A Cylinder-Type Multimodal Traveling Wave Piezoelectric Actuator

A Simple Model of the Energy Harvester within a Linear and Hysteresis Approach

In this article, a model of an energy harvester, the mechanical part of which is an inverted pendulum, is proposed. We investigated the stability of a linearized system. It was proven that the stabilizing control of the pendulum, based on the feedback principle, enables the stabilization of the system. We have identified the zones of stability and the amplitude-frequency characteristics. In the second part of this article, a generalization of the dynamic system for the case of the hysteresis friction in the mechanical joint is considered. The role of nonlinear effects within the design Preisach model and the phenomenological Bouc-Wen model is shown.

Design of a Short-Beam Linear Traveling-Wave Piezoelectric Motor

A straight short-beam linear piezoelectric motor constructed with two sets of ceramic actuators separated with the 1/4 wavelength interval is designed in this article. The piezoelectric ceramic actuators are fabricated in the whole body, which is driven by a two-phase circuit with the same amplitude but a phase difference of π /4. Traveling wave (TW) is formed by superimposing standing waves generated by each set of ceramic actuators. At the ends of the short beam, a wave-reduction mechanism with larger cross-sectional area is designed so that wave reflection is effectively diminished to preserve the TW. The currently developed short-beam linear piezoelectric motor is estimated, which can produce an ideal output speed of 169 mm/s while applying voltage of V_pp = 300 V at 45.49 kHz. Instead of operating as a stator to drive a carriage for example, the short-beam linear piezoelectric motor is implemented on a guide slider, and therefore, a linear piezoelectric motor stage is built. While driving the linear stage employed with a preload 300 GW and a friction coefficient of about 0.15, the propulsion force is measured about 4.8 N, the speed is about 56 mm/s, and the position resolution can achieve in the submicrometer scale.

Design of a Low-Frequency Harmonic Rotary Piezoelectric Actuator

Piezoelectric actuators usually operate under a high frequency driving signal. Here we report a harmonic rotating piezoelectric actuator by coupling a harmonic wave generator and a friction rotor, in which the actuator can be actuated by a low-frequency sinusoidal signal with positive bias. The harmonic wave is generated by a two-stage magnifying mechanism consisting of a displacement amplifier and a harmonic rod. Applying piezoelectricity theory, the actuator’s output characteristic equations are deduced. What is more, the output characteristics of piezoelectric actuators are tested with the established experimental system. Results show that the generated harmonic displacements can drive the actuator to work normally at a driving voltage of larger than 90 V and the maximum total harmonic displacement of the piezoelectric actuator comes up to 427.6 μm under the driving voltage of 150 V. Meanwhile, the error between the measured and calculated values of the harmonic displacement is less than 7%. Furthermore, the rotational speed of the piezoelectric actuator reaches 5.45 rpm/min at 150 V voltage and 5 Hz driving frequency.