Entire Operating Region Research Articles

Analysis of quasi double gate method for performance prediction of deep submicron double gate SOI MOSFETs

In this paper, we analyse for the first time the effectiveness of the quasi-double gate (QDG) method for performance prediction of short channel double gate (DG) silicon-on-insulator metal–oxide–semiconductor field-effect transistors (MOSFETs) over the entire operating region. An analytical model has been developed to explain the abnormally low values (≪60 mV/decade) of subthreshold slope that are obtained in QDG devices. We extract the low field mobility (μo), subthreshold slope (S), threshold voltage (Vth), transconductance-to-drain current ratio (gm/Ids) and peak transconductance (gm)max in linear and saturation regions for deep submicron QDG devices. We demonstrate that the QDG method can accurately predict gm/Ids, (gm)max and μo values for a deep submicron real DG device in the linear and strong inversion regions.

Robust Tuning of Feedback Linearizing Controllers via Bifurcation Analysis

Abstract Feedback linearization is a nonlinear controller design strategy that results in an explicit formulation of the feedback control law. This method can result in excellent performance if an accurate dynamic process model is available. However, feedback linearization suffers from a lack of robustness if plant-model mismatch exists. The approach presented in this work analyzes the robustness properties of the closed-loop process with specific regard to the controller tuning parameter. Due to this, it is possible to tune the controller such that robustness over the entire operating region is guaranteed even under the assumption of certain types of model mismatch. This method is illustrated with an example and conclusions about its applicability to more general model and controller formulations are presented.

Structured-specified robust-multivariable-controller design for practical applications using genetic algorithms

In the conventional μ-synthesis control design, the order of the controller is higher than that of the plant and it is difficult to implement. Therefore a control design based on simple elements such as PIDs and first-order systems is desirable. A synthesis technique, blended with multiobjective characteristics, for the design of structured specified μ-suboptimal controllers is presented. The design is based on a genetic-algorithm-optimisation approach and the resulting controllers ensure stability and high performance for the entire operating region. A multivariable example involving a supermanoeuverable HIMAT aircraft is used to illustrate the applicability of the design.

A Fuzzy Logic Based Discrete Mode Power System Stabilizer

ABSTRACTA Fuzzy Power System Stabiliser (FPSS) design using discrete inputs is presented. The FPSS basically utilises only one measurable plant signal as input, namely, the generator speed. The speed signal is discretised resulting in three inputs to the FPSS. A simplified power system represented by a single generator transmitting power to the infinite bus is considered for investigations. The system is simulated in simulink while the FPSS is implemented using Fuzzy Logic Toolbox. There are six rules for the fuzzification and two rules for defuzzification. To provide satisfactory behaviour in the entire region of operation of the generator, additional signals namely, generator's active and reactive power are used as inputs to FPSS. Simulation studies show the superior performance of the proposed FPSS compared to an optimally designed Conventional Power System Stabiliser.

An accurate charge control model for spontaneous and piezoelectric polarization dependent two-dimensional electron gas sheet charge density of lattice-mismatched AlGaN/GaN HEMTs

The present paper proposes an improved charge control model of lattice-mismatched AlGaN/GaN HEMTs, valid over the entire operating region. The model for estimation of two-dimensional electron gas (2-DEG) sheet carrier concentration accounts for the strongly dominant spontaneous and piezoelectric polarization at the AlGaN/GaN heterointerface. The dependence of 2-DEG sheet carrier concentration on the aluminum composition and AlGaN layer thickness has been investigated in detail. Current–voltage characteristics developed from the 2-DEG model include the effect of field dependent mobility, velocity saturation and parasitic source/drain resistances. Close proximity with experimental data confirms the validity of the proposed model.

