A device for measuring periodic biosignals emitted by an individual, associated with vehicle safety equipment.

Abstract

The present invention relates to a device for measuring at least one periodic vital sign from an individual, intended to be attached to a safety device of a vehicle so as to be placed between said device and said individual, comprising: a vibration sensor, * a stack including an active layer extending parallel to a main plane and made of a piezoelectric material and two contact electrodes arranged on at least one face of the active layer; * a flexible support layer extending parallel to the main plane and including a printed circuit with two electrical terminals, the support layer being intended to be placed on an individual; * The present invention relates to a vibration sensor comprising: an electrical connection layer arranged between the laminate and the support layer for connecting each contact electrode to an electrical terminal; and an acoustic damping member intended to be arranged between a safety device and the vibration sensor, the acoustic damping member being integral with the support layer and arranged above the laminate and spaced apart from the laminate.

Description

Technical Field

[0001] The present invention relates to the field of collecting periodic biosignals emitted by the human body, particularly heart rate or respiratory rate. In particular, the present invention relates to an apparatus provided with a vibration sensor, which is associated with a safety device (e.g., seat belt) of a vehicle and enables measurement of the user's heart rate.

Background Art

[0002] Road accidents are a major problem for developed countries. The main causes of accidents include fatigue and drowsiness during driving. Within the European Union (EU), the latter cause accounts for 20% - 35% of serious accidents, and it is estimated that nearly 6,000 people die annually. In the EU, it is considered possible to save 4,000 lives and prevent tens of thousands of injuries every year by integrating in-vehicle fatigue detectors into vehicles.

[0003] Parallel to this, research and development centered on autonomous vehicles has been accelerating. In fact, if it is still far from the state where autonomous driving can be put into the market, everything seems to indicate that the first stage of "partial autonomous driving" under the responsibility ability of the driver will become common within these years. In this regard, when the driver has to resume control in an emergency situation, it is necessary for the driver to surely have all of his / her attentiveness and reaction ability. In this regard, several public and private institutions, including automobile and equipment manufacturers, are currently trying to find a feasible solution for automatic fatigue detection in vehicles.

[0004] Some assumed solutions, such as connected watches, bracelets or clothing belts, are too invasive for the user and ensure monitoring of the driver's physiological variables only when considering that the driver wears and / or connects them.

[0005] Another solution proposes integrating a module for measuring heart rate into the driver's torso using the vehicle's seat belt. For example, document CN106725395 proposes a module for measuring heart rate that has two metal electrodes sandwiching the polyester strap of the seat belt. The heart rate causes an insulating material placed between the two metal electrodes to contract, changing the distance between the two metal electrodes and thus correcting the capacitance value, providing information about the driver's heart rate. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention also relates to solutions related to vehicle safety devices. In particular, the present invention relates to a small, highly sensitive device equipped with a vibration sensor capable of capturing and analyzing periodic biological signals of an individual in a vehicle. [Means for solving the problem]

[0007] The present invention relates to an apparatus for measuring at least one periodic biosignal from an individual, the apparatus being mounted on a vehicle safety device and intended to be positioned between the individual and the apparatus. The apparatus comprises a vibration sensor, the vibration sensor is - A laminate comprising an active layer extending parallel to the main plane and made of a piezoelectric material, and two contact electrodes disposed on at least one surface of the active layer, - A flexible support layer configured to transmit deformation to the active layer of a laminate with each pulse of a biological signal, wherein the support layer extends parallel to the main plane and includes a printed circuit having two electrical terminals, and is intended to be placed on an individual. - An electrical connection layer is placed between the laminate and the support layer, connecting each contact electrode to an electrical terminal. It includes a vibration sensor equipped with [specific features]. The device further comprises an acoustic damping member intended to be positioned between the safety device and the vibration sensor, the member being firmly connected to the support layer and positioned above the laminate, spaced apart from the laminate.

[0008] According to other advantageous non-limiting features of the present invention, either alone or in any technically feasible combination, the following may be achieved: - The acoustic damping member is made of a flexible material having a hardness of 10 Shore 00 to 80 Shore 00, and is equipped with a cover that is firmly connected to the support layer by its peripheral edge. - The cover is heterogeneous and includes a second rigid material selected from metals or polymers having a hardness of 10 Shore D to 80 Shore D. - The device comprises a mechanical damping member, which is integrated entirely or partially on or within the acoustic damping member, and the mechanical damping member is intended to come into direct or indirect contact with the safety device. - The mechanical damping member comprises at least one damper and a body that optionally forms a mass, - The active layer of the laminate has a thickness of 20 microns or less and a Young's modulus of 60 GPa or more. - The device comprises an impedance matching layer (40) having an acoustic impedance in the range of 5.105 Pa·s / m to 3.106 Pa·s / m, and positioned on the surface of the support layer opposite to the surface in contact with the electrical connection layer. - The piezoelectric material of the active layer is selected from single-crystal, polycrystalline, or composite ceramics. - The contact electrode has a cumulative thickness of less than twice the thickness of the active layer. - The support layer is self-supporting and has a thickness of 500 microns or less. - The impedance matching layer has a thickness of 10 microns or more. - The electrical connection layer is formed by an interposer or an anisotropic conductive film. - The support layer includes a film placed on the printed circuit surface opposite to the surface in contact with the electrical connection layer. - The laminate and the support layer each have a first surface area and a second surface area in the main plane, and the first surface area is 30% or less of the second surface area. - The support layer is provided with a reinforcing structure firmly connected to the peripheral zone of the support layer, and the sound-damping member is firmly connected to the reinforcing structure. - The printed circuit board includes wire connection elements for connecting the vibration sensor to an electronic terminal. - The vibration sensor is equipped with a peripheral sealing portion, -The device further comprises an electronic terminal connected to a vibration sensor, which analyzes and interprets the raw signal and extracts a periodic biological signal or an output parameter representing the periodic biological signal. - The electronic terminal comprises an analog stage for adjusting the raw signal measured by a vibration sensor, an analog-to-digital conversion stage for the signal coming from the adjustment stage, and a digital signal processing stage for forming a digital signal and calculating output parameters representing the biosignal. - Electronic terminals are equipped with a communication stage with external systems.

