Design and analysis of a stiffness adjustable structure using an endoskeleton

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Abstract

In this paper, we present a novel stiffness adjustable structure that changes its stiffness by pulling a tendon. It adopts an endoskeleton structure where rigid segments and compliant segments are alternately connected in series. The stiffness of this structure is controlled by compressing the compliant segments with an axial force. A tendon that runs through the endoskeleton and is fixed at the tip provides the axial compression force when pulled. We analyze the structure using the cylindrical isolation bearing model. The bending stiffness of the proposed structure was simulated and compared with experimental results. The structure can be stiffened approximately fifty-times the original stiffness. This stiffness adjustable structure can be used to increase the efficiency of a system that uses compliance, e.g., a robotic fish that uses a compliant fin for its propulsion system.

Keywords

Variable stiffness structure Adjustable stiffness structure Endoskeleton Soft robotics 

Nomenclature

E

Young’s Modulus

I

second moment of inertia

R

radius of cylinder

γ

characteristic radius factor

t

thickness of rigid segment

F

load on end-tip of the structure

K

pseudo torsional spring constant

cθ

parametric angle coefficient

(EI)′

effective bending stiffness of bonded cylindrical layer

θi

deflection angle of i th compliant segment from fixed-end

G

Shear Modulus

S

shape factor

l

compressed length

D

deflection

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References

  1. 1.
    Park, Y. J., Jeong, U. S., Lee, J. S., Kim, H. Y., and Cho, K. J., “The effect of compliant joint and caudal fin in thrust generation for robotic fish,” IEEE RAS and EMBS Int. Conf. on Biomedical Robotics and Biomechatronics (BioRob), pp. 528–533, 2010.Google Scholar
  2. 2.
    Zoppi, M., Molfino, R., and Cerveri, P., “Modular micro robotic instruments for transluminal endoscopic robotic surgery: New perspectives,” IEEE/ASME Int. Conf. on Mechatronics and Embedded Systems and Applications (MESA), pp. 440–445, 2010.Google Scholar
  3. 3.
    Kim, M. S., Chu, W. S., Lee, J. H., Kim, Y. M., and Ahn, S. H., “Manufacturing of inchworm robot using shape memory alloy (SMA) embedded composite structure,” Int. J. Precis. Eng. Manuf., Vol. 12, No. 3, pp. 565–568, 2011.CrossRefGoogle Scholar
  4. 4.
    Kawamura, S., Yamamoto, T., Ishida, D., Ogata, T., Nakayama, Y., Tabata, O., and Sugiyama, S., “Development of passive elements with variable mechanical impedance for wearable robots,” IEEE Int. Conf. on Robotics and Automation, Vol. 1, pp. 248–253, 2002.Google Scholar
  5. 5.
    Mitsuda, T., Kuge, S., Wakabayashi, M., and Kawamura, S., “Haptic displays implemented by controllable passive elements,” IEEE Int. Conf. on Robotics and Automation, Vol. 4, pp. 4223–4228, 2002.Google Scholar
  6. 6.
    Nakabayashi, M., Kobayashi, R., Kobayashi, S., and Morikawa, H., “Bioinspired propulsion mechanism using a fin with a dynamic variable-effective-length spring: Evaluation of thrust characteristics and flow around a fin in a uniform flow,” Journal of Biomechanical Science and Engineering, Vol. 4, No. 1, pp. 82–93, 2009.CrossRefGoogle Scholar
  7. 7.
    Chalhoub, M. S. and Kelly, J. M., “Effect of bulk compressibility on the stiffness of cylindrical base isolation bearings,” Int. J. of Solids and Structures, Vol. 26, No. 7, pp. 743–760, 1990.CrossRefGoogle Scholar
  8. 8.
    Howell, L. L., “Compliant mechanisms,” Wiley-IEEE, 2001.Google Scholar

Copyright information

© Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Biorobotics Laboratory, School of Mechanical & Aerospace Engineering / IAMDSeoul National UniversitySeoulRepublic of Korea

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