Torsional Actuator and Stepper Motor Based on Piezoelectric d15 Shear Response

Abstract

Two novel devices, torsional actuator and torsional stepper motor, are described and their performance is investigated in detail. Both devices were designed to produce large angular displacement and large torque output from the piezoelectric d15 shear response. In the torsional actuator, the large displacement can be achieved due to built-in amplification of piezoelectric strain using the aspect ratio of a piezoelectric tube. It is shown that the displacement can be controlled by changing the length of the tube, and that the blocking torque developed is independent of the length. It is also shown that the performance of the actuator does not change under external torque load, and that the prestress in radial direction improves the mechanical strength of the actuator without affecting the produced displacement. In the stepper motor, the unlimited angular displacement of the rotor is produced by accumulating the piezoelectric strain by using a direct coupling mechanism between the stator and the rotor, where a clutch drives the rotor by locking it. The direct coupling makes it possible to transmit the whole power generated in the piezoelectric tube to the rotor, and thus achieve the high efficiency of the motor. Also, the locking mechanism allows smooth motion either in a continuous or stepwise fashion within a 360° interval with a precise control over angular positioning. In addition, the advantage of both devices is their simplicity and a possibility to produce them in the compact package.

Piezoelectric Response of Plastic Ionic Molecular Crystals: Role of Molecular Rotation

“…The predicted figures of merits indicate that the quinuclidinium and the dabco compounds have potential for application in shear mode energy harvesting devices. Most energy harvesting devices rely on the longitudinal piezoelectric response, but shear devices have also been studied [8][9][10][110][111][112][113][114].…”

“…Piezoelectric, ferroelectric, and relaxor-ferroelectric materials are key components in a range of technologies including sonar, ultrasound, radio frequency (RF) filters, accelerometers, motion sensors, micropositioning systems, and mechanical energy harvesting devices [1][2][3][4][5][6][7][8][9][10][11][12]. Characteristic for these materials is the coupling of mechanical and electrical properties.…”

Piezoelectric Response of Plastic Ionic Molecular Crystals: Role of Molecular Rotation

“…Piezoelectric, ferroelectric, and relaxor-ferroelectric materials are key components in a range of technologies including sonar, ultrasound, radio frequency (RF) filters, accelerometers, motion sensors, micropositioning systems, and mechanical energy harvesting devices. − These materials display a characteristic coupling of mechanical and electrical properties. In the direct piezoelectric effect, an applied stress σ j induces a polarization P i at a fixed electrical field E , d i , j = false( ∂ P i / ∂ σ j false) E .…”

A burst type signal generator for ultrasonic motor control

“…Most of piezoelectric motors used for various purposes are excited with signal, generated by signal generators [2,4,5,6,7,10,11], which requires some kind of traditional power supply. In order to use ultrasonic motors in areas, where traditional power supplies or electricity is unavailable, a new type of piezoelectric motor control technique is needed.…”

“…In order to obtain constant rotational or linear movement of piezoelectric motor, excitation signal should be harmonic, and in order to obtain step motion, excitation signal should be burst type [7]. In fact that the driving speed of the motor depends on both the amplitude and frequency of the excitation signal, the maximum speed or step size is obtained when burst type excitation signal frequency corresponds frequency of resonant vibrations of the piezoelectric motor stator [2,7].…”