[0009] The present invention also relates to a vehicle safety system, - A safety device associated with the seat and firmly attached to the vehicle chassis at at least one direct or indirect contact point, -A device for measuring at least one periodic biosignal of an individual, as described above, attached to a safety device by a slide fastener, - comprising at least one mechanical energy absorber positioned at at least one contact point to insulate the safety device from mechanical vibrations of the chassis.

[0010] - The safety device can be directly connected to the chassis by at least three contact points, and a mechanical energy absorber is integrated into at least one of the contact points. The safety device can be connected to a sheet, which is firmly connected to the chassis by at least one contact point, and a mechanical energy absorber is integrated into that contact point. [Brief explanation of the drawing]

[0011] Other features and advantages of the present invention will become apparent from the following detailed description of the invention, with reference to the accompanying drawings. [Figure 1] A safety system comprising an apparatus for measuring at least one periodic biological signal of an individual in a vehicle according to the present invention is shown. [Figure 2a] All or part of the apparatus according to the present invention is shown in a schematic cross-sectional view. [Figure 2b] All or part of the apparatus according to the present invention is shown in a perspective cross-sectional view. [Figure 3a] All or part of the apparatus according to the present invention is shown in a schematic cross-sectional view. [Figure 3b] All or part of the apparatus according to the present invention is shown in a perspective cross-sectional view. [Figure 4] Different shapes of the vibration sensor of the apparatus according to the present invention are shown in a plan view. [Figure 5] Various configurations of an apparatus for measuring periodic biological signals according to the present invention are shown. [Figure 6a] Two examples of acoustic damping members (i)(ii) and two examples of mechanical damping members (iii)(iv) for the apparatus according to the present invention are shown. [Figure 6b] An apparatus according to the present invention associated with a vehicle safety device is shown. [Figure 7a] A spectrogram A measured by a vibration sensor (alone) included in the apparatus according to the present invention and a spectrogram B measured by the apparatus according to the present invention are shown. [Figure 7b] A spectrogram B captured and processed by the apparatus according to the present invention, a spectrogram B' extracted from the spectrogram B, a spectrogram B'' after applying a frequency filter, and a biological signal B''' as a waveform are shown.

[0012] The same reference number in the figures may be used for elements of the same type. Some figures include schematic diagrams that are not to scale for readability. In particular, the thickness of layers along the z-axis is not to scale with respect to the lateral dimensions along the x and y axes, and the relative thickness of layers between them is not necessarily considered. Different possibilities (the variations and embodiments described and / or detailed in the following description) should be understood as not mutually exclusive and may be combined together. [Modes for carrying out the invention]

[0013] The present invention relates to a device 200 for measuring at least one periodic, regular, or irregular biosignal of an individual. The periodic biosignal may, in particular, be heart rate or respiratory rate. The device 200 is intended to be mounted on a safety device 1 in a vehicle such that the device 200 is positioned between the individual and the device 1 (Figure 1). The term “safety device 1” is understood to mean any device intended to secure a user to a seat in a vehicle, in particular a seat belt, one or more safety bars, a safety harness, etc. The vehicle may also be understood more broadly to include any means of transportation for a person, such as rolling, flying, gliding, or floating.

[0014] The device 200 is preferably attached to the safety device 1 by a slide fastener, i.e., a fastener that can be clipped to the device 1 to fix the device 200 in a given position and can slide (when not clipped) to allow each user to adjust the position of the device 200 on their chest according to their size and obesity. Optionally, the fastener system may allow a range of motion around the working position for user comfort.

[0015] The device 200 includes a vibration sensor 100 and an acoustic damping member 110. Various configurations of the vibration sensor 100 according to the present invention are shown in Figures 2a, 2b, 3a, and 3b, and will be described below. The vibration sensor 100 comprises a laminate 10 extending parallel to a main plane (x, y), that is, the main surface of the laminate 10 is substantially parallel to the main plane (x, y), and the thickness of the laminate 10 is measured along an axis z perpendicular to the main plane. In this invention, the term “layer” means that the thickness of the layer (or laminate) is generally significantly thinner than the lateral dimension of the layer (in the main plane).

[0016] The laminate 10 includes an active layer 11, which is made of a piezoelectric material. The piezoelectric material is preferably selected from piezoelectric ceramics in single crystal, polycrystalline, or composite form (matrix, generally corresponding to a dispersion of piezoelectric ceramic powder in a polymer). Examples of ceramics include: lithium niobate (LiNbOs), lithium tantalate (LiTaOs), potassium niobate (KNbOs), (BaTiOs), quartz (SiO2), lead magnesium niobate-lead titanate (PMN-PT), lead zirconate titanate (PZT), materials based on potassium sodium niobium lithium antimony (KNN-LS), or materials modified with calcium titanate (KNN-LS-CT), materials based on potassium sodium lithium niobium tantalum antimony (KNNLNTS), bismuth sodium titanate (BNKLBT), etc. As is well known, an active layer 11 made of piezoelectric material will become polarized when it is subjected to deformation, particularly deformation caused in this case by the angular frequency of a periodic biological signal (and thus generate a flow of charge that yields a measurable electrical signal).

