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SUMMARYHigh-precision stages require high-speed and highprecision control to improve their production throughput and quality. However, their motion speed and accuracy are expected to reach a limit in the near future if the conventional high-precision stage structure is used. Therefore, the authors designed and fabricated a "catapult stage," which has a structure that can be decoupled into a fine stage and coarse stage. The catapult stage is different from conventional dual stages in which the fine stage is disturbed by the coarse stage because they contact each other. This paper proposes a novel control system design for the catapult stage and a control method that shortens the settling time by using final state control (FSC). So far, FSC has mainly been used for applications such as hard disk drives, for which the initial states are zero. However, it is important to consider the initial states for the catapult stage because the initial position, velocity, and acceleration of the catapult stage are not equal to zero. Simulations and experiments were performed to demonstrate the effectiveness of the proposed methods. C⃝ 2016 Wiley Periodicals, Inc. Electr Eng Jpn, 195(4): 39-49, 2016; Published online in Wiley Online Library (wileyonlinelibrary.com).

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Mode Switching Control (MSC) is a control method which switches from one control mode to another according to switching conditions. MSC has been widely used in robots and hard disk drives. Considering thrust limitations, however, the switching condition is generally conservative since there are not any clear criteria to switch the control modes. Therefore, this paper proposes a new index of switching condition which uses initial state variables in Final-State Control (FSC) with thrust limitations. The novelty of the index is that feedforward inputs which take an initial state to a final state in finite time can be generated automatically, while taking into account thrust limitations. The effectiveness of the proposed index is shown by simulations.

Precise positioning stages with high-speed and high-precision control performance are increasingly required for improving production efficiency and quality. In this paper, a final-state control method considering input limitation is applied to a novel high-precision dual stage during acceleration. In the method, the timing to activate the final-state control is automatically determined by a proposed criterion. The method can significantly reduce the calculation time so that realtime implementation becomes possible. Experimental results illustrate that the method can reduce the maximum thrust of the fine stage without degrading control performance.