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Published Articles


The Volume 3, No 4, December 1998




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Parameter Estimation for Rigid-Body Mass Moments of Inertia

S.A. McInerny


https://doi.org/10.20855/ijav.1998.3.427


Two procedures that have the potential to reduce the time required to measure rigid-body mass moments of inertia by a factor of five, are presented. These procedures estimate the mass moments of inertia of a rigid-body from multiple-input, multiple-output (or multiple sets of single-input, multiple-output) vibration test data. The procedures are alternatives to the trifilar pendulum method of measuring the mass moments of inertia of a rigidbody. The first procedure described is the most direct, but requires that the forces on the test specimen at each of the mount attach points be directly measured using dynamic force gauges. The least squares method is then applied to an over determined set of equations involving only the six unique elements of the moment of inertia matrix. The second procedure, which does not require measurement of mount forces, is based on a sum of scalar equations (consisting of weighted vector norms) that eliminates the system damping matrix from consideration. The least squares method is then applied to an over determined set of equations for the six unique elements of the inertia matrix and the twenty-one unique elements of the system stiffness matrix.


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Adaptive Active Control of Machine-Tool Vibration in a Lathe

I. Claesson and L. Hakansson


https://doi.org/10.20855/ijav.1998.3.428


In turning operations the relative dynamic motion between the cutting tool and workpiece, or vibration, is a frequent problem. This affects the results of the machining, and in particular, the surface finish. Tool life is also influenced by vibration. Noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. With proper machine design, i.e. improved stiffness of the machine structure, the problem of relative dynamic motion between the cutting tool and workpiece may be partially solved. However, by use of active control of the machine-tool vibration, a further reduction of the dynamic motion between the cutting tool and workpiece can be achieved. It was found that adaptive feedback control of the tool vibration in the cutting speed direction, based on the fil-tered-x LMS-algorithm, enables a reduction in vibration, by up to 40 dB at 1.5 kHz, and by approximately 40 dB at 3 kHz. It was also observed that the introduction of leakage in the filtered-x LMS-algorithm improved the stability properties of the feedback control system. A significant improvement in the workpiece surface finish was observed and a substantial reduction in the noise level was obtained with adaptive control.


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Vibration of a Rod-clutch System

L. Cveticanin


https://doi.org/10.20855/ijav.1998.3.429


The vibrations of a rod-clutch system are analyzed in this paper. The motion of the system is described with two second order nonlinear differential equations. The parameters of the clutch define the character of the rod motion. If the motion of the rod is chaotic and the clutch the rod is connected to the rod with certain properties the motion of the rod becomes periodic or the clutch represents an absorber of vibrations. A numerical example is given to prove the analytical results.


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