| 摘要 |
PURPOSE:To increase the positioning speed for repetitive shift and stop of a stepper, etc., by controlling the distance, the speed, vibrating state, etc., against an X/Y stage at a time point where the X/Y stage is switched to the position servo from the speed servo so that those factors are all equal at every step. CONSTITUTION:The speed servocontrol is performed in a section SS between time points tA and tE and the position control is carried out in a section PS between time points tE and tP respectively. The section includes an acceleration section AB where the acceleration is applied at a fixed speed, a high and fixed speed section BC where the X/Y stage moves at a high and fixed speed Vmax, a deceleration section CD where the deceleration is applied, and a low and fixed speed section where the X/Y stage moves at a low and fixed speed Vmin. The length of linear sections AB, BC and CD of acceleration and deceleration and a DOWN speed switching point C are decided from the difference of the present position (start point A) and a target position point P, i.e., the shift distance of the X/Y stage. It is available to set automatically the reference time T used for decision of tolerance at an optimum level in order to minimize the time between the start point A and a stop point P. Otherwise the speed Vmin is optimized for each step in order to minimize the time needed for position servocontrol. |
