Journal
MECHANISM AND MACHINE THEORY
Volume 92, Issue -, Pages 230-239Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.mechmachtheory.2015.05.014
Keywords
Static balancing; Zero stiffness; Pseudo-rigid-body model; Compliant mechanisms; Laparoscopic grasper; Rigid-body-replacement-method
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Funding
- VIDI Innovational Research Incentives Scheme grant [NWO-STW 7583]
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Monolithic and thus fully compliant surgical graspers are promising when they provide equal or better force feedback than conventional graspers. In this work for the first time a fully compliant grasper is designed to exhibit zero stiffness and zero operation force. The design problem is addressed by taking a building block approach, in which a pre-existing positive stiffness compliant grasper is compensated by a negative stiffness balancer. The design of the balancer is conceived from a 4-bar linkage and explores the rigid-body-replacement method as a design approach towards static balancing. Design variables and sensitivities are determined through the use of a pseudo-rigid-body model. Final dimensions are obtained using rough hand calculations. Justification of the pseudo rigid body model as well as the set of final dimensions is done by non-linear finite element analysis. Experimental validation is done through a titanium prototype of 40 mm size having an unbalanced positive stiffness of 61.2 N/mm showing that a force reduction of 91.75% is achievable over a range of 0.6 mm, with an approximate hysteresis of 1.32%. The behavior can be tuned from monostable to bistable. The rigid-body-replacement method proved successful in the design of a statically balanced fully compliant mechanism, thus, widening the design possibilities for this kind of mechanism. (C) 2015 Elsevier Ltd. All rights reserved.
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