A novel active squeeze film journal air bearing actuated by high power piezoelectric transducers is presented.
The proposed bearing uses in-air squeeze film levitation to suspend the rotating spindle without contact. Unlike
conventional journal bearings, the presented bearing journal is formed by multiple independently vibrating
surfaces driven individually by piezoelectric transducers. Langevin type piezoelectric transducers with a special
radiation surface are developed. Detailed design procedures to develop the ultrasonic transducers are presented.
A complete spindle-bearing system is constructed to test the proposed squeeze film bearing. Load carrying forces
are measured at different vibration amplitude and compared with the calculated results. The proposed squeeze
film journal bearing is operated in ultrasonic frequency range. The achieved load capacity is about 50N, which
is five times of the load capacity achieved by the previous squeeze film bearings reported in the literatures.
An active spindle system with an Electro-Magnetic Actuator (EMA) is developed for micromachining. The process of developing controllers for this mechatronic system requires reasonable models that expose the important dynamic effects without being excessively complicated. This paper develops a MIMO model with four inputs and two outputs based on the bond graph method. This model considers the bidirectional bearing compliance as well as the external load effect. System state space equations are produced automatically from the bond graph model. Simulations in several conditions are done in both time and frequency domain. Results from simulation and experiments are compared.