A Novel Method of Stabilizing the Vibration Velocity at the End of Piezoelectric Transducers - Advanced Research on Computer Education, Simulation and Modeling - page 39

A Novel Method of Stabilizing the Vibration Velocity at
the End of Piezoelectric Transducers*
HuiJuan Dong 1 , Jian Wu 2 , WeiGang Bao 1 , and GuangYu Zhang 1
1 School of Mechatronics Engineering of Harbin Institute of Technology, Harbin, 150001
2 Pearl River Water Research Institute, Pearl River Water Resources Committee,
Guangzhou, 510611
Abstract. The vibration velocity at the end of a piezoelectric transducer is diffi-
cult to be stabilized. This paper theoretically analyzes the relationship of its
admittance and frequency, and the main reasons of over voltage and over cur-
rent caused by the traditional current-based stabilizing vibration velocity
method. In light of the above, the authors present a novel method, which takes
advantages over the traditional one in terms of the time and the amplitude of the
overshoot voltage or current. Accordingly, the transducer and its generator can
be effectively protected.
Keywords: piezoelectric transducer, admittance, frequency, current-based sta-
bilizing vibration velocity.
1 Introduction
The vibration velocity at the output end of a transducer is required constant during the
ultrasonic machining process, but it fluctuates with the changes of load [1]. And thus
an ultrasonic generator should have a function of keeping the vibration velocity con-
stant automatically. As the vibration velocity is proportional to the current of the
transducer [2][3], the traditional current-based stabilizing vibration velocity method
[4] is available, in which the exciting voltage of the transducer is adjusted after the
resonant frequency being successfully traced to keep its current constant. It is noted
that the traditional method only offers an efficient solution under the condition of load
being increasing. However, an unacceptable increasing of the current using the tradi-
tional method was seen in tests when the load decreased, which might cause the dam-
age of the transducer.
In order to solve these problems, a novel method termed as asymmetric automatic
regulation of the vibration velocity was described and implemented in this work. The
point is that the increasing velocity of the exciting voltage is slower than that of the
resonant frequency when the load increases. And the decreasing velocity of the exciting
voltage is faster than that of the resonant frequency when the load decreases. The ex-
periments carried out demonstrated that it takes advantage over the traditional method
mentioned in terms of the accuracy of stabilizing the current and the transducer safety.
* Sponsored by National Natural Sciences Foundation of China (50674036).