Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
  • B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
  • B81B3/0018—Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
  • B81B3/0021—Transducers for transforming electrical into mechanical energy or vice versa
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
  • F16F15/005—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion using electro- or magnetostrictive actuation means

Definitions

• the present invention relates to a piezoelectric microsystem for the active vibratory isolation of vibration sensitive components.
• microelectronics micro-optics
• MEMS micro-optics
• MOEMS electromechanical filters
• surface wave sensors ultrasonic transducers
• Stability is a major problem for the use of certain electronic systems, such as frequency generators, gyros, or even for certain accelerometers.
• any suspension In general, the purpose of any suspension is obviously to limit the acceleration of the system to be isolated in the frequency range of stresses.
• the known solutions propose a compromise between the stiffness and the damping of the connection: the attenuation of the modal suspensions induced by the increase of the damping of the system results in a reduction of the high frequency cut and by a bad insulation in this range.
• the invention proposes for its part a new, stable and robust strategy that makes it possible to effectively solve the problem of the insulation compromise.
• the invention proposes a microsystem for active vibratory isolation, characterized in that it comprises a support which comprises a frame and at least two beams which intersect at an intersection zone and carry or are intended to carry an element to be stabilized, said beams carrying at least one piezoelectric layer and electrodes which define different piezoelectric zones, at least two of which are piezoelectric measurement zones, adapted to deliver output signals and which are sensitive to the deformations of the beam (s) carrying them, and of which at least one is a piezoelectric activation zone, controlled according to the output signals of the piezoelectric measurement zones according to a stabilization control law.
• the support is preferably in silicon, but may be in other materials.
• the microsystem according to the invention comprises two cross beams, one of these beams carrying measuring piezoelectric zones, sensitive to the deformations of this beam, the other carrying piezoelectric zones of activation.
• the two beams are perpendicular.
• the microsystem according to the invention comprises three measurement zones, one central zone disposed at the intersection zone between the two cross beams, the two others arranged on one of the two beams, either side of this central area, with a separation from it. Also, it has two activation zones, arranged on the other beam, on either side of the central zone.
• the element that is to be stabilized is located at the intersection zone of the two beams.
• the microsystem integrates a component to stabilize deposited with the other components of the microsystem.
• the microsystem comprises means for subsequently receiving the component to be stabilized.
• FIG. 1 is a schematic representation in perspective of a microsystem according to a possible embodiment of the invention
• FIG. 2 composed of FIGS. 2A and 2B, illustrates the arrangement of the electrodes of the microsystem of FIG. 1
• Figure 2A is a top view of the microsystem of Figure 1
• Figure 2B is a side view of the beam 2b and shows the arrangement of the electrodes thereon
• FIGS. 3a and 3b are theoretical Bode diagrams of a microsystem of the type of FIG. 1, on the one hand free (solid lines) and on the other hand controlled (dashed lines);
• FIG. 4 is a photograph in top view of a microsystem according to one embodiment of the invention.
• the microsystem illustrated in FIG. 1 comprises a silicon support which comprises on the one hand a frame 1 and on the other hand a network 2 of beams which extend inside this frame 1 and which carry the suspended mass 3 that one seeks to stabilize.
• the support 1 has a generally square shape, while the network of beams 2 consists of two beams 2a and 2b, which extend in a cross, perpendicular to each other, in the frame 1. More specifically, the two beams 2a and 2b extend from the edges of said frame 1, parallel thereto, and intersect in the center of said frame 1, at an intersection area 2c, the suspended mass
• the various beams (2a, 2b) of the network 2 carry a piezoelectric thin film 4 (see FIG. 2B), on which are superposed different electrodes which define on this layer different zones (4a, 4b, 4c):
• FIG 2B shows only the beam 2b but by analogy, the skilled person will be able to represent the electrodes on the beam 2a from Figure 2B).
• the beams 2a and 2b and the frame 1 which carries them are made of silicon;
• a measurement piezoelectric zone 4c defined at the intersection zone 2c and sensitive to deformations at the zone 2c;
• the measurement zones 4a are preferably located at the ends of the beam 2a;
