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In this paper we examine the relationship between the composition of a firm's institutional ownership and the existence of internal control material weaknesses (ICMWs) under SOX Sections 302 and 404. We find a significantly positive relationship between the level of total institutional ownership and ICMW existence. The positive relationship is mainly driven by the transient investors who, with short-term investment horizons, may have little incentive to engage in costly and effective monitoring. When partitioning ICMWs into pervasive (more severe) and contained (less severe) types, we find that firms with pervasive ICMWs are associated with a lower (higher) level of dedicated (transient) institutional ownership. We also find that firms with pervasive ICMWs have significantly fewer resources to invest in internal control systems than do firms with contained ICMWs., Introduction In this study we investigate the association between a firm's institutional ownership and the existence of internal control material weakness (ICMW hereafter) under Sections 302 and 404 of the [...]

Electromyography (EMG), or the study of muscle activation patterns, has long been used to infer central nervous system (CNS) control of the musculoskeletal system and the evolution of that control. As the activation of the muscles at the level of the periphery is a reflection of the interaction of descending influences and local reflex control, EMG is an important tool in integrated investigations of the evolution of coordination in complex, musculoskeletal systems. Yet, the use of EMG as a tool to understand the evolution of motor control has its limitations. We here review the potential limitations and opportunities of the use of EMG in studying the evolution of motor control in vertebrates and provide original previously unpublished data to illustrate this. The relative timing of activation of a set of muscles can be used to evaluate CNS coordination of the components in a musculoskeletal system. Studies of relative timing reveal task-dependent variability in the recruitment of different populations of muscle fibers (i.e., different fiber types) within a single muscle, and left-right asymmetries in activation that need to be taken into account in comparative studies. The magnitude of muscle recruitment is strongly influenced by the instantaneous demands imposed on the system, and is likely determined by local reflex-control systems. Consequently, using EMG to make meaningful inferences about evolutionary changes in musculoskeletal control requires comparisons across similar functional tasks. Moreover, our data show that inferences about the evolution of motor control are limited in their explanatory power without proper insights into the kinematics and dynamics of a system.

The Nehari problem plays an important role in [H.sup.[infinity]] control theory. It is well known that [H.sup.[infinity]] control problem can be reduced to solving this problem. This note gives a parameterization of all suboptimal solutions of the Nehari problem for a class of infinite-dimensional systems. Many earlier solutions of this problem are seen to be special cases of this new parameterization. It is also shown that for finite impulse response systems this parameterization takes a particularly simple form. Index Terms--Delay systems, [H.sup.[infinity]]-control, infinite-dimensional systems, Nehari problem.

In this paper, we analyze the effects of power lines parameters' uncertainties on the efficiency of a PowerLine Communication (PLC) system. An estimate of the upper and lower bounds' system response due to the uncertainties is given. The analyzed system is schematized as a connection of multiport devices described by their scattering parameter matrices and an adjoint method for sensitivity calculations, based on the use of a wavelet expansion, is used to determine the bounds. The wavelet based sensitivity analysis allows a direct determination of the time domain sensitivity avoiding computationally expensive convolution integral calculations; in addition a fast and accurate bounds calculation is obtained avoiding statistical Monte Carlo simulations. The bounds determination allows the estimate of noteworthy quantities for the tuning of currently used modulation schemes for PLC such as orthogonal frequency-division modulation. Index Terms--Power lines communication, sensitivity analysis, uncertain parameters.

This paper presents a new logic of operation for time overcurrent relays. With the application of the proposed technique, the sensitivity of time overcurrent relays is increased. In order to obtain this, the relay operates with a dynamic pickup setting, such as load current. Additionally, fast operation of overcurrent relays is obtained. The functional structure is described and the logic of overcurrent relay is evaluated under different operative states. We describe the functional structure of the proposed relay and its implementation in laboratory tests. Index Terms--Overcurrent relay, pickup current, sensitivity.

For a sliding mode (SM) system containing parasitic dynamics, a model of chattering and a model of the averaged motions of the order equal to the original order of the system are obtained via the use of the locus of a perturbed relay system (LPRS) method. The latter model proves that the averaged motions in an SM system differ from those in the reduced-order model. In particular, such phenomena as the nonideal disturbance rejection and the nonideal input tracking are observed. It is shown that the non-reduced-order model transforms into the reduced one when the parasitic dynamics are removed. Yet, the chattering and the averaged motion--being the two components of the motion in the SM system--belong to two different frequency ranges (spectra). As a result, a frequency characteristic shaping aimed at achieving the desired frequency of chattering and enhancing the closed-loop performance becomes possible. This opportunity is explored in this paper. Examples that illustrate the proposed approach are provided. Index Terms--Compensation, discontinuous control, frequency-domain analysis, sliding mode.

New definitions of approximability are presented for nonlinear second-order sliding mode control systems. Such robustness properties are compared with those already known for first-order methods. Sufficient conditions are obtained for second-order regularization, a sliding error estimate is derived, and some relevant examples are discussed. Index Terms--Approximability, nonlinear uncertain control systems, regularization, second-order sliding mode control.

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 [...]

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.

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.

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.

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.