Date:

Monday, March 3rd, 2003

Speaker:

Mark J. Balas

Affiliation:

CU-Boulder

e-mail:

mark.balas@colorado.edu

Title:

Adaptive Disturbance Control With Applications to a Deployable Optical Telescope (Or How a Mathematician Survived in the Dark World of Engineering)

Abstract:

Precision structures operated at nanometer accuracy are often at the mercy of persistent low-level disturbances, which cannot be directly measured. In space, these disturbances result from small imbalances in the very reaction wheels that control the attitude and pointing of the structure, as well as vibrations from the spacecraft cooling system and other on-board excitations. In ground-based experiments, there are even more opportunities for disturbances to leak into the structure, e.g. air-handling machinery, floor vibration, and gravity off-loading devices; such disturbances compromise the success of any experiment where precision interferometry is being demonstrated.

Estimation and control of persistent disturbances has been a substantial part of our research effort in aerospace structure control at the University of Colorado at Boulder since 1990 [1]. In applications of adaptive techniques for aerospace structures, we have used Direct Model Reference Adaptive Control theory for Distributed Parameter and Large-Scale Systems, developed by Balas and Wen in [8]-[9] and Balas in [2], for its simplicity and power in handling large-scale structural dynamics, as demonstrated in [3]-[4]. However the need for an adaptive approach for persistent disturbances has driven some of our current work in the direction of [5]-[13].. This has had immediate application to the research being done on the Deployable Optical Telescope experiment at AFRL-Kirtland where the laboratory vibration environment is very poorly known and disturbances capable of compromising the experiment are clearly present. In our recent work at AFRL-Kirtland, we have applied the results of [10]-[13] to adaptively estimate unknown persistent disturbances and remove them as part of the on-line structure control effort in the ground-based demonstration of the AFRL Deployable Optical Telescope.

Now that all that is said, what I want to do in this talk is give you an idea of what control is all about in the engineering world. And to visit some mathematical problems in the context of this wandering. I was going to call this "My Life in the Bush of Ghosts" but the title was already taken long ago in a novel by Amos Tutuola.

References

1) M. Balas, Active Control of Persistent Disturbances in Large Precision Aerospace Structures, Advances in Optical Structure Systems, J. Breakwell, V. Genberg, and G. Krumweide, eds., SPIE, Vol 1303,1990