Method for detecting seat occupancy in a vehicle and method for detecting permanent settling of seat foam

Abstract

The invention relates to a method for detecting the occupancy of a vehicle seat, the method comprising the following steps: a) calculation (48) of an adjusted reference capacitance value by subtracting the representative value of a settling from the reference capacitance value, c) measurement (52) of an initial capacitance value between the first electrode and the second electrode, d) measurement (54) of capacitance values ​​by the capacitive transducer with interdigitated electrodes, e) determination (56) of the occupancy state from the capacitance values, of the adjusted reference capacitance value, g) after the predefined time, measurement (60) of a subsequent capacitance value between the first electrode and the second electrode, h) calculation (62) of a representative value of a settling by subtracting the subsequent capacitance value from the initial capacitance value, i) recording of the representative value of a settling calculated during step h).Figure to be published with the abbreviation: Figure 3.

Description

Title of the invention: Method for detecting the occupancy of a vehicle seat and method for detecting definitive settling of the foam of a seat Technical field of the invention

[0001] The present invention relates to a method for detecting the occupancy of a vehicle seat. The present invention also relates to a method for detecting definitive settling of the foam of a vehicle seat. The invention is particularly applicable to motor vehicle seats. State of the prior art

[0002] Vehicle seats have a metal or plastic structure covered with padding generally made of polyurethane foam. After a certain number of uses of a seat, the seat foam settles and sags. [Fig.l] shows an example of loss of thickness of a seat padding depending on the number of uses. This loss of thickness also depends on the weight or weights of the different users of the seat.

[0003] Furthermore, more and more vehicle seats are equipped with a system or method for determining seat occupancy such as that described in the patent published under number FR 2012255. These systems are used in particular by the central unit of the vehicle for safety purposes to authorize or not the deployment of a safety airbag. However, after a few years, these detection systems become less reliable in particular due to the settling of the seat foam.

[0004] In addition, the sagging and settling of the seat foam can cause back pain for drivers, particularly for people who spend many hours in their vehicles, such as taxi drivers or heavy goods vehicle drivers. Presentation of the invention

[0005] A first aim of the present invention is to propose a method for detecting the occupancy of a seat which remains reliable over time despite the settling of the seat foam. Advantageously, the occupancy detection method makes it possible to determine the occupancy of a seat more reliably because the occupancy detection method takes into account the aging and final sagging of the seat foam linked to its use.

[0006] A second aim of the present invention is to propose a detection method from a settling of the foam in a seat.

[0007] Advantageously, the detection method detects a lasting settling of a foam of a seat of a vehicle seat linked to a large number of uses of the seat and to generate a warning allowing the driver to know that it is desirable to change his seat. Summary of the invention

[0008] The present invention relates to a method for detecting the occupancy of a seat of a motor vehicle, the detection method being implemented by a detection system comprising at least one capacitive transducer with interdigital electrodes, at least one first electrode and one second electrode, a voltage source connected to the first electrode and to an electrode of the at least one capacitive transducer with interdigital electrodes, a controller comprising a capacitance measurement unit, a clock and a memory comprising a predefined time, as well as at least one reference capacitance value, at least one threshold value and at least one detection range associated with said at least one capacitive transducer with interdigital electrodes as well as a value representative of a settlement, the method comprising the following steps: (a) calculation of an adjusted reference capacity value by subtracting said value representing a settlement from the reference capacity value, b) energizing the first electrode and an electrode of the at least one capacitive transducer with interdigital electrodes, c) measuring an initial capacitance value between the first electrode and the second electrode, d) measurement of several capacitance values ​​between the electrodes of at least one capacitive transducer with interdigital electrodes, (e) determination of the seat occupancy status from the measured capacity values, the at least one adjusted reference capacity value, the at least one detection range and the at least one threshold value, f) when an occupied state is determined, starting the clock, g) after the predefined time, measurement of a subsequent capacitance value between the first electrode and the second electrode, (h) calculation of a representative value of settlement by subtracting the subsequent capacity value from the initial capacity value, i) replacement of the representative value of a settlement recorded in the memory by the representative value of a settlement calculated during step h). The characteristics set out in the following paragraphs may, optionally, be implemented. They may be implemented independently of each other. others or in combination with each other: - the memory comprises at least a first capacity variation range, a second capacity variation range, the method further comprising the following steps: - measurement of several capacitance values ​​between the electrodes of at least one interdigital electrode transducer, - determination of the seat occupancy status from the values ​​of the measured capacity values, the adjusted reference capacity value, the first variation range, the second variation range and the threshold value. - the preset time is between 5 minutes and 60 minutes. - The preset time is between 15 minutes and 25 minutes.

