Engineering topics

Vidyasagar, M.

Publications and source records attributed to Vidyasagar, M..

5 records

NASA NTRS1990

A comparison of different models for beam vibrations from the standpoint of control design

Different models for beam vibrations are analyzed from the standpoint of designing finite-dimensional controllers to stabilize the beam vibrations. A distributed system described by an undamped Euler-Bernoulli equation cannot be stabilized by any finite-dimensional controller, i.e., any controller which can be described an ordinary differential equation with constant coefficients. If viscous damping is included, a similar problem occurs in that all the poles can not be moved to the left of a given vertical line. These negative results should be interpreted as a commentary on the limitations of these models, rather than on the control of real beams. If a Rayleigh damping model is used, a finite-dimensional controller may be designed to move the closed loop system poles essentially as far to the left in the complex plane as desired. This result will also hold for certain hysteresis damping models. This has implications for the settling time of the vibrations.

Morris, K. A.↗

NASA NTRS1987

Parametric conditions for stability of reduced-order linear time-varying control systems

Using a single framework, parametric conditions are derived which encompass those for both local and global BIBO stability of a linear multivariable discrete-time reduced-order time-varying control system. These conditions indicate that the system will be BIBO stable if the norm of the system-parameter error matrix is bounded by an l exp 1 function superimposed on an l exp infinity function.

Ma, C. C. H.↗

NASA NTRS1987

Direct globally convergent adaptive regulation of stable multivariable plants

A simple globally convergent direct methodology for adaptive regulation of stable plants, assuming convergence of the parameters, is presented. The development is strictly in terms of the input-output representations and is based on the stable coprime factorization approach.

Ma, C. C. H.↗

NASA NTRS1986

Fault-tolerant control of large space structures using the stable factorization approach

Large space structures are characterized by the following features: they are in general infinite-dimensional systems, and have large numbers of undamped or lightly damped poles. Any attempt to apply linear control theory to large space structures must therefore take into account these features. Phase I consisted of an attempt to apply the recently developed Stable Factorization (SF) design philosophy to problems of large space structures, with particular attention to the aspects of robustness and fault tolerance. The final report on the Phase I effort consists of four sections, each devoted to one task. The first three sections report theoretical results, while the last consists of a design example. Significant results were obtained in all four tasks of the project. More specifically, an innovative approach to order reduction was obtained, stabilizing controller structures for plants with an infinite number of unstable poles were determined under some conditions, conditions for simultaneous stabilizability of an infinite number of plants were explored, and a fault tolerance controller design that stabilizes a flexible structure model was obtained which is robust against one failure condition.

Razavi, H. C.↗

NASA NTRS1974

Maximum power transfer in n ports with passive loads

The problem of drawing maximum power from an n port by suitably terminating it with another passive n port is studied. Methods are derived for determining sets of passive impedance matrices which are 'optimal' in the sense that they draw maximum power from a given n port. It is shown that, in all nontrivial cases, if there exists any (passive or otherwise) optimum-load impedance matrix, then there exist, in fact, infinitely many passive optimum-load impedance matrices.

Vidyasagar, M.↗