[0017] The active layer 11 is advantageously provided with a thickness of 20 microns or less and a Young's modulus of 60 GPa or more. These physical characteristics give the active layer 11 a high level of sensitivity (related to the fact that, with a thin active layer 11 and a high Young's modulus, the measured voltage is correspondingly larger for a given deformation), and give the sensor 100 a high signal-to-noise ratio, enabling the detection of sound waves at frequencies related to the periodic biological signals of the target. The thinness of the active layer 11 also facilitates the miniaturization of the sensor 100. To further improve the sensitivity of acoustic wave detection, the thickness of the active layer 11 can be 10 microns or less, or even 5 microns or less. The thickness of the active layer 11 will be ensured to be sufficient to generate a bias voltage of typically over 500 microvolts during deformation. The lateral dimensions of the active layer 11 (in the main plane (x, y)) may be selected to be, for example, 500 microns to 50 mm, and naturally, smaller dimensions are preferred for the sake of miniaturizing the vibration sensor 100.

[0018] The laminate 10 also includes two contact electrodes 12, 13 positioned on one or both sides of the active layer 11 (i.e., either side of the active layer 11), allowing for the free circulation of charge driven by the polarization of the layer 11 (representing periodic biological signals). Preferably, the contact electrodes 12 and 13 have a cumulative thickness of less than twice the thickness of the active layer 11, or less than the thickness of the active layer 11, and therefore, each electrode 12 and 13 advantageously has a thickness of less than 10 microns or less than 5 microns. The contact electrodes 12 and 13 may be formed from a pure metal material (e.g., Ag, Au, Pd, Pt, Cu, Ni, W, or Ti), a conductive alloy, or a two-dimensional (2D) conductive material (e.g., graphene). A diffusion barrier (e.g., made from TiN, WN, or TaN) and an adhesive layer (e.g., made from Cr or Ti) may be provided between the conductive material of each electrode 12 or 13 and the active layer 11.

[0019] Advantageously, the laminate 10 consists only of an active layer 11 and two contact electrodes 12 and 13.

[0020] The vibration sensor 100 also includes a flexible support layer 30 that extends parallel to the main plane (x, y) and includes a printed circuit 31 with two electrical terminals 32, 33. An electrical connection layer 20 (which also forms part of the vibration sensor 100) is located between the laminate 10 and the support layer 30 and connects each contact electrode 12, 13 to the electrical terminals 32, 33.

[0021] The electrical connection layer 20 is formed by an interposer or an anisotropic conductive film (ACF). In all cases, the objective is that the two contact electrodes 12 and 13 of the laminate 10 can be reached on one identical surface of the laminate 10, which is then associated with the connection layer 20. When the contact electrodes 12 and 13 are located on the bottom surface and the other surface (referred to as the top surface) of the active layer 11, respectively, it is advantageous to provide a conductive via 14 that penetrates the active layer 11 and electrically connects the electrode 12 located on the top surface to a stud portion 12a located on the bottom surface, which is electrically insulated from the other electrode 13 also located on the bottom surface. The interposer may be composed of a thermoplastic (insulating) resin and a conductive material (e.g., nickel) that enables connection between each contact electrode 12, 13 and the electrical terminals 32, 33. Conventionally, anisotropic conductive films consist of conductive beads dispersed in an insulating polymer matrix. When pressure or thermocompression is applied to the laminate 10 / ACF20 / support layer 30, perpendicular electrical conduction is established between electrodes 12a, 13 and terminals 32, 33 via the conductive beads (usually with extra thickness), while the interlayer zone remains insulating. There are also anisotropic conductive adhesives (ACAs) that can be used to form the electrical connection layer 20. These adhesives are based on the same principle as the aforementioned anisotropic conductive film (ACF), except that the polymer matrix is ​​replaced by a liquid precursor that can be thermally activated (by polymerization) to form the final polymer. The final result remains similar to that of ACF (conductive beads dispersed in an insulating matrix), but given the fact that the application is carried out in the liquid phase, it is possible to significantly reduce the thickness of the electrical connection layer 20. A more basic solution could also be considered, namely, implementing a conductive paste for connecting each electrode and stud on the underside to the corresponding terminals 32, 33, and an insulating filler material for electrically insulating the electrodes 12a, 13 from each other and the terminals 32, 33 from each other. The electrical connection layer 20 is in contact with only one of the main surfaces of the laminate 10, and the edge of the laminate 10 and the other main surface are completely free from mechanical contact with the connection layer 20. Therefore, the electrical connection layer 20 is composed at least partially of a conductive material and provides a direct vertical connection between the electrode and the terminal, in contrast to connections by cables or wires, for example, optionally covered with an insulator. The absence of cables improves the sensitivity of the vibration sensor 100 and avoids the introduction of additional rigidity into the structure associated with the cables and welds. Therefore, preferably, the electrical connection layer 20 is in direct and uniform contact with the entire main surface of the laminate 10. On the other sides, the layer 20 is advantageously in direct and uniform contact with the surface of the support layer 30. The electrical connection layer 20 typically has a thickness of less than 50 microns, and in particular, a thickness of 1 to 10 microns.

[0022] The support layer 30 is, advantageously, a self-supporting layer having a thickness of 500 microns or less. This provides it with the necessary flexibility. In one modified form, the support layer 30 is essentially composed of a material that forms the printed circuit 31 (for example, a composite material of epoxy resin reinforced with glass fibers). In another variant, the support layer 30 also comprises a film 35, and the printed circuit 31 is located between the film 35 and the electrical connection layer 20 (Figures 2a and 3a). Thus, the material and thickness of the film 35 can be selected and adjusted to give the support layer 30 the desired flexibility. The film 35 may be made of, for example, metal, polyvinyl chloride (PVC), or epoxy and glass fiber. As an example, the film 35 (if present) may have a thickness of 50 to 300 microns, and the printed circuit 31 may have a thickness of 30 to 200 microns. Typically, the support layer 30 has a rigidity of 1,150,000 N / m to 6,900,000 N / m. The flexibility of the support layer 30, in relation to its thickness and rigidity, allows for the effective transmission of deformation to the active layer 11 with each pulse of the biological signal.