[0009] The invention also relates to a method for detecting a definitive settling of the foam of a seat of a vehicle, in particular of a motor vehicle, the detection method being implemented by a detection system comprising at least one capacitive transducer with interdigital electrodes, at least a first electrode and a second electrode, a voltage source connected to the first electrode and to an electrode of the at least one capacitive transducer with interdigital electrodes, a controller comprising a capacitance measurement unit, a clock and a memory comprising a settling threshold, predefined time, as well as at least one threshold value, at least one reference capacitance value and at least one detection range associated with said at least one capacitive transducer with interdigital electrodes, the method comprising the following steps: - energizing the first electrode and an electrode of at least one interdigital electrode transducer, - measurement of an initial capacitance value between the first electrode and the second electrode, - measurement of several capacitance values ​​between the electrodes of at least one interdigital electrode transducer, - determination of the seat occupancy status from the measured capacity values, the at least one reference capacity value, the at least one detection range and the at least one threshold value, - when an occupied state is determined, a clock is started, - after said predefined time, measurement of a subsequent capacitance value between the first electrode and the second electrode, - calculation of a representative value of a settlement by subtracting the subsequent capacity value from the initial capacity value, - comparison of the representative value of a settlement with the settlement threshold, and if said representative value of a settlement is greater than the settlement threshold, ge generation of a warning signal representative of a certain quantity of final settlement of the seat foam. The preset time is between 5 minutes and 60 minutes. The preset time is between 15 minutes and 25 minutes. Brief description of the figures

[0010] [Fig-1] is a curve representing the settling of the foam of a seat as a function of the number of uses of this seat,

[0011] [Fig.2] is a schematic view of an example of a detection system capable of implementing the method of detecting occupancy and the method of detecting definitive settling of the foam of a seat,

[0012] [Fig.3] is a flowchart representing the steps of the occupancy detection method according to the invention;

[0013] [Fig.4] is a flowchart representing the steps of the method for detecting definitive settling of the seat foam according to the invention. Detailed description of the invention

[0014] With reference to [Fig. 1], an example of a detection system 2 has been shown. This detection system 2 comprises a flexible support 4, a first 5 and a second 6 capacitive transducers with interdigital electrodes carried by the flexible support, and a voltage source 8.

[0015] The flexible support 4 is made of an impermeable and elastic material. The flexible support 4 may for example be made of a material among thermoplastic polyurethane, polydimethylsiloxane (known by the acronym PDMS), polyvinyl alcohol (known by the acronym PVA), silicone, polyethylene (known by the acronym PE), poly (ethylene 2, 6-naphthalenedicarboxylate) (known by the acronym PEN) and polyimide (known by the acronym PI).

[0016] The capacitive transducers with interdigital electrodes 5, 6 each comprise two coplanar comb-shaped electrodes which interpenetrate each other. One electrode of each capacitive transducer 5, 6 is connected to the voltage source 8 via a first conductive track 10, 11. The other electrode of each transducer 5, 6 is connected to a first ground 12 and respectively a second ground 14 via a second conductive track 16, 17. Preferably, each capacitive transducer is connected to a different ground, as illustrated in [Fig. 2]. Preferably, the interdigital capacitive transducers 5, 6 and / or the conductive tracks 12, 16 are produced on the flexible support by electronic printing.

[0017] The voltage source 8 is capable of generating a potential between 5 Volts and 12 Volts.

[0018] The detection system 2 further comprises a first electrode 18, a second electrode 20 and a controller 22.

[0019] The first electrode 18 and the second electrode are parallel to the conductive tracks 10, 16. They are adjacent to the conductive tracks 10, 16. More particularly, they are located at a distance of between 20 and 150 millimeters relative to the nearest conductive track 12, 16. The first electrode 18 comprises a first free end 24 and a second end connected to the voltage source 8. The first end 24 of the first electrode is free, that is to say it is not connected to any electronic component. The second electrode 20 comprises a first free end 24 and a second end connected to a third ground 26.

[0020] Preferably, the first electrode 18 and the second electrode 20 extend over a length of between 20 and 150 millimeters and preferably between 50 and 110 millimeters.

[0021] Preferably, the first electrode 18 and the second electrode 20 are produced on the flexible support by electronic printing. The controller 22 is a computing unit. It includes a central processing unit 23, such as a processor or a microprocessor. The central processing unit 23 may be a programmable device that uses software, a specific integrated circuit (ASIC), or a part of an engine control unit (ECU). The controller 22 comprises a capacity measurement unit 28, a clock 30 and a memory 32, for example a random access memory, denoted RAM and / or a read-only memory. The capacitance measuring unit 28 is connected to the first conductive track 10 and the second conductive track 16. It is capable of measuring, at a defined frequency, first capacitance values ​​Ci between the electrodes of the first capacitive transducer 5.

[0022] These first capacitance values ​​Ci are potential differences between the electrodes of the first capacitive transducer 5.

[0023] In the same way, the capacitance measuring unit 28 is connected to the first conductive track 11 to the second conductive track 17 to measure at a defined frequency, second capacitance values ​​C2 between the electrodes of the second capacitive transducer 6.

