Design and Prototyping of Biaxial Flexible Support Table for Fine Positioning Through Controlled Magnetic Attraction Forces

Abstract

High-precision positioning can be obtained by reducing sliding friction and securing support rigidity. A prototype of a biaxial positioning table with non-contact drive by magnetic force and flexible mechanism support was developed to meet these requirements. The magnetic poles of a permanent magnet and an electromagnet were placed opposite to each other with an appropriate gap between them, and the attraction force between the two poles was used as the actuator for fine feed. The table was supported with a flexible mechanism composed of metal (A2017) beams with notches and elastic hinges assembled into a square frame shape. The permanent magnets were commercial neodymium magnets, and the electromagnets were self-made of S45C core bars. Two types of attraction force, maximum and minimum, were set depending on the number of neodymium magnets and the magnetic pole gap. The relationship between the applied current and attraction force for each type was calibrated using an electronic balance. Upon increasing and decreasing the applied current to the electromagnets, a linear relationship was shown between them. The relationship between the attraction force and the X- and Y-axes displacements was simulated by finite element analysis. Based on both results, the relationship between the applied current and displacement was estimated. The fine-feed experiment was conducted in both directions of the X- and Y-axes by applying current to electromagnets in a stepwise sequence. The displacements of total strokes in the long-stroke feed on applying the maximum attraction force were 340 μm and 315 μm for the X-axis and 160 μm and 133 μm for the Y-axis. These values are 2.0–2.8 times larger than the estimated displacement. Additionally, 3%–12% of the other axes interference occurred between the X- and Y-axes. In the high resolution feed applying the minimum attraction force, the displacement per step was 75 nm and 78 nm for the X-axis and 35 nm and 39 nm for the Y-axis. Cooperative feed with a combination of long stroke and high resolution was verified to be feasible.