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M. Geiser, M. Heller
This paper addresses the flight dynamics modelling and analysis as well as the basic stabilization study of the SAGITTA Demonstrator in early design stages. A focus is to support the process of control effectors specification with trim, maneuvering and stabilization requirements to reduce the count of design iterations. The SAGITTA Demonstrator, flying testbed of the open innovation project SAGITTA, represents a flying wing configuration, which is characterized by (static) lateral-directional instability in regions of its flight envelope. Regarding the trim curve analysis, it is common practice to investigate the target flight envelope for regions where it is not possible to trim the aircraft due to limited control power. Without the control effectors being specified, the evaluation of the trimmability has to be replaced by the derivation of least control moment needs ensuring trimmability. Besides the mere ability to trim the aircraft in different mission relevant flight conditions, every aircraft has to meet requirements regarding its dynamic charcteristics. For manned aircraft, these requirements are usually derived from the need to guarantee a certain level of flying and handling qualities. In case of autonomous unmanned systems, handling qualities are less relevant but instead requirements driven by the designated mission and hence the maneuver performance come to the fore. In this context, a lower bound for the needed roll control effectiveness to achieve a desired steady state bank angle within a given time will be derived analytically. Typically, an assessment of the stabilization capability is conducted in case of an inherent unstable design by means of nonlinear simulation after control effectors and control laws have (preliminary) been specified. This bears the risk of an undesirable high count of design iterations until an adequate trade-off between the degree of instability and the superior design objectives (as performance, low observability, etc.) will be achieved. In contrast to that approach, a basic stabilization study is accomplished prior to the specification of control effectors or control laws. This study applies a novel methodology balancing the destabilizing moment build-up due to a sideslip disturbance independently against the counteracting control moment development in terms of a worst case approximation of the real effective moment build-up of a controlled aircraft.
Deutscher Luft- und Raumfahrtkongress 2012, Berlin
Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2013
21,0 x 29,7 cm, 8 Seiten
Stichworte zum Inhalt:
stabilization capability study, UAV flight dynamics