Jérôme Delamare

Magnetic micro-actuators and systems (MAGMAS)

Magnetic interactions provide outstanding performances for powerful integrated micro-actuators. This paper explains how magnetic interactions involving permanent magnets, currents, and various magnetic materials remain very effective and even improve as dimensions are reduced. The technological problems that have slowed the development of magnetic micro-actuators and systems (MAGMAS) are progressively being solved. As long as materials scientists continue to develop better thick-film patterned permanent magnets compatible with microsystem technologies, MAGMAS will have a promising future.

Classification and synthesis of permanent magnet bearing configurations

Quite a number of configurations allow to get passive permanent magnet thrust or radial bearings. However, most of existing devices are based on the same two or three structures. In many cases, a different geometrical structure keeping the same magnetic and mechanical characteristics would allow a simpler and cheaper realisation. We present here a synthesis of passive bearings allowing original structures.

Magnetostrictive-piezoelectric composite structures for energy harvesting

In this paper, harvesters coupling magnetostrictive and piezoelectric materials are investigated. The energy conversion of quasi-static magnetic field variations into electricity is detailed. Experimental results are exposed for two macroscopic demonstrators based on the rotation of a permanent magnet. These composite/hybrid devices use both piezoelectric and magnetostrictive (amorphous FeSiB ribbon or bulk Terfenol-D) materials. A quasi-static (or ultra-low frequency) harvester is constructed with exploitable output voltage, even in quasi-static mode. Integrated micro-harvesters using sub-micron multilayers of active materials on Si have been built and are currently being characterized.

A low-cost air data attitude heading reference system for the tourism airplane applications

A cheap tourism airplane ADAHRS unit is developed by fusing magnetometers, rate gyros and accelerometers (MEMS technology). The rigid body orientation is modeled with quaternion, which eliminates attitude estimation singularities. The real-time implementation is done unifying a quaternion formulation of Wahbas problem with a multiplicative extended Kalman filter. It includes the gyro bias model. A quaternion measurement model is introduced. It avoids the linearization step that induces undesirable effects. Accelerometers detect gravitational acceleration and centrifugal forces, resulting in incorrect attitude estimation (e.g. false horizon and subjective vertical). Therefore, some pressure sensors are added, resulting in a robust solution. The real-time implementation uses a PCMCIA data acquisition card and a TabletPC. Simulated and real data validate the ADAHRS

Field emission and material transfer in microswitches electrical contacts

Material transfer from one electrical contact part to the other has already been reported in microswitches operating under hot switching conditions. By using an atomic force microscope with a conductive cantilever, we highlighted that electrons are emitted from the cathode when electrode separation becomes less than a few tens of nanometers. This electronic emission proves to follow Fowler–Nordheim theory and leads to the damage of the opposite contact member (anode) by impact heating. Anode material evaporates under this extreme heating and deposits on the opposite contact member (cathode), leading to a material transfer from anode to cathode.

Autonomous, Low Voltage, High Efficiency, CMOS Rectifier for Three-Phase Micro Generators

The paper reports on the design, fabrication and testing of a fully integrated, low voltage rectifier for three-phase micro-generators. Focus is applied to the design of a stand-alone rectifier for three-phase AC inputs in the range of 1-3.3 V, 5-500 mA at 10-100 kHz. Specific low powering issues such as low-voltage rectification, self-powering, automatic start-up and anti-parasitic protection are clearly presented. These issues have been solved thanks to original designs and concepts realized using CMOS 0.35 mum technology. The measurements on the fabricated mu-rectifier coupled to a three-phase micro-generator indicate its full functionality and high conversion efficiency, up to 90 %.

A compact magnetic suspension with only one axis control

An original type of magnetic suspension, which is compact and well adapted to high speed rotation is discussed. This suspension is based on a permanent radial bearing, which allows radial and angular stability simultaneously. Axial stability is reached thanks to a unidirectional active axial bearing. This suspension operates with a plane air gap and is well adapted to the levitation of flat rotors. >

Planar brushless magnetic micromotors

Novel planar magnetic micromotors and microgenerators of active diameter 8 mm were developed, delivering estimated torques of 100 muN.m at speeds in excess of 140 000 r/min. Such high performances are due to an innovative use of deep lithography and silicon etching for the fabrication of the stator coils. The hybrid design of the micromotors combines a pair of double-layer three-phase stator coils and a disc-shaped SmCo rotor with eight or 15 axial pairs of poles, all enclosed in a case fabricated using watch-industry micromachining

Thermal energy conversion by coupled shape memory and piezoelectric effects

This work gives experimental evidence of a promising method of thermal-to-electric energy conversion by coupling shape memory effect (SME) and direct piezoelectric effect (DPE) for harvesting quasi-static ambient temperature variations. Two original prototypes of thermal energy harvesters have been fabricated and tested experimentally. The first is a hybrid laminated composite consisting of TiNiCu shape memory alloy (SMA) and macro fiber composite piezoelectric. This composite comprises 0.1 cm3 of active materials and harvests 75 µJ of energy for each temperature variation of 60 °C. The second prototype is a SME/DPE machine which uses the thermally induced linear strains of the SMA to bend a bulk PZT ceramic plate through a specially designed mechanical structure. The SME/DPE machine with 0.2 cm3 of active material harvests 90 µJ over a temperature increase of 35 °C (60 µJ when cooling). In contrast to pyroelectric materials, such harvesters are also compatible with both small and slow temperature variations.

Temperature threshold tuning of a thermal harvesting switch

This paper presents an original energy harvester making use of a temporal variation of temperature and converting it to electricity. Such a device combines piezoelectric and magnetic materials in order to be able to react to small and slow variations of temperature. Therefore it can be integrated for powering nodes in a wireless sensor network. We report here how to tune the behavior of such generator. By modifying the gap between the hard magnet and the soft magnetic material, it is possible to finely control the hysteresis between the two thresholds but also the position of those thresholds. Finally, like for the electrical load, there is an optimal gap which allows the harvesting of a maximum power.