The nonlinear equations for coupled elastic flapping–twisting motion of a dragonfly-inspired smart flapping wing are used for a flapping wing actuated from the root by a PZT unimorph in the piezofan configuration. Excitation by the piezoelectric harmonic force generates only the flap bending motion, which, in turn, induces the elastic twist motion due to interaction between flexural and torsional vibration modes. An unsteady aerodynamic model is used to obtain the aerodynamic forces. Numerical simulations are performed using a wing whose size is the same as the dragonfly Sympetrum frequens wing. It is found that the value of average lift reaches its maximum when the smart flapping wing is excited at a frequency closer to the natural frequency in torsion. Moreover, consideration of the elastic twisting of the flapping wing leads to an increase in the lift force. It is also found that the flapping wing generates sufficient lift to support its own weight and carry a small payload. Therefore, the piezoelectrically actuated smart flapping wing based on the geometry of a Sympetrum frequens wing and undergoing flapping–twisting motions can be considered as a potential candidate for use in micro air vehicle applications.

Flapping

Unimorph

Wing twist

Lift (data mining)

Aerodynamic force

10.1080/19475411.2011.649804

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Citations (16)

Stability Analysis

Foundations of engineering mechanics (2017)

Ranjan Ganguli Vijay Panchore

Floquet theory

Liénard equation

Matrix (chemical analysis)

10.1007/978-981-10-6098-4_4

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Citations (0)

Rotating Beams Isospectral to Axially Loaded Nonrotating Uniform Beams

AIAA Journal (2013)

Sandilya Kambampati Ranjan Ganguli V. Mani

In this paper, the stiffness and mass per unit length distributions of a rotating beam, which is isospectral to a given uniform axially loaded nonrotating beam, are determined analytically. The Barcilon–Gottlieb transformation is extended so that it transforms the governing equation of a rotating beam into the governing equation of a uniform, axially loaded nonrotating beam. Analysis is limited to a certain class of Euler–Bernoulli cantilever beams, where the product between the stiffness and the cube of mass per unit length is a constant. The derived mass and stiffness distributions of the rotating beam are used in a finite element analysis to confirm the frequency equivalence of the given and derived beams. Examples of physically realizable beams that have a rectangular cross section are shown as a practical application of the analysis.

Axial symmetry

Isospectral

Astron

Added mass

10.2514/1.j051990

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Citations (11)

Structural damage detection in a helicopter rotor blade using radial basis function neural networks

Smart Materials and Structures (2003)

R Roopesh Kumar Reddy Ranjan Ganguli

A neural network approach is used for detection of structural damage in a helicopter rotor blade using rotating frequencies of the flap (transverse bending), lag (in-plane bending), elastic torsion and axial modes. A finite element method is used for modeling the helicopter blade. Radial basis function (RBF) neural networks are used and several combinations of modes are investigated for training and testing the neural network. Using the first 10 modes of the rotor blade for damage detection yields accurate results for the soft in-plane hingeless rotor considered in this study. Using a parametric study of the blade rotating frequency in conjunction with the neural network, it is found that a reduced measurement set consisting of five modes (the first two torsion modes, the second lag mode and the third and fourth flap modes) also gives good results for damage detection. Furthermore, taking only the first four flap modes also results in good damage detection accuracy. Three rotating frequency sets are therefore identified in this paper for structural damage detection in a helicopter rotor using RBF neural networks.

Helicopter rotor

10.1088/0964-1726/12/2/311

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Citations (78)