Keywords: piezoelectric actuators, piezoelectric sensors, smart structures, tetrahedral space frame, positive position feedback, PPF, finite element method, modelling, vibration control, micromachining, precision machining
Finite element modelling and vibration control of a tetrahedral space frame applied to micromachining
This paper presents the modelling and vibration control of the tetrahedral space frame. The tetrahedral frame is a structure that is used in precision machining applications. When machining at a high precision requirement, structural vibration is of the utmost concern. This research develops finite element models using ANSYS and Matlab that can be used to implement a positive position feedback controller. In order to control and reduce the vibration magnitude, collocated piezoelectric actuators and sensors are placed at the optimal positions on the tetrahedral space frame. ANSYS is used to conduct a modal analysis on the structure to obtain the mode shapes, which determines the weakest positions and critical vibration modes under certain machining conditions. In Matlab, a finite element model is created which uses Timoshenko's beam elements and it is further converted to state-space allowing the model to be controlled using programme simulations. A positive position feedback controller is chosen due to its non-sensitivity to spillover effects.