Active Isolation of Multiple Structural Waves on a Helicopter Gearbox Support Strut

Sutton, T.J.; Elliott, S.J.; Brennan, M.J.; Heron, K.; Jessop, Daniel

doi:10.1006/jsvi.1997.0972

Cited by 67 publications

(44 citation statements)

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“…Another method is the Individual Blade Control (IBC), in which the rotor blades are designed with actively adjustable trailing edge flaps [4] or integral blade tip twist mechanisms [5] to minimize the N/rev aerodynamic loads using smart material actuators. In addition, the Active Control of Structural Response (ACSR) methods attempt to reduce the vibratory loads at the fuselage by modifying the vibratory load transmission paths [6]. Despite the promising nature of these approaches, successful applications of these technologies on full-scale vehicles are limited due to restrictions in high efficiency actuators, heavy weight penalties, high power requirements and system complexities.…”

Section: Introductionmentioning

confidence: 99%

Development of adaptive helicopter seat systems for aircrew vibration mitigation

2008

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Helicopter aircrews are exposed to high levels of whole body vibration during flight. This paper presents the results of an investigation of adaptive seat mount approaches to reduce helicopter aircrew whole body vibration levels. A flight test was conducted on a four-blade helicopter and showed that the currently used passive seat systems were not able to provide satisfactory protection to the helicopter aircrew in both front-back and vertical directions. Long-term exposure to the measured whole body vibration environment may cause occupational health issues such as spine and neck strain injuries for aircrew. In order to address this issue, a novel adaptive seat mount concept was developed to mitigate the vibration levels transmitted to the aircrew body. For proof-of-concept demonstration, a miniature modal shaker was properly aligned between the cabin floor and the seat frame to provide adaptive actuation authority. Adaptive control laws were developed to reduce the vibration transmitted to the aircrew body, especially the helmet location in order to minimize neck and spine injuries. Closed-loop control test have been conducted on a full-scale helicopter seat with a mannequin configuration and a large mechanical shaker was used to provide representative helicopter vibration profiles to the seat frame. Significant vibration reductions to the vertical and front-back vibration modes have been achieved simultaneously, which verified the technical readiness of the adaptive mount approach for full-scale flight test on the vehicle.

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Section: Introductionmentioning

confidence: 99%

Development of adaptive helicopter seat systems for aircrew vibration mitigation

2008

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“…The unsteady forces experienced by the rotor blades are generally transmitted at multiples of the blade passing frequency through the hub to the fuselage. Some active damping approaches that are applied directly to the rotating blades have been proposed [9], however, due to cost considerations it is more practical to apply corrective action across the gearbox at the opposite end of the propeller shaft [10] or in parallel with the attachment to the receiving structure [11]. Although the latter two approaches will reduce the locally measured fuselage vibration, the change in impedance due to this control force at the other end of the shaft can lead to an increase in blade vibration [12].…”

Section: Introductionmentioning

confidence: 99%

Design of remotely located and multi-loop vibration controllers using a sequential loop closing approach

Ubaid

Daley

Pope

2015

Control Engineering Practice

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In some applications, vibration control objectives may require reduction of levels at locations where control system components cannot be sited due to space or environmental considerations. Control actuators and error sensors for such a scenario will need to be placed at appropriate locations which are potentially remote from the points where ultimate attenuation is desired. The performance of the closed loop system, therefore, cannot be assessed simply by the measurement obtained at this local error sensor. The control design objective has to take into account the vibration levels at the remote locations as well. A design methodology was recently proposed that tackles such problems using a single-loop feedback control architecture. The work in this paper describes an extension of this control design procedure to enable the systematic design of multiple decentralised control loops. The approach is based upon sequential loop closing and conditions are provided that ensure that closed loop stability is maintained even in the event of failure in some control loops. The design procedure is illustrated through its application to a laboratory scale slab floor that replicates the problems associated with human induced vibration in large open-plan office buildings. The experimental results demonstrate the efficacy of the approach and significant suppression of the dominant low frequency modes in the floor is achieved using two independent acceleration feedback control loops.

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“…Kawaguchi et al (1996) presented an active vibration reduction (AVR) system to reduce the longitudinal and lateral vibrations of a BK117 helicopter gearbox using hydraulic actuators. Sutton et al (1997) used an actual helicopter strut set up under realistic loading conditions. They showed that attenuations of 30-40 dB are possible in the kinetic energy transmitted to the fuselage over a range of frequencies between 250 and 1250 Hz.…”

Section: Introductionmentioning

confidence: 99%

Oracle separation of complexity classes and lower bounds for perceptrons solving separation problems

Vereshchagin¹

1995

Izv. Math.

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Active periodic structures exhibit unique dynamic characteristics that make them act as tunable mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called the 'pass bands' and wave propagation is completely blocked within other frequency bands called the 'stop bands'. The spectral width of these bands can be tuned according to the nature of the external excitation.In this paper, the emphasis is placed on developing a new class of these periodic structures called active periodic struts (APS) which can be used to support gearbox systems on the airframes of helicopters. When designed properly the APS can stop the propagation of vibration from the gearbox to the airframe within critical frequency bands and consequently minimize the effects of transmission of undesirable vibration and sound radiation to the helicopter cabin. The theory governing the operation of this class of APS is presented and their tunable filtering characteristics are demonstrated experimentally as a function of their design parameters.The presented concept of the APS can be easily employed in many applications to control the wave propagation and the force transmission in an attempt to stop/confine the propagation of undesirable disturbances.

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Active Isolation of Multiple Structural Waves on a Helicopter Gearbox Support Strut

Cited by 67 publications

References 0 publications

Development of adaptive helicopter seat systems for aircrew vibration mitigation

Development of adaptive helicopter seat systems for aircrew vibration mitigation

Design of remotely located and multi-loop vibration controllers using a sequential loop closing approach

Oracle separation of complexity classes and lower bounds for perceptrons solving separation problems

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