Proposal of multirate PWM positioning control considering resonance mode for precision stage

Motion control techniques are employed on nanoscale positioning in industrial equipments, for example, NC machine tools, exposure systems, and so on. The advanced motion control techniques are based on the precise current control. However, speed-up of the precise current response has a serious limitation because of the carrier period of an inverter. In addition, the positional response has to be slower than the current response. In our past paper, we designed and fabricated an experimental precision stage. Then, we achieved a novel ultrahigh-speed nanoscale positioning based on multirate PWM control. The positional error was in 100 nm. The positioning time was 2 msec which was only 20 times as long as the carrier period. However, it was difficult to achieve faster and preciser positioning because of resonance modes of the stage. In this paper, we propose multirate PWM control considering resonance mode. Finally, simulations and experiments are performed to show the advantages of the proposed method.