Cedrat Technologies, innovation in mechatronics

The recent progresses made in the manufacturing of new plasmonic photomobile films are offering innovative solutions for light induced motion actuators and devices. Indeed, such films can be assimilated as transducers thanks to their ability to convert light into displacement with strokes up to several millimeters. By adjusting the incident light parameters (wavelength, exposure time…) the photomobile films actuation can be controlled to answer many applications requesting high displacements and low forces. In these regards, the behaviour of the photomobile films were characterized prior to their integration in more complex devices.

In the context of Condition Based Maintenance (CBM) for aircrafts, Structural Health Monitoring (SHM) is one main field of research. Detection and localization of damages in a structure request reliability of the equipment and repeatability of the measurements and process. An electronic device called Lamb Wave Detection System (LWDS) have been developed and manufactured to manage piezo-electric patches either in emission or reception mode with a high commutation rate. Besides, integration of the piezo patches is another crucial aspect of reliability. Several methods as modelling and dispersion curves can define the frequency range of Lamb waves to optimize the piezo-electric coupling. This work which takes part of the H2020 ReMAP project about adaptative aircraft maintenance planning, is presented in the article.

Required improvements of piezoelectric elements actuation and measurement system efficiency and robustness are introduced as a critical feature for structural health monitoring (SHM) applications. An electronic module (Lamb wave detection system: LWDS) allowing to use each piezoelectric element in an array either in emission or reception mode is presented. The high commutation rate between these two states, for each transducer separately, is a key enhancement for SHM methods. The robustness of the sensor integration is also studied considering the patches size and bonding method. Coupled dispersion curve are introduced Comparison of FEM simulation and experiments of the piezo-electric coupling are presented. This work takes part of the H2020 REMAP project about adaptive aircraft maintenance planning.

In many cases piezoelectric actuators reach limitations in terms of maximum displacement and cycling frequency. Most amplified actuator technologies struggle to go over the millimeter of stroke. Furthermore certain closed-loop applications demand stroke measurement integrated into the actuator. While few amplifiers on the market can offer 20Amps current over a few 100ms, development of high power supply units runs parallel with actuator improvements. However with the introduction of high power supplies comes the problem of self-heating of the piezo ceramic. Finally extreme environmental conditions in terms of harsh conditions and high temperatures need to be addressed in order to open these markets for piezo actuators. Cedrat Technologies has been heavily investigating in solutions to overcome all of these drawbacks and these solutions are presented here.

The torque measurement usually comes from strain gauges bonded on a shatf. the main concern in this measurement is due to the fact that these gauges are also rotating and the integration of electronic on rotating parts is definitely a blocking point.

In a contact of always smaller and smarter mechatronics devices, the needs of more integrated sensors becomes critical. Particularly, small mechanisms using small actuators like piezo actuators require compact sensors, with performances that measure up to the actuators characteristics.

Ultrasonic-based SHM (Structural Health Monitoring) applications commonly rely on the use of piezo-electric patches to emit and receive ultrasonic waves. The objective is to study the propagation of the waves through a structure to assess its structural integrity. Because of the elevated number of echoes and possible modes of propagation of the waves within the structure, those applications suffer from a burden of signal processing. This paper presents a composite piezo-electric patch that was designed and successfully tested for reducing the complexity of the SHM detection schemes by selecting the mode and direction of the Lamb waves received. The piezo-composite is composed of a row of eight independent ceramic pillars separated with polymer, so it is a 1-D matrix of independent piezo-patches. Used with adequate electronics and signal processing, it was shown that it allowed selecting the direction and the mode of the Lamb waves.