The continuing drive to extend the 24 hour, all-weather operational capabilities of helicopters is demanding more advanced flight control systems with higher levels of feedback gain to achieve the desired command tracking and disturbance rejection performance requirements. Achieving robust high gain feedback in helicopter flight control system design is problematic, however, because the rotor and fuselage are dynamically coupled in the frequency range of the desired closed-loop crossover, and the rotor thus becomes an integral part of the dynamic system that has to be controlled. The rotor system is also the dominant source of inter-axis coupling and dynamic uncertainty. The concept of Rotor State Feedback (RSF) is intended to augment conventional rigid-body feedback with measurements of the rotor dynamics to allow explicit and robust control of the coupled body/rotor modes at higher bandwidths than would otherwise be achievable. To this end, DERA, GKN Westland Helicopters and the University of Bristol have been conducting an experimental evaluation of RSF controllers using the University's Experimental Rotor Rig Facility and have also been applying modern multivariable controller design techniques to better exploit the additional degrees of freedom. The tests have included frequency sweeps and small, moderate and large amplitude step responses, with the results being related to full-scale in the context of ADS-33D flying qualities requirements. The programme has proven: The Rotor Rig exhibits coupled body/rotor dynamics and model uncertainty representative of the Westland Lynx. The Rotor Rig provides a flexible environment for experimental testing of high bandwidth controllers. High bandwidth control requires RSF or sufficient dynamic compensation to estimate the rotor states. Up to a 50 % increase in closed-loop bandwidth can be gained via RSF with respect to conventional limited authority rigid-body feedback. Robust performance is maintained in the presence of 30 % on-axis model uncertainty and 100 % off-axis model uncertainty. It is thus concluded that the concept of Rotor State Feedback yields potentially significant advances in robust high bandwidth control.
Experimental evaluation of high bandwidth helicopter flight control system designs exploiting rotor state feedback
Experimentelle Bewertung der Entwicklungen von Hubschrauber-Flugleitsystemen hoher Bandbreite unter Nutzung der Rotorzustandsrückführung
1997
13 Seiten, 8 Bilder, 9 Tabellen, 16 Quellen
Conference paper
English
British Library Conference Proceedings | 1997
|British Library Conference Proceedings | 1997
|British Library Conference Proceedings | 1997
|EXPERIMENTAL EVALUATION OF FLIGHT CONTROL SYSTEM DESIGNS EXPLOITING ROTOR STATE FEEDBACK
British Library Conference Proceedings | 2001
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