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Inderjit Chopra - One of the best experts on this subject based on the ideXlab platform.
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aeroelastic modeling of trailing edge flap Helicopter Rotors including actuator dynamics
AIAA ASME ASCE AHS Structures Structural Dynamics and Materials Conference, 2004Co-Authors: Jinwei Shen, Inderjit ChopraAbstract:The effect of actuator dynamics on a Helicopter rotor with trailing-edge flaps for vibration control is investigated. Trailing-edge flap, actuator, and elastic rotor blade equations of motion are formulated using Hamilton's variational principle. The coupled nonlinear, periodic equations are solved using finite elements in space and time. The baseline correlation study is based on wind-tunnel test data for a typical five-bladed bearingless rotor system. Good agreement is seen for the blade flap bending, chord bending, and torsion moments. It is shown that actuator dynamics cannot be neglected for a trailing-edge flap system with torsionally soft actuators. The parametric study performed using both coupled flap/actuator model and prescribed flap motion model indicated that the placement of trailing-edge flaps at 78% radius resulted in minimum flap input for this rotor. The vibration reduction level and trend are close between the predictions of both models at different forward speeds. Control inputs predicted by the coupled model show less sensitivity to the forward speed than that of prescribed model.
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design of piezostack driven trailing edge flap actuator for Helicopter Rotors
Smart Materials and Structures, 2001Co-Authors: Taeoh Lee, Inderjit ChopraAbstract:A piezoelectric actuator is investigated to activate a trailing-edge flap mechanism for Helicopter vibration suppression. This paper presents the development of a piezostack-based actuator with a new stroke amplification mechanism. A double-lever amplification concept is introduced, which is a dual-stage lever-fulcrum stroke amplifier that extends the capability of the conventional lever-fulcrum mechanism. Both the design and fabrication of the on-blade trailing-edge flap actuator are addressed. The first prototype actuator was designed and fabricated using two piezostack segments. An amplification factor of 19.4 and constant response covering up to 8/rev (52.3 Hz) were measured under non-rotating conditions, and a consistent actuator displacement of up to 600g of centrifugal loading was experimentally obtained for the vacuum spin testing. A major design refinement resulted in the second prototype actuator that uses five piezostack segments. The bench-top testing of the second prototype actuator showed 1.87 mm (73.7 mil) of free stroke, and uniform performance of up to 150 Hz. In vacuum spin testing, the second prototype actuator showed approximately 13% loss in actuation stroke at 700g of centrifugal loading, and no further degradation at 115% overloading condition. The double-lever amplification mechanism with piezostack actuation showed the potential for operation in a rotating environment.
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design of high force high displacement actuators for Helicopter Rotors
Smart Materials and Structures, 1996Co-Authors: Dhananjay K Samak, Inderjit ChopraAbstract:This paper presents the development of electromechanical actuators based on the concept of mechanical amplification with piezo and electrostrictive stacks as drivers to achieve high force and high displacement actuation. The actuators were designed for two different applications. The first actuator, with an piezo stack, was developed to actuate a `Flaperon' which consisted of a small movable surface to trip the boundary layer, located on the top surface of a wing model with span and chord of 12 in each and of NACA 0012 airfoil. The actuator was designed to produce 8 lbs of force with peak displacement of 10 mils at a maximum frequency of 40 Hz. The second actuator, with an electrostrictive stack as a driver, was designed to move a leading edge droop flap hinged at 25% chord of a wing model with span of 8 in, chord of 4 in and a VR-12 airfoil. This actuator was designed to produce 8.5 lbs of force with peak displacement of 10 mils at a maximum frequency of 45 Hz. Experiments were performed on both stacks to evaluate their important characteristics such as block force, free displacement and stiffness, that were essential in the design of the actuators. The results showed that the block force obtainable from a piezo stack was higher and that of an electrostrictive stack was lower than that specified by the respective manufacturers, while the free displacements are about the same. The dynamic response of the actuators over a frequency range of 33 Hz was evaluated. Results showed that 7 lbs of actuator force was obtainable in both cases, with the flaperon actuator producing 15 mils of dynamic displacement at 15 Hz and the droop flap actuator producing about 6 mils of displacement at 16 Hz. The results were inconclusive beyond 16 Hz due to the setup resonance. The droop flap actuator did not achieve the desired performance because the design calculations were based on the block force listed by the manufacturer which was about 20% higher than the measured value. This led to the conclusion that before the design process begins, the performance of the stack alone should be carefully measured in order to achieve the required performance. Thus, a simple actuator based on a mechanical amplification concept could be effectively designed to produce high force and high displacements.
