Excitation of an Asymmetric Displacement without Residual Vibration and its Application to Construct a Piezoelectric Actuator 이명호 Lab. Of Intelligent Material and Technology

Abstract This paper deals with a new excitation method of a piezoelectric actuator in order to achieve its asymmetric displacement as a function of time elapsed without its residual vibration : The method is to use the rectangular pulse of voltage and is aimed to develop a new type piezoelectric actuator with a function of a both direction operation. Analysis on displacement of such an actuator driven by the rectangular pulse, and proposal of its application to concrete actuators with its experimental description are reported.

Introduction A piezoelectric actuator is one of attractive devices in the modern engineering, due to its inherent multi-functions and small construction. its quick response Electrical pulse driving was considered to prevent the mechanical residual vibration of the actuator. The prevention of residual vibration succeeds to a quick response of the actuator. This asymmetric operation of an actuator can be variously applied, for example, to construct a part-feeder, a linear movement-device and a rotary one. In the first part of this paper are described some responses of a piezoelectric actuator by input voltage wave form of pulse. The second part contains applications of such actuators and experimental results on them.

2.1 A piezoelectric actuator and its equivalent circuit Fig. 1(a) is only a representative of general piezoelectric actuator. The lowest response of vibration is dominant for actuator operations, even if the actuator has many responses. There are such following correspondences that motional current q˙m(t) and electric charge qm(t) are equal to a speed of vibration and a displacement, respectively, at a certain point of the actuator. By analyzing q˙m(t) and qm(t) in the equivalent circuit when the input voltage wave form of pulse in fig. 1(b) is supplied, vibrational characteristics of the actuator can obtained.

2.2 Input voltage wave form of pulse In order to achieve a sharp rising-up displacement of the actuator, such rectangular pulse as shown in figure is first applied and in the next step, after a somewhat interval, the voltage goes down slowly. By such asymmetric voltage wave form, we expect, the asymmetric operation of an actuator can be made possible.

2.2 Input voltage wave form of pulse

From these results, it is found that actuator displacement responses of a sharply rising-up and gently sloping-down characteristic can easily obtained and the form of characteristic is differently changed by input voltage wave form. A specific feature of the characteristic appears at the condition (B-N)≥2.0 ; that is, one or tow plateaus are yielded in the gently sloping-down part.

2.2 Input voltage wave form of pulse The characteristic shown in fig.5 is one example to the wave form of pulse shown in Fig. 2(b) We say in addition that the input voltage wave form of pulse shown in Fig. 6 can also be utilized to yield the asymmetric displacement response.

3. Applications Applying the asymmetric displacement responses mentioned above, it is possible to construct some actuator with a function of both direction operation by only one channel electrical excitation.

Applications resonance frequency : 110 [kHz] and the quality factor : 50 resonance frequency : 110 [kHz] and the quality factor : 50 resonance frequency : 32.8 [kHz] and the quality factor : 370

구동원리

Conclusions We proposed a new excitation methode of a piezoelectric vibration without residual displacement to achieve the asymmetric displacement responses as a function of time elapsed, and moreover we presented its application to construct an actuator. We want to investigate piezoelectric actuators using such a phenomenon and improve their characteristics further.