A Miniature cantilever-type ultrasonic motor was fabricated using multilayer piezoelectric ceramics (MLPC) made of (Sr,Ca)2NaNb5O15 (SCNN), a Pb-free piezoelectric material, and the electrical driving properties were investigated. The displacement of SCNN-MLPC was 177 nm at 100 V, which was 10-fold the voltage of MLPC made of Pb(Zr,Ti)O3–Pb(Ni,Nb)O3–Pb(Zn,Nb)O3 (PZT). The ultrasonic motor using SCNN-MLPC started to rotate at 3.8 Vp–p, and showed the following characteristics: a revolution speed of Ω0=517 rpm, a torque of T0=1.4 µN m, and an efficiency of η=7% at 13.4 Vp–p. The power consumption, in this case, was 0.3 mW, which is not so high. On the other hand, an ultrasonic motor of the same form made of PZT-MLPC showed Ω0=610 rpm, T0=1.6 µN m, and η=9% at 1.9 Vp–p, and the same power consumption as the SCNN motor. That is, it was found that the SCNN motor was not so different from the PZT motor in terms of their characteristics; however, the SCNN motor needed 10 times as high a voltage as the PZT motor in electrical driving. In conclusion, it can be said that we succeeded in realizing a miniature cantilever-type ultrasonic motor using Pb-free MLPC.

We compute the massless five-point amplitude of open superstrings using the non-minimal pure spinor formalism and obtain a simple kinematic factor in pure spinor superspace, which can be viewed as the natural extension of the kinematic factor of the massless four-point amplitude. It encodes bosonic and fermionic external states in supersymmetric form and reduces to existing bosonic amplitudes when expanded in components, therefore proving their equivalence. We also show how to compute the kinematic structures involving fermionic states.

This paper deals with thin rotary and linear ultrasonic motors using a double-mode piezoelectric ceramic vibrator; a rectangular plate vibrator of the first longitudinal and second bending modes is utilized. A specific merit of the motors is that their thickness can meet the restriction of 10 mm, which is one of the practical requirements of a light load gearless motor. The rotary motor is intended for application in card forwarding, and the linear motor, in magnetic-head traveling and so on. Construction and characteristics of the motors are described herein.

No abstract

The present paper deals with some ultrasonic motors using longitudinal and bending multimode vibrators with their mode couplings caused by externally additional asymmetry or internal nonlinearity. A rectangular plate vibrator with two corners on one diagonal line cut to make its resonance modes couple with each other was used, along with a rectangular plate vibrator under the condition that two resonance frequencies are obtained, for example, as f L/f B=2.0, because internal nonlinear coupling of parametric vibration between two resonance modes is generated under this condition. Using these vibrators with mode couplings, it was found that some ultrasonic motors of simple form can be constructed. The ultrasonic motor using the phenomenon of mode-coupling vibrations dealt with here is not completely new, and a few trial constructions have already been reported [Jpn. J. Appl. Phys. 24 (1985) Suppl. 24-2, p. 739]. However, their motions were not reversible in ordinary driving with an electrical signal of a constant frequency. In contrast, the motors that the authors proposed in this paper can be expected to have a reversible motion.