Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
  • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
  • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
  • G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance

Definitions

• the present invention relates to the field of sensors. More specifically, the present invention relates to a measurement device exploiting an indirect measurement of permittivity between two electrically conductive bodies respectively forming a measurement probe and a reference element, for example a reference probe.
• This device comprises two electrically conductive bodies constituting respectively a measurement probe 10 and a reference probe 20, electrical supply means 30 capable of delivering a continuous electrical voltage of controlled amplitude, an integrating stage 50 comprising a switching system of capacity 53 and control means 40 adapted to define cyclically, at a controlled frequency, a series of two sequences: a first sequence T1 during which the electrical supply means 30 are connected to the measurement probe 10 to apply a electric field between the measurement probe 10 and the reference probe 20 and accumulate electrical charges on the measurement probe 10, then a second sequence T2 during which the electrical supply means 30 are disconnected from the measurement probe 10 and this is connected to a summing point of the integrating stage 50 to transfer loads da ns the integrator stage 50 and obtain at the output thereof a signal representative of the permittivity existing between the measurement probe 10 and the reference probe 20.
• the integrator stage 50 comprises an operational amplifier 51, a first integration capacitor 52 mounted in feedback on this amplifier 51 and a second capacitor 53 switched between the output and the input of the operational amplifier 51 at the rate of the sequences controlled by the control means 40, so that, at an established equilibrium regime, a voltage is obtained at the output of the operational amplifier 51 with equilibrium equal to -E.Cs / C53, relationship in which -E denotes the amplitude of the voltage across the terminals of the power supply means 30 and Cs and C53 denote respectively the values of the capacities defined between the measurement probe 10 and the reference probe 20 on the one hand, and the second switched capacitor 53 on the other hand.
• the switching of the electrical supply means 30 and of the second capacitor 53 is ensured by reversing switches 42, 43 controlled by a time base 41.
• the capacitor Cs is charged under the supply voltage delivered by the module 30, which is assumed here to be equal to -E.
• the present invention now aims to provide a new device incorporating the concept described in document WO-0025098, but having higher performance than that of known prior devices.
• the present invention aims to propose new means for better identifying the environment of the measurement probe, to improve the detection of a transient phenomenon, for example eliminating the effect of an obstacle permanent interposed between the measurement probe and the zone of appearance of a transient phenomenon.
• the present invention can find in particular, but not exclusively, application in the detection of a person or an object on a seat of a motor vehicle.
• a device comprising at least one main measurement probe, means capable of sequentially applying a controlled supply voltage between the main measurement probe and a reference element and means able to integrate the electrical charges accumulated on the main measurement probe, characterized in that it also comprises at least one auxiliary measurement probe, also connected sequentially to means of controlled electrical supply and to integration means of loads, the said auxiliary measurement probe having, with respect to a potential detection area, a different capacity from the main measurement probe, so that the comparative exploitation of the signals originating respectively from the two measurement probes allows determine the influence of the main measuring probe.
• the auxiliary measurement probe has a small controlled area compared to the main measurement probe.
• the auxiliary measurement probe is located at a distance from the potential detection zone, different from the main measurement probe.
• the auxiliary measurement probe is located in the same plane at a distance from the reference element different from the main measurement probe.
