Patent attributes
A planar motor permits a thinner design, controlled vibration, and highly accurate positioning by disposing X-axis and Y-axis coreless type linear motors on the same plane without using an expensive linear guide and by incorporating high-accuracy capacitance displacement sensors in X and Y directions. Two pairs of permanent magnets are disposed such that they are respectively orthogonalized with respect to two axes that are orthogonalized with each other on a movable stage and that they generate magnetic fluxes in a direction perpendicular to a surface of the movable stage. Furthermore, the permanent magnets of one pair are disposed symmetrically to each other about one of the two axes, while those of the other pair are disposed symmetrically to each other about the other axis. Two pairs of coils are provided such that they oppose and match the two pairs of permanent magnets. A cross-shaped common electrode is installed to the movable stage and disposed such that it opposes a fixed electrode composed of two electrodes disposed on a fixed electrode base. Displacements of the movable stage can be determined from changes in capacitance of capacitors formed by the cross-shaped common electrode and the fixed electrodes.