[0023] Advantageously, the laminate 10 and the support layer 30 each have a first and second surface area in the main plane (x, y), with the first surface area being 30% or less of the second surface area. The laminate 10 may be positioned in the central part of the support layer 30, particularly to facilitate assembly, or it may be positioned on the periphery so as not to interfere as possible with the deformation of the support layer 30 caused by the periodic pulsation of the biological signal to be measured. However, the overall objective is to optimize the deformation experienced by the laminate 10 according to the geometric shape of the vibration sensor 100. Although shown in a square form, it should be noted that the laminate 10 of the vibration sensor 100 can, of course, have any shape.

[0024] According to the first embodiment of the vibration sensor 100, the support layer 30 is intended to come into contact with an individual. The support layer 30 then deforms due to the periodic pulsation of the biological signal, and this deformation is transmitted to the active layer 11 of the laminate 10.

[0025] According to the second embodiment, the vibration sensor 100 is, ideally, 5.10 5 Pa·s / m~3.10 6 The system further comprises an impedance matching layer 40 having an acoustic impedance contained in Pa·s / m. This acoustic impedance is set to facilitate the transmission of pulses of biological signals to the support layer 30, and is equal to the acoustic impedance of muscle and fat (1.3 × 10⁻¹⁰). 6 Pa·s / m~1.5×10 6 The impedance is intentionally selected to be close to the impedance included in Pa·s / m. For example, the impedance matching layer 40 is made of silicone (acoustic impedance 1.6 × 10 6 It may be formed from Pa·s / m) or bioplastics, for example, the brand Ecoflex (registered trademark) (acoustic impedance 1.053 × 10 6 It may be formed from Pa·s / m). The impedance matching layer 40 is positioned relative to the support layer 30 on the surface of the support layer 30 opposite to the surface in contact with the electrical connection layer 20. The impedance matching layer 40 typically has a thickness of 10 microns or more, for example, 50 microns to 5 mm. If the support layer 30 includes a film 35, that film is in contact with the impedance matching layer 40. The impedance matching layer 40 is intended to come into contact with the individual. In addition to effectively transmitting pulses due to its impedance matching with body tissue, this layer 40 also facilitates the retention of the sensor 100 against the individual, as its flexible and deformable material tends to "adhere" to the contact surface by the adhesive friction of clothing. Therefore, the presence of the impedance matching layer 40 in the second embodiment of the sensor 100 is particularly preferable when the measurement environment around the individual from whom the biosignal is to be captured is noisy.

[0026] In any of the embodiments described, it may be advantageous for the vibration sensor 100 to include a peripheral seal 60 that surrounds at least the impedance matching layer 40 (if present) or all or part of the support layer 30 (if the impedance matching layer 40 is absent), as shown in Figures 3a and 3b. This seal 60 allows for the accommodation of local topology when the sensor 100 is positioned in contact with an individual.

[0027] The support layer 30 of the vibration sensor 100 may also include a reinforcing structure 50 rigidly connected to the peripheral zone of the support layer 30. The function of the reinforcing structure 50 is to immobilize the periphery of the support layer 30 and the impedance matching layer 40 (if present), and thus highlight their deformation caused by the periodic pulsation of the biological signal to be measured. The reinforcing structure 50 can take various shapes, for example, as follows: - Continuous frames (Figure 4(a)), preferably rings (as shown in Figure 2b), but optionally rectangles, triangles, or other polygons, - A discontinuous frame consisting of two rigidity regions (Figure 4(b)), three rigidity regions (Figure 4(c)), or more.

[0028] The reinforcing structure is advantageously formed from materials having a hardness of more than 30 Shore D, such as PET (polyethylene terephthalate), PMMA (polymethyl methacrylate), PU (polyurethane), PVC (polyvinyl chloride), PP (polypropylene), etc. Given the reduced overall thickness of the assembly comprising the laminate 10, connecting layer 20, support layer 30, and potentially impedance matching layer 40, it may be prudent to provide a system that facilitates the handling of the sensor 100 and promotes its robustness, and the reinforcing structure 50 is involved in such a system.

[0029] The apparatus 200 according to the present invention includes, in addition to the vibration sensor 100 described above, an acoustic damping member 110 intended to be placed between the safety device 1 and the vibration sensor 100. This member 110 is positioned above the stack 10 of vibration sensors 100, spaced apart from the stack 10, and is firmly connected to the support layer 30. It is positioned at a certain distance from the stack 10 (along the z-axis in the figure) (and therefore without contact with the stack 10), typically about 0.1 mm to 10 mm, so as not to hinder its deformation in relation to the support layer 30. The acoustic damping member 110 preferably takes the form of a cover (Figure 6a(i), (ii)), and its periphery is attached to the support layer 30, or to the reinforcing structure 50, if present. As an example, the thickness of the cover on top of the laminate 10 can vary between 0.1 mm and 20 mm. The acoustic damping member 110 aims to insulate the acoustic sensor 100 (more specifically, the support layer 30 that deforms due to vibration, and the active layer 11 that is sensitive to such deformation) from ambient acoustic disturbances propagating through the air, namely engine noise, road noise, air friction on the main body, the voices of passengers in the vehicle, radio, etc. It is preferably composed of an elastomer-type flexible material such as silicone, sorbothane, or rubber. More generally, the flexible material of the acoustic damping member 110 can be identified by its Shore hardness, having a hardness of 10 Shore OO to 80 Shore OO. In addition to its acoustic damping function, the member 110 contributes to the robustness of the device 200, particularly by protecting the active layer 11 of the vibration sensor 100.

[0030] In one modified form, the acoustic damping member 110 may include several types of materials. If it is in the form of a cover, it is called a heterogeneous cover. The second material is selected to be rigid in the properties of a metal or polymer (e.g., aluminum, PVC). If the second material is a polymer, its hardness is preferably selected between 10 Shore D and 80 Shore D. The heterogeneous cover 110 is formed from an alternating arrangement of at least one first layer 110a made of a flexible material and at least one second layer 110b made of a rigid material, as shown in Figure 6a(ii). The heterogeneous cover may also be composed of one or more porous materials, such as polyurethane foam.

[0031] Advantageously, the device 200 further comprises a mechanical damping member 120 which serves to insulate the vibration sensor 100 from mechanical vibrations generated by the vehicle engine, road conditions, and / or user movement and transmitted to the safety device 1 via the frame. Thus, the mechanical damping member 120 is intended to be in contact (directly or indirectly) with the safety device 1. This mechanical damping member 120 may be positioned on or integrated whole or partially within the acoustic damping member 110.

[0032] According to the first option, the mechanical damping member 120 consists of a main body 120a that forms a mass and at least one damper 120b (Figure 6a(iii)). The main body 120a is positioned relative to the acoustic damping member 110, and the damper is positioned on the side of the safety device 1.

[0033] The damper 120b is defined by its stiffness k, which ranges from 0 (friction only) to 7 N / mm, and by its coefficient of friction f, which ranges from 0 (stiffness only) to 0.6. Each damper 120b may be formed, for example, by a metal spring, resin, rubber or silicone column, or a simple mixture (rubber / metal) or hydraulic damper element. The main body 120a has a mass m of 1g to 1kg. The mechanical damping member 120 forms a "mass-spring-piston" system that acts as a high-pass mechanical filter. By adjusting the mass m, stiffness k, and friction coefficient f, it is possible to change the characteristics of the mechanical filter, and in particular to dampen the mechanical vibrations transmitted to the safety device 1. It should be noted that the mass of the acoustic damping member 110 and the mass of the vibration sensor 100 must be taken into consideration and added to the mass of the main body 120a in order to achieve the desired mechanical filter characteristics. Mechanical filters aim to cross over / attenuate parasitic frequencies located in the region of interest. Therefore, in the ideal case, the filter's cutoff frequency should be set to cut out all stray frequencies originating from the chassis (mechanical vibrations).

[0034]

number

[0035] It is desirable that the frequency be approximately 150 Hz, and its attenuation rate

[0036]

number

[0037] It is desirable to make this value as close to 1 as possible to achieve the best possible damping. In practice, of course, a compromise is made between this ideal case and the design constraints of the device 200.

[0038] According to the second option, the mechanical damping member 120 is partially integrated with the acoustic damping member 110, i.e., the main body 120a consists of a layer of the rigid material 110b that constitutes the acoustic damping member 110 (for example, in the form of a heterogeneous cover as shown in Figure 6a). The damping portion 120b of the mechanical damping member 120 is then attached to the acoustic damping member 110 and may be formed by the different elements described in the first option.

[0039] According to the third option, the mechanical damping member 120 is fully integrated with the acoustic damping member 110. For this purpose, the mechanical damping member 120 (included in the acoustic damping member 110) may be formed from a composite material having viscoelastic properties.

[0040] The device 200 according to the present invention may generally have a circular, square, rectangular, or polygonal shape in the main plane (x, y). As shown in Figure 6b, it is intended to be positioned between the safety device 1 and an individual seated in a vehicle. The side of the device 200 located on the side of the support layer 30 of the vibration sensor 100 (and the side of the impedance matching layer 40, if present) is positioned against the individual's chest, preferably in an area where the heart rate or respiratory rate can be palpated. The other side of the device 200 located on the side of the acoustic damping member 110 (and mechanical damping member 120 (if present)) is held against the safety device 1. Contact between the device 200 and the device 1 is preferably performed by a slide fastener 201 (Figure 6b), in particular, the side of the device 200 is firmly connected (adhesively bonded or mechanically attached) to a support element 201a of the coupler 201, which is attached to the safety device 1 by a slide clip 201b.

[0041] The apparatus 200 according to the present invention has the advantage of significantly attenuating frequencies outside the range of frequencies to be measured (typically a range of 0.2 Hz to 500 Hz for heart rate and respiratory rhythm, or frequencies below 70 Hz), and also attenuating parasitic frequencies located within the target frequency range. In particular, it has been observed that speech and other ambient sounds do not contaminate the measurement signal. Therefore, the personal sound environment when the measurement is performed does not need to be quiet and silent. This is possible due to the specific structure of the vibration sensor 100 and the presence of the acoustic attenuation member 110. In addition, the presence of the mechanical damping member 120 (or, as described below with reference to the safety system to which the present invention pertains) significantly dampens mechanical vibrations generated by the motor in operation, and optionally vibrations transmitted to the safety device 1 via road irregularities and the vehicle chassis. Neutralizing these parasitic mechanical vibrations enables reliable and reproducible capture of an individual's biosignals by the vibration sensor 100.

[0042] Advantageously, the device 200 is associated with a fabric 130 and a foam 140 to improve user comfort (Figure 6b). The fabric 130 can, for example, border the support layer 30 and, if an impedance matching layer 40 is present, the impedance matching layer 40, which can generally border all or part of the vibration sensor 100, thus providing a smooth and uniform contact surface with the individual, thereby accommodating variations in user form, clothing type, and / or adjustment of the safety device 1. The foam 140 typically forms a link between the fabric 130 and the fastener 201, which is flexible and deformable and does not change, or only slightly changes, the mechanical filter defined by the mechanical damping member 120. The fabric 130 may be made from cotton, nylon, or polyethylene, and the foam 140 may be made from polyurethane, polyethylene, or polystyrene.

