Adaptive Control Of Non Minimum Phase Systems

Author : Anna L. Hartman
Publisher :
ISBN 13 : 9781303754661
Total Pages : 52 pages
Book Rating : 4.7/5 (546 download)

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Download or read book Adaptive Control of Nonminimum Phase Systems Using Sensor Blending with Application to Launch Vehicle Control written by Anna L. Hartman and published by . This book was released on 2011 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research project was to investigate the use of a simple direct adaptive controller in the guidance of a large, flexible launch vehicle. The adaptive controller, requiring no on-line information about the plant other than sensor outputs, would theoretically be a more robust candidate controller in the presence of unmodeled plant dynamics than a model-based fixed gain linear controller. NASA's seven-state FRACTAL academic model for ARES I-X was employed as an example launch vehicle on which to develop the controller. To better understand the dynamic issues, a simplified model was analyzed which incorporated the inherent instability and the nonminimum phase nature of the launch vehicle: an inverted pendulum with an attachable slosh tank. Controllers were formulated for this simplified plant with slosh dynamics using control algorithms developed on a reduced-order model consisting of the rigid body dynamics without slosh. The controllers must reject three different persistent input disturbances: persistent pulse, step, and sinusoid. It was assumed, based on the original optical encoder sensor setup on the pendulum, that only position feedback was directly available, and that rates would have to be derived or estimated. For comparison, a fixed gain linear controller was developed using the well-known Linear Quadratic Gaussian methodology using state estimation to obtain rate estimates and incorporating disturbance accommodation. For a stable adaptive controller, we used direct adaptive control theory developed by Balas, et al. For this theory we needed CB>0 and a minimum-phase open-loop transfer function. A new transmission zero selection method was employed to develop a blended output shaping matrix which would satisfy these conditions robustly. Approximate differentiation filters were used to obtain rates for the adaptive controller and added a disturbance rejection loop. Following the work on the pendulum, the same method was applied to develop an adaptive controller for the FRACTAL launch vehicle model. An adaptive controller stabilizes a rigid body version of FRACTAL; however, the same controller does not stabilize the full order FRACTAL model at this time.