The Experimental Determination of Squeeze-Film Dynamic Coefficients Using the State Variable Filter Method of Parametric Identification

1989 ◽  
Vol 111 (2) ◽  
pp. 252-259 ◽  
Author(s):  
J. Ellis ◽  
J. B. Roberts ◽  
M. D. Ramli
Keyword(s):  
Parametric Identification ◽  
Squeeze Film ◽  
Filter Method ◽  
State Variable ◽  
Dynamic Coefficients ◽  
Low Weight ◽  
State Variable Filter ◽  
Film Stiffness ◽  
Forced Excitation

The state variable filter method of parametric identification is applied in the determination of squeeze-film dynamic coefficients from forced excitation tests on an experimental rig. The experimental squeeze-film damper had a centralizing spring, a central circumferential oil feed groove, and no end seals. Forced excitation tests are recorded at various journal support system natural frequencies and at different journal eccentricities. From these tests, estimates of the direct squeeze-film damping, stiffness and inertial coefficients are derived and presented. These results are shown to be in good agreement with results recently obtained using an independent frequency domain technique. The experimental damping and inertial coefficients were found to be considerably larger than values predicted by conventional short-bearing theory, but relatively insensitive to the support system’s natural frequency (and the forcing frequency) for most of the range investigated. The fluid film stiffness coefficient values at low values of the system’s natural frequency agreed with results from static stiffness tests. Two geometrically identical journals were used, one of steel and one of a low-weight, magnesium alloy. The use of the low weight journal markedly reduced the scatter in the inertial and film stiffness coefficients.

A New Approach for the Determination of Cam Follower System Parameters

1988 ◽  
Vol 202 (5) ◽  
pp. 361-368
Author(s):  
M K Baru ◽  
J Ellis
Keyword(s):  
Parametric Identification ◽  
Filter Method ◽  
New Approach ◽  
State Variable ◽  
Cam Follower ◽  
State Variable Filter ◽  
Stiffness And Damping ◽  
Design And Manufacture

This paper reports a first investigation in the use of the state variable filter method of parametric identification in the determination of the mass, stiffness and damping content of cam follower systems. Simulated and real experimental data are processed by the technique with good results. Further developments are necessary (extension to higher order systems and inclusion of Coulomb damping) with the long-term aim of applying the results in the design and manufacture of dynamically tuned cams.

Determination of Squeeze-Film Dynamic Coefficients From Experimental Transient Data

1987 ◽  
Vol 109 (1) ◽  
pp. 155-163 ◽  
Author(s):  
M. D. Ramli ◽  
J. B. Roberts ◽  
J. Ellis
Keyword(s):  
Parametric Identification ◽  
Optimization Techniques ◽  
Squeeze Film ◽  
Dynamic Coefficients ◽  
Free Decay ◽  
Transient Data

A technique for obtaining estimates of the direct damping and inertial coefficients of a squeeze-film bearing is described. This involves applying parametric identification and optimization techniques to digitized, free-decay experimental displacement records. The experimentally obtained coefficients, derived by this technique, were found to be significantly higher in magnitude (in some cases by a factor of about 10) than the corresponding values derived from conventional short-bearing theory, and to be virtually independent of the frequency of vibration.

A Comparison of Identification Methods for Estimating Squeeze-Film Damper Coefficients

1988 ◽  
Vol 110 (1) ◽  
pp. 119-127 ◽  
Author(s):  
J. Ellis ◽  
J. B. Roberts ◽  
A. Hosseini Sianaki
Keyword(s):  
A Priori ◽  
Simulated Data ◽  
Experimental Tests ◽  
Forced Response ◽  
Squeeze Film ◽  
Filter Method ◽  
Single Degree Of Freedom ◽  
Response Data ◽  
State Variable ◽  
State Variable Filter

The problem of identifying the dynamic coefficients relating to inertia, damping, and stiffness, in a single degree of freedom model of squeeze-film behavior, is discussed. It is demonstrated that two methods—referred to as “invariant imbedding” and “state variable filter”—are applicable, and that both yield a recursive scheme for sequentially estimating all three coefficients. The methods are compared through an analysis of simulated data, where the coefficient values are known a-priori. This is followed by a presentation of some typical results obtained from experimental tests, using both transient and forced response data. The comparisons indicate that the state variable filter method is much superior, with respect to both computational efficiency and accuracy.

