Device for measuring periodic vital signals emitted by an individual, associated with a safety apparatus of a vehicle
A device for measuring at least one periodic vital signal from an individual, intended to be attached to a safety apparatus of a vehicle so as to be arranged between the individual and the apparatus, the device comprising: a vibration sensor comprising: a stack of layers and including an active layer made of piezoelectric material and two contact electrodes arranged on at least one face of the active layer, a flexible support layer including a printed circuit comprising two electrical terminals, the support layer being intended to be arranged on the individual, an electrical connection layer, arranged between the stack of layers and the support layer, for connecting each contact electrode to an electrical terminal, an acoustic attenuation member intended to be arranged between the safety apparatus and the vibration sensor, the member being integral with the support layer and arranged above and spaced apart from the stack of layers.
1 . A device for measuring at least one periodic vital signal from an individual, intended to be attached to a safety apparatus of a vehicle so as to be arranged between the individual and the apparatus, the device comprising:
a vibration sensor comprising:
a stack of layers extending parallel to a main plane and including an active layer of piezoelectric material and two contact electrodes arranged on at least one face of the active layer;
a flexible support layer configured to transmit a deformation to the active layer of the stack of layers, at each pulse of the vital signal, the support layer extending parallel to the main plane and including a printed circuit comprising two electrical terminals, the support layer configured to be arranged against the individual; and
an electrical connection layer arranged between the stack of layers and the support layer, the electrical connection layer connecting each contact electrode to an electrical terminal;
an acoustic attenuation member configured to be arranged between the safety apparatus and the vibration sensor, the acoustic attenuation member being rigidly connected to the support layer and arranged above and spaced apart from the stack of; and
an electronic terminal connected to the vibration sensor to analyze and interpret a raw signal and extract the periodic vital signal or an output parameter representative of the periodic vital signal.
2 . The device of claim 1 , wherein the acoustic attenuation member comprises a cover composed of a flexible material having a hardness of between 10 Shore 00 and 80 Shore 00, and rigidly connected to the support layer by a periphery of the cover.
3 . The device of claim 2 , wherein the cover is heterogeneous and comprises a second rigid material, the second rigid material comprising a metal or a polymer having a hardness of between 10 Shore D and 80 Shore D.
4 . The device of claim 1 , further comprising a mechanical attenuation member on or integrated in whole or in part in the acoustic attenuation member, the mechanical attenuation member configured to be in direct or indirect contact with the safety apparatus.
5 . The device of claim 4 , wherein the mechanical attenuation member comprises at least one damper.
6 . The device of claim 1 , wherein the active layer of the stack of layers has a thickness of less than or equal to 20 microns and a Young's modulus greater than or equal to 60 GPa.
7 . The device of claim 1 , further comprising an impedance matching layer having an acoustic impedance between 5·10 5 Pa*s/m and 3·10 6 Pa*s/m, and arranged on a face of the support layer opposite a face of the support layer in contact with the electrical connection layer.
8 . The device of claim 7 , wherein:
the contact electrodes have a cumulative thickness of less than twice the thickness of the active layer;
the support layer is self-supporting and has a thickness of less than or equal to 500 microns; and
the impedance matching layer has a thickness greater than or equal to 10 microns.
9 . The device of claim 8 , wherein the support layer includes a membrane arranged on a face of the printed circuit opposite a face of the printed circuit in contact with the electrical connection layer.
10 . The device of claim 1 , wherein the support layer comprises a stiffening structure rigidly connected to a peripheral zone of the support layer, the acoustic attenuation member being rigidly connected to the stiffening structure.
11 . The device of claim 1 , wherein the electronic terminal comprises:
an analog stage for conditioning a raw signal measured by the vibration sensor;
an analog to digital conversion stage of the signal coming from the conditioning stage; and
a digital signal processing stage for shaping the digital signal and calculating an output parameter representative of the vital signal.
12 . A vehicle safety system, comprising:
a safety apparatus associated with a seat and rigidly connected to a chassis of the vehicle at least at one direct or indirect contact point;
a device according to claim 1 for measuring at least one periodic vital signal of an individual, the device attached to the safety apparatus by a sliding fastener; and
at least one mechanical energy absorber placed at least at one contact point so as to insulate the safety apparatus from mechanical vibrations of the chassis.
13 . The vehicle safety system of claim 12 , wherein the safety apparatus is directly connected to the chassis by at least three contact points, and further comprising a mechanical energy absorber integrated into at least one of the at least three contact points.
14 . The vehicle safety system of claim 12 , wherein the safety apparatus is connected to the seat, is the seat being rigidly connected to the chassis by at least one contact point, and further comprising a mechanical energy absorber integrated into said the at least one contact point.
15 . The device of claim 5 , wherein the mechanical attenuation member further comprises a body forming a mass.
16 . The device of claim 3 , further comprising a mechanical attenuation member on or integrated in whole or in part in the acoustic attenuation member, the mechanical attenuation member configured to be in direct or indirect contact with the safety apparatus.
17 . The device of claim 16 , wherein the mechanical attenuation member comprises at least one damper.
18 . The device of claim 17 , wherein the active layer of the stack of layers has a thickness of less than or equal to 20 microns and a Young's modulus greater than or equal to 60 GPa.
19 . The device of claim 18 , further comprising an impedance matching layer having an acoustic impedance between 5·10 5 Pa*s/m and 3·10 6 Pa*s/m, and arranged on a face of the support layer opposite a face of the support layer in contact with the electrical connection layer.