Noliac (Denmark)

Piezoelectric devices find numerous applications in Science projects, when precise and fast positioning is needed, particularly in harsh environment. This paper reviews some of the latest environmental tests performed on piezoelectric devices, illustrating how they enable higher performance or even new technical solutions. In the field of particle accelerators and instrumentation, two applications can be mentioned: the precise goniometer to be installed in the Large Hadron Collider (LHC) and active Lorentz force detuning compensation systems*. Multilayer actuators have been demonstrated over a wide range of temperatures, from cryogenic (4K) to 220°C, in UHV and under radiation. Other examples can be mentioned within the ITER project: the In-Vessel Viewing System (IVVS) and the Electron Cyclotron Emission (ECE) diagnostic**. For these applications, a piezo motor is needed. The Piezo Actuator Drive (PAD) was demonstrated at high temperature, UHV and submitted to high magnetic fields.

A piezoelectric transformer based converter is presented in this paper, which not only is capable of generating high voltages, but also incorporates a bi-directional power stage. Applications of high capacitive loads, such as dielectric electro active polymers (DEAP) [1], often suffer from poor overall system efficiency, as only a small fraction of the supplied electrical energy is transferred to mechanical energy (<10%). The bi-directional power stage enables the recovery of the electrical energy stored in the highly capacitive load, improving the system efficiency significantly. The presented converter is capable of generating voltages of up to 1700V, from a 24V supply, and demonstrates efficiencies of up to 70%, which leads to a system efficiency improvement of 50%. The main achievements of this work are the demonstration of bi-directional functionality and energy recovery, as well as the investigation of the general behavior of the highly dynamic converter and the development of a new control strategy.

The Piezoelectric Actuator Drive (PAD) is a type of rotary motor that transforms the linear motion of piezoelectric stack actuators into a precise rotational motion. The very high stiffness of the actuators employed make this type of motor suited for open-loop control, but the inherent hysteresis exhibited by piezoelectric ceramics causes losses. Therefore, this paper presents a straightforward method to measure piezoelectric stack actuator equivalent parameters that includes nonlinearities. By folding the nonlinearities into a newly-defined coupling coefficient, the inherent hysteretic behavior of piezoelectric stack actuators can be greatly reduced through precompensation. Experimental results show a fitting accuracy of 98.8 % between the model and measurements and a peak absolute error reduction by a factor of 10 compared to the manufacturer-provided parameter. This method improves both the static and dynamic performance of the Piezoelectric Actuator Drive (PAD) while still permitting open-loop control.

Research and development within piezoelectric transformer (PT) based converters are rapidly increasing as the technology is maturing and starts to prove its capabilities.Especially for high voltage and high step-up applications, PT based converters have demonstrated good performance and DC/AC converters are widely used commercially.The availability of PT based converters for DC/DC applications are very limited and are not that developed yet.I this paper an interleaved multi layer Rosen-type PT for high step-up and high output voltage is developed, for driving a 2.5kV dielectric electro active polymer actuator [17].The targeted application utilises an inductor-less half-bridge driving topology, where the reward of eliminating the series inductor is a reduction in component count, size and price.The absence of a series inductance calls for other means to avoid large hard switching losses and obtain soft switching capabilities.This can be achieved by utilising an advantageous PT structure, which is the main advantage of the interleaved Rosen-type PT.Furthermore the design should be further optimised, in order to achieve soft switching capability.The goal of this paper is to develop a soft switching optimised PT, capable of generating output voltages higher than 2kV from a 24V supply voltage.Furthermore finite element method (FEM) has been the main tool through the PT development.

An industrializable process for manufacturing of piezoelectric ultrasound transducer elements is demonstrated. The PZT film is deposited by chemical solution deposition on SOI wafers, and standard MEMS processes are utilized to make cantilevers, bridges and membranes. The PZT film of -50% of the devices exposed to thermal aging were found to fail at 85degC - 85%RH (relative humidity), while a real-life test of 8-10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cycles at resonance only gives a slight change in Q-value and resonance frequency.

SYNOPSIS The paper describes a laboratory installation and measuring programme to investigate whether the extent of power consumption by the fan of an Air Solar Collector can be reduced to obtain a reasonable efficiency.