A gain-scheduled L2 control to nuclear steam generator water level

This paper is concerned with the design of a gain-scheduled controller with guaranteed L2 performance for the water level control of a nuclear steam generator which has parameter varying dynamics. The proposed controller guarantees both stability and a prescribed L2 performance in the entire operating region. The systematical design method for the controller which is automatically adjusted along the reactor power, in terms of Linear Matrix Inequalities (LMIs), is shown. The main benefit of this method is to avoid most of difficulties such as gain-interpolation or griding technique in a classical gain scheduling control. The computer simulation demonstrates the effectiveness of the proposed controller in full operating range and its superiority to conventional PID controllers. ©

ANN Based Adaptive Control of Multistage Flash Seawater Desalination PlantsS

Abstract This paper presents an Artificial Neural Network (ANN) based adaptive control scheme for a multistage flash (MSF) sea water desalination plant. The detailed dynamic model of an 18-stage MSF plant has been developed and validated by measurements on the actual plant which is in operation in the United Arab Emirates. The non-linear behaviour of the model makes a fixed controller unfit for operation in the operating region that is normally chosen in which the controller parameters have to be tuned at each of a number of points based on the linearized version of the plant model. An ANN is trained with the information derived from simulation based optimal design at selected points in the operating region. The underlying control law is one which uses integral performance criteria and provides optimal PID controller parameters. With the ANN so trained and inserted in an adaptive control loop, the system maintains optimality in the entire operating region.

Evolutionary linearisation in the frequency domain

Feu solutions have been found so far to frequency domain MIMO system linearisation problems owing to practical difficulties in obtaining derivatives of the nonlinear model. The authors develop an evolutionary linearisation technique to achieve an automated linearisation goal, directly using the plant I/O data. It allows linearisation for an entire operating region and for the entire interested frequency range, the benefits of which cannot be matched by existing methods.

Self-Tuning Control with Fuzzy Rule-Based Supervision for HVAC Applications

Abstract This paper examines the development of fuzzy rule-based supervisors for a self-tuning controller based on the well-known Generalised Predictive Control (GPC) algorithm. First, to compensate for the input non-linearity, a fuzzy rule-based gain scheduling scheme is proposed that makes use of qualitative prior knowledge about changes in the plant gain over the entire operating region. Next, a simple fuzzy rule-based supervisor is proposed that adjusts the tuning knobs of the controller according to expert opinion based on qualitative descriptions of application dependent performance criteria, so that the performance of the control loop will improve gradually. The performance of the combinations of fuzzy rule-based supervisor and self-tuning controller is evaluated using a detailed component-based simulator developed to test building energy management systems.

Modeling of on-state MOSFET operation and derivation of maximum channel field

A novel approach to modeling MOSFET operation in the threshold region is proposed. A two-dimensional Poisson equation is solved analytically and the current continuity equation is solved iteratively in a self-consistent feedback scheme. The I-V characteristics and the profiles of channel field and mobile charge sheet are found over the entire region of device operation. The boundary between linear and saturation regions of device operation is inherently nonexistent in the model. The physical mechanism underlying the high values of maximum channel field E/sub L/ beyond channel pinch-off is highlighted. A simple analytical E/sub L/ model is derived. A comparison of this E/sub L/ model with previous models is made in the context of the experimental data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The effect of the two-dimensional gas degeneracy on the I-V characteristics of the modulation-doped field-effect transistor

A modulation-doped field-effect transistor model for long-channel devices is discussed and results presented. The model takes into account an arbitrary electrons degeneracy condition. It describes the drain current accounting for both the drift and the diffusion components in the constant mobility approximation. The additional effective electric field that arises due to dependence of the subband bottom on concentration is also taken into account. It is shown that at low temperatures (78 K) the degeneracy of the channel electrons plays an important role in the entire region of the device operation including the saturated region of the I-V characteristics.

The no-gain theorem and localized response for the decoupled P -&amp;lt;tex&amp;gt;heta&amp;lt;/tex&amp;gt;power network with active power losses included

In this paper a no-gain theorem for electric power systems is presented using the S- E model based decoupled active power-phase angle P - \theta network, in which each transmission element consists of two branches, representing transmitted power and loss power. The theorem gives necessary and sufficient conditions such that if a power system is perturbed from its normal operating point then the magnitude of the change in active power through either branch of a given transmission line S- E graph is not greater than the sum of the magnitudes of the changes in active power through the sources. These conditions are given as a region of allowable perturbations, which are derived as a set of inequalities. Based on this result we present a proof, valid for systems with losses, of localized steady state response. Specifically, we prove that the effects of a single fault in a given power system diminish as one moves away from the fault, subject only to the constraint that the operating point of the system remains within the allowable regions given by the no-gain theorem. This result is often assumed without proof to be valid in the entire operating region.