Tatiana Smirnova

Analog versus Digital Control of Boring Bar Vibration

In workshops where metal cutting is performed, the machining processes frequently introduces productivity degrading vibration problems and annoying sound, sometimes almost at unbearable levels. Besides producing disturbing noise, the vibrations affect the surface finish of the workpiece and the tool life. Two different approaches based on feedback control are investigated, both applied for the control of an active boring bar. The first approach is based on a digital adaptive feedback controller; the feedback filtered-X LMS algorithm. The second approach is based on an analog controller; a feedback controller with gain and phase orthogonally adjustable, thus flexible for the control of systems with different dynamic properties. Based on open loop frequency response function estimates, robustness and stability of both the digital and the analog feedback control system are discussed. A comparison of the two controllers concerning their boring bar vibration attenuation performance shows that the analog controller attenuates the vibration in same order of magnitude as the digital controller which is approximately by up to 40 dB.

Modeling a Clamped Boring Bar using Euler‐Bernoulli Beam Models with Various Boundary Conditions

This paper addresses modeling of a clamped boring bar using Euler‐Bernoulli beam theory. Euler‐Bernoulli beams with a number of different boundary conditions were used to model a clamped boring bar. Estimates of the boring bar’s natural frequencies and mode shapes were produced with each of the boring bar models. The estimates produced by the distributed‐parameter system models are compared with eigenfrequencies and mode shapes estimated based on experimental modal analysis of the actual boring bar clamped in a lathe.