UBC Theses and Dissertations
Modeling and active damping of structural vibrations in machine tools Amir Hossein, Hadi Hosseinabadi
Feed drives of High Speed Machine (HSM) tools deliver fast motions for rapid positioning of tool or work-piece. The inertial forces generated by acceleration and deceleration of large machine tool components excite structural modes of the machine tools and cause residual vibrations. Unless avoided, the vibrations lead to poor surface finish and instability of the drive's control loop. In this thesis, structural flexibilities are represented by linear and torsional springs and dampers to develop a mathematical model of the feed drive dynamics. The model includes the contribution of structural vibrations in measuring table position by a linear encoder. An identification algorithm is introduced to facilitate the estimation of rigid body and structural dynamics in frequency domain. The identified mathematical model is used to mimic the real machine in simulations with the purpose of analyzing the interaction between structural dynamics and a high bandwidth adaptive sliding mode controller. Meanwhile, efficiency of finite element modeling approaches in predicting this interaction prior to the physical production is investigated by replacing the machine dynamics by a FEM based model. The mathematical model is used to design a Kalman Filter which estimates the table's acceleration by taking double digital derivative of the encoder signal. The table's acceleration is used to modify the control loop to minimize the effect of undesired structural vibrations. It is shown that the vibrations can be actively damped, and the bandwidth of the drive can be increased. The increase in the servo loop bandwidth provides smoother motion and improves the tracking performance significantly.
Item Citations and Data
Attribution-NonCommercial-NoDerivs 2.5 Canada