteristics permitting control system synthesis to be done on the basis of a numerical approach using experimental data. The method is applicable when the system is linear-time-invariant and open-loop stable. The major merits of the algorithm are two-fold: 1) Arbitrary placement of the closed-loop system equation is possible, and 2) explicit knowledge of an open-loop system model is not needed for the controller synthesis.

In this paper, an integral criterion is developed for overall analysis and appraisal of the performance, reliability and economy of a computer-based control system. A concept of performability is discussed, and the economic optimality is based on the overall benefits from the manufacturer to the user. A case study for a hydroturbine governing system is given. A comparison between different system configurations shows that it is helpful and beneficial to select a system possessing high indices and excellent quality. Keywords: Performance; Function; Reliability; Performability; Economic optimality; Computer-based control system

Currently, neural networks are being used to solve problems related to control. One way to determine the reliability of the neuro-control technique is to test it on a variety of realistic problems. Another way is to compare it directly with existing traditional control techniques, to see whether it works well and where it needs further refinement. In this article, we compare the neuro-control algorithm to three other control algorithms; fuzzy logic control, generalized predictive control, and proportional-plus-integral control. Each of these four algorithms is implemented on a water bath temperature control system. The four systems are compared through experimental studies under identical conditions with respect to set-point regulation, the effect of unknown load disturbances, large parameter variation, and variable deadtime in the system. It is found that the neuro-control system compares well with the other three control systems and offers encouraging advantages. From the results of the experimental studies, however, the best characteristics of each of these different classes of control systems may be combined for realizing a more efficient and intelligent control scheme.

Model-based monitoring systems based on state observer theory are attractive for machine monitoring because practical, inexpensive, and reliable sensors can be located remote to the signal(s) of interest. Then, a model of the machine plus an estimation algorithm are utilized to convert the output of the remote sensors to signals representing the desired local behavior. While this type of monitoring system has shown much promise in the laboratory, it has not been widely accepted by industry because, in practice, these systems often have poor performance with respect to accuracy, bandwidth, reliability (false alarms), and robustness. In this paper, the limitations of the deterministic state observer are investigated quantitatively from the machine monitoring viewpoint. The limitations in the transient and steady-state observer performance are quantified based on the estimation error bounds, and from these error bounds, performance indices are selected. Then, based on the relationships between the indices, a main index is determined in order to represent the overall observer performance. The index is the condition number of the observer eigenvectors in [L.sub.2] norm. It is shown that observers with small condition numbers are guaranteed to have small error bounds. This index can be utilized as a quality condition for any linear observer regardless of how it is designed as well as form the basis for an observer design methodology for high performance observer-based monitoring systems.

A Superconducting Cyclotron is now under development at LNS-Catania as a part of a heavy ion-facility. The features of the distributed control system of this accelerator and the experiences gained during its functioning Will be reported together with its future improvements.

All real-world control systems have saturation nonlinearity in final control elements (including actuators). When controllers involve integral action, reset windup can cause instability as well as make system performance unsatisfactory. Based on the describing function method and the generalized Popov criterion, this paper presents analysis of the global stability of a control system having a saturating second-order plant, both with and without using a deadbeat limiting scheme to constrain its controller output. The improvement of system performance by incorporating the anti-windup feature in the controller is illustrated by computer simulations.

The fundamental concept of feedback to control dynamic systems has played a major role in many areas of engineering. Increases in complexity and more stringent requirements have introduced new challenges for control systems. This paper presents an introduction to and appreciation for intelligent control systems, their application areas, and justifies their need. Specific problem related to automated human comfort control is discussed. Some analytical derivations related to neural networks and fuzzy optimal control as elements of proposed intelligent control systems, along with experimental results, are presented. A brief glossary of common terminology used in this area is included.

In this essay, on the observance of the 50th anniversary of the founding of ASME's Dynamic Systems and Control Division, I try to connect the technology of control to the way in which control practitioners think. Despite some tension between the conclusions implied in the introductory paragraphs and conclusions drawn later in the essay, I have left them to stand in their original form to emphasize tensions in control thinking, for which the source might not be apparent. The opinions expressed here are strictly my own, but I must acknowledge the creative proddings of my colleagues in getting these thoughts recorded at all.