High Performances Embedded Measurement Systems for multiDegrees of Freedom Microsystems – MyMeSys

The proposed method consists in extending and then merging three measurement techniques previously developed at FEMTO-ST Institute: 1) high bandwidth displacement measurement with magnetic principle, 2) high precision displacement measurement with the self-sensing principle (i.e. using an actuator as a sensor at the same time which is possible for reversible systems such as piezoelectric actuators), 3) and force measurement by using an effector with gauges and SU8 resin. These techniques have been independently developed for one dof microsystem in the past . The aim here is to extend them first for multi-axis microsystems and then mergen them in order to benefit the advantages of each (high precision, high bandwidth, force and position measurement). As the proposed sensor is new, a calibration system devoted for that will be also developed during the project.

The 10 first months consists in studying the force measurement system, called Sensufit. A post-doc (6months) and an internship (4months) are hired for that. In order to success that, the task (called Task4) has been splitted into 5 sub-tasks: ST1) structure design and verification of the sensivity of the gauges to be used, ST2) study and extension to multi-axis measurement, ST3) study of a new microfabrication process for the measurement system, ST4) microfabrication in clean room, ST5) integration of the sensor in the actuator and performances verification.
Sub-tasks ST1, ST2 and ST3 are the basis of this measurement system and have been finished at month 5. Experimental tests on the gages are successful and promising. A start-up from FEMTO-ST (called Percipio Robotics) has also been contacted for the subcontract of the fabrication (ST4). An internship is now working on the last subtask.
New knowledges on microtechnologies and on piezoresistivity have been acquired during this M6. Furthermore, more knowledges on the compatibility of SU8 resin and microsystems have also been acquired. The Percipio Robotics company may also be interested to the final development of Mymesys (high precision, bandiwth position/force multi-axis sensor).
On the other hand, preliminaries results on the modeling and the compensation of nonlinearities in piezoelectric actuators have been done. The aim is to integrate these results in the design of the further self-sensing technique such that it is possible to reach very high precision of measurement.

The development of embedded sensors for microsystems from this project will allow the emergence of new technological tools for semi or completely automated microassembly and micromanipulation. Such automation important implies the increase of throughout of microsystems, the increase of the precision and the diminution of the costs of fabrication and of the final products. Many actual miniaturized products found in specific applications (medical, military, aerospace, etc.) will be therefore less expensive. Furthermore, new miniaturized products will appear for daily applications (domestic, agribusiness, farming, etc.).

- Results on the characterization of the gages:
X. Xu, J. Agnus and M. Rakotondrabe, '2 dimensionnal platinum piezoresistive micro force sensor', RSI, in preparation, IOP RSI (Review of Scientific Instrument), under preparation.
- Once the microfabrication of the force measurement finished, a request of french patent is expected.
- Preliminaries results on the nonlinearities for the self-sensing measurement:
Micky Rakotondrabe, 'Classical Prandtl-Ishlinskii modeling and inverse multiplicative structure to compensate hysteresis in piezoactuators', ACC, pp.1646-1651, Canada, June 2012.
Micky Rakotondrabe, 'Modeling and Compensation of Multivariable Creep in multi-DOF Piezoelectric Actuators', IEEE - ICRA, pp.4577-4581, St Paul Minnesota USA, May 2012.

Micromanipulation and microassembly are tasks that aim to characterize or to produce complex and hybrid miniaturized systems that classical microfabrication techniques could not perform. So far, the throughput and precision of micromanipulation and microassembly tasks as well as the packaging of the systems used for them are strongly limited by the lack of convenient sensors. On the one hand, automatic assembly manufacturing systems use camera and visual servoing techniques and are characterized by a very low throughput of assembly. On the other hand, recent proof of concept has been done on high bandwidth micro-actuators based on exteroceptive sensors which are able to perform high throughput movement along several degree of freedom (DOF). Based on this proof of concept in microactuation, this project proposes to improve the current throughput and number of controllable DOF of micromanipulation systems.

The objectives of MiMeSys is thus to study and develop a multi-DOF, embeddable, highly accurate and high bandwidth micromanipulators based on integrated position and force sensors and control strategies The results are going to accelerate the development of high precision, high throughput micromanipulation and microassembly manufacturing systems dedicated to the fabrication of the next generation of ‘tridimensional’ and integrated microsystems. Transfer will be done using licensing of patents deposited during the project to industry and especially to a company which is supporting this project.