Department of Electrical Engineering

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IIT Jodhpur

In this paper, the problem of control design for discrete two-time-scale systems using piecewise constant periodic output feedback is considered. The discrete two-time-scale system is decomposed into a slow and fast subsystem and then a composite controller is designed which provides an output injection gain. The output injection gain has been used to compute periodic output feedback. The method is illustrated by a numerical example.

World University root node

IEEE Region 10 Annual International Conference, Proceedings/TENCON

Periodic output feedback control for two-time-scale discrete systems

The problem of controller design for higher order system via reduced model is investigated. The paper describes a technique for designing a stabilizing controller for the stable higher order system via its reduced order model. The method uses the parameterization of all compensators that stabilize a given plant. It is shown that the compensator which is obtained from reduced model not only stabilizes reduced model but also the higher order system. The developed method is illustrated with numerical example.

Control of higher order system via its reduced model

The paper presents the design of a linear observer for estimation of concentrations of xenon, iodine, and delayed neutron precursors in different regions of a large pressurized heavy water reactor, from measurement of zonal power levels. The nuclear reactor is described by a 56th order nonlinear model. The model is linearized around the rated reactor power. The control law requires the feedback of 56 states while only 14 are measured, thereby necessitating a 42nd order observer. By redefining the state and control variables, the problem of designing the observer of order 42 is decomposed into design problems of fourteen observers of order 3 each, which is comparatively much simpler task. The performance of the observer has been investigated by simulation.

Control of xenon induced spatial oscillations in a large PHWR

The resist debris (RD) formation dependence on beam stepping to beam size ratio in electron beam lithography (EBL) is theoretically and experimentally investigated. The theoretically simulated results show a distinct variation in RD formation as the beam stepping to beam size ratio is varied from 0.5 to 2.0. The corresponding experimental results show a very close resemblance with the simulated results. It is further demonstrated that this undesirable phenomenon of RD formation gives another dimension to look at the problem of proximity exposure effect in EBL and can also be well utilized in certain cases.

Vacuum

Resist debris formation in electron beam lithography

This paper presents a method of model reduction for interval systems using the Padé approximation to allow retention-dominant poles, where the denominator dm(s) of the reduced model is formed by retaining the dominant poles of the original interval system, and the numerator nm (s) of the reduced model is obtained by matching the first r interval time moments of the reduced model with that of the system. A numerical example illustrates the procedure.

International Journal of Modelling and Simulation

Interval system reduction using Padé approximation to allow retention of dominant poles

In this paper a method is presented to design an output feedback compensator for a higher-order system via its reduced-order model. The advantages of the method are two-fold: first is, the states are not required for feedback and secondly when the compensator is placed in the closed loop with the higher-order system it guarantees the closed-loop stability. The method is simple and can be easily implemented. The method is illustrated via a numerical example. © 1998 Elsevier Science Ltd. All rights reserved.

Automatica

A new algorithm for compensator design for higher-order system via reduced model

A variable structure model following control (VSMFC) strategy for the control of most types of industrial robots (according to a classification ofCoiffet 1983) has been presented. For 99% of the robots given in the classification of Coiffet (1983), the dynamics of each link can be represented by a simple model with the nonlinearities and coupling dynamics decoupled from the linear part (Stoten 1985). This facilitates the designer to have a modified VSMFC law, which will maintain sliding mode motion of the error and its derivative, referred to as the representative point (RP), on a user chosen switching line and to drive the RP to the origin of the error plane (error is defined as the difference between the states of the reference model and those of the plant). When in sliding mode the system remains insensitive to parameter variations and disturbances. © 1997 Taylor & Francis Group, LLC.

International Journal of Systems Science

Variable structure model following control for industrial robots

The problem of finding a unit in H∞, i.e., an H∞ function the inverse of which is also HINF, which interpolates to given points in the right-half plane has important applications in a number of feedback stabilization problems, i.e., strong stabilization (stabilization by a stable compensator) and simultaneous stabilization (finding a common fixed compensator which stabilizes a finite set of possible plants). The present paper gives an overview of the interpolation theory and some remarks observed with different mappings used in literature to find a unit in H∞. A new algorithm is also presented to construct a unit in H∞.

Proceedings - IEEE International Symposium on Circuits and Systems

On interpolation with units in HINF

The paper presents the γ-δ Routh approximation for interval systems The interval γ's and δ's are evaluated for the higher order interval systems, and then an rth-order approximant is obtained by retaining the first r, interval γ's, and δ's. A numerical example illustrates the procedure.

IEEE Transactions on Automatic Control

γ-δ Routh approximation for interval systems

In this paper, a method is proposed to design a periodic output feedback controller for discrete two-time scale system. Using explicitly invertible transformation the two-time scale system is converted into the decoupled form which gives a slow subsystem and a fast subsystem. Then by using two stage feedback design a composite controller is designed which provides output injection gain. This output injection gain has been used to compute the periodic output feedback gain. The method does not require the states of the system for feedback. The method is illustrated by numerical examples.