Accession Number : ADA338998

Title :   Autonomous Frequency Domain Identification: Theory and Experiment

Corporate Author : JET PROPULSION LAB PASADENA CA

Personal Author(s) : Yam, Y. ; Bayard, D. S. ; Hadaegh, F. Y. ; Mettler, E. ; Milman, M. H.

PDF Url : ADA338998

Report Date : 15 APR 1989

Pagination or Media Count : 217

Abstract : The analysis, design, and on-orbit tuning of robust controllers require more information about the plant than simply a nominal estimate of the plant transfer function. Information is also required concerning the uncertainty in the nominal estimate, or more generally, the identification of a model set within which the true plant is known to lie. The identification methodology that was developed and experimentally demonstrated makes use of a simple but useful characterization of the model uncertainty based on the output error. This is a characterization of the additive uncertainty in the plant model, which has found considerable use in many robust control analysis and synthesis techniques. The identification process is initiated by a stochastic input u which is applied to the plant p giving rise to the output y. Spectral estimation (h = Puy/Puu) is used as an estimate of p and the model order is estimated using the product moment matrix (PMM) method. A parametric model P is then determined by curve fitting the spectral estimate to a rational transfer function. The additive uncertainty Dm = p - P is then estimated by the cross-spectral estimate delta = Pue/Pun where e = y - Y is the output error, and Y = Pu is the computed output of the parametric model subjected to the actual input u. The experimental results demonstrate the curve fitting algorithm produces the reduced-order plant model which minimizes the additive uncertainty. The nominal transfer function estimate P and the estimate delta of the additive uncertainty Dm are subsequently available to be used for optimization of robust controller performance and stability.

Descriptors :   *MATHEMATICAL MODELS, *SPACE SYSTEMS, *STRUCTURAL ANALYSIS, *FREQUENCY DOMAIN, ALGORITHMS, SOFTWARE ENGINEERING, OPTIMIZATION, ADAPTIVE CONTROL SYSTEMS, PARAMETRIC ANALYSIS, TRANSFER FUNCTIONS, AUTOMATION, PLATFORMS, SYSTEMS ANALYSIS, CONTROL THEORY, ONLINE SYSTEMS, FLEXIBLE STRUCTURES, MANNED SPACECRAFT, UNMANNED SPACECRAFT, CURVE FITTING.

Subject Categories : Unmanned Spacecraft
      Manned Spacecraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE