Department of Electrical Engineering

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IIT Jodhpur

Effects of trace levels of Ge transferred to Si surfaces during thermal processing of SiGe wafers are presented here. Si wafers were coprocessed in an oxidation furnace with SiGe relaxed graded buffer layers grown on Si. Total X-ray fluorescence measurements on Si wafers showed Ge concentrations in varying degrees depending on oxidation temperature, time, and the number of coprocessed SiGe wafers. The Ge concentration level increases with increase of oxidation time, temperature, and SiGe wafer quantity. It was also observed that the furnace shows "memory" of the process during subsequent process runs. A chlorine-based purge of the oxidation tube after processing SiGe wafers helps reduce the Ge concentration remarkably. Metal oxide semiconductor capacitance and gate leakage characterization were used to evaluate the effects of transferred Ge on the gate oxide. The interface state density is marginally higher on Si wafers with transferred Ge. © 2003 The Electrochemical Society. All rights reserved.

World University root node

Electrochemical and Solid-State Letters

Analysis of trace levels of Ge transferred to Si wafer surfaces during SiGe wafer processing

In this paper, an improved lattice filter structure is presented to model a two-dimensional (2-D) signal such as an image. The proposed structure generates a forward and a backward prediction error field at each stage of lattice structure, unlike other lattice structures [1][11] wherein three or more backward prediction error fields are generated at each stage. This method is computationally efficient and possesses all the advantages of lattice algorithm. Simulation results show that the proposed lattice method results in better compression with lower computational cost than other lattice methods in literature [17].

IEEE Region 10 Annual International Conference, Proceedings/TENCON

A lattice algorithm for lossless image compression using half-plane support data

In this paper a new algorithm for discrete-time sliding mode control using only output samples is proposed. It is shown that the output feedback gain can be directly obtained using the reaching law of discrete-time sliding mode control. The main contribution of this work is that instead of using the system states, the output samples are used for designing the controller. © 2003 EUCA.

European Control Conference, ECC 2003

Discrete sliding mode control using fast output sampling feedback

The feasibility of integrating the RF MEMS switches in space and wireless communication systems has generated tremendous interest in related design, fabrication and characterization methodologies. The space applications make long term reliability of the devices a very pertinent issue and involves both the process and device characterization. In this paper we describe the experimental setup and measurement results on RF MEMS switches fabricated for DC to 30 GHz applications. The on-wafer experimental setup, based on standard manual microprobe station provides dual pulse actuation voltage waveforms with programmable period and amplitude, ranging from 10-5 to 1 sec and 0-200 volts respectively. The usefulness of the dual-pulse testing is demonstrated by the minimal charge generation in the dielectric layer and capacitance measurements with negligible variations over long measurement periods. © 2003 IEEE.

DTIP 2003 - Design, Test, Integration and Packaging of MEMS/MOEMS 2003

On-wafer electro-mechanical characterization of silicon MEMS switches

A systematic procedure for design of variable structure model following load frequency controller for a single{area power system has been presented. The variable structure model following control (VSMFC) technique presented in this paper not only guarantees invariance to a class of parameter variations and disturbances but also possess other attractive features of variable structure systems (VSS) like robustness to unknown disturbances, simplicity in design, and reduced order dynamics when in sliding mode. The simulation result of the variable structure model following control strategy to load frequency control is presented by changing all parameters by 30% to 50% from their nominal values. These results show that systems performance is robust to parameter variations and disturbances. © 2003 EUCA.}, author_keywords={Load-frequency control; Power system control; Variable structure model following control; Variable-structure system}, keywords={Controllers; Electric control equipment; Electric frequency control; Electric load management; Electric power system control; Press load control, Load frequency controllers; Load-frequency control; Nominal values; Power system controls; Systems performance; Unknown disturbance; Variable structure model; Variable structure system, Structural design}, correspondence_address1={Patre, B.M.; S.G.G.S. College of Engineering and TechnologyIndia; email: bmpatre@yahoo.com}, publisher={Institute of Electrical and Electronics Engineers Inc.}, isbn={9783952417379}, language={English}, abbrev_source_title={Eur. Control Conf., ECC}, document_type={Conference Paper}, source={Scopus},

Robust variable structure model following load frequency controller

The paper presents a new algorithm for a variable structure model following controller (VSMFC) design for discrete time systems using a fast output sampling technique. The reaching law approach is used to guarantee the sliding mode motion. This methodology is easy to implement since the method is based on output feedback. It is shown that the proposed fast output sampling variable structure model following controller (FOS VSMFC) gives the same results as obtained by state feedback VSMFC. To demonstrate the design technique a VSMFC is designed for the tip position control of a single flexible link. The simulation results show the effectiveness of the proposed method.

International Journal of Control

Variable structure model following controller using non-dynamic multirate output feedback

The paper presents discrete time sliding mode control (DSMC) for permanent magnet (PM) stepper motor which is known to be differentially flat system. Discretization of continuous time model of the stepper motor has been carried out and linearizing outputs are selected. Discrete state variables and control inputs are obtained in terms of linearizing outputs and their higher order differences. Linearized equations for the system are thus obtained and auxilary control is designed using reaching law approach. Then the actual control is obtained in terms of flat output and state variables. It is shown that system states reach to zero from given initial conditions. © 2003 EUCA.

Discrete sliding mode control of permanent magnet stepper motor using flatness property

A method of designing an output feedback compensator for vibration control of a flexible smart cantilever beam based on its reduced order model is presented. By retaining the first two vibration modes the state space model is obtained from a smart structure Finite Element Model (FEM). A reduced order model is obtained by retaining the first vibration mode. It has been shown that an output feedback compensator can be obtained for the smart structure model from the state feedback gains designed from its reduced order model. It has also been shown that if the compensator is placed in the closed loop with the higher order system, it guarantees the closed loop stability. As the states are not needed for feedback, the method is simple and can be easily implemented.

Systems Science

Design of output feedback compensator for smart structure model via reduced order model

The paper presents the design of state feedback control for a large pressurized heavy water reactor (PHWR) by developing a reduced-order model for the same. The nonlinear mathematical model of the PHWR is linearized around an operating point corresponding to full-power operation of the reactor. The linear model has 14 inputs and outputs each and 56 states. Application of the reduction technique leads to a simplified model characterized by only 14 states. This 14th-order simplified model is used to design a linear quadratic regulator, and state feedback gains for the original 56th-order system are obtained without any significant difficulty. The transient performance of the closed-loop system is tested by simulation of the original nonlinear model of the PHWR.

Nuclear Technology

Spatial control of a large PHWR via reduced model

A robust fast output sampling sliding mode control (FOSSMC) method for discrete-time systems with uncertainty is presented. Recently a FOSSMC was designed for a constant discrete-time system, however, this control law does not ensure the robustness of the system to parameter uncertainty and external disturbances. The authors present a FOSSMC that for known parameter variations and external disturbances does guarantee the robustness of the sliding mode motion.