A novel mode switching control for fast settling and high precision positioning

In the past several years there has been increasing interest in high-density data storage and large flat panel display. The manufacturing equipments are required to have high precision accuracy and high product throughput The control algorithm should perform fast point-to-point motion and high precision positioning to meet these requirements. Mode switching control approaches are widely used to meet these requirements. This paper proposes a new MSC algorithm with an application to dual stage for long range and high precision positioning. The proposed MSC uses a proximate time-optimal servomechanism for the fast point-to-point motion and a time-delay controller for the high precision positioning around the reference position. Unlike the conventional MSC approaches, the new method does not require an initial value compensation at the instance of mode switching. This is because the TDC controller is capable of calculating smooth control input using a previous PTOS control input and state variables during the mode switching. Experimental results show that the proposed method enables smooth mode switching and improves the settling time and the precision accuracy after settling by over than 33 % and 45 %, respectively.