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design of high force high displacement actuators for Helicopter Rotors
Smart Structures and Materials 1994: Smart Structures and Intelligent Systems, 1994Co-Authors: Dhananjay K Samak, Inderjit ChopraAbstract:We develop electromechanical actuators based on the concept of mechanical amplification with piezo and electrostrictive stacks as drivers to achieve high force and high displacement actuation. The actuators were designed for two different applications. Experiments were performed on both stacks to evaluate their important characteristics such as block force, free displacement, and stiffness that were essential in the design of the actuators. The results showed that the block force obtainable from piezo stack was higher and that of electrostrictive stack was lower than that specified by the respective manufacturers while the free displacements are about the same. The dynamic response of the actuators over a frequency range of 33 Hz was evaluated. Results showed that the actuation force of 7 lbs was obtainable in both cases with flaperon actuator producing 15 mils of dynamic displacement at 15 Hz and droop flap actuator producing about 6 mils of displacement at 16 Hz. The results were inconclusive beyond 16 Hz due to the setup resonance. Droop flap actuator did not achieve the desired performance because the design calculations were based on block force listed by the manufacturer which was about 20% higher than the measured value. This led to the conclusion that before design process begins, the stack alone performance should be carefully measured to achieve required performance. Thus, a simple actuator based on mechnaical amplification concept could be effectively designed to produce high force and high displacements.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Giovanni Bernardini - One of the best experts on this subject based on the ideXlab platform.
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pressure feedback based blade vortex interaction noise controller for Helicopter Rotors
International Journal of Aeroacoustics, 2018Co-Authors: Sara Modini, Giovanni Bernardini, G Graziani, Massimo GennarettiAbstract:With the aim of alleviating the noise annoyance emitted by blade–vortex interactions occurring on Helicopter main Rotors, the present work presents a methodology suitable for the identification of ...
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Aeroacousto-Elastic Modeling for Response Analysis of Helicopter Rotors
Springer Optimization and Its Applications, 2012Co-Authors: Massimo Gennaretti, Giovanni BernardiniAbstract:Vibratory loads and noise emission are by-products of the steady flight of Helicopter Rotors. The fuselage vibrations caused by the vibratory loads from the main rotor affect Helicopter ride comfort and have a negative impact both on the fatigue-life of the structure and on functionality of onboard instruments. Furthermore, it is a common experience that the flight of Helicopters may be clearly perceived by the hearing of the corresponding sound field generated. In particular flight conditions, the acoustic annoyance from the main rotor may become severe, and this affects the environmental and public acceptance of Helicopters. Therefore, the design of a new-generation Helicopter has to include the limitation of vibratory loads and noise emission among its goals, and in this context the availability of reliable simulation tools for their prediction is of primary importance. In this chapter, the formulation developed at the Department of Mechanical and Industrial Engineering of University Roma Tre for the derivation of an aeroacousto-elastic simulation tool for Helicopter Rotors is described, highlighting the important role played by the unsteady aerodynamic model in such a kind of solvers.
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novel boundary integral formulation for blade vortex interaction aerodynamics of Helicopter Rotors
AIAA Journal, 2007Co-Authors: Massimo Gennaretti, Giovanni BernardiniAbstract:A direct panel method based on a novel boundary integral formulation for the velocity potential is presented and applied to Helicopter Rotors experiencing blade-vortex interaction. It avoids the numerical instabilities arising in the standard direct panel method in case of blade/wake impingement. This aerodynamic formulation yields a unified approach for the calculation of free-wake evolution and the blade-pressure field; it is fully 3-D, includes body-thickness effects, and can be applied to blades with arbitrary shape and motion. Blade-pressure predictions and the corresponding acoustic fields correlate well with wind-tunnel test data for Helicopter Rotors in descent flight, in which severe blade-vortex interaction occurs.
