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This paper presents a control design methodology for high-precision positioning; in particular, the compensation for the effects of vibration modes and nonlinear friction on the positioning performance is taken into account in this methodology. In the controller design, the servo bandwidth of the feedback control loop should be expanded to compensate for the nonlinear friction, while robust stability against frequency variations in the vibration modes should be ensured. In this study, therefore, a strain feedback for vibration modes is adopted to provide robustness against the frequency variations and to improve the disturbance suppression performance by expanding the bandwidth of a disturbance observer; this strain feedback is based on the use of a piezoelectric element. The efficacy of the proposed positioning control approach has been verified by conducting experiments using a prototype for industrial table drive systems.

SUMMARYSeismic electromagnetic (EM) phenomena have been observed at many laboratories with specially designed systems. Recently we can utilize radio receivers, personal computers, and communication systems with higher performances and reasonable cost. It is possible to observe seismic EM phenomena not only by specially designed systems but also by a simple observation system integrated by these devices and systems. We have created an observation system for seismic EM phenomena with them in the very high frequency (VHF) band, from 76 MHz to 90 MHz, assigned for FM broadcasting exclusive use in Japan. We are surrounded by many EM waves, such as broadcasting, communication usage, and man-made noises. Thus, we have newly developed the dual frequency observation method. In this paper, we describe an observation method that can identify whether a received signal is a broadband EM wave or an artificial FM radio wave. Next, the observation results for broadband EM waves from galactic noise and solar flares are presented. Then, the observation results for FM radio waves reflected from sporadic E layer and the Leonid meteors are shown. Finally, the observation results for the detected broadband EM waves associated with the Geiyo earthquake are described.

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This paper presents a novel control methodology for robust high-precision positioning systems. This methodology is based on strain feedback using a piezoelectric element. The mechanical vibration modes at around the control bandwidth cause deterioration of system stability. This prevents the positioning performance from being robust, particularly against variations in the vibration frequency. In this research, therefore, a robust positioning system was designed by applying an additional compensation loop by strain feedback; here, a piezoelectric element that acts as a strain sensor detects the vibration signal. This makes the performance of the system robust. The proposed compensation approach has been verified by numerical analyses and by experiments using a positioning device for industrial galvano scanners.