Ground and Air Resonance of an Advanced Bearingless Rotor in Hover

Jang, Jin-Seok; Chopra, Inderjit

doi:10.4050/jahs.33.20

Cited by 15 publications

(4 citation statements)

References 12 publications

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“…It is important to highlight that in the literature there are different models to study the GR, such as including the stiffness of the blades, additional DOFs of fuselage and dynamics of shock absorbers mounted on the landing gears (Lytwyn et al., 1971; Janowski and Tongue, 1988; Jang and Chopra, 1998; Bielawa, 2006; Lee and Kim, 2010). However, the model used herein is also widely used for studying the GR (e.g., Coleman and Feingold, 1956; Gandhi and Malovrh, 1999; Bielawa 2006; Sanches et al., 2014; Bergeot et al., 2017), and it is employed in this work to introduce the idea of stabilizing a range of rotor speed using a single controller.…”

Section: Gr Dynamic Modelmentioning

confidence: 99%

“…This phenomenon typically occurs in hinged (articulated) rotors. However, helicopters using the soft-inplane hingeless (Lytwyn et al., 1971) and bearingless rotors (Jang and Chopra, 1998) are also susceptible to this problem. A classical analysis of this phenomenon was developed by Coleman and Feingold (1956) using a simple linear mechanical model.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Gr Dynamic Modelmentioning

confidence: 99%

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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“…For the beams with no elastic couplings, the cross-sectional stiffness matrix K is given by (1) where EA is the extensional stiffness, GJ is the torsional stiffness, EI y and EI z are the flap and lag bending stiffnesses, respectively, and EC ω is the warping stiffness. For the complete details of the sectional analysis, the reader is referred to [10].…”

Section: Cross-sectional Analysismentioning

confidence: 99%

“…The coupled interaction among various disciplines, such as aerodynamics, dynamics, aeroelasticity and structures, poses a great challenge for the design of rotor blades. The bearingless main rotor (BMR) hub system lacks the conventional mechanical hinges and the pitch bearing which are used to control the blade dynamic behavior, resulting in advantages such as lower part count, lower weight, and less maintenance cost [1,2]. The BMR hub system (Fig.…”

Section: Introductionmentioning

confidence: 99%

Evolutionary Shape Optimization of Flexbeam Sections of a Bearingless Helicopter Rotor

Dhadwal¹,

Jung²,

Kim³

2014

Composites Research

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The shape optimization of composite flexbeam sections of a bearingless helicopter rotor is studied using a finite element (FE) sectional analysis integrated with an efficient evolutionary optimization algorithm called particle swarm assisted genetic algorithm (PSGA). The sectional optimization framework is developed by automating the processes for geometry and mesh generation, and the sectional analysis to compute the elastic and inertial properties. Several section shapes are explored, modeled using quadratic B-splines with control points as design variables, through a multiobjective design optimization aiming minimum torsional stiffness, lag bending stiffness, and sectional mass while maximizing the critical strength ratio. The constraints are imposed on the mass, stiffnesses, and critical strength ratio corresponding to multiple design load cases. The optimal results reveal a simpler and better feasible section with double-H shape compared to the triple-H shape of the baseline where reductions of 9.46%, 67.44% and 30% each are reported in torsional stiffness, lag bending stiffness, and sectional mass, respectively, with critical strength ratio greater than 1.5.

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Bibliography

2013

Mechanical Instability

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Ground and Air Resonance of an Advanced Bearingless Rotor in Hover

Cited by 15 publications

References 12 publications

On the controllers' design to stabilize ground resonance helicopter

On the controllers' design to stabilize ground resonance helicopter

Evolutionary Shape Optimization of Flexbeam Sections of a Bearingless Helicopter Rotor

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