Sercel Inc.

Maurice Moreau

Jean-Paul Menard

An anti-stiction method is proposed in an inertial micro-electro-mechanical device. The device includes: a mobile mass, suspended to an armature via a spring, and having at least one mobile electrode; and at least one fixed electrode rigidly attached to the armature, each fixed electrode cooperating with one of the at least one mobile electrode to form a pair of electrodes. The anti-stiction method carries out a step of detecting, for at least one stuck pair of electrodes, a stiction associated to a stiction force and a step of applying, during a predetermined time period, a predetermined voltage between the electrodes of at least one of the pair or pairs of electrodes, so as to create an electrostatic force which generates a displacement of the mobile mass according to the direction of the stiction force.

Anti-stiction method in an inertial MEMS, corresponding computer program product, storage means and device

The invention relates to an accelerometer comprising a moving mass () and a fixed part (), which uses variations in capacitance () in order to detect the movement of the mass (). The inventive accelerometer comprises a first series of electrodes () which are solidly connected to the mass () and which are interdigitated with a series of electrodes () which are solidly connected to the fixed part (). According to the invention, each moving electrode (), together with an adjacent fixed electrode (), forms a capacitance which varies according to the position of the moving mass (). The accelerometer further comprises an electronic circuit which is used to detect the variation in at least one capacitance between the moving mass () and the fixed part (), in the form of a moving mass displacement indicator. The invention is characterised in that one or more or the electrodes () or the moving mass () and/or the fixed part () takes the form of a finger with a large base and a profile which narrows in the direction of the free end thereof. Moreover, the recurring return stress can be selected such that the mechanical power has an essentially zero power zone at the mechanical resonance frequency of the electrodes.

Accelerometer with reduced extraneous vibrations owing to improved electrode shape

An accelerometer uses variations in capacitance to detect and measure the movement of a moving mass in relation to a fixed part. The accelerometer comprises a first series of electrodes, which are solidly connected to the mass and which are interdigitated with a second series of electrodes. The second series of electrodes are solidly connected to the fixed part. The accelerometer further comprises an electronic circuit which: detects the variation in at least one capacitance between the moving mass and the fixed part, in the form of a moving mass displacement indicator; and also generates an electrostatic stress in order to return the moving mass to the initial position thereof.

Accelerometer with reduced extraneous vibrations owing to improved return movement

A slave mobile plate accelerometer using variations of capacitance to detect the movement of a mass. The apparatus comprises at least one pair of fixed electrodes rigidly attached to an armature, and at least one mobile electrode suspended by springs from the armature, between the two fixed electrodes of each pair of fixed electrodes, to form two capacitors, each mobile electrode being adapted to move between the fixed electrodes of each pair of fixed electrodes, due to the effect of acceleration, so causing a variation of the capacitance of each capacitor. The accelerometer further includes an electronic circuit for adjusting the electrostatic stiffness of at least one combination of a fixed electrode and a mobile electrode and a control system for detecting the variation of the capacitance of each capacitor.

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Landemont, France

Maurice Moreau