A modified pseudo-rigid-body modeling approach for compliant mechanisms with fixed-guided beam flexures

Abstract

Abstract. In the present paper, we investigate a modified pseudo-rigid-body (MPRB) modeling approach for compliant mechanisms with fixed-guided beam flexures by considering the nonlinear effects of center-shifting and load-stiffening. In particular, a fixed-guided compliant beam is modeled as a pair of fixed-free compliant beams jointed at the inflection point, where each fixed-free beam flexure is further modeled by a rigid link connected with an extension spring by a torsion spring, based on the beam constraint model (BCM). Meanwhile, the characteristic parameters of the proposed MPRB model are no longer constant values, but affected by the applied general tip load, especially the axial force. The developed MPRB modeling method is then applied to the analysis of three common compliant mechanisms (i.e. compound parallelogram mechanisms, bistable mechanisms and 1-DOF translational mechanisms), which is further verified by the finite element analysis (FEA) results. The proposed MPRB model provides a more accurate method to predict the performance characteristics such as deformation capability, stiffness variation, as well as error motions of complaint mechanisms with fixed-guided beam flexures, and offers a new look into the design and optimization of beam-based compliant mechanisms.

Design and Analysis of Flexible Hinge Used for Unfolding Spacecraft Solar Panels

“…The relationship of the force and deformation of the mechanism with rigid bodies is similar to the compliant mechanism. When the flexible hinge is under a z-direction torque, the flexible unit in the flexible hinge can be replaced by the fixed-guide beam unit, which is one type of structure in the pseudo-rigid body method (Liu and Yan 2017;Midha et al 2015). The model is shown in Fig.…”

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“…The lateral deformation of the input end can be considered as the addition of the normalized lateral compression caused by axial force and normalized lateral displacement caused by beam bending . The normalized lateral displacement is derived as follows [ 36 ]: where is the normalized thickness of the rigid body, is the normalized lateral force applied on the input end, ( i = B′, D, H′) is the normalized vertical deformation of the input end, and is the angle of the input end. The lateral deformation loss of points B′, D, and H′ in the lever mechanism-based input end can be obtained as Equation ( 14 ): …”

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“…5. This method has been proposed by Howell [1], and has been applied to other mechanisms [4,9]. This model is particularly useful for the large deection analysis.…”

“…But, the error of the maximum stress value between PRBM and FEA is so large. To increase accuracy, a modied pseudorigid-body model (M-PRBM) approach is applied for xed-guided bistable compliant mechanisms [9]. Kennedy et al [10] designed a ratchet mechanism by using two xed-pinned compliant beams and two xed-guided compliant beams.…”