This study presents innovative three-degree-of-freedom piezoelectric actuators. Under the piezoelectric force and dry friction, the piezoelectric actuators not only can move in the Z-axis direction, but also rotate around the Y-axis and Z-axis. The Z-axis displacement can reach 62 mm and the rotation angle around the Y-axis and Z-axis can reach 270° and 360°, respectively. Compared with the literature, this innovative actuator design achieves one-degree-of-freedom translation and two-degree-of-freedom rotation. Equations of motion are derived based on the piezoelectric properties and Newton’s law. Two types of actuators are created in this study. In the first type, the centers of four piezoelectric buzzers are attached to an arm while in the other type each rim of the four piezoelectric buzzers is attached to the arm. Experimental results are compared with theoretical results. According to the experimental results, the present actuator can accomplish a translational velocity of 11 mm s−1, a Y-axis angular velocity of 8.96 rad s−1, a Z-axis angular velocity of 2.63 rad s−1, and a force of 2.49 mN. By using four piezoelectric buzzers, this study creates piezoelectric actuators capable of both translational and rotational motions.

This study investigates the disk drive dynamics when a disk surface deforms and a disturbance force is exerted on a pickup head in near-field optical disk drives. Serving as an actuator, a piezotube is connected to the suspension of the pickup head. A model is constructed to investigate the pickup head dynamics. Equations of motion for focusing and track-following are derived in the presence of disk surface deformation and the disturbance force on the pickup head. A proportional and derivative control method is carried out in numerical examples. There exists a critical proportional gain that influences the number of resonances in the frequency spectra. Numerical results show that there is only one resonance or none in the frequency spectra when the proportional gain is larger than the critical proportional gain. Hence, the tracking error ratio becomes smaller than one within a wide frequency range, if few resonances appear in the frequency spectra.