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aeroelastic response of Helicopter Rotors using a 3d unsteady aerodynamic solver
Aeronautical Journal, 2006Co-Authors: M Gennaretti, Giovanni BernardiniAbstract:The prediction of blade deflections and vibratory hub loads concerning Helicopter main Rotors in forward flight is the objective of this work. They are determined by using an aeroelastic model derived through the coupling between a nonlinear blade structural model and a boundary integral equation solver for three-dimensional, unsteady, potential aerodynamics. The Galerkin method is used for the spatial integration, whereas the periodic blade response is determined by a harmonic balance approach. This aeroelastic model yields a unified approach for aeroelastic response and blade pressure prediction that may be used for aeroacoustic purposes, with the possibility of including effects from both blade-vortex interaction and multiple-body aerodynamic interaction. Quasi-steady aerodynamic models with wake-inflow from the three-dimensional aerodynamic solver are also applied, in order to perform a comparative study. Numerical results show the capability of the aeroelastic tool to evaluate blade response and vibratory hub loads for a Helicopter main rotor in level flight conditions, and examine the sensitivity of the predictions on the aerodynamics model used.
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a novel potential flow boundary integral formulation for Helicopter Rotors in bvi conditions
AIAA CEAS Aeroacoustics Conference, 2005Co-Authors: Massimo Gennaretti, Giovanni BernardiniAbstract:A direct panel method based on a novel boundary integral formulation for the velocity potential is presented and applied to Helicopter Rotors experiencing blade-vortex interaction (BVI). It avoids the numerical instabilities arising in the standard direct panel method in case of blade/wake impingement. This aerodynamic solver yields a unified approach for the calculation of free-wake evolution and blade pressure field. It is fully 3D, includes body thickness eects, and can be applied to blades with arbitrary shape and motion. Blade pressure predictions and the corresponding acoustic fields correlate well with wind tunnel test data for Helicopter Rotors in descent flight, where severe BVI occurs.
Massimo Gennaretti - One of the best experts on this subject based on the ideXlab platform.
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pressure feedback based blade vortex interaction noise controller for Helicopter Rotors
International Journal of Aeroacoustics, 2018Co-Authors: Sara Modini, Giovanni Bernardini, G Graziani, Massimo GennarettiAbstract:With the aim of alleviating the noise annoyance emitted by blade–vortex interactions occurring on Helicopter main Rotors, the present work presents a methodology suitable for the identification of ...
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Aeroacousto-Elastic Modeling for Response Analysis of Helicopter Rotors
Springer Optimization and Its Applications, 2012Co-Authors: Massimo Gennaretti, Giovanni BernardiniAbstract:Vibratory loads and noise emission are by-products of the steady flight of Helicopter Rotors. The fuselage vibrations caused by the vibratory loads from the main rotor affect Helicopter ride comfort and have a negative impact both on the fatigue-life of the structure and on functionality of onboard instruments. Furthermore, it is a common experience that the flight of Helicopters may be clearly perceived by the hearing of the corresponding sound field generated. In particular flight conditions, the acoustic annoyance from the main rotor may become severe, and this affects the environmental and public acceptance of Helicopters. Therefore, the design of a new-generation Helicopter has to include the limitation of vibratory loads and noise emission among its goals, and in this context the availability of reliable simulation tools for their prediction is of primary importance. In this chapter, the formulation developed at the Department of Mechanical and Industrial Engineering of University Roma Tre for the derivation of an aeroacousto-elastic simulation tool for Helicopter Rotors is described, highlighting the important role played by the unsteady aerodynamic model in such a kind of solvers.
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novel boundary integral formulation for blade vortex interaction aerodynamics of Helicopter Rotors
AIAA Journal, 2007Co-Authors: Massimo Gennaretti, Giovanni BernardiniAbstract:A direct panel method based on a novel boundary integral formulation for the velocity potential is presented and applied to Helicopter Rotors experiencing blade-vortex interaction. It avoids the numerical instabilities arising in the standard direct panel method in case of blade/wake impingement. This aerodynamic formulation yields a unified approach for the calculation of free-wake evolution and the blade-pressure field; it is fully 3-D, includes body-thickness effects, and can be applied to blades with arbitrary shape and motion. Blade-pressure predictions and the corresponding acoustic fields correlate well with wind-tunnel test data for Helicopter Rotors in descent flight, in which severe blade-vortex interaction occurs.
