Dhemetrios Boussalis

Noncolocated structural vibration suppression using zero annihilation periodic control

The zero annihilation periodic (ZAP) controller is applied to the problem of vibration control of a noncolocated flexible structure. It is shown that even though the transfer function is nonminimum-phase, a plant inverse controller can be designed which elicits a deadbeat closed-loop response. The transfer function under investigation arises from a noncolocated actuator/sensor configuration used on the ASTREX flexible structure at USAF/Phillips Laboratory. Several simulation examples are given to demonstrate the ZAP control method. As expected from the theory, the closed-loop response is deadbeat, and the vibrations are damped instantaneously.<<ETX>>

Multivariable neural network vibration control based on output feedback

This paper presents a multivariable direct adaptive control concept for vibration suppression in flexible space structures. The adaptive controller is implemented by a combination of forward neural networks. Tuning of the controller gains (neural network synaptic weights) takes place in real-time and is performed by a nonlinear least squares algorithm. The control scheme is based on output rather than state feedback, an approach motivated from the fact that, in most applications, the system state is not readily available. The results are demonstrated by simulation using a high fidelity 6-input 6-output dynamic model of the testbed at the JPL/USAF-PL Large Spacecraft Control Laboratory.<<ETX>>

Figure Control Concepts For Segmented Reflector Telescopes

This paper presents an overview of the control analysis activity related to the development of figure control technologies for large space telescopes with precision segmented, actively controlled, primary reflectors. The issues addressed here involve the development of geometric and dynamic models, characterization of figure estimation errors and optimal sensor placement, and the development of quasi-static and dynamic control concepts. The most significant simulation results obtained during an extensive performance evaluation are also presented.

Adaptive spacecraft attitude control with application to space station

The attitude control problem for Earth orbiting platforms is considered. A model reference adaptive control law has been developed that stably maintains spacecraft attitude at the torque equilibrium under the influence of large mass variations and external disturbances. The result is demonstrated through simulation using the nonlinear dynamic model of the space station Freedom.<<ETX>>

Neural network based adaptive control of nonlinear plants using random search optimization algorithms

A method for utilizing artificial neural networks for direct adaptive control of dynamic systems with poorly known dynamics is presented. The neural network weights (controller gains) are adapted in real time using state measurements and a random search optimization algorithm. The results are demonstrated via simulation using two highly nonlinear systems.<<ETX>>

Modeling And Stability Analysis Of A Class Of Flexible Space Structures

Stability in the Lyapunov sense of flexible space structures under a decentralized control scheme is considered. Properties of the local subsystems, associated controllers and interconnection patterns are utilized to develop Lyapunov functions for the large-scale system. The results are sufficient conditions for exponential stability.