Abstract
Using a new type of linear motor which has some advantages over conventional linear motor, we developed an ultraprecision positioning device whose stage was supported by linear ball guide ways. With very rigid structure of the device, the stage displacement was fed back by PI-D control using linear encoder of 0.034nm resolution. In this study, much attention was paid to the electric control system. It can compensate for the disturbance of induced electromotive voltage, which is generated in proportion to the stage velocity. We studied how the equivalent time constant T of control system has influence on the motor electric current Io and stage displacement deviation Δx, when the command of stage displacement xr was kept to be zero. The following results could be obtained. 1)With decrease of the time constant T of the current control system, the change of motor current Io became smaller and at the same time the change of stage deviation Δx became smaller. 2)At the smallest time constant T of the current system, the displacement resolution of 0.2nm could be obtained. 3)There is a possibility obtaining the displacement resolution of less than 0.1nm with more decrease of T.
