Tuning of a Rigid-Body Dynamics Model of a Flapping Wing Structure With Compliant Joints

Abstract

A method for validating rigid-body models of compliant mechanisms under dynamic loading conditions using motion tracking cameras and genetic algorithms is presented. The compliant mechanisms are modeled using rigid-body mechanics as compliant joints (CJ): spherical joints with distributed mass and three-axis torsional spring dampers. This allows compliant mechanisms to be modeled using computationally efficient rigid-body dynamics methods, thereby allowing a model to determine the desired stiffness and location characteristics of compliant mechanisms 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), compliant mechanisms that feature self-contact to produce nonlinear stiffness, 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 (RMSE) 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 RMSE of less than 2 deg over the flapping cycle.

Screw Dynamics of a Multibody System by a Schoenflies Manipulator

“…The Lagrange equation of the first type takes the Lagrange multiplier and treats the constraint as an additional equation [9]. The Lagrange equation of the second type allows one to establish the ordinary differential equations of a mechanical system and obtain the solution of the equation by using a numerical algorithm [10]. For example, the inverse dynamics of the Stewart platform were derived by using the Lagrange method [11,12].…”

Topology synthesis of a 3-kink contact-aided compliant switch

“…Contact-aided compliant mechanisms inherit most advantages of compliant mechanisms, and with contact permitted between their constituents and external surfaces and/or between members themselves, CCMs can be designed to deliver intricate mechanical characteristics. CCMs have many applications in compliant joints [4,5], surgical tools [6,7], mechanical devices [8][9][10][11] and flapping wing mechanisms [12,13] and offer immense potential yet to be tapped. Many design methods exist for compliant mechanisms that could be broadly classified into pseudo-rigid-body model and structural optimization approaches [1,8,10,[14][15][16][17][18][19].…”

Tailoring energy absorption with functional grading of a contact-aided compliant mechanism

“…Surgical devices can perform better when designed as contact-aided mechanisms [10]. Passive morphing in ornithopter wings based on optimization of contact-aided mechanisms has been successfully demonstrated in [11][12][13][14]. Cellular contact-aided compliant mechanisms (C3M) take advantage of self-contact mechanisms integrated in each unit cell.…”