Analysis, Design, and Control of a Novel Elastomeric Bearing Positioning Stage

As products are required with higher precision, vibration control becomes more important for precision machining and inspection. A stage with both fast positioning and relative vibration eliminated can improve product quality. Elastomeric bearings are widely used in the seismic engineering and precision machining fields. By utilizing their stiffness anisotropy, miniaturized bearings can be made of rubbers and have the same function as much larger compliant mechanism-based designs. This provides possible advantages in precision positioning. In this paper, to model the system dynamics of the stage, the mechanical properties of elastomeric bearings are determined through essential material tests of the load cells in this system. The results show that the bearing stiffness is both frequency- and time-dependent. A single-degree-of-freedom precision stage containing four elastomeric bearings is then designed and realized. The stiffness of the elastomeric bearings is modeled as a generalized Maxwell model by system dynamics testing of the controller design. A closed-loop control system comprising an AVM40-20 voice coil motor, an ASP-10-CTR capacitance probe, and an Integral Sliding Mode controller is proposed for the precision stage. Signal processing for the entire system is performed under an NI cRIO-9014 LabVIEW field-programmable gate array real-time controller. In comparison with a previous compliant mechanism-based design, the stage size is reduced from 130 x 40 x 15 mm(3) to 30 x 33 x 33 mm(3), the positioning stroke is increased from 101 to 139 mu m, and the bandwidth is increased from 29 to 350 Hz.