Natarajan Narasimhamurthi

Analysis, design, and implementation of an AC bridge for impedance measurements

The paper reviews the digital AC bridge. A more accurate and thorough analysis of the bridge is presented. Based on the analysis a simple adaptive algorithm is proposed in order to ensure fast conversion. In addition, a new design of the bridge, based on the TMS 320C25, is given. The system is implemented with the Dalanco Spry model 25 DSP board, on a software system designed whereby an IBM PC host computer provides control of the bridge. Experimental results are presented. >

Estimating the parameters of a sinusoid sampled by a clock with accumulated jitter

This paper provides a state-space based approach to determining the parameters of a sinusoid that is sampled by a clock with accumulated timing-jitter. The problem is formulated as a standard state estimation problem and two solutions are provided: one that does not depend on the statistics of the timing-jitter; the other is based on the second-order statistics of the timing-jitter. Explicit error bounds are provided for the absolute value, mean absolute valve and mean squared value of the error estimated parameters are provided.

On-Line Real Power Scheduling in Marginally Secure Power Systems

In this paper an efficient algorithm is derived for scheduling real power in systems where the phase angles across lines are not small and, hence, have to be taken into consideration. The approach is based on assigning a cost to the loading on the transmission system. The cost lunction chosen in this paper simplifies the problem of scheduling to a load-flow type problem so that when the solution to the load- flow problem is obtained, the optimal dispatch solution is also automatically obtained. Thus there is no need to alternate between a load-flow step and an optimization step and this results in considerable computational savings.

STARLITE : A steering autonomous robot's lane investigation and tracking element

The problem of determining the offset to lane markings is an important one in designing vision-based automotive safety systems that operate on structured road environments. The lane offset information is critical for lateral control of the automobile. In this paper, we investigate the use of this information for an autonomous robots lane-keeping task. We employ a deformable template-based algorithm for determining the location of lane markings in visual images taken from a side-looking camera. The matching criteria involves a modification of the standard signal-to-noise (SNR) ratio-based matched filtering criteria. A KL-type color transformation is used for transforming the RGB channels of the given image onto a composite color channel, in order to eliminate some of the noise. The standard perspective transformation is used for transforming the offset information from image coordinates onto ground coordinates. The resulting algorithm, named STARLITE is robust to shadows, specular reflections, road cracks, etc. Experimental results are provided to illustrate the performance of STARLITE and compare its performance to the AURORA algorithm, and the SNR-based matched filter.

Extraction of handwritten information in geometrically distorted documents

In this paper, a technique for extracting the distortion parameters in filled-in forms is presented. The technique determines the transformations that is required to convert a filled-in form to match a known master and then extracts filled-in information. The method involves determining corresponding lines and keypoints between the master and the filled-in form and using the correspondence to determine the appropriate transformation. The correspondence problem is solved using results from geometric hashing voting scheme.

Shape determination from intensity images-a new algorithm

A novel algorithm for the determination of surface shapes from intensity measurements is presented. The proposed model allows the estimation of the normals at any point on the surface and of the depth at any point in the image plane along the viewer (camera) direction. Simple shape descriptors for characterizing most developable surfaces are derived. It is shown that the principal curvatures of the surface are simply eigenvalues of the restriction of the shape matrix to the tangent space. The proposed algorithm allows incorporation of prior information obtained from stereopsis and other vision processes. Tests with intensity images have shown the algorithm to be convergent, robust, and accurate.<<ETX>>

Model reduction by state truncation with applications to compensator reduction

In this paper, we consider the model reduction of stable transfer functions given by n(s) = C(s-A)-1B, C ¿ Rm×n, A ¿ Rn×n, B ¿ Rn×p and study the reduced order models obtained by truncating some states. For this class of models, we show that the reduced order model is stable if an auxiliary transfer function has a stable inverse. We introduce a subclass of such reductions called positive-real reduction which preserves stability and show that the balanced reduction [1, 2] is a special case of this. We also provide bounds on the error at each frequency. We apply the reduction procedure to the reduction of feedback controllers and show that the reduction is possible if the order of the controller exceeds that of the plant.

Inequalities between L-2 and L-infinity norms of strictly proper stable transfer functions

In this paper we shall derive two inequalities between the L2 and L¿ norms of stable transfer functions defined by H(s) = C(sI - A)-1B and show that ||H||F ¿ ¿2Tr(-A)||H||¿ and for a single input or single output transfer function ||H||2 ¿ 1.172(d1 2 + 2d2)1/4 ||H||¿ where det(sI - A) = sn + d1sn-1 + d2sn-2 + ...

Transient stability determination using differential inclusions

This paper formalizes the ideas presented in [1]. It is shown that, the power system dynamics can be modeled as dx/dt ¿ G(x) (which we call differential inclusion) where x is a 2-vector and G() is a point to set mapping. The concept of fuzzy trajectories is defined as the solution to the above equation. The structure of G(x) provides as with a simple characterization of the solution.