Due to the lack of convenient sensors for many actuated microsystems, including piezoelectric microsystems, several projects and research have been emerging these last years on the development of new techniques of measurement or new technologies of sensors for the micro and nano-scale. Among the emerging techniques is the self-sensing which consists in using an actuator as sensor at the same time.
Self-sensing techniques can potentially be applied to reversible smart or active materials but most of the works concern the piezoelectric materials because of the good background on them. Consider a piezoelectric structure. The application of voltages to the electrodes makes the material deform thanks to the converse piezoelectric effect, and then obtain an actuation function. During the deformation of the material, electrical charges appearing on its surface due to the direct piezoelectric effect can be amplified using a well designed electronic amplifier and can be used to estimate the displacement thanks to a convenient observer: the sensing function is obtained (Fig.1). The idea of self-sensing, using the same piezoelectric structure as both actuation and sensor, started with the work of Dosch et al. [Dosch et al., JIMSS, 1992]. Since, it has been used for the vibration damping control. Later, self-sensing has been applied for the control of piezotubes in atomic force microscopy. However, self-sensing methods were limited to short-term (less than one second in time) measurement, making them unusable for many applications of micro/nano positioning where the measurement of constant signals during some hundreds of seconds are required. This is due to the inevitable charges leakages that typify piezoelectric materials. Our development in piezoelectric self-sensing has as challenge the consideration of measurement at low frequency additionnally to the measurement at high frequency signals, and this in long-period condition. This involves novelties both in the electrical circuit and in the observer design.
The applications of such static and dynamic piezoelectric self-sensing are numerous, in particular in precise positioning: images scanning though scanning probe microscopes (AFM...), micromanipulation and microassembly, medical devices based on piezoelectric actuators, microvalves...
Fig. Principle of the self-sensing.
Piezoelectric devices, self-sensing, piezoelectric sensors, observers, integrated sensors, multi-DoF measurement in self-sensing, static and dynamic.
Samples of publications
- Micky Rakotondrabe, Alexandru Ivan, Sofiane Khadraoui, Philippe Lutz and Nicolas Chaillet, 'Simultaneous displacement and force self-sensing in piezoelectric actuators and applications to robust control of the displacement', IEEE/ASME - Transactions on Mechatronics (T-mech), Vol 20, No 2, Page 519 - 531, April 2015.
- Micky Rakotondrabe, 'Combining self-sensing with an Unkown-Input-Observer to estimate the displacement, the force and the state in piezoelectric cantilevered actuator', ACC, (American Control Conference), pp.4523-4530, Washington DC USA, June 2013.
- Alexandru Ivan, Micky Rakotondrabe, Philippe Lutz and Nicolas Chaillet, 'Current integration force and displacement self-sensing method for cantilevered piezoelectric actuators', Review of Scientific Instruments (RSI), Vol.80(12), 2126103, December 2009.
- Alexandru Ivan, Micky Rakotondrabe, Philippe Lutz and Nicolas Chaillet, 'Quasi-static displacement self-sensing method for cantilevered piezoelectric actuators', Review of Scientific Instruments (RSI), Vol.80(6), 065102, June 2009.
- Micky Rakotondrabe, Ioan Alexandru Ivan, Sofiane Khadraoui, Cédric Clévy, Philippe Lutz and Nicolas Chaillet, 'Dynamic displacement self-sensing and robust control of cantilevered piezoelectric actuators dedicated to microassembly tasks', IEEE/ASME - AIM, (International Conference on Intelligent Mechatronics) 2010, pp:557-562, Montreal Canada, July 2010.
- Ioan Alexandru Ivan, Joël Agnus and Micky Rakotondrabe, 'Technique de micropositionnement à multidegrés de liberté pour actionneurs piézoélectriques et dispositifs associés', french Patent INPI FR-N°12/52554.
- Ioan Alexandru Ivan, Joël Agnus and Micky Rakotondrabe, 'Micropositioning device with multidegrees of freedom for piezoelectric actuators and associated method', international PCT patent, USA Patent, US20150054520 A1
- Ioan Alexandru Ivan, Joël Agnus and Micky Rakotondrabe, 'Micropositioning device with multidegrees of freedom for piezoelectric actuators and associated method ', international PCT patent, european Patent, EP2828968 A1