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a novel potential flow boundary integral formulation for Helicopter Rotors in bvi conditions
AIAA CEAS Aeroacoustics Conference, 2005Co-Authors: Massimo Gennaretti, Giovanni BernardiniAbstract:A direct panel method based on a novel boundary integral formulation for the velocity potential is presented and applied to Helicopter Rotors experiencing blade-vortex interaction (BVI). It avoids the numerical instabilities arising in the standard direct panel method in case of blade/wake impingement. This aerodynamic solver yields a unified approach for the calculation of free-wake evolution and blade pressure field. It is fully 3D, includes body thickness eects, and can be applied to blades with arbitrary shape and motion. Blade pressure predictions and the corresponding acoustic fields correlate well with wind tunnel test data for Helicopter Rotors in descent flight, where severe BVI occurs.
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Boundary Integral Equation Methods for Aerodynamics
1992Co-Authors: Luigi Morino, Massimo GennarettiAbstract:T HE objective of this chapter is to review the boundary-integral-equation methods in potential aerodynamics of airplanes and Helicopter Rotors, with emphasis on the "direct velocity-potential formulation," which was introduced by Morino' and further developed by him and his collaborators, in particular by Gennaretti. For the sake of clarity, the formulation is presented at levels of increasing complexity, starting with incompressible nonlifting problems and ending with the most recent developments: a boundary-integral-equation formulation for the velocity potential equation for compressible flows, in a frame of reference in arbitrary motion, and with applications to aerodynamics of airplanes and Helicopter Rotors. The formulation is given in terms of the velocity potential, for which an explicit treatment of the wake is required; special emphasis is given to the formulation for the wake transport. Recently obtained numerical results are included. Other methods, in particular those by Hess' and by Maskew, are also presented. In the remainder of this section we present an outline of this chapter. In Sec. n we present a review of the development of boundary-integral methods (in airplane and Helicopter-rotor aerodynamics) with emphasis on the "direct velocity-potential formulation." Next, we present the mathematical aspects of the methodology. In order to introduce some fundamental concepts of the boundary-integral-equation methodology, we begin with incompressible potential flows (Sec. IE). Lifting flows require the introduction of potential wakes; this concept, which may not be familiar to the reader, is presented in Sec. IV, which includes a detailed discussion of the treatment of the wake, of the condition at the trailing edge, and of the numerical discretization of the problem. Then we extend the potential-flow formulation to compressible flows (Sec. V); the integral formulation for airplanes is treated in Sec. VI and its extension to
Sathyamangalam Ramanarayanan Viswamurthy - One of the best experts on this subject based on the ideXlab platform.
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Smart Helicopter Rotors - Smart Helicopter Rotors
Advances in Industrial Control, 2016Co-Authors: Ranjan Ganguli, Dipali Thakkar, Sathyamangalam Ramanarayanan ViswamurthyAbstract:Exploiting the properties of piezoelectric materials to minimize vibration in rotor-blade actuators, this book demonstrates the potential of smart Helicopter Rotors to achieve the smoothness of ride associated with jet-engined, fixed-wing aircraft. Vibration control is effected using the concepts of trailing-edge flaps and active-twist. The authors’ optimization-based approach shows the advantage of multiple trailing-edge flaps and algorithms for full-authority control of dual trailing-edge-flap actuators are presented. Hysteresis nonlinearity in piezoelectric stack actuators is highlighted and compensated by use of another algorithm. The idea of response surfaces provides for optimal placement of trailing-edge flaps. The concept of active twist involves the employment of piezoelectrically induced shear actuation in rotating beams. Shear is then demonstrated for a thin-walled aerofoil-section rotor blade under feedback-control vibration minimization. Active twist is shown to be significant in reducing vibration caused by dynamic stall. The exposition of ideas, materials and algorithms in this monograph is supported by extensive reporting of results from numerical simulations of smart Helicopter Rotors. This monograph will be a valuable source of reference for researchers and engineers with backgrounds in aerospace, mechanical and electrical engineering interested in smart materials and vibration control. Advances in Industrial Control aims to report and encourage the transfer of technology in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. The series offers an opportunity for researchers to present an extended exposition of new work in all aspects of industrial control
