Department of Electrical Engineering

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IIT Jodhpur

In this paper a method is proposed to design a robust controller for uncertain system using fast output sampling technique. An LMI approach is used to design robust feedback for the uncertain system. The fast output sampling control allows the realization of the robust state feedback gain simultaneously for family of linear models. But in practice there are two problem with exactly realizing this state feedback i.e. poor error dynamics and noise sensitivity. Hence the problem is further posed as LMI problem to overcome the undesired effects. The method does not require the states of the system for feedback. The method is illustrated by a practical system example.

World University root node

Proceedings of the IEEE International Conference on Industrial Technology

Robust controller design for a pressurized heavy water reactor

In electron beam lithography (EBL), by way of underexposure or underdevelopment, the formation of tiny resist fragments called resist debris (RD) over the exposed pattern areas reflects proximity effects (PE). The theoretically simulated results and corresponding experimental results discussed clearly indicate that the fragment distribution predicts both intrapattern and interpattern PEs of the EBL. The fragment spacing and size is indicative of electron beam size and beam to beam stepping distance used for the pattern exposure.

Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures

Resist debris formation and proximity exposure effect in electron beam lithography

The paper presents the design of piecewise constant periodic output feedback control for a discrete-time singularly perturbed system resulting from the discretization of a continuous-time standard singularly perturbed system. By a suitable linear transformation of state variables, the given continuous-time singularly perturbed model is converted into a block triangular form in which the fast subsystem is decoupled. The discrete-time model corresponding to the transformed model also exhibits a two time scale property if sampling period is larger than the parameter e. Now, an output injection matrix is found that stabilizes the slow subsystem. The periodic output feedback gain is then calculated only for the slow subsystem and the same for the fast subsystem is set equal to zero. Finally the periodic output feedback gain for the composite system is obtained using the periodic output feedback gains computed separately for the slow and fast subsystems. An approach has been suggested whereby the determination of periodic output feedback gain for the slow subsystem can be converted into an optimization problem. By minimization of the suggested performance index the closed loop system behavior is improved. The method has been applied to a large pressurized heavy water reactor (PHWR) for control of xenon-induced spatial oscillations. A particular grouping of state variables has been suggested for obtaining the model in standard singularly perturbed form. The periodic output feedback gain is then calculated. The efficacy of control has been demonstrated by simulation of transient behavior of the nonlinear model of the PHWR. Index Terms-Large heavy water reactor, periodic output feedback, singular perturbation, spatial control. © 2000 IEEE.

IEEE Transactions on Nuclear Science

Spatial control of a large PHWR by piecewise constant periodic output feedback

In this paper, the problem of pole placement by periodic output feedback is presented. The poles of the discrete time control system could be assigned arbitrarily (with the natural restriction that they should be located symmetrically with respect to the real axis), provided that the number of gain changes is not less than the system's controllability index. Linearized models of aircraft are obtained at 10 different flight conditions and controller is designed for controlling the longitudinal dynamics of aircraft using periodic output feedback. The family of 8 plants, representing the longitudinal dynamic, is also simultaneously stabilized. The controller consisted of solely of gain elements and did not include a dynamical system, such as an observer, hence easier to implement on line.

Control of longitudinal dynamics of aircraft using periodic output feedback

The challenge in the endpoint control of flexible manipulators is of obtaining an exact model of the nonlinear flexible system and then simulating it for further analysis. But being an infinite dimensional they pose problems in terms of predicting the behaviour and also exact mathematical representation. This problem of obtaining exact model can be solved if the behaviour of the flexible link system can be represented by a neural network, which would help further simulation, analysis and control thus eliminating the requirement of the exact mathematical representation of the system.

Modeling and identification of flexible link using neural networks

In this paper a method is presented to design an output feedback compensator for a higher order discrete time 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.

Output feedback compensator design for higher order discrete system via reduced model

The paper presents the design of spatial control system of a large Pressurized Heavy Water Reactor(PHWR) with the constraint that the closed loop system be stable even if one output sensor has failed. Linear state models are obtained corresponding to the normal operating condition and different failure modes of the reactor. Each model is found to possess two time scale property. Application of a standard singular perturbation approach decouples the fast varying modes which are ignored to eliminate the stiffness. Thus a reduced model is obtained for each operating mode of the reactor. Convex programming is used to search for an output injection gain which stabilizes all reduced models simultaneously. This output injection gain is the realized simultaneously in all operating modes by a controller based on periodic output feedback.

Approach to the design of fault-tolerant spatial control system for a large PHWR

Fabric classification plays an important role in textile industry. Fabrics classification and determining the blend composition involves tedious work and time consumption. Knowledge based systems like Artificial neural networks may be successfully employed to over come such problems. In this paper a method is presented to classify and determine blend composition using neural networks. By inputting the mechanical properties measured from Kawabata evaluation system to the neural network, one can get the desired results. A comparative study in the results is made between the backpropagation and Radial basis function algorithms to test the suitability of the same for the proposed textile application.

Neural network based fabric classification and blend composition analysis

In this paper, we consider design of stabilizing controller for linear structured uncertain discrete two-time-scale system which can be represented by interval matrix representation. The slow and fast uncertain subsystems are obtained using interval arithmetic. It is shown that a state feedback and output feedback control law designed to stabilize the slow uncertain subsystem will stabilize the original full order system, provide that fast uncertain subsystem is asymptotically stable. The results obtained are illustrated by a numerical example.

IEEE Region 10 Annual International Conference, Proceedings/TENCON

On the design of stabilizing controller for uncertain two-time-scale discrete systems

In the paper a method is proposed to design a periodic output feedback controller for a singularly perturbed discrete system. A state feedback controller designed from the singularly perturbed discrete system has been used to compute 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 a practical example of a fifth order steam power system. © IEE, 1999.