• FIG. 1 previously described schematically represents a device in accordance with the state of the art disclosed in document WO-0025098
• FIG. 2 schematically represents the detection of a passenger in a vehicle seat, using measurement probes in accordance with document WO-0025098
• FIG. 3 diagrammatically represents the same device in the case of an obstacle interposed between the measurement probes and the detected body
• FIG. 4 diagrammatically represents, in a plan view, a main measurement probe and an auxiliary measurement probe, in accordance with a first embodiment of the present invention
• FIG. 1 previously described schematically represents a device in accordance with the state of the art disclosed in document WO-0025098
• FIG. 2 schematically represents the detection of a passenger in a vehicle seat, using measurement probes in accordance with document WO-0025098
• FIG. 3 diagrammatically represents the same device in the case of an obstacle interposed between the measurement probes and the detected body
• FIG. 4 diagrammatically represents, in a plan view, a main measurement probe and an auxiliary measurement
• FIG. 5 shows the same main and auxiliary measurement probes in accordance with a first embodiment of the present invention, in the case of the detection of a body with a surface different from FIG. 4,
• FIG. 6 schematically represents, in a sectional view, a main measurement probe and an auxiliary measurement probe, in accordance with a second embodiment of the present invention,
• FIGS. 7 and 8 schematically represent, respectively in a sectional view and a plan view, a main measurement probe and an auxiliary measurement probe, in accordance with a third embodiment of the present invention
• FIG. 9 and 10 schematically represent an example of supply of the measurement probes illustrated in Figures 7 and 8 and the resulting detection
• - Figure 11 shows a plan view of probes according to another alternative embodiment of the present invention
• FIG. 12 represents a plan view on an enlarged scale in the transverse direction and compressed in the longitudinal direction of the same probes
• FIG. 13 represents a cross-sectional view of the same probes and illustrates more precisely the field lines according to a particular implementation
• FIG. 14 illustrates a diagram of results obtained using the probes illustrated in FIGS. 11 to 13, which diagram makes it possible to discriminate between different detection configurations.
• FIG. 14 illustrates a diagram of results obtained using the probes illustrated in FIGS. 11 to 13, which diagram makes it possible to discriminate between different detection configurations.
• the detailed description which follows will be made with reference to the detection of a person on a seat of a motor vehicle.
• the present invention is not limited to this particular application.
• FIG. 2 shows diagrammatically two measurement probes 10 integrated in the seat 90 of a motor vehicle seat for the possible detection of a person P.
• the detection of the person P can be carried out by sequentially applying a controlled electrical voltage between the measurement probes 10 and a reference element, such as the chassis of the motor vehicle, then integrating the loads thus accumulated on the measurement probes 10.
• the two probes referenced 10 in FIG. 2 can serve one as a measurement probe and the other as a reference element.
• the same measurement probes 10 for the detection of the same person P have been shown diagrammatically in FIG. 3, but in the case where an obstacle O, such as a mat of balls or a towel, is interposed between the seat cushion , and therefore probes 10, and person P.
• an obstacle O such as a mat of balls or a towel
• the object of the present invention is to propose means making it possible to eliminate this difficulty.
• an auxiliary measurement probe 100 having a surface area significantly smaller than that of the main measurement probe.
• the auxiliary measurement probe has a square outline.
• the invention is however not limited to this particular arrangement.
• the auxiliary measurement probe 100 may take any other appropriate geometry, such as for example a circular contour.
• the auxiliary measurement probe 100 is located at the same distance from the potential detection zone, for example the upper surface of a seat, as the main measurement probe 10.
• the surface and the location of the auxiliary measurement probe 100 are such that it always experiences the same external influence during the appearance of a transient external phenomenon, whatever the amplitude of this phenomenon.
• the surface and the location of the auxiliary measurement probe 100 are such that it is always located entirely under the person P when the latter takes place on the seat.
• the surface and the location of the main measurement probe 10 are such that the surface of this main measurement probe 10 influenced by the transient external phenomenon, depends on the amplitude of this phenomenon, for example in the case of detection. of a person in a motor vehicle seat, depends on the body size of the person P.
• the auxiliary measurement probe 100 can be centered on the detection zone, have a greater transverse dimension of the order of a few centimeters, for example less than 3 cm, preferably less than 1 cm and a total area less than a few square centimeters, for example less than 9 cm 2 , preferably less than 4 cm 2 .
• the main measurement probe 10 preferably has at least one dimension greater than the largest possible dimension of the body P capable of being detected.
• the main measurement probe 10 can be of any geometry such as for example sinusoidal or rectangular. In the latter case, it develops a surface of the order of a few cm over several dm, for example of the order of a few cm, such as of the order of 5 cm, over more than 30 cm, preferably more than 40 cm.
• the use of the auxiliary electrode illustrated in FIGS. 4 and 5 makes it possible to standardize the measurement as a function of the distance from the body P.
• the exploitation of the signal resulting from the integration of the charges accumulated on the auxiliary measurement probe 100 makes it possible to know the distance separating the body P from the auxiliary measurement probe 100, since the importance of the body P has no influence on This measure.
• an auxiliary measurement probe 100 located at a distance from the potential detection zone, for example the upper surface of a seat of seat, different from the main measurement probe 10, but preferably having an area identical to that of the main measurement probe.
• the auxiliary measurement probe 100 is also close to the main measurement probe 10.
• the distance between the two probes 100 and 10 from the body to be detected must be constant.
• the main measurement probe 10 preferably has at least one dimension greater than the largest possible dimension of the body P capable of being detected.
• the main measurement probe 10 can also comply with the provisions described above with reference to FIGS. 4 and 5.
• a main measurement probe 10 and an auxiliary measurement probe 100 placed at a different distance (asymmetrical) relative to a reference element
• the two measurement probes, main 10 and auxiliary 100 can be coplanar with the reference element 110.
• the auxiliary probe 100 is located between the measurement probe 10 and the reference element 110.
• the center distance 11 between the two measurement probes 10 and 100 is of the order of a few millimeters
• the center distance 12 between auxiliary probe 100 and the reference element 110 is of the order of a few centimeters but at least twice its size.
• the main 10 and auxiliary 100 measurement probes preferably have identical surfaces, but can be of any geometry, for example rectangular.
• the reference element 110 can also have a surface identical to the main 10 and auxiliary 100 measurement probes.
• the main 10 and auxiliary 100 measurement probes can have different surfaces of known ratio.
• the main measurement probe 10 at least, preferably has at least one dimension greater than the largest possible dimension of the body P capable of being detected.
• the other probe 100 or 10 can itself serve as an auxiliary reference element.
• the main 10 and auxiliary 100 measurement probes are each sequentially connected to a source of electrical power of known amplitude and then the electrical charges accumulated on these probes are integrated, preferably with means comparable to those defined in the document
• the power supply means and the charge integration means can be the same for the different probes 10 and 100. In this case switching / multiplexing means alternately switch the probes 10 and 100 at the terminals of these means. As a variant, it is possible to provide electrical supply means and means for integrating different charges for the various probes 10 and 100.
• the reference element can be formed of a reference probe or of a mass constituted for example by the earth or a neighboring metallic mass, for example the chassis of a motor vehicle.
• the present invention can relate to a large number of applications. We previously mentioned the detection of the presence of a user on a motor vehicle seat, in particular for the control of an airbag system. However, the present invention is not limited to this particular application. The present invention may for example also relate, inter alia, to anti-intrusion detection fields or even fluid level detectors. We will now describe the alternative embodiment according to the present invention illustrated in Figures 11 to 13 attached.
• the probe 110 serves as a reference probe.
• the probe 10 constitutes the main measurement probe, while the probe 100 constitutes the auxiliary measurement probe.
• the probe 10 can constitute the main measurement probe, while the probe 100 serves as a reference probe.
• each probe 10, 100 and 110 is elongated. Its length L is typically greater than 10 times its width, very preferably its length L is typically greater than 20 times its width.
• the probe 100 has a U-shaped configuration.
• the probe 100 comprises two main strands 102, 104, parallel between them and arranged respectively on either side of the probe 10.
• the probe 100 frames the probe 10.
• the two strands 102, 104 are connected between them by a connecting element 103.
• the electrode 10 is very insensitive to the edge effects of the electric field and only gives signal information when the passenger is very close to the probe.
• the electrode 100 is very sensitive to the edge effects of the electric field and gives signal information even when the passenger is very far from the probe (for example typically up to twenty centimeters from the probe).
• the probe 10 and the probe 100 have varying widths along their length. More precisely still, preferably, each of the probes 10 and the probe 100 have varying widths along their length. More precisely still, preferably, each of the probes 10 and the probe 100 have varying widths along their length. More precisely still, preferably, each of the probes 10 and the probe 100 have varying widths along their length. More precisely still, preferably, each of the probes 10 and the probe 100 have varying widths along their length. More precisely still, preferably, each of the probes 10 and
• 100 comprises three sections: a central section 16, 106 and two end sections 18,19; 108, 109.