The Complete Determination of Squeeze-Film Linear Dynamic Coefficients From Experimental Data

1990 ◽  
Vol 112 (4) ◽  
pp. 712-724 ◽  
Author(s):  
J. Ellis ◽  
J. B. Roberts ◽  
A. Hosseini Sianaki
Keyword(s):  
Experimental Data ◽  
Initial Conditions ◽  
Parametric Identification ◽  
Squeeze Film ◽  
Time Interval ◽  
Cross Terms ◽  
Complete Set ◽  
Data Tables ◽  
Linearized Model ◽  
State Variable Filter

This paper describes the use of the State Variable Filter (SVF) method of parametric identification to estimate the complete set of twelve linear hydrodynamic coefficients for a squeeze-film bearing system. Simulated force and displacement data are used to assess the algorithm and issues such as noise tolerance, the influence of sample time interval and input signal complexity are investigated. Real experimental data from a squeeze-film rig are processed by the SVF method and the technique used to derive linearized model coefficients is explained. For the first time, all twelve coefficients in the general linear model are estimated from experimental data. Tables and graphs are used to present the coefficient values. Sixteen parameters (including four parameters relating to initial conditions) are identified in each experiment. The direct coefficients show the same trends and orders of magnitude reported in earlier and simpler tests, relating to a single-degree-of-freedom system. The damping cross-terms are found to be virtually zero whereas the inertial and stiffness cross-terms appear to be significantly nonzero.

A Study on New Identification Technique With Application to Squeeze Film Bearing System

1993 ◽  
Author(s):  
Ting Nung Shiau ◽  
Chun Pao Kuo ◽  
G. J. Sheu ◽  
P. L. Kuo
Keyword(s):  
Hybrid Method ◽  
Parameters Identification ◽  
Experimental Simulation ◽  
Squeeze Film ◽  
Filter Method ◽  
Noise Effect ◽  
Initial Values ◽  
Identification Technique ◽  
State Variable Filter ◽  
Identification Techniques

Two identification techniques, which are the Method of Feasible Directions (MFD) based on optimization concept and the Hybrid Method (HM) combining the merits of the State Variable Filter method (SVF) and MFD, are proposed for the parameters identification of rotor system with squeeze-film damper (SFD). The parameters of SFD, including hydrodynamic inertia, damping and stiffness, are identified and the results obtained by using MFD and HM are compared to those using SVF. The accuracy and efficiency of using these techniques are demonstrated by the experimental simulation with various noise levels and different initial values. The results indicate that the choice of initial values is of no significant effect on SVF method and the accuracy of SVF depends on the level of noise. However, for MFD method, it is almost independent of noise effect but significantly affected by the choice of initial values. The Hybrid Method (HM) is proposed to overcome these handicaps and found of better accuracy and efficiency than SVF and MFD. Then, it is highly recommended for the parameters identification of system with noise effect.

scholarly journals Determination of positive realizations with reduced numbers of delays or without delays for discrete-time linear systems

2012 ◽  
Vol 22 (4) ◽  
pp. 451-465 ◽  
Author(s):  
Tadeusz Kaczorek
Keyword(s):  
Transfer Function ◽  
Linear Systems ◽  
Discrete Time ◽  
Sufficient Conditions ◽  
Diagram Method ◽  
State Variable ◽  
Discrete Time Systems ◽  
Time Systems ◽  
Time Linear

A new modified state variable diagram method is proposed for determination of positive realizations with reduced numbers of delays and without delays of linear discrete-time systems for a given transfer function. Sufficient conditions for the existence of the positive realizations of given proper transfer function are established. It is shown that there exists a positive realization with reduced numbers of delays if there exists a positive realization without delays but with greater dimension. The proposed methods are demonstrated on a numerical example.

Automatic 3-D Crack Propagation Calculations in Industrial Components: A Pure Hexahedral versus a Combined Hexahedral-Tetrahedral Approach

2007 ◽  
Vol 348-349 ◽  
pp. 45-48
Author(s):  
Guido Dhondt
Keyword(s):  
Crack Propagation ◽  
Computing Time ◽  
Propagation Direction ◽  
Hexahedral Elements ◽  
Crack Propagation Direction ◽  
Low Weight ◽  
Out Of Plane ◽  
Hexahedral Meshes ◽  
Crack Faces

In recent years, increased loading and low weight requirements have led to the need for automatic crack tracing software. At MTU a purely hexahedral code has been developed in the nineties for Mode-I applications. It has been used extensively for all kinds of components and has proven to be very flexible and reliable. Nevertheless, in transition regions between complex components curved cracks have been observed, necessitating the development of mixed-mode software. Due to the curvature of the crack faces, purely hexahedral meshes are not feasible, and therefore a mixture of hexahedral elements at the crack tip, combined with tetrahedral in the remaining structure has been selected. The intention of the present paper is to compare both methods and to point out the strength and weaknesses of each regarding accuracy, complexity, flexibility and computing time. Furthermore, difficulties arising from the out-of-plane growth of the crack such as the determination of the crack propagation direction are discussed.

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