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an optimization approach to vibration reduction in Helicopter Rotors with multiple active trailing edge flaps
Aerospace Science and Technology, 2004Co-Authors: Sathyamangalam Ramanarayanan Viswamurthy, Ranjan GanguliAbstract:The use of multiple active trailing edge flaps for vibration reduction in a Helicopter rotor is investigated using an optimization approach. The strong aeroelastic interaction between the unsteady aerodynamic environment and rotating blades are modeled using a comprehensive aeroelastic analysis for Helicopter Rotors. Pareto optimal points are investigated for tradeoff studies between vibration reduction and control deflections for one, two and four active trailing edge flaps. Numerical results using gradient-based optimization techniques show that four active trailing edge flaps placed at the blade tip and actuated at higher harmonics of the rotation speed yield a vibration reduction of about 72 percent in forward flight when vibration alone is minimized. Such flaps can be actuated by smart materials. It is shown that using upto four trailing edge flaps at the blade tip (outer 20%) is optimal for reducing vibration with reasonably low control angle deflections and therefore low power requirements. It is possible to achieve significant reductions in control deflections by settling for somewhat lower vibration reductions.
Ranjan Ganguli - One of the best experts on this subject based on the ideXlab platform.
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Smart Helicopter Rotors - Smart Helicopter Rotors
Advances in Industrial Control, 2016Co-Authors: Ranjan Ganguli, Dipali Thakkar, Sathyamangalam Ramanarayanan ViswamurthyAbstract:Exploiting the properties of piezoelectric materials to minimize vibration in rotor-blade actuators, this book demonstrates the potential of smart Helicopter Rotors to achieve the smoothness of ride associated with jet-engined, fixed-wing aircraft. Vibration control is effected using the concepts of trailing-edge flaps and active-twist. The authors’ optimization-based approach shows the advantage of multiple trailing-edge flaps and algorithms for full-authority control of dual trailing-edge-flap actuators are presented. Hysteresis nonlinearity in piezoelectric stack actuators is highlighted and compensated by use of another algorithm. The idea of response surfaces provides for optimal placement of trailing-edge flaps. The concept of active twist involves the employment of piezoelectrically induced shear actuation in rotating beams. Shear is then demonstrated for a thin-walled aerofoil-section rotor blade under feedback-control vibration minimization. Active twist is shown to be significant in reducing vibration caused by dynamic stall. The exposition of ideas, materials and algorithms in this monograph is supported by extensive reporting of results from numerical simulations of smart Helicopter Rotors. This monograph will be a valuable source of reference for researchers and engineers with backgrounds in aerospace, mechanical and electrical engineering interested in smart materials and vibration control. Advances in Industrial Control aims to report and encourage the transfer of technology in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. The series offers an opportunity for researchers to present an extended exposition of new work in all aspects of industrial control
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an optimization approach to vibration reduction in Helicopter Rotors with multiple active trailing edge flaps
Aerospace Science and Technology, 2004Co-Authors: Sathyamangalam Ramanarayanan Viswamurthy, Ranjan GanguliAbstract:The use of multiple active trailing edge flaps for vibration reduction in a Helicopter rotor is investigated using an optimization approach. The strong aeroelastic interaction between the unsteady aerodynamic environment and rotating blades are modeled using a comprehensive aeroelastic analysis for Helicopter Rotors. Pareto optimal points are investigated for tradeoff studies between vibration reduction and control deflections for one, two and four active trailing edge flaps. Numerical results using gradient-based optimization techniques show that four active trailing edge flaps placed at the blade tip and actuated at higher harmonics of the rotation speed yield a vibration reduction of about 72 percent in forward flight when vibration alone is minimized. Such flaps can be actuated by smart materials. It is shown that using upto four trailing edge flaps at the blade tip (outer 20%) is optimal for reducing vibration with reasonably low control angle deflections and therefore low power requirements. It is possible to achieve significant reductions in control deflections by settling for somewhat lower vibration reductions.