[0024] Finally, the capacitance measuring unit 28 is connected to the first electrode 18 and to the second electrode 20 to measure an initial capacitance value Ci and a subsequent capacitance value Cu.

[0025] The clock 30 is adapted to measure a predefined time. The clock can be implemented by an oscillator internal to the central processing unit or by outputs of scales.

[0026] The memory 32 comprises a first reference capacitance value CR[ and a first threshold value Si associated with the first capacitive transducer with interdigital electrodes 5, a second reference capacitance value CR2 and a second threshold value S2 associated with the second capacitive transducer with interdigital electrodes 6. The first reference capacitance value CRb, the first threshold value Si, the second reference capacitance value CR2 and the second threshold value S2 have been predetermined during a prior phase. Examples of these values ​​are described in patent FR 2012255. The memory 32 further comprises a determined deviation, a curve representing average capacitance values ​​as a function of time, a value T representative of a settling of the foam of a seat, a predefined time Tp as well as a first detection range PD1 associated with the first capacitive transducer 5 and a second detection range PD2 associated with the second capacitive transducer 6.

[0027] The memory 32 further comprises an executable code making it possible to implement the occupancy detection method described below and / or an executable code making it possible to implement the method of detecting a definitive settling of the foam of a seat also described below.

[0028] The memory 32 may also include: - two first PI capacitance variation ranges defined, one for the first capacitive transducer 5 and the other for the second capacitive transducer 6; the first variation ranges being representative of a state occupied by a human person, - at least two capacitance variation sub-domains DU, D12 defined for each capacitive transducer 5, 6, each capacitance variation sub-domain being representative of a morphological type of a person, - two second capacitance variation ranges P2 defined, one for the first capacitive transducer and the other for the second capacitive transducer 6, the second variation ranges P2 being representative of a state occupied by a thing, an animal or a child, - at least two capacitance variation sub-domains D21, D22 defined for each capacitive transducer 5, 6, each capacitance variation sub-domain D21, D22 being representative of a range of child age values.

[0029] The capacity values ​​of these ranges and sub-domains, the value of the determined deviation are the values ​​described in the patent published under number FR 2012255.

[0030] With reference to [Fig. 3], the occupancy detection method begins with a step 48 during which the controller 22 calculates a first adjusted reference capacity value CRA| by subtracting the value T representative of a settlement from the first reference capacity value Cri.

[0031] In the same way, the controller 22 calculates a second adjusted reference capacitance value Cra2 by subtracting the value T representative of a settlement from the second reference capacitance value CR2. This step is implemented each time the starting contactor is engaged and the flow of current is authorized.

[0032] This step 48 makes it possible to readjust the value of the reference capacity by taking into account the drift in the capacity measurements generated by the settling of the seat foam. The value T representing the settling was updated during the last use of the seat, as explained below.

[0033] Then, during a step 50, the controller 22 controls the voltage source 8 to energize the first electrode 18, an electrode of the first capacitive transducer with interdigital electrodes 5 and an electrode of the second capacitive transducer with interdigital electrodes 6. During a step 52, the capacitance measurement unit 28 measures an initial capacitance value Ci between the first electrode 18 and the second electrode 20. Then, it transmits this value to the central processing unit 23. During a step 54, the measuring unit 28 measures at a defined frequency, several first capacitance values ​​Ci between the electrodes of the first interdigital electrode transducer 5 and several second capacitance values ​​C2 between the electrodes of the second interdigital electrode transducer 6. During a step 56, the central processing unit 23 determines the occupancy state of the seat from the determined deviation, the first capacity values ​​C i, the first adjusted reference capacity value C rai, the first threshold value Si, the second capacity values ​​C2, the second adjusted reference capacity value Cra2 and the second threshold value S2.

[0034] For this determination step, the central processing unit 23 also uses the determined deviation and the curve representing average capacity values ​​as a function of time recorded in its memory 32.

[0035] This determination is, for example, carried out by implementing the determination method claimed in the patent published in the name of the applicant under the number FR 2012255. In this patent, the capacitance values ​​are called capacitance values. To implement this step 56, the central processing unit 23 implements the instructions, the values ​​of the curves and the value of the determined deviation described in the patent published under the number FR 2012255.

[0036] The purpose of step 56 is to determine an occupied state of the seat. The term "occupied state" in the present patent application means a state occupied by a human person of at least 10 kilograms or an animal of at least 10 ki lograms or object of at least 10 kilograms. To determine this occupied state, the first capacitance variation range PI described in patent FR 2012255 is replaced by the first detection range PDi for the first capacitive transducer 5, and by the second detection range PD2> for the second capacitive transducer 6. The first detection range PDi defined for the first capacitive transducer 5 is, for example, between 12 xlO3 and 150 xl03picoFrarads. The second detection range PD2 defined for the second capacitive transducer 6 is, for example, between 10 xl0 3 and 150 x