An In-situ Identification Method for Joint Parameters in Mechanical Structures

Abstract

This paper presents an improved scheme based on the frequency response functions (FRFs) for in-situ identification of joint parameters of mechanical structures. Despite that measurement of FRFs at joint locations is essential for identifying the joint parameters of a structural dynamic system, it is often impossible to measure FRFs at joint locations. To this end, the present paper suggests an indirect estimation technique for unmeasured FRFs which are required for identification but not available. Theoretical investigation is made to delineate the effects of measurement noise and modeling error on indirect estimation and identification. Two index functions are introduced, which can indicate the quality of estimation or identification along the frequency. The index functions are proven to be useful not only as a weighting function in the identification procedure but also for evaluating the frequency region appropriate for identification. A series of simulations as well as experiments are performed for validation of the method.

Identification of Dynamic Bearing Parameters: A Review

“…For fluid-film bearings where the dynamic characteristics change for the reverse direction of rotation of the rotor an external auxiliary means of excitation described by Muszynska and Bently (1990) can be used. Hong and Lee (1992) and Hong et al (1999) extended the method for flexible rotor-bearing system by using a model updating technique (Friswell and Mottershead, 1995). Murphy and Wagner (1991) presented a method for the extraction of stiffness and damping coefficients for hydrostatic bearings using a synchronously orbiting intentionally eccentric journal as the sole source of excitation.…”

Comparative Assessment of Frequency Dependent Joint Properties Using Direct and Inverse Identification Methods

“…Due to these characteristics common to direct measurements, the test can often be time consuming and only able to determine single stiffness terms in the joint stiffness matrix. Inverse methods have been developed as another approach to characterize joint stiffness properties [1,[5][6][7].…”

“…Other methods [5][6][7] incorporate the use of elastic beam theory in place of the rigid inertia elements and thus permit incorporating preload into the identification experiment. Hong and Lee [6] develop a method in which an unconstrained structure (base structure) and an experimental setup (base structure connected to joints) is used to identify joint properties.…”

“…In most applications, the constrained structure is not completely known. This requires the need to estimate unobserved frequency response functions [7]. Joint locations are typically unobserved coordinates due to obstructions and lack of experimental equipment; yet, these frequency response functions are required for estimation of the unknown joint properties in the identification formula.…”

“…The second step in the inverse identification method, developed by Hong et al [7], consists of using the identification formula for unknown joint properties.…”