Coupled rotor-fuselage vibration reduction using open-loop blade pitch control
01 Aug 1993-Mathematical and Computer Modelling (Elsevier Science Publishers B. V.)-Vol. 18, Iss: 3, pp 131-156
TL;DR: In this paper, the nonlinear equations of motion for a coupled rotor/flexible fuselage system have been derived using computer algebra on a special purpose symbolic computing facility and the trim state and vibratory response of the helicopter are obtained in a single pass by applying the harmonic balance technique and simultaneously satisfying the trim and the vibratory responses of the rotor and fuselage degrees of freedom.
Abstract: A fundamental study of vibration reduction in helicopters using higher harmonic blade pitch control was performed The nonlinear equations of motion for a coupled rotor/flexible fuselage system have been derived using computer algebra on a special purpose symbolic computing facility The trim state and vibratory response of the helicopter are obtained in a single pass by applying the harmonic balance technique and simultaneously satisfying the trim and the vibratory response of the helicopter for all rotor and fuselage degrees of freedom The influence of the fuselage flexibility on the vibratory response is studied New insight on vibration reduction in coupled rotor/fuselage is obtained from the sensitivity of the hub shears to the frequency and amplitude of the open loop HHC signal in the rotating frame It is shown that conventional higher harmonic control through the swashplate, is capable of suppressing either the hub loads or only the fuselage vibrations, but not both simultaneously It is demonstrated that for simultaneous reduction of hub loads and fuselage vibrations, a multiple frequency higher harmonic control input signal provided in the rotating frame is required
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TL;DR: Based on the comparison of the various approaches, it appears that the actively controlled flap has remarkable potential for vibration reduction.
Abstract: This paper presents a concise review of the state of the art for vibration reduction in rotorcraft using active controls. The principal approaches to vibration reduction in helicopters described in the paper are 1) higher harmonic control, 2) individual blade control, 3) vibration reduction using an actively controlled flap located on the blade, and 4) active control of structural response. The special attributes of the coupled rotor/flexible fuselage vibration reduction problem are also briefly discussed to emphasize that vibration reduction at the hub is not equivalent to acceleration reduction at specific fuselage locations. Based on the comparison of the various approaches, it appears that the actively controlled flap has remarkable potential for vibration reduction.
243Â citations
TL;DR: In this article, the authors demonstrate that the field of aeroelasticity continues to play a critical role in the design of modern aerospace vehicles, and several important problems are still far from being well understood.
Abstract: The primary objective of this paper is to demonstrate that the field of aeroelasticity continues to play a critical role in the design of modern aerospace vehicles, and several important problems are still far from being well understood. Furthermore, the emergence of new technologies, such as the use of adaptive materials (sometimes denoted as smart structures technology), providing new actuator and sensor capabilities, has invigorated aeroelasticity, and generated a host of new and challenging research topics that can have a major impact on the design of a new generation of aerospace vehicles.
150Â citations
TL;DR: In this paper, a coupled rotor/e exible fuselage aeroelastic response model is developed for vibration reduction studies based on active control of structural response (ACSR), and the structural model is capable of representing e exible, hingeless rotors combined with a fuselage, and a rigid platform combined with the actuators required for modeling the ACSR system.
Abstract: A ree ned coupled rotor/e exible fuselage aeroelastic response model is developed for vibration reduction studies based on active control of structural response (ACSR). The structural model is capable of representing e exible, hingeless rotors combined with a e exible fuselage, and a rigid platform combined with the actuators required for modeling the ACSR system and is combined with a free wake model. The ine uence of rotor/fuselage coupling and improved aerodynamics on the vibratory hub loads is investigated.
22Â citations
10 Apr 1995
13Â citations
TL;DR: In this paper, the authors present new periodic control strategies for the control of flapping motion of an individual helicopter rotor blade in forward flight, which is represented by a periodic control model.
Abstract: The primary objective of this paper is to present new periodic control strategies for the control of flapping motion of an individual helicopter rotor blade in forward flight, which is represented ...
12Â citations
References
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01 Mar 1982
TL;DR: In this paper, a class of algorithms for the multicyclic control of helicopter vibration and loads is derived and discussed, characterized by a linear, quasi-static, frequency-domain model of the helicopter response to control.
Abstract: A class of algorithms for the multicyclic control of helicopter vibration and loads is derived and discussed. This class is characterized by a linear, quasi-static, frequency-domain model of the helicopter response to control; identification of the helicopter model by least-squared-error or Kalman filter methods; and a minimum variance or quadratic performance function controller. Previous research on such controllers is reviewed. The derivations and discussions cover the helicopter model; the identification problem, including both off-line and on-line (recursive) algorithms; the control problem, including both open-loop and closed-loop feedback; and the various regulator configurations possible within this class. Conclusions from analysis and numerical simulations of the regulators provide guidance in the design and selection of algorithms for further development, including wind tunnel and flight tests.
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