Abstract
Abstract. To overcome the limitations of conventional bistable mechanisms, this paper proposes a novel type of bistable mechanism with linear negative stiffness and large in-plane lateral stiffness. By connecting the novel negative-stiffness mechanism in parallel with a positive-stiffness mechanism, a novel quasi-zero stiffness compliant mechanism is developed, which has good axial guidance capability and in-plane lateral anti-interference capability. Analytical models based on a comprehensive elliptic integral solution of bistable mechanism are established and then the stiffness curves of both conventional and novel bistable mechanisms are analyzed. The quasi-zero stiffness characteristic and High-Static-Low-Dynamic-Stiffness characteristic of the novel compliant mechanism are investigated and its application in constant-force mechanism and vibration isolator is discussed. A prototype with adjustable load-carrying capacity is designed and fabricated for experimental study. In the two experiments, the effectiveness of the proposed quasi-zero stiffness mechanism used in the field of constant-force output and vibration isolation is tested.
Highlights
Compliant mechanisms, which gain their output motion from the deformation of flexible members, possess several attractive advantages over classical movable joints, including low cost, reduced assemble time, increased precision, no wear, no friction and no backlash (Howell, 2001)
Passive vibration isolation is of vital importance to many precise instruments, but low frequency vibration isolation has always been a tough topic, since it will result in low static stiffness, large static displacements and low loading capacity of precise instruments (Kovacic et al, 2008a)
Carrella et al (2007) and Kovacic et al (2008a) proposed a kind of nonlinear quasi-zero stiffness vibration isolator consisting of a vertical linear spring produced positive stiffness and two nonlinear pre-stressed oblique springs acted as a negative stiffness structure
Summary
Compliant mechanisms, which gain their output motion from the deformation of flexible members, possess several attractive advantages over classical movable joints, including low cost, reduced assemble time, increased precision, no wear, no friction and no backlash (Howell, 2001). Nonlinear vibration isolation mechanisms have a number of disadvantages, including difficulty in obtaining mathematical expressions of stiffness, jump phenomenon degrading isolator’s performance (Kovacic et al, 2008b) and easy interference from the excitation amplitude and damping (Liu et al, 2013) To overcome those issues, in this paper, a bistable compliant mechanism, which is designed based on fixed-guided beams and has constantnegative-stiffness characteristic, is applied as a negativestiffness mechanism of a quasi-zero stiffness mechanism. The novel bistable compliant mechanism with constant negative stiffness is connected parallelly with a linear positive-stiffness compliant mechanism to obtain a linear quasi-zero stiffness mechanism, which is applied as a low frequency vibration isolator and a constant-force mechanism.
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