Office National D'etudes Et De Recherches Aerospatiales

Office National D'etudes Et De Recherches Aerospatiales (onera)

Onera (office National D'etudes Et De Recherches Aerospatiales)

Office National D'etudes Et De Recherche Aerospatiales (onera)

Onera

Onera (office National D'eudes Et De Recheres Aerospatiales)

Olivier Le Traon

Denis Janiaud

Serge Muller

Jean Guerard

Claude Chartier

Marc Pernice

Raphaël Levy

Vincent Gaudineau

Bernard Lecorre

Guillaume Aoust

Steve Masson

Béatrice Verlhac

Rachid Taibi

Michael Bahriz

Stève Masson

Béatrice Bourgeteau

Bernard Le Corre

Thomas Perrier

Michaël Bahriz

An electric measurement circuit possesses an electrical reaction leg for forming an oscillator from a resonator, and furthermore possesses a measurement leg the input of which is supplied by the electrical reaction leg. The measurement leg contains an adjustable phase shifter so that an additional excitation force that is applied to the resonator in the measurement leg can be adjusted in phase quadrature with respect to an excitation force that is applied to the resonator in the electrical reaction leg. Such an electrical measurement circuit is particularly suitable for forming a photoacoustic gas detector.

Electrical measurement circuit, gas detector and method for measuring a gas concentration

A resonator includes a prong of which the width between edges is close to &#x3bb;/2. The pressure variation at one edge is then in phase opposition with that at the other edge. Acoustic coupling with an incident wave having the wavelength is thus improved. The ratio between the width between edges and the height of the prong is chosen so that only the fundamental mode with bending oscillation of the prong is present. It to prongs of a tuning fork embedded in a solid shared base optimized to contain the energy in the tuning fork while avoiding energy losses in the support. Finally, the tuning fork is advantageously combined with a unit for containing acoustic energy including a rigid reflecting screen.

Mechanical resonator optimised to operate in a fluid

Mechanical resonators for making timepieces have the drawback of not being simultaneously efficient, compact, and inexpensive. The invention is a planar structure of a mechanical resonator () that is suitable for reducing bulkiness and manufacturing cost and comprises a bar (R) vibrating in longitudinal expansion/compression resonance and two beams, () each vibrating simultaneously in longitudinal expansion/compression and it bending oscillation in the plane of the structure and connected to the bar by a connection element () on the median plane (&#x3c0;) of the bar, thereby enabling the effects of the transverse deformations of the bar, due to the Poisson ratio of the material, to not be transmitted to the attachment pads (PF) of the resonator. Thus, the quality factor of the resonator can be very high.

Planar structure of a mechanical resonator decoupled by bending oscillation and expansion/compression vibrations

The device () comprises a cylindrical resonator (R) vibrating in extension-compression along its longitudinal axis (&#x394;) and having a vibration node (N) in its mid-plane (&#x3c0;), the vibration naturally generating radial extension/compression deformations, and a mechanical decoupling module comprising a hollow cylinder () surrounding the resonator and a membrane () positioned in the aforementioned mid-plane and rigidly connected to the cylindrical surface of the resonator and to the internal cylindrical surface of the hollow cylinder. The hollow cylinder vibrates in extension/compression in antiphase with the vibration of the resonator, enabling the effects of the radial deformations of the hollow cylinder and of the resonator to compensate each other in an area (ZF) located on the external surface of the hollow cylinder close to the mid-plane.

Module for the mechanical uncoupling of a resonator having a high quality factor

The Coriolis-effect gyrometer has a tuning fork having two tines, which tuning fork is formed in a plate of piezoelectric crystal and provided with electrodes composed of ribbon conductors supported solely by the faces of the tines parallel to the plate. The drive excitation and drive detection electrodes are connected to an oscillator circuit, and the Coriolis detection electrodes are connected to a detection circuit. For each of the faces parallel to the plate of each of the tines the drive detection ribbon is disposed between the drive excitation ribbon and the Coriolis detection ribbon and is connected to the inverting input of an operational amplifier, the non-inverting input of which is connected to the electric ground, said operational amplifier forming part of the oscillator circuit.

Electrodes and associated electronic circuits for a piezoelectric vibrating gyrometer

The present disclosure relates to a vibrating element which is planar parallelly to an electrical crystallographic axis of a piezoelectric material such as quartz. The element comprises a beam holding electrodes, a stationary portion rigidly connected to one end of the beam, and a solid portion rigidly connected to the other end of the beam. The structure with facets from the chemical machining of the element has an axis of symmetry parallel to the electrical axis, and the solid portion has a center of gravity on the axis of symmetry. The useful vibration modes of the vibrating element, according to which the solid portion is reciprocatingly rotated about the axis of symmetry and reciprocatingly moved parallel to the plane of the element, are uncoupled. The measurement of an angular speed by a rate gyroscope including said vibrating elements is more precise.

Element vibrating in two uncoupled modes, and use in vibrating rate gyroscope

A sensor comprises two identical vibrating members operating with a common working frequency and joined to each other by a mechanical decoupling device. The device comprises a frame and two connecting bridges each supporting one member. The frame comprises a succession of mass portions and thinned portions so that the frequency of one mode of structural resonance of the frame is substantially equal to the common working frequency, and each connecting bridge is disposed in a node of vibration of the frame at the common working frequency. Thus, the vibrations of the two vibrating members are decoupled from each other.

Mechanical decoupling device for monolithic differential vibrating sensor

The invention concerns a transducer constituting the sensitive member of a sensor whose frequency varies as a function of the intensity of force applied to it. The force transducer comprises a beam having length and rectangular cross-section with thickness and width and flexionally vibrating. The beam has a thickness reduced over a central portion of its length, its width remaining constant.

Force transducer having a central portion of reduced thickness

A vibrating rate gyro structure machined in a plate of material and comprising a fixed part, a resonator, and a mechanical system connecting the resonator to the fixed part. The mechanical system comprises a first mobile mass part connected to one end of the resonator, a second mobile mass part ( ) connected to the resonator and situated in the vicinity of the other end of the resonator, two flexible arms situated on both sides of the resonator and each connecting the first mobile mass part to the second mobile mass part, and two other flexible arms situated on both sides of the resonator and connecting the second mobile mass part to the fixed part.

Monolithic vibrating rate gyro structure

A monolithic miniature accelerometer machined in a plate of material, comprising a fixed part, two first mobile mass parts referred to as inertial masses, two hinge blades each having one end fastened to one of the two mobile mass parts, and two resonators each having one end fastened to one of the two mobile mass parts, a third mobile mass part fastened to the other end of each of the two resonators and of each of the two hinge blades, and a flexible stem situated between the first two mobile mass parts and connecting the third mobile mass part to the fixed part.

Monolithic miniature accelerometer

A monolithic accelerometric transducer comprises a fixed part, two mobile mass parts and a resonator having ends fastened to said mobile parts, a flexible frame around the two mobile parts, and two connecting members connecting the frame to the second mobile part and to the fixed part. The frame provides a mechanical filter between the resonator and the fixed part which is not affected by the vibrations of the resonator. The quality factor Q of the resonator is not degraded and the measurement provided by the transducer is more accurate. In a differential output accelerometer, the position of the transducer is deduced from that of another, identical transducer by rotation of 180.degree. about an axis parallel to the resonator, the fixed parts of the transducers being fastened together.

Growing community of inventors

Vauhallan, France

Olivier Le Traon