Vibration performance evaluation of planar flexible multibody systems with joint clearance

Abstract

Clearances are necessary in assemblage of mechanisms to allow the relative motion between the members. This clearance is due to machining tolerances, wear, material deformations, and imperfections, and it can worsen mechanism performance such as precision and vibration. As a new study in this topic, the effect of joint stiffness on the variation of instantaneous natural frequencies and mode shapes of a flexible four-bar mechanism with a clearance between coupler and follower is studied in this paper. To model the clearance, the continuous contact approach is used. The Lankarani's and Nikravesh's continuous contact force model is used to model the contact force arising from contact between journal and bearing. Finite element method is used to determine the instantaneous natural frequencies and their corresponding mode shapes. The stiffness of the clearance is modeled as a linear spring added to the assembled stiffness matrix. To validate the clearance model in rigid mechanism, the dynamic response is compared with the results in the literature. To show the validity of the formulation which calculates the instantaneous natural frequencies, two methods are used and compared with each other in the case no clearance exists. The results show that taking the joint stiffness into account has a considerable effect on the instantaneous natural frequencies and their corresponding mode shapes of a flexible multibody system.

Design Framework for Motion Generation of Planar Four-Bar Linkage Considering Clearance Joints and Dynamics Performance

“…Dynamic modeling of the mechanism systems has been identified as an important tool in the analysis, design, optimization, and simulation. To establish the dynamic model and achieve the dynamics analysis of mechanical systems with clearance joints, scholars have presented many novel and effective methods, such as [24][25][26][27][28]. Based on the dynamic models, scholars around the world have carried out many significant research works about the dynamic response, performance evaluation, and optimization of mechanical systems with clearance joints.…”

Kinematic performance of planar 5R symmetrical parallel mechanism subjected to clearances and uncertainties

“…The complete differential-coefficient theory has been used to analyze the position-stance error of the moving platform of a planar changeable parallel mechanism [11]. The influence of the clearances size and fiction coefficient on the dynamic response of planar multi-body system is numerically analyzed [12][13][14]. Finally, an optimization method for the dynamic design of planar mechanism with clearances at joints has been studied [15].…”

Measurement method of rotation angle and clearance in intelligent spherical hinge

“…Olivier A. Bauchau presented a comprehensive approach to the modeling of joints with clearance in nonlinear, flexible multibody systems [11]. Saeed Ebrahimi adopted a continuous contact approach to model clearance in planar flexible multibody systems [12]. Pfister developed a novel fibre optic laser Doppler position sensor for single-blade tip clearance measurements [13].…”