Nonlinear Dynamic Feedback Research Articles

The differential algebraic approach in nonlinear dynamical feedback controlled landing maneuvers

A differential algebraic approach is proposed for the synthesis of a dynamical feedback controller regulating a spacecraft smooth descent toward the surface of a planet which exhibits nonnegligible atmospheric resistance. An exact linearization-based controller is synthesized using Fliess' generalized observability canonical form of the controller system. The smooth controlled trajectory is regulated by means of assumed amplitude modulated thrusting capabilities of the spacecraft. The robustness of the regulator is tested in the presence of significant unmodelled spatial changes in the coefficient of atmospheric resistance. A simulation example is provided. >

Robustness of Multivariable Non-Linear Adaptive Feedback Stabilization

Here considered is the stabilizing property of the adaptive nonlinear dynamic feedback control proposed in (Hmamed and Radouane, 1983) for multivariable systems in the presence of uncertainty. A multivariable system is decomposed into a set of single-input subsystems and the second Luenberger canonical form is obtained. This representation is suitable for non-linear adaptive control of unknown systems. The measure of robustness of the proposed scheme is defined in terms of bounds of allowable perturbations such that the stability is preserved. It is shown that the system can always remain stable for a large class of perturbations.

System analysis techniques applied to the forrester world model—part I: Sensitivity analysis

System analysis techniques can be used to study models such as the nonlinear dynamic feedback World Dynamics Model developed by Jay W. Forrester. Through application of sensitivity analysis it was discovered that the capital-investment parameters of the Forrester model exert the greatest influence on model behavior. Due to high sensitivity of these variables, careful inspection of their function and continual updating of their interrelations with other parameters must be performed to insure model accuracy. In many cases perturbation of a multiplier produces the same relative effect as an equal percentage change in one of the parameters designed as control variables. A change in the relation of the multiplier and its dependent variable offers an alternative to the direct control policies suggested by Forrester.