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Ramnath, R. V.

Publications and source records attributed to Ramnath, R. V..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Nonlinear attitude dynamics of satellites

A study of predicting the rotational motion of a rigid body satellite orbiting the earth under the influence of external torques is presented. The attitude motion in response to external torques is formulated as a perturbation from a nominal torque-free case; the equations of motion are parameterized by the ratio of the orbital and attitude frequencies. The independent variable time is extended into a space of higher dimension by using new fast and slow scales. The theory is applied for predicting the attitude dynamics of an asymmetric rigid-body satellite.

Ramnath, R. V.↗
NASA NTRS1978

On the attitude motion of an orbiting rigid body under the influence of gravity gradient torque

An investigation is made of the rotational motion of a rigid body orbiting the earth, under the influence of the geogravity-gradient torque. The attitude dynamics are formulated as perturbations from a nominal case. The perturbed equations are solved asymptotically, by the multiple scales technique. The independent variable, time, is extended into a space of higher dimension by means of new scales, fast, slow, etc. Integration of the equations is carried out separately in the new variables. The rapid and slow aspects of the attitude dynamics are systematically separated, resulting in a more efficient computer implementation and enhanced physical insight. The theory is applied to predict the attitude dynamics of an asymmetric rigid body satellite. A comparison is made of the maximum errors as the step size increases as predicted by the multiple scales solution and direct numerical integration. An improvement in computational speed of an order of magnitude is demonstrated.

Tao, Y. C.↗
NASA NTRS1973

A new approach to the design of time varying control systems with application to the space shuttle booster

A general approach toward the analysis and design of closed loop control for slowly time-varying linear systems was investigated. The approach is by the method of generalized multiple scales, in which slow and fast dynamics are systematically separated by employing different clocks which measure time at varying rates. The clocks, which are necessarily nonlinear functions of time, so that the system dynamics are asymptotically invariant with respect to the new time scale. A transfer function relating the output to the input for general linear slowly time-varying systems is developed and represents the actual system under certain conditions. The clock functions are shown to satisfy an algebraic characteristic equation and can be determined in general in terms of the coefficients.

Ramnath, R. V.↗