[0043] The device 200 associated with the safety device 1 inside the vehicle enables the measurement of at least one raw signal representing the periodic biosignals of an individual seated inside the vehicle. To analyze and interpret the raw signal and subsequently extract periodic biosignals or information related to these biosignals, the device 200 further comprises an electronic terminal 150 electrically connected to the vibration sensor 100. It should be noted that the device 200 may comprise the vibration sensor 100 (Figures 5(a), (b)) or multiple (two or more) sensors 100 (Figure 5(c)) connected to the electronic terminal 150. If there are several sensors 100, the same or different biosignals (heart rate and respiration) of an individual can be measured.

[0044] To connect the vibration sensor 100 to the electronic terminal 150, the printed circuit board 31 of the vibration sensor 100 may include wire connection elements 31b, for example, strips in the form of a web, as shown in Figures 2a, 2b, 3a, 3b and 5(a). The end pieces of the wire connection elements 31b are equipped with electrical contact connectors connected to electrical terminals 32, 33 of the printed circuit board 31, which can be connected to the electronic terminal 150. The electronic terminal 150 can be attached to the sensor 100, or it can be positioned at a distance from the sensor 100, particularly on a mounting module for attachment to the safety device 1 or another part of the vehicle. The electronic terminal 150 can be connected to or integrated with more complex external systems, such as a fixed or optionally movable monitor. Alternatively, the electronic terminal 150 can be positioned on the acoustic damping member 110 and can form all or part of the main body 120a of the mechanical damping member 120. This configuration ensures a very small size for the device 200. In this case, a wire connection element 31b can be assumed for electrically connecting the vibration sensor 100 and the terminal 150, but the contact plugs 82, 83 rise vertically from the printed circuit 31 of the sensor 100 to the surface of the acoustic damping member 110, for example, via a reinforcing structure 50 (Figure 5(b)).

[0045] Terminal 150 may include various electronic stages that enable the analysis and interpretation of the raw signal measured by the vibration sensor 100. An analog stage for adjusting the raw signal measured by the vibration sensor 100 first amplifies and filters the electrical signal received from the sensor 100. This stage typically consists of a first block of charge amplification type, where the resistance ratio sets the amplification gain of the electrical signal received from the sensor 100, and a second block of Sallen & Key filter type, which enables filtering of frequencies exceeding the acoustic spectrum of the target biosignal. Next, the electronic terminal 150 includes an analog-to-digital conversion stage for the signal coming from the adjustment stage. Then, a digital signal processing stage, consisting of a microcontroller, performs signal formation by calculating the Shannon energy envelope function. Finally, from the formed signal, the desired output parameters representing the biosignal can be calculated.

[0046] The collected data relating to biosignals or desired output parameters can be interpreted in real time and can trigger responses from secondary systems included in or outside the device 200. These responses may include, for example, informational feedback (visual, auditory, mechanical, vibrational, etc.) and / or trigger one or more of the following actions: - Mechanical (plural): Opening / closing a system. - Electrical (multiple options possible): System on / off / change, hydraulic, pneumatic, thermal, etc. In all cases, the secondary system's response is intended to notify or warn an individual (typically the vehicle driver) if the detected biosignals reveal a risk of drowsiness or other abnormal conditions.

[0047] To allow the transmission of desired output parameters to possible external systems, the electronic terminal 150 may include a communication stage. For example, well-known connection protocols (CAN (Controller Area Network), UART (Universal Asynchronous Receiver / Transmitter), USB (Universal Serial Bus)) or wireless data transmission (Wi-Fi, Bluetooth, etc.) may be used. To make the device 200 autonomous, it is also possible to provide a preferably rechargeable battery that allows energy to be supplied to different stages of the aforementioned vibration sensor 100 and / or electronic terminal 150. When the terminal 150 is away from the area of ​​the vehicle's dashboard, it can be powered by the vehicle's battery.

[0048] As described above, the device 200 can be disassembled into the following various configurations: -A portable autonomous device that can be placed on any vehicle safety device 1, - A mounting device in which terminal 150 is connected to sensor 100 by a wire, or is integrated into a more complex external system that is fixed (mounted on the vehicle's dashboard or integrated with the dashboard).

[0049] The present invention also relates to a vehicle safety system comprising a safety device 1 that is firmly connected (directly or indirectly) to the vehicle chassis at at least one contact point 2 (Figure 1). The safety device 1 can typically be directly connected to the chassis via at least three contact points 2, for example, for a seat belt. Alternatively, if the safety device 1 is firmly connected to a vehicle seat, and the seat is firmly connected to the chassis at one or more contact points 2, the safety device 1 can be indirectly connected to the chassis.

[0050] The safety system includes the aforementioned device 200, attached to the safety device 1 by a slide fastener 201, for measuring at least one periodic biosignal of an individual (e.g., the driver of the vehicle). When the device 200 includes a mechanical damping member 120, it isolates the vibration sensor 100 from the mechanical vibrations of the engine transmitted to the safety device 1 by the chassis, as shown in the following application embodiment, enabling the collection and efficient analysis of personal biosignals within a moving vehicle.

[0051] The device 200 according to the present invention can also be implemented within a safety system without the mechanical damping member 120. In this case, the safety system includes at least one mechanical energy absorber 210 positioned at at least one contact point 2 to isolate the safety device 1 from chassis vibrations upstream of the vibration sensor 100. When the safety device 1 is connected to the chassis at three (or optionally four) contact points 2, it is advantageous to place a mechanical energy absorber 210 at at least one contact point 2, or actually at each of the contact points 2. When the safety device 1 is connected to a seat, the mechanical energy absorber 210 is preferentially placed at the contact point 2(s) between the seat and the vehicle chassis.

[0052] Naturally, when the safety device 1 is directly connected to the chassis, a mechanical energy absorber 2 is placed at the contact point 2 (or more) between the seat and the chassis. 10 It is also possible to place them. The mechanical energy absorber 210 forms a mechanical filter and therefore comprises a body (mass) and a damper (rigidity, coefficient of friction), as described with reference to the mechanical damping member 120.

