The nano-motion actuator (NMA) had been designed for precise track following on a spinstand which evaluated read and write performance of a high-density magnetic recording. A required specification of the original NMA was a resonance frequency of over 5 kHz and working distance of over 10 lm. However, according as industrial researches of the perpendicular magnetic recording progress, a phenomenon that is called WATER (Wide Area Track ERasure) should be evaluated on the spin-stand. Since required working distance to evaluate the WATER reaches to over 50 lm, an X-Y stage on the spin-stand was cooperated with the NMA, as usual. However, the piggyback system which combined the X-Y stage with the NMA could not observe the WATER phenomenon continuously on a disk medium. Therefore, a new NMA which had a large working distance of over 50 lm was required. The new NMA was designed and simulated several resonance modes by using 2D or 3D of EFM analysis. The new actuator called as NMAk501 realized the working distance of 43.3 lm and the resonance frequency of 5.33 kHz with a mechanical damper. As wide servo bandwidth was reached to 2.75 kHz to apply a PID controller, clear and sharp step responses could be showed at a 1 and a 10 nm, respectively. Furthermore, when precise positioning stability was evaluated, the NMA-k501 was positioning within 0.101 nm at 3r.

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We developed a new laser device using a composite-type optical fiberscope for laser surgery to treat twin-twin transfusion syndrome. The composite-type optical fiberscope (2.2 mm in external diameter) consists of a centrally located single fiber for laser treatment (0.1 mm in diameter) and its surrounding fibers for diagnosis. This fiberscope enables transmission of 40-W Yb fiber laser. The Yb fiber laser can be focused to 10mm focal length using two lenses on the tip of the fiberscope. In this research, we emitted the laser to in vivo porcine mesenteric vessel with blood flow both with an established laser fiber of 0.6-mm diameter (0.6-mm normal fiber) and with our composite-type optical fiberscope to compare the cautery performance of those devices. According to the experimental results, the composite-type optical fiberscope has a cautery efficiency equal to that of a 0.6-mm normal fiber, and it can contract the vein diameter about 35% as compared to the vein diameter before laser irradiation.

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Our new laser surgery device may be useful for many surgical applications because it allows simultaneous diagnosis and treatment as well as intuitive aiming at a target despite its ultrasmall 1.1-mm diameter.

A new design method for a generalized predictive control (GPC) system based on parametrization of two‐degree‐of‐freedom integral controllers has been proposed. The objective is to guarantee stability of the control system without depending on the design parameters and to achieve low sensitivity against the plant perturbation and the disturbance. The design procedure consists of two steps. First, we design a basic integral controller for a nominal plant using the linear quadratic Gaussian (LQG) method and parametrize a class of two‐degree‐of‐freedom stabilizing controllers. Next, we tune the feedforward controller to incorporate the GPC method into our control structure. A numerical example is presented to show the effectiveness of the proposed method by comparing it with the conventional GPC method. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 62–70, 1999

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