Abstract
In the project for new definition of the kilogram we need a positioning system tocontrol the scaning probe microscope to count silicon atoms. For this purpose, Wework on a two-stage moving structure. The stage with fine positioning resolution isactuated by a PZT and the other one with coarse resolution is driven by a voice coilmotor (VCM). For measurements, We use heterodyne laser interferometers as thedisplacement sensors. All of the measurement signals and feedback control signalsare processed in the single board computer in VME main frame. The system usessoftware PI controller to control PZT stage and sets a control band. When PZT stageis out of the control band, the VCM stage must change the moving speed to make PZTstage go back inside the band. At the present, our system can travel 1 mm range withless than 0.3 nm rms difference between prescribed position and measurement position.