This research is concerned with the flight dynamic, pitch flight control and flying
qualities assessment for the reference BWB aircraft. It aims to develop the
longitudinal control laws which could satisfy the flying and handing qualities
over the whole flight envelope with added consideration of centre of gravity (CG)
variation.
In order to achieve this goal, both the longitudinal stability augmentation system
(SAS) and autopilot control laws are studied in this thesis. Using the pole
placement method, two sets of local Linear-Time-Invariant (LTI) SAS controllers
are designed from the viewpoints of flying and handing qualities assessment
and wind disturbance checking. The global gain schedule is developed with the
scheduling variable of dynamic pressure to transfer gains smoothly between
these two trim points. In addition, the poles movement of short period mode with
the varying CG position are analysed, and some approaches of control system
design to address the problem of reduced stability induced by CG variation are
discussed as well. To achieve the command control for the aircraft, outer loop
autopilot both pitch attitude hold and altitude hold are implemented by using the
root locus method.
By the existing criteria in MIL-F-8785C specifications being employed to assess
the augmented aircraft response, the SAS linear controller with automatic
changing gains effectively improve the stability characteristic for the reference
BWB aircraft over the whole envelope. Hence, the augmented aircraft equals to
a good characteristic controlled object for the outer loop or command path
design, which guarantee the satisfactory performance of command control for
the BWB aircraft.
The flight control law for the longitudinal was completed with the SAS controller
and autopilot design. In particular, the SAS was achieved with Level 1 flying and
handing qualities, meanwhile the autopilot system was applied to obtain a
satisfactory pitch attitude and altitude tracking performance.
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/7423 |
| Date | 02 1900 |
| Creators | Zhu, Yan. |
| Contributors | Whidborne, James F. |
| Publisher | Cranfield University |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Masters, MSc by Research |
| Rights | © Cranfield University 2012. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. |
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