Estimation of an Active Boring Bar's Control Path Frequency Response Functions by Means of its Three-Dimensional Model with Coulomb Friction

摘要

In metal cutting boring bar vibrations may be attenuated using an active boring bar with an embedded piezoceramic actuator, attached error sensor and a suitable controller. In the design of active boring bars accurate modelling of control path frequency response functions (FRF), i.e. FRF between the actuator voltage and the boring bars response signal (which is commonly acceleration), are of importance, e.g. for the decision concerning the favorable position of the actuator inside the active boring bar to maximize vibration suppression. This paper addresses the influence of the Coulomb friction force on the transfer function estimates between the actuator voltage and the boring bar acceleration calculated based on the "3-D" FE model of an active boring bar. Two types of approximations of the Coulomb friction force, the arctangent and the bilinear models, are evaluated concerning modelling the contact between the surface of the boring bar and the clamping house. Results of incorporation of the two different Coulomb friction force models into the active boring bar's SDOF model as well as "3-D" FE-model enabling variable contact between the boring bar, the clamping screws and the clamping house are presented in terms of control path FRF:s.