• the end sections 18, 19 on the one hand, and 108, 109 on the other hand have identical widths for a given probe 100 or 200.
• the probe 100 comprises a central section 16 of length L16 and of great width £ 16 and two end sections 18, 19 of length L18 and L19 of small width £ 18, £ 19 less than £ 16 .
• the probe 100 comprises a central section 106 of length L106 and of small width £ 106 and two end sections 108, 109 of length L108, L109 and of wide width £ 108, £ 109 greater than £ 106.
• the probe 10 is very sensitive to a centered external element. , that is to say placed opposite the central section 16 while the probe 100 is very sensitive to an off-center element, that is to say an element placed opposite the end sections 108, 109.
• each probe 10, 100 and 110 is non-rectilinear.
• each probe 10, 100, 110 is formed of different segments, rectilinear individually, connected in pairs by their ends by transition elements made up of dihedrons whose concavities are alternated, that is to say oriented alternately in one direction then in the other.
• the probes 10, 100 and 110 are in the form of zig zag undulations.
• Such a geometry allows elongation by deformation of the support.
• This characteristic is particularly important when the probes 10, 100 and 110 are integrated in a vehicle seat. Indeed, this geometry allows an extension of the probes when a driver or passenger takes place on the seat.
• the distance which separates the probe 110 from the probe 10 or from the probe 100 is greater than the distance which separates the probes 10 and 100 between them.
• the supply voltage application means are adapted to apply a voltage sequentially between the probes 10 and 100 in an operating phase, and between the probe 110 and each of the two probes 10 and 100 during a other operating phase.
• the field lines obtained during the application of a voltage between the probes 10 and 100 are referenced C1 while the field lines obtained during the application of a voltage between the probe 110 and each of the two probes 10 and 100 are referenced C2.
• the detection range is very reduced because the field lines C1 are strongly curved.
• the probe 110 can be placed approximately 2 cm from the probes 10 and 100. As indicated above in the context of the present invention, the signals from the various probes are used in a comparative manner. .
• the present invention can for example exploit one of the following relationships:
• U / C representing the signal taken from the probe 100 during the application of a supply voltage between, on the one hand the probes 10 and 110 connected together and serving as a reference probe, and on the other hand share the probe 100
• C represents the signal taken from the probe 10 during the application of a supply voltage between on the one hand the probes 100 and 110 connected together and serving as a reference probe, and d on the other hand the probe 10,
• UC representing the signal taken from the probe 100 during the application of a supply voltage between the probe 110 and simultaneously the probes 10 and 100.
• UA / U
• CU representing the signal taken from the probe 10 during the application of a supply voltage between the probe 110 and simultaneously the probes 10 and 100,.
• CU / U the comparison of the summation of the signals UC + CU defined previously, with the signal C defined previously, which corresponds to the diagram illustrated in FIG. 14, makes it possible to discriminate four zones:
• zone B which corresponds to an environment without wet obstacle, for example an occupied seat without wet obstacle
• a zone C which corresponds to an environment occupied with a wet obstacle, for example a seat occupied with a wet obstacle, and a zone D of an environment occupied at a distance, for example a seat occupied with a passenger distant from the seat.

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• 2001
  • 2001-06-28 FR FR0108529A patent/FR2826723B1/fr not_active Expired - Fee Related
• 2002
  • 2002-06-27 WO PCT/FR2002/002234 patent/WO2003002949A2/fr active Application Filing
  • 2002-06-27 JP JP2003508887A patent/JP4307248B2/ja not_active Expired - Fee Related
  • 2002-06-27 US US10/482,611 patent/US7098673B2/en not_active Expired - Fee Related
  • 2002-06-27 CA CA002451961A patent/CA2451961A1/fr not_active Abandoned
  • 2002-06-27 EP EP02764932A patent/EP1399714A2/de not_active Withdrawn

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