Study of Operational Modal Analysis Techniques on the Structural Dynamic Design of Machine Tool

Operational Modal Analysis (OMA), is an output-only technique used in estimating modal parameters. It has several advantages over the traditional Experimental Modal Analysis (EMA)—for one, it is in-situ testing, which allows measurements of structures in operation, revealing their true dynamic characteristics, and dispenses expensive input-excitation equipment. Being nondestructive, OMA is especially suitable for health monitoring and fault diagnosis of large structures. The technology was first introduced to the field of civil engineering in 1990, and gained significant attention; in recent years, it has been widely applied in the fields of automobile and aerospace engineering; and lately, it is heatedly discussed in the field of system identification. However, few papers discussing this latest development are found in Taiwan. This two-year research project aims at adopting the OMA approach (1) to renovate system parameter identification technology, (2) to improve the surface grinder’s dynamic performance, (3) to complete an OMA technical capacity and sensitivity analysis, (4) to develop a parameter identification auto-tuning technique, (5) to explore the relationship between machine tool structure and cutting stability, and (6) to improve and apply to the particle swarm optimization. The ultimate goal of this project is to construct a product development platform which will integrate technology of analysis, modeling, testing, and control strategies. The first year of research will focus on four major tasks: (i) to build up an OMA technical capacity by using a simpler mechanical modules to study and compare three OMA methods—Stochastic Subspace Identification (SSI), Enhanced Frequency Domain Decomposition (EFDD) and Least Squares Complex Frequency (LSCF); (ii) to construct a theoretical and analytical model for the mechanical modules, and its dynamic formula; (iii) to update model, including completing a structural dynamic simulation, model verification, and a total solution of the modification; and (iv) the first-stage research of PSO. Based on the research results of the first year, the second year will focus on upgrading the dynamic performance of a surface grinder, which entails (i) a study of dynamic characteristics of the machine tool, including modeling, identification of improvements of OMA techniques in cutting/grinding, a structural sensitivity analysis , and the relationship between dynamics and stability during the cutting process; (ii) a study on control and prevention of vibration, including the structural dynamic modification, multi-objective searching by PSO technique, the fundamental work for entering the field of Multidisciplinary Design Optimization (MDO), and finally the publication of the two-year research results.

Project ID:PB10007-7263
External Project ID:NSC100-2221-E182-045