In ultrasonic wire bonding the required vibrations are generated by an ultrasonic transducer driven in its longitudinal
mode. Asymmetries lead to additional orthogonal motions, which result in unwanted fluctuating normal forces in the
friction contact. In this publication, a novel design of an ultrasonic transducer with control actuators is presented. The
parasitic vibrations are damped in an active control and by the semi-active piezoelectric shunt damping with inductance-resistance
networks. A Finite-Element model is developed to optimize the dimensions and the placement of the
piezoceramics and to tune the electrical networks. Measurements are conducted on a prototype transducer which validate
the simulation results.
Structural vibrations can be reduced by shunted piezoelectric elements. The passive piezoelectric damper considered
here, consists of a piezoelectric element connected to a host structure and shunted by an inductor-resistor
network. The paper gives an in depth analysis on the tuning of the inductor and resistor parameters of the
electric network with regard to different optimization goals. The calculations are based on a 2-degree-of-freedom
model of the host structure and the shunted piezoelectric element. Three optimization goals are studied: The
objective of eigenvalue optimization is to get both pairs of eigenvalues to be equal. Then the damping ratio of
the host structure is maximized, leading to a minimized decay time of the free vibration. In the H2 optimization
the total vibration energy within the host system is minimized, leading to optimal results in case of a broad-band
excitation. In the H∞ optimization the objective is to minimize the maximum amplitude of the host structure
over the whole frequency spectrum. Analytical solutions for these optimization goals are already known in the
special case of a host structure without damping. In the more general case of a viscously damped host structure
analytical solutions for the eigenvalue and H2 optimization goal are derived. In case of the H∞ optimization goal
an analytical solution cannot be found and perturbation theory is used to calculate an analytical approximation.
The approximation is compared to the numerical solution in order to check its accuracy.
Shunted piezoceramics can be used to dissipate vibration energy of a host structure and therefore reduce vibration
amplitudes. The piezoceramic converts a portion of the mechanical energy into electric energy which is
then dissipated in an electric network. One semi-active control technique is the synchronized switch damping
on inductance (SSDI), which has a good damping performance and can adapt to a wide range of excitation
frequencies. In the standard SSDI a switch is closed during maximum deformation for one half of the electrical
period time. This results in an inversion of the electrical charge. For the rest of the half-period the switch is
opened and the charge remains constant. This results in a nearly rectangular voltage signal, which is in antiphase
with the deformation velocity. In case of multimodal excitation, more sophisticated switching laws are developed with the aim to extract vibration energy from higher modes (i.e. Richard).
This paper describes a novel multimodal switching law for vibration damping. An observer is designed to
obtain an estimation of the first two vibration modes, which are used to determine the switching times. In
simulations the increase in energy dissipation is evaluated and compared to the standard SSDI technique. With
the new switching algorithm an improvement in energy dissipation is observed. The theoretical results are
validated by measurements carried out on a clamped-free beam. The location of the piezoceramics is chosen to optimize the electro-mechanical coupling with the first vibration mode of the beam. The modal observer is realized in a realtime environment. Measurements show a good agreement with the theoretical results.
In this paper the damping capability of piezoelectric shunting is analysed for bladings. Beside the broadly
used inductance-resistance networks, negative capacitance techniques are considered. For the validation of the
theoretic results, a test rig with a model of a bladed disk with eight blades has been manufactured and equipped
with two collocated piezoceramics at each blade. One of the piezoceramics is used as an actuator for an engine
order excitation. The second piezoceramics is used for shunt damping. The experimental results of the test rig
are compared with numerical results. Therefore, the structure and the piezoceramics are modeled in a finite
element program. The modal excitation forces of the piezoelectric actuators are derived for all modes of the
structure by a static analysis with a specific voltage applied to the piezoceramics. In addition, using the modal
displacement field of the static analysis the modal excitation forces can be calculated. Furthermore, the number
of degrees of freedom of the system is reduced by a modal reduction technique. The electrical behavior of the
piezoceramics connected to each blade is modeled by one degree of freedom and coupled with the mechanical
system described above. The different damping concepts are compared with respect of their effectiveness.
Piezoelectric shunt damping is new technique to damp mechanical vibrations of structures. Because of the
piezoelectric effect, vibration energy is converted into electrical energy. In the attached network some part of
the energy is dissipated. Switching shunts offer the possibility to adapt to varying excitation frequencies. In
this paper, the damping performance of different switching techniques are calculated considering all important
network parameters and non-idealities in the switching boards. Measurements on a clamped beam are performed
to validate the results, and the switching techniques are applied to a squealing disc brake. It is shown that due
to the piezoelectric shunt damping the sound pressure level can be reduced considerably.
This paper describes piezoelectric switching techniques for vibration damping. The dynamical behaviour of a
piezoceramics connected to a switching LR shunt and the dissipated energy are obtained using a fundamental
piezoelectric model. All calculations are performed in a normalized way and highlight the influence of the
electromechanical coupling coefficient of the piezoceramics and the shunt parameters. For the first time, a precise result
for the dynamics of a shunted piezoceramics is derived. The analytic results are used to determine the optimal switching
sequence and external branch parameters in order to maximize the damping performance. The results are validated by
measurements of a clamped beam.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.