• the space 9 separating these activation zones 4b from the measurement zone 4c is smaller than the space separating the measurement zones 4b from the zone 4c, the zones 4b extending over a longer branch length and being wider than areas 4a; the measurement zones 4b are preferably located at the ends of the beam 2b;
• zone 2c comprises a square electrode 6c, which is connected to a measurement output via a track 7a extending along from one of the branches of the beam 2a, to the frame 1.
• the height of an edge of this square electrode is for example of the order of 500 micrometers.
• the electrodes defining the zones 4a and 4b are those referenced respectively by 6a and 6b in FIG. 2A.
• the thickness of the silicon structure is for example between 0.5 and 100 micrometers, whereas the piezoelectric layer 4 is for example a thin film, with a thickness of 0.1 to 10 micrometers.
• the width of the beams 2a and 2b is optimized to firstly allow a sufficient signal / noise ratio and secondly to allow optimization of the activation.
• the beam 2a which carries the measuring piezoelectric zone 4a has a width equal to half the width of the beam 2b which carries the activation electrodes 6b.
• the width of this beam 2b is for example of the order of mm, for a total length of the order of 5mm for each of the branches of the beams 2a and 2b.
• the electrodes 6a are of a slightly smaller width than the beam 2a, so as to allow the passage of the track 7a.
• the electrodes 6b are slightly smaller than the width of the branch
• Electrodes 6a and 6b are for example of a length equal to half the length of the branches of the beams 2a and 2b
• the control law of the piezoelectric controllers is chosen so as to damp and compensate the deformations of the microsystem according to the invention and to actively stabilize the suspended mass 3.
• the signal yi generated by the piezoelectric zone 4c during a deformation of the intersection zone 2c is sent, with the signals y2 and y3 generated by the piezoelectric zones 4a, on a signal conditioning electronics 5 which generates the voltage V to apply to activation zones 4b.
• This signal conditioning electronics 5 (also called a microcontroller) comprises a gain controller 5a, as well as an input of this one a charge amplifier 5b and output a voltage amplifier 5c.
• this electronics 5 is carried by the support (1) of the microsystem.
• the gain of the controller 5a is for example of the type:
• the sensitive components (electrical, optical, etc.) to be isolated can be attached later to the microsystem or the suspension or be integrated directly thereto, if for example silicon-based components.
• suspension device can advantageously be integrated on printed electronic circuit boards (PCB or "Printed Circuit Board”) or in complete systems.
• PCB printed electronic circuit boards
• the piezoelectric layers are, for example, PZT ceramics (Lead Titano-Zirconiate) sol gel, integrated directly onto the substrates of SOI (silicon on insulator).
• PZT ceramics Lead Titano-Zirconiate sol gel
• piezoelectric materials can be used such as Aluminum Nitrate (AIN), Zinc oxide (ZnO), and other perovskites similar to PZT, also depositing by other techniques such as PVD (physical vapor deposition) and CVD (chemical vapor deposition).
• AIN Aluminum Nitrate
• ZnO Zinc oxide
• PVD physical vapor deposition
• CVD chemical vapor deposition
• a cross structure has been made (see FIG. 4) from a SOI wafer (silicon on insulator) which contained a layer of monocrystalline silicon (Si) of 5 ⁇ m thickness over a buried oxide layer. approximately 1 ⁇ m, all bonded to a silicon substrate (Si).
• the substrate below the structure is excavated (from the lower side) until buried oxide (buried oxide) by dry etching, and the cross shape is released by dry etching from the upper surface.
• a basic solution as for example potash KOH.
• the first tests carried out show a yield greater than 90% on a Si substrate of 10 centimeters in diameter.
• Figures 3a and 3b illustrate the Bode diagrams obtained through such an active control.
• the solid line curve is representative of a free microsystem; the dotted line curve represents a microsystem under active control according to the invention,
• the resonance is strongly attenuated.
• the peak before resonance ("overshoot") is relatively low, which makes it possible not to have amplification of the response of the system to the frequencies related to the peak.
• the proposed microsystem allows a substantially smooth linear control, that is to say without re-emission of energy at high frequency.
• microsystem according to the invention can be integrated or placed on an electronic card or an optical medium.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Aviation & Aerospace Engineering (AREA)
• Mechanical Engineering (AREA)
• Micromachines (AREA)

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• 2006
  • 2006-04-20 FR FR0603494A patent/FR2900144B1/fr not_active Expired - Fee Related
• 2007
  • 2007-04-20 WO PCT/FR2007/000676 patent/WO2007122330A1/fr active Application Filing
  • 2007-04-20 EP EP07731337A patent/EP2018347A1/de not_active Withdrawn

Non-Patent Citations (1)

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