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research-article

Tuning of a structural dynamics model with compliant joints using rigid-body dynamics

[+] Author and Article Information
Joseph Calogero

ASME Member, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802
jcalogero7@gmail.com

Mary Frecker

ASME Fellow, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802
mxf36@psu.edu

Zohaib Hasnain

ASME Member, Department of Aerospace Engineering, The University of Maryland, Hampton, VA 23666
zohaibhasnain@gmail.com

James E. Hubbard Jr.

ASME Fellow, Department of Aerospace Engineering, The University of Maryland, Hampton, VA 23666
hubbard@nianet.org

1Corresponding author.

ASME doi:10.1115/1.4038441 History: Received June 30, 2017; Revised October 10, 2017

Abstract

A method for validating rigid-body models of discrete flexible joints under dynamic loading conditions using motion tracking cameras and genetic algorithms is presented. The flexible joints are modeled using rigid-body mechanics as compliant joints: spherical joints with distributed mass and three axis torsional spring-dampers. This allows flexible joints to be modeled using computationally efficient rigid-body dynamics methods, thereby allowing a model to determine the desired stiffness and location characteristics of discrete flexible joints spatially distributed into a structure. An experiment was performed to validate a previously developed numerical dynamics model with the goal of tuning unknown model parameters to match the flapping kinematics of the leading edge spar of an ornithopter with contact-aided compliant mechanisms (CCMs) inserted. A system of computer motion tracking cameras was used to record the kinematics of reflective tape and markers placed along the leading edge spar with and without CCMs inserted. A genetic algorithm was used to minimize the error between the model and experimental marker kinematics. The model was able to match the kinematics of all markers along the spars with a root mean square error of less than 2% of the half wingspan over the flapping cycle. Additionally, the model was able to capture the deflection amplitude and harmonics of the CCMs with a root mean square error of less than 2 degrees over the flapping cycle.

Copyright (c) 2017 by ASME
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