Orientation Compensation of an Inchworm Stage with Optical Navigation

The orientation compensation of a three-degrees-of-freedom inchworm stage with optical navigation is described. As the stage does not use any guide or preload, a closed loop feedback control system is employed to retain the accurate orientation of the stage. The stage consists of piezoelectric actuators (piezos) for thrusting and electromagnets for positioning. A non-excited electromagnet is moved by the deformation of piezos, and excited electromagnets retain their positions. However, a weak electromagnetic force prevents the stage from retaining its accurate position. In addition, a friction force reduces the displacement of the non-excited electromagnet. Therefore, the orientation of the stage is measured using a light source and an optical detector, and the deformation of the piezos is controlled. The orientation error is reduced by using optical navigation.