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A new methodology of combining the finite element model of a structure with the results of the experimental modal analysis technique was applied to a tool-holder system with a taper joint to identify its joint stiffness and damping characteristics. The underlying background is briefly introduced followed by an experimental verification of the proposed method.

This paper presents a new on-line control scheme utilizing the Forecasting Compensatory Control (FCC) method for improving cylindricity in boring operations. The proposed control method was implemented through the development of a laser-based in-process cylindricity measurement, a digital microcomputer, and a piezoelectric actuator system. Through on-line cutting experiments, the improvement in cylindricity accuracy was found to be in excess of 60 percent.

The basic problem in modal analysis of machine tool structures is the extraction of modal parameters from the measured transfer function data. Conventionally this task is performed in two steps. The transfer function is determined using a Digital Fourier Analyzer followed by a suitable curve fitting procedure. In order to avoid the inherent problems associated with these procedures a new approach for modal analysis is proposed in this paper. Anticipating the stochastic nature of the systems excitation and response Modified Autoregressive Moving Average Vector models (MARMAV) are proposed. The modeling procedure yields a parametric representation of the structural behavior allowing the extraction of the modal information in one step, directly, rather than in two as in the conventional approaches. The mathematical foundation for the approach is given along with its application to a simulated three-degree-of-freedom system and a knee type milling machine. The newly proposed procedure is commensurate to the existing ones in light of the computational efforts involved; however, it eliminates the subjective judgment of the analyst since the modeling procedure is based on rigorous statistical adequacy checks. Finally, the proposed approach is amenable for implementation in a computer-based machine tool structural dynamics analyzer.

A sensitivity analysis of the discrete-to-continuous transformation used in the “indirect” modeling of continuous-time systems from sampled experimental data is presented. For the transformation of poles it is shown that small errors in the discrete-time domain may yield large errors in corresponding continuous-time parameters, such as time constants, natural frequencies, and damping factors, if very fast sampling is used. An important consequence of this phenomenon is the introduction of large errors in the modal parameter estimates of the lower frequency modes of multiple degree-of-freedom systems. In order to alleviate this problem appropriate sensitivity specifications, leading to a lower bound for the allowable values of the sampling period, are introduced. The transformation of residues by the step approximation method is also examined, and, the results of the analysis are finally used for the development of guidelines for the appropriate selection of the sampling period so that the transformation sensitivity be confined within prespecified design limits.