Design and Optimization of a Contact-Aided Compliant Mechanism for Passive Bending

A contact-aided compliant mechanism (CCM) called a compliant spine (CS) is presented in this paper. It is flexible when bending in one direction and stiff when bending in the opposite direction, giving it a nonlinear bending stiffness. The fundamental element of this mechanism is a compliant joint (CJ), which consists of a compliant hinge (CH) and contact surfaces. The design of the compliant joint and the number of compliant joints in a compliant spine determine its stiffness. This paper presents the design and optimization of such a compliant spine. A multi-objective optimization problem with three objectives is formulated in order to perform the design optimization of the compliant spine. The goal of the optimization is to minimize the peak stress and mass while maximizing the deflection, subject to geometric and other constraints. Flapping wing unmanned air vehicles, also known as ornithopters, are used as a case study in this paper to test the accuracy of the design optimization procedure and to prove the efficacy of the compliant spine design. The optimal compliant spine designs obtained from the optimization procedure are fabricated, integrated into the ornithopter's wing leading edge spar, and flight tested. Results from the flight tests prove the ability of the compliant spine to produce an asymmetry in the ornithopter's wing kinematics during the up and down strokes.

[1]  Larry L. Howell,et al.  Tension-based multi-stable compliant rolling-contact elements , 2010 .

[2]  Kalyanmoy Deb,et al.  A fast and elitist multiobjective genetic algorithm: NSGA-II , 2002, IEEE Trans. Evol. Comput..

[3]  Mary Frecker,et al.  Passively morphing ornithopter wings constructed using a novel compliant spine: design and testing , 2012 .

[4]  M. Frecker,et al.  Stress Relief in Contact-Aided Compliant Cellular Mechanisms , 2009 .

[5]  Larry L. Howell,et al.  A Flexure-Based Bi-Axial Contact-Aided Compliant Mechanism for Spinal Arthroplasty , 2008 .

[6]  G. K. Ananthasuresh,et al.  Contact Aided Compliant Mechanisms: Concept and Preliminaries , 2002 .

[7]  Henry Won,et al.  Development of the Nano Hummingbird: A Tailless Flapping Wing Micro Air Vehicle , 2012 .

[8]  Mary Frecker,et al.  Design Optimization of a Compliant Spine for Dynamic Applications , 2011 .

[9]  Kalyanmoy Deb,et al.  Running performance metrics for evolutionary multi-objective optimizations , 2002 .

[10]  Anupam Saxena,et al.  Systematic Synthesis of Large Displacement Contact-Aided Monolithic Compliant Mechanisms , 2012 .

[11]  Aimy Wissa,et al.  DESIGN OF A PASSIVELY MORPHING ORNITHOPTER WING USING A NOVEL COMPLIANT SPINE , 2010 .

[12]  Mary Frecker,et al.  Design of contact-aided compliant cellular mechanisms with curved walls , 2012 .

[13]  G. K. Ananthasuresh,et al.  A Novel Compliant Mechanism for Converting Reciprocating Translation Into Enclosing Curved Paths , 2004 .

[14]  Kalyanmoy Deb,et al.  Multi-objective optimization using evolutionary algorithms , 2001, Wiley-Interscience series in systems and optimization.

[15]  Qingfu Zhang,et al.  Multiobjective evolutionary algorithms: A survey of the state of the art , 2011, Swarm Evol. Comput..

[16]  R. H. Brown.  The Flight of Birds: II. Wing Function in Relation to Flight Speed , 1953 .

[17]  Mary Frecker,et al.  Testing of novel compliant spines for passive wing morphing , 2011 .

[18]  Mary Frecker,et al.  Flight Testing of Novel Compliant Spines for Passive Wing Morphing on Ornithopters , 2013 .

[19]  Larry L. Howell,et al.  A compliant contact-aided revolute joint , 2005 .

[20]  G. K. Ananthasuresh,et al.  Synthesis of contact‐aided compliant mechanisms for non‐smooth path generation , 2007 .

[21]  Mary Frecker,et al.  Two-Step Design of Multicontact-Aided Cellular Compliant Mechanisms for Stress Relief , 2012 .