Effect of free play in rotor blades hinges on the non‐linear ground resonance of a helicopter

Kowaleczko, Grzegorz; Dżygadło, Zbigniew

doi:10.1108/00022660210448438

Cited by 5 publications

(4 citation statements)

References 4 publications

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“…Mathematical models play an important role in helicopter design as they allow simulation of helicopter behavior on the computer at low cost (Cao et al , 2004; Kowaleczko and Dzygadlo, 2002; Straub and Charles, 2001; Xiang et al , 2002). An elastic rotor blade undergoing flap, lag, torsion and axial motions is considered.…”

Section: Aeroelastic Analysismentioning

confidence: 99%

Optimal location of centre of gravity for swashplateless helicopter UAV and MAV

Ganguli

Jehnert

Wolfram

et al. 2007

Aircraft Engineering and Aerospace Technology

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PurposeTo investigate the use of centre of gravity location on reducing cyclic pitch control for helicopter UAV's (unmanned air vehicles) and MAV's (micro air vehicles). Low cyclic pitch is a necessity to implement the swashplateless rotor concept using trailing edge flaps or active twist using current generation low authority piezoceramic actuators.Design/methodology/approachAn aeroelastic analysis of the helicopter rotor with elastic blades is used to perform parametric and sensitivity studies of the effects of longitudinal and lateral center of gravity (cg) movements on the main rotor cyclic pitch. An optimization approach is then used to find cg locations which reduce the cyclic pitch at a given forward speed.FindingsIt is found that the longitudinal cyclic pitch and lateral cyclic pitch can be driven to zero at a given forward speed by shifting the cg forward and to the port side, respectively. There also exist pairs of numbers for the longitudinal and lateral cg locations which drive both the cyclic pitch components to zero at a given forward speed. Based on these results, a compromise optimal cg location is obtained such that the cyclic pitch is bounded within ±5° for a BO105 helicopter rotor.Originality/valueThe reduction in the cyclic pitch due to helicopter cg location is found to significantly reduce the maximum magnitudes of the control angles in flight, facilitating the swashplateless rotor concept. In addition, the existence of cg locations which drive the cyclic pitches to zero allows for the use of active cg movement as a way to replace the cyclic pitch control for helicopter MAV's.

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Section: Aeroelastic Analysismentioning

confidence: 99%

Optimal location of centre of gravity for swashplateless helicopter UAV and MAV

Ganguli

Jehnert

Wolfram

et al. 2007

Aircraft Engineering and Aerospace Technology

View full text Add to dashboard Cite

show abstract

“…That approach can be used to study anisotropic rotors (blades different among them). In addition, different studies involving parametric vibrations and nonlinear analysis about GR phenomenology for isotropic and anisotropic rotors can be found in Janowski and Tongue (1988), Gandhi and Malovrh (1999), Kowaleczko and Dzygadlo (2002), Kunz (2002), Sanches et al. (2011, 2012, 2014), Bergeot et al.…”

Section: Introductionmentioning

confidence: 99%

On the controllers' design to stabilize ground resonance helicopter

Silva

Bueno

Abreu

2019

Journal of Vibration and Control

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Ground resonance (GR) in helicopters is a potentially catastrophic instability commonly caused by coalescence of the regressive cyclic blade lag mode with the fuselage motion in certain rotor speed ranges. It can limit the helicopter operational envelope and the design of this type of vehicle can become a difficult task. Although a broad class of actuators allows the use of active and semi-active techniques to design feedback-based control systems, a limited number of works in the literature introduce formulations to compute the controller gain to suppress this phenomenon. Also, commonly, a control approach defines a feedback, particularly to a specific rotor speed. In this context, this work introduces an alternative methodology to design an active control system to stabilize GR of a helicopter. The proposed approach can suppress this instability in all rotor speed ranges by using only one control gain. Two strategies are proposed based on linear matrix inequalities (LMIs). The Lyapunov stability criteria are used and the unstable rotor speed is considered as an uncertain parameter to define an associated convex space. Using convex optimization, a robust control gain is computed until all the unstable rotor speed range is stabilized. Numerical simulations are carried out to demonstrate the effectiveness of this methodology. The results confirm the viability of the proposed approach to design active and semi-active controllers.

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“…Also in Poland, within designing new helicopters, methods of ground resonance analysis were developed (Szrajer, 1989;Zerek, 1989), which applied the simplified model of main rotor including masses of hub and lagging blades. Ground resonance improved model with allowed transition and angular motion of helicopter and introduced aerodynamic loads of stiff rotor blades were presented by Kowaleczko and Dzygadlo (2002). For the ILX-27 unmanned helicopter, detailed finite element model was applied to define structure corrections necessary for ground resonance protection (Kowaleczko and Gorecki, 2016).…”

Section: Introductionmentioning

confidence: 99%

A simulation investigation of helicopter ground resonance phenomenon

Stanisławski

2019

AEAT

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Purpose The purpose of this paper is to present a simulation method applied for investigation of helicopter ground resonance phenomenon. Design/methodology/approach The considered physical model of helicopter standing on ground with rotating rotor consists of fuselage and main transmission gear treated as stiff bodies connected by elastic elements. The fuselage is supported on landing gear modeled by spring-damper units. The main rotor blades are treated as set of elastic axes with lumped masses distributed along blade radius. Due to Galerkin method, parameters of blades motion are assumed as a combination of bending and torsion eigen modes. A Runge–Kutta method is applied to solve equations of motions of rotor blades and helicopter fuselage. Findings The presented simulation method may be applied in preliminary stage of helicopter design to avoid ground resonance by proper selection of landing gear units and blade damper characteristics. Practical implications Ground resonance may occur in form of violently increasing mutual oscillations of helicopter fuselage and lead-lag motion of rotor blades. According to changes of stiffness and damping characteristics, simulations show stable behavior or arising oscillations of helicopter. The effects of different blade balance or defect of blade damper are predicted. Originality/value The simulation method may help to determine the envelope of safe operation of helicopter in phase of take-off or landing. The effects of additional disturbances as results of blades pitch control as swashplate deflection are introduced.

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Effect of free play in rotor blades hinges on the non‐linear ground resonance of a helicopter

Cited by 5 publications

References 4 publications

Optimal location of centre of gravity for swashplateless helicopter UAV and MAV

Optimal location of centre of gravity for swashplateless helicopter UAV and MAV

On the controllers' design to stabilize ground resonance helicopter

A simulation investigation of helicopter ground resonance phenomenon

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