[0053] Finally, it is conceivable to implement both a device 200 equipped with a mechanical damping member 120 and a mechanical energy absorber 210 offset over all or part of the direct or indirect contact points 2 between the safety device 1 and the chassis. Such a configuration would further improve the quality of the raw signal measured by the vibration sensor 100 by significantly limiting parasitic noise and vibration associated with engine operation and vehicle movement.

[0054] Typical embodiments: Next, a manufacturing embodiment of the vibration sensor 100 and the device 200 will be described. Naturally, this embodiment is not limiting, as there are other methods of laminating and assembling different types of layers that can be carried out to manufacture the device 200 according to the present invention. To manufacture the laminate 10 of the vibration sensor 100, it is possible to use a transfer method similar to that described by T Dufay et al. in the publication "Flexible PZT thin film transferred on polymer substrate" (Surface and Coatings Technology, Elsevier, 2018, 343, pp. 148-152). A solution of PZT (lead zirconate titanate) precursor is deposited on a sacrificial substrate (e.g., aluminum) by spin coating to form a viscous layer. Openings are formed through the above layer to allow electrical pathways to pass through. Next, a heat treatment at 650°C is applied to crystallize the PZT, forming an active layer 11 made from a piezoelectric material with a thickness of 5 microns. A 400 nm thick platinum contact electrode 12 is deposited on the upper (free) surface of the active layer 11 fabricated from PZT by chemical vapor deposition (e.g., PECVD (Plasma Enhanced Chemical Vapor Deposition)), and then covered with a polyurethane adhesive layer. Openings are also formed through the electrode / adhesive layer laminate to allow electrical pathways to pass through. To facilitate handling of the active layer 11, a 200 micron thick temporary layer made of polymer (e.g., PET) is attached to the heat-compressed polyurethane adhesive layer. The temporary layer is left open to allow electrical pathways to pass through and is filled with conductive adhesive, which forms conductive vias 14 that electrically contact the contact electrode 12. Next, the sacrificial substrate is chemically etched until the underside of the active layer 11 fabricated from PZT is exposed. Other contact electrodes 13 and stud portions 12a that electrically contact the vias 14 are formed on the underside of the PZT by aluminum deposition (approximately 400 nm).

[0055] This manufacturing method enables the creation of a PZT film having large lateral dimensions, which is then cut to define an active layer 11 having desirable lateral dimensions for its integration into the vibration sensor 100 according to the present invention. In the described embodiment, the active layer 11 has lateral dimensions of 5 mm × 15 mm (along the main plane (x, y)).

[0056] Next, a printed circuit board (PCB) 31 is selected, having a thickness of 100 microns, a lateral dimension substantially identical to that of the active layer 11, and equipped with two electrical terminals 32 and 33. An anisotropic conductive film (ACF) 20 is laminated on the printed circuit 31. Using a ("pick and place") handling machine, the active layer 11 is positioned opposite the connecting layer 20 so that each electrode 12a and 13 (on the underside of the active layer 11) aligns with the electrical terminals 32 and 33 of the printed circuit 31, and then assembly is performed by thermocompression bonding. Next, the temporary polymer layer can be removed. Next, the printed circuit 31 is bonded to a PVC film 35 with a thickness of 300 microns and a lateral dimension (or diameter) of 50 mm to complete the formation of the support layer 30. The impedance matching layer 40, made of 3 mm thick silicone, can be assembled to the film 35 by lamination, screen printing, or molding. The polypropylene reinforcement structure 50 and the silicone peripheral seal 60 are attached to the periphery of the film 35 by fitting. A silicone cover forming the acoustic damping member 110 is molded onto the reinforcing structure 50 and then bonded above and at a distance from the active layer 11. It has a thickness of 2 mm. A mechanical damping member 120 can also be formed, which consists of a rubber column 120b joined to a 5 mm thick steel body 120a. The body 120a is bonded to the acoustic damping member 110. The column 120b is bonded at its free end to a support element 201a of a fastener 201 which can be associated with a vehicle safety device 1 (a seat belt 1 in this example). The fastener 201 may be formed from, for example, polyoxymethylene. For user comfort, the assembly may be covered with a fabric 130 and / or foam 140 around the periphery of the measurement area.

[0057] In this embodiment, the printed circuit 31 includes wire elements 31b (webs) that allow the electrical terminals 32 and 33 of the printed circuit 31 to be connected to an electronic terminal 150 via electrical contact plugs. The terminal 150 includes an electronic stage as described in the general description. It is located, for example, under a user's seat.

[0058] An example of applying the device 200, thus formed, to measuring the driver's heart rate is shown in Figures 7a and 7b. To measure the heart rate, the device 200 is positioned to the left of the individual's chest, with its height adjusted along the seat belt 1, the impedance matching layer 40 of the vibration sensor 100 positioned in contact with the individual's clothing, and the mechanical damping member 120 in contact with the seat belt 1 via a slide clip 201.

[0059] Figure 7a shows two raw spectrograms A and B, acquired by the vibration sensor 100 as described above, on a frequency scale in the range of 0 to 150 Hz (acquisition frequency is 128 kHz). In the case of spectrogram A, the measuring device does not have either the acoustic damping member 110 or the mechanical damping member 120, and the safety system also does not have the mechanical energy absorber 210. In the case of spectrogram B, the device 200 according to the above embodiment includes the acoustic damping member 110 and the mechanical damping member 120. When the vehicle is stationary, both spectrograms A and B show regular peaks, which, after processing, provide reliable information about the driver's heart rate, and this information is reliable regardless of the ambient noise level inside the vehicle. Conversely, as soon as the vehicle is in motion, engine vibrations generate enormous parasitic noise and vibrations that render spectrogram A unusable. The device 200 according to the present invention makes it possible to obtain a much less noisy spectrogram B due to the presence of the acoustic damping member 110 and the mechanical damping member 120. It should be noted that if the vehicle safety system includes at least one mechanical energy absorber 210 at the direct or indirect contact point 2(or more) between the seat belt 1 and the chassis, similar results can be obtained with the device 200 without the mechanical damping member 120.

[0060] Figure 7b shows an extract B' of spectrogram B over approximately 15 seconds during the period the vehicle was operating. Regular peaks representing the driver's heart rate are even more clearly distinguishable. Spectrogram B'' is obtained by normalizing the signal by applying a filter between 40Hz and 70Hz. The peaks shown on spectrogram B'' can be visualized as waveforms. This is signal B''', revealing the peak representing the driver's heart rate. Therefore, from signal B''', it is possible to extract the periodic signal and / or output parameters representing the individual's heart rate with a high level of accuracy. Therefore, it is possible to reliably detect changes in heart rate (or respiratory rate) that are likely to indicate that the driver is drowsy or in other dangerous situations. In such cases, the device 200 can trigger an action as described above (e.g., a sound or light signal). As described above, generally speaking, the non-invasive device 200 for measuring periodic biological signals according to the present invention provides reliable information about the driver's biological signals regardless of the sound environment inside the vehicle, whether stopped or in operation.

[0061] Naturally, the present invention is not limited to the embodiments and examples described, and modified embodiments may be provided without departing from the scope of the invention as defined by the claims.

Claims

1. A device (200) for measuring at least one periodic biosignal from the individual, which is intended to be attached to the device (1) so as to be positioned between the individual and the vehicle safety device (1), wherein the device (200) - A vibration sensor (100), * A laminate (10) comprising an active layer (11) extending parallel to the main plane (x, y) and made of a piezoelectric material, and two contact electrodes (12, 13) disposed on at least one surface of the active layer (11), * A flexible support layer (30) configured to transmit deformation to the active layer (11) of the laminate (10) in each pulse of the biosignal, wherein the support layer (30) includes a printed circuit (31) extending parallel to the main plane (x, y) and having two electrical terminals (32, 33), and the support layer (30) is intended to be positioned relative to the individual, * An electrical connection layer (20) is positioned between the laminate (10) and the support layer (30), connecting each contact electrode (12, 13) to an electrical terminal (32, 33), A vibration sensor (100) equipped with, - An acoustic damping member (110) intended to be positioned between the safety device (1) and the vibration sensor (100), the acoustic damping member (110) being firmly connected to the support layer (30) and positioned above the laminate (10) and spaced apart from the laminate (10), is provided in the apparatus (200).

2. The apparatus (200) according to claim 1, wherein the sound dampening member is made of a flexible material having a hardness of 10 Shore OO to 80 Shore OO and comprises a cover that is firmly connected to the support layer (30) by its peripheral edge.

3. The apparatus (200) according to claim 2, wherein the cover is heterogeneous and comprises a second rigid material selected from metals or polymers having a hardness of 10 Shore D to 80 Shore D.

4. The device (200) according to claim 1, further comprising a mechanical damping member (120) which is integrated in whole or in part on or within the acoustic damping member (110), wherein the mechanical damping member (120) is intended to come into direct or indirect contact with the safety device (1).

5. The apparatus (200) according to claim 4, wherein the mechanical damping member (120) comprises at least one damper and a body that optionally forms a mass.

6. The apparatus (200) according to claim 1, wherein the active layer (11) of the laminate (10) has a thickness of 20 microns or less and a Young's modulus of 60 GPa or more.

7. 5.10 5 Pa・s / m~3.10 6 The apparatus (200) according to claim 1, comprising an impedance matching layer (40) having an acoustic impedance included in Pa·s / m and disposed on the surface of the support layer (30) opposite to the surface in contact with the electrical connection layer (20).

8. - The contact electrodes (12, 12a, 13) have a cumulative thickness of less than twice the thickness of the active layer (11), - The support layer (30) is self-supporting and has a thickness of 500 microns or less. - The apparatus (200) according to claim 7, wherein the impedance matching layer (40) has a thickness of 10 microns or more.

9. The apparatus (200) according to claim 1, wherein the support layer (30) includes a film (35) disposed on the surface of the printed circuit (31) opposite to the surface in contact with the electrical connection layer (20).

10. The apparatus (200) according to claim 1, wherein the support layer (30) is provided with a reinforcing structure (50) firmly connected to the peripheral zone of the support layer (30), and the sound dampening member (110) is firmly connected to the reinforcing structure (50).

11. - The apparatus (200) according to claim 1, comprising an electronic terminal (150) connected to the vibration sensor (100) for analyzing and interpreting the raw signal and extracting the periodic biological signal or output parameters representing the periodic biological signal.

12. The aforementioned electronic terminal (150) - An analog stage for adjusting the raw signal measured by the vibration sensor (100), - An analog-to-digital conversion stage for the signal coming from the aforementioned analog stage, - The apparatus (200) according to claim 11, comprising a digital signal processing stage for forming a digital signal and calculating output parameters representing the biological signal.

13. It is a vehicle safety system, - A safety device (1) associated with the seat and firmly connected to the vehicle chassis by at least one direct or indirect contact point (2), - A device (200) for measuring at least one periodic biosignal from an individual according to one of claims 1 to 12, which is attached to the safety device (1) by a slide fastener (201), A vehicle safety system comprising: at least one mechanical energy absorber (210) positioned at at least one contact point (2) to insulate the safety device (1) from mechanical vibrations of the chassis.

14. The vehicle safety system according to claim 13, wherein the safety device (1) is directly connected to the chassis by at least three contact points (2), and a mechanical energy absorber (210) is integrated with at least one of the contact points (2).

15. The vehicle safety system according to claim 13, wherein the safety device (1) is connected to the seat, the seat is firmly connected to the chassis by at least one contact point (2), and a mechanical energy absorber (210) is integrated with the contact point (2).

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