Controller performance improvements for reentry through Earth's atmosphere for low L/D spacecraft /
Development of space-based industry created on the International Space Station is limited by reentry through Earth's atmosphere. The Lyapunov method is applied to improve reentry controller performance through Earth's atmosphere. A Predictor Corrector controller (PCCPA) derived from the...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2001.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=726103001&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Development of space-based industry created on the International Space Station is limited by reentry through Earth's atmosphere. The Lyapunov method is applied to improve reentry controller performance through Earth's atmosphere. A Predictor Corrector controller (PCCPA) derived from the Apollo program reentry guidance is the baseline against which candidate controllers are compared. Controllers designed to guide the reentry vehicle to within 1 nm of the final target while satisfying a 51.55 BTU/ft²/sec heat rate constraint and a 4 g load constraint are evaluated in a six degree of freedom simulation environment. Three Lyapunov controllers developed in the initial design phase are subjected to variations in vehicle L/D. Controller gains are iteratively determined to satisfy reentry requirements for nominal reentry. However, different controller gain sets have different levels of performance robustness. Only one controller, the Lyapunov Controller, Gain Set 3, satisfies reentry requirements over a larger range of L/D variations than the PCCPA. In the final design phase, three hybrid reentry controllers are developed by combining Lyapunov based guidance routines with PCCPA transition logic and are evaluated for variations in vehicle L/D, weight and initial flight path angle (γ₀). The Hybrid Predictor Corrector/Lyapunov Controller #1 demonstrates the greatest performance robustness and satisfies all reentry requirements over a larger range of L/D, weight, and γ₀ variations than the PCCPA. The hybrid controller, #3, meets all reentry requirements for a larger range of L/D variations than the PCCPA. The hybrid controller, #2, fails to outperform the PCCPA. All seven reentry controllers are linearized at four operating points and linear robust control analysis techniques are employed to quantify controller performance. Two robustness parameters,[], a guaranteed domain of stability, and J[w], a measure of system performance to the worst possible direction of the unit initial condition vector, are evaluated for each controller at all operating points. [] has greater flexibility than J[w] because it can be evaluated for unstable linear controllers that are stabilizable and [] can be evaluated for systems that experience control position and rate saturation. [] also forecasts controller robustness and accurately indicates that the HPCLC1 is the most robust controller considered in this study. |
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| Item Description: | Vita. "Major Subject: Aerospace Engineering". |
| Physical Description: | xix, 153 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 102-107). |