Abstract
This paper introduces the design of a fully-compliant Spherical Joint (SJ), obtained by the in-parallel connection of two identical open chains each composed of three equal circular flexible beams, having coincident centers of curvature and mutually orthogonal axes of minimum rotational stiffness. Thanks to its particular topology, the SJ provides a fully isotropic behavior, the two chains being placed in space so as to be symmetric with respect to the beams’ center of curvature. At first, the overall system compliance matrix is derived by means of an analytical procedure, in order to obtain a parametric formulation of the SJ behavior within the small deflection range. Then, after finite element validation of the analytical model, an optimization study of the beam geometry is developed, with the aim of maximizing the ratio between the SJ primary to secondary compliance factors. At last, the potential advantages and drawbacks of the proposed design are discussed by numerically evaluating the joint performance in terms of parasitic motions within the large deflection range (namely, when large external loads are applied to the envisaged center of spherical motion).
Highlights
A Compliant Mechanism (CM) may be defined as a single- or multi-piece flexible device that can provide both the mobility of a traditional rigid-link mechanism and the stiffness of a conventional structure [1,2]
The design of a compliant joint, suitable for realizing approximatively spherical motions and featuring two open chains connected in parallel, has been introduced and analyzed
The closed form compliance equations of the proposed spherical joint have been presented as a function of the beam dimensions and employed material
Summary
A Compliant Mechanism (CM) may be defined as a single- or multi-piece flexible device that can provide both the mobility of a traditional rigid-link mechanism and the stiffness of a conventional structure [1,2]. CMs may be envisaged as a promising paradigm to enable the Design For No-Assembly concept and, according to [14], they become ideal candidates for the development of high-precision manipulators when driven by high-resolution positioning actuators (such as piezoelectric or electromagnetic motors [15,16,17]) Aside these numerous advantages, a series of challenging issues must be considered, namely: (a) continuous rotational motions cannot be achieved by means of flexible members; (b) in many applications, CM resistance to fatigue must be carefully addressed; (c) the analysis and design of CMs is more complex when compared to traditional mechanisms; (d) differently from rigid-link mechanisms, CMs may be subjected to non negligible deformations along undesired directions.
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