Ultrasonic motors using shear-type piezoelectric ceramics
The shear piezoelectric constant value for d<inf>15</inf> has a higher value compared with constant d<inf>31</inf> or d<inf>33</inf>. Also, the value of the shear electromechanical coupling coefficient k<inf>15</inf> is bigger than that of k<inf>31</inf> or k<inf>33</inf>. A design for an ultrasonic motor based on the shear coefficients has the potential for superior performance, relative to conventional d<inf>31</inf> and d<inf>33</inf> based ones. Thus, this paper presents ring type, tube type, disk type and rod type piezoelectric ceramic elements, which use the d<inf>15</inf> shear piezoelectric constant effect. The application methods and driving mechanism of the typical ultrasonic motors which use the shear piezoelectric ceramic elements are analyzed. The applications of shear piezoelectric ceramic elements accords with the requirements of the development trends of ultrasonic motors, such as large strain and miniaturization.