The novelty of correcting optical mirrors surface in a few microns of the desired precisely-shaped are supported by electroactive polymer actuating/sensing devices. The P(VDF-TrFE-CFE) terpolymer with the 10 % DINP plasticizer has field as EAP which showed 10 times higher in longitudinal strain with respect to the neat one and the increase of total axial strain from 0.4 % - 3.0 % with the multilayer sample 1 to 8 layers respectively. The actuator stack was integrated to the mirror in order to prove the concept of adaptive mirror which is able to reach to goal of a few micron mirror deformation.
An important limitation in the classical energy harvesters based on cantilever beam structure is its monodirectional
sensibility. The external excitation must generate an orthogonal acceleration from the beam plane to induced flexural
deformation. If the direction of the excitation deviates from this privileged direction, the harvester output power is drastically
reduced. This point is obviously very restrictive in the case of an arbitrary excitation direction induced for example by human
body movements or vehicles vibrations.
In order to overcome this issue of the conventional resonant cantilever configuration with seismic mass, a multidirectional
harvester is introduced here by the authors. The multidirectional ability relies on the exploitation of 3 degenerate structural
vibration modes where each of them is induced by the corresponding component of the acceleration vector. This specific
structure has been already used for 3 axis accelerometers but the approach is here totally revisited because the final
functional goal is different. This paper presents the principle and the design considerations of such multidirectional
piezoelectric energy harvester.
A finite element model has been used for the harvester optimisation. It has been shown that the seismic mass is a relevant
parameter for the modes tuning because the resonant frequency of the 1st exploited flexural mode directly depends on the
mass whereas the resonance frequency of the 2nd flexural mode depends on its moment of inertia.
A simplified centimetric prototype limited to a two orthogonal direction sensibility has permitted to valid the theoretical
The integration of autonomous wireless elements in health monitoring network increases the reliability by suppressing
power supplies and data transmission wiring. Micro-power piezoelectric generators are an attractive alternative to
primary batteries which are limited by a finite amount of energy, a limited capacity retention and a short shelf life (few
years). Our goal is to implement such an energy harvesting system for powering a single AWT (Autonomous Wireless
Transmitter) using our SSH (Synchronized Switch Harvesting) method. Based on a non linear process of the
piezoelement voltage, this SSH method optimizes the energy extraction from the mechanical vibrations.
This AWT has two main functions : The generation of an identifier code by RF transmission to the central receiver and
the Lamb wave generation for the health monitoring of the host structure. A damage index is derived from the variation
between the transmitted wave spectrum and a reference spectrum.
The same piezoelements are used for the energy harvesting function and the Lamb wave generation, thus reducing mass
and cost. A micro-controller drives the energy balance and synchronizes the functions. Such an autonomous transmitter
has been evaluated on a 300x50x2 mm<sup>3</sup> composite cantilever beam. Four 33x11x0.3 mm<sup>3</sup> piezoelements are used for the
energy harvesting and for the wave lamb generation. A piezoelectric sensor is placed at the free end of the beam to track
the transmitted Lamb wave.
In this configuration, the needed energy for the RF emission is 0.1 mJ for a 1 byte-information and the Lamb wave
emission requires less than 0.1mJ. The AWT can harvested an energy quantity of approximately 20 mJ (for a 1.5 Mpa
lateral stress) with a 470 μF storage capacitor. This corresponds to a power density near to 6mW/cm<sup>3</sup>.
The experimental AWT energy abilities are presented and the damage detection process is discussed. Finally, some
envisaged solutions are introduced for the implementation of the required data processing into an autonomous wireless
receiver, in terms of reduction of the energy and memory costs.
The damping of vibration resonance is a crucial problem for light and elongated structures. Different kinds of solutions have been developed in order to address the problem of volume or mass, or temperature dependence which are common to the passive approach. In the semi-passive technique proposed here, damping is obtained through the use of piezoelectric patches bonded on the structure. These piezoelements are controlled with a very simple approach only requiring switches which are driven periodically and synchronously with the structure motion. The overall control circuit requires a very few amount of energy. Results obtained on a beam and on a plate demonstrate that this self-adaptive technique is able to control simultaneously different modes on a broad frequency range.
Ultrasonic motors have very interesting features as high torque at low speed and low inertia. The principle of such motors is based on a double energy conversion. This paper deals with the measurements required to characterize these conversions. Experimental results on some structures investigated in our laboratory are proposed.
A new structure of a multi-mode piezoelectric motor is proposed and uses two longitudinal actuators and a mechanical coupler. The basic principle is first presented and the corresponding modeling based on numerical tools and electromechanical circuits is performed to design a first prototype. Preliminary measurements indicates the reliability of the principle, a good agreement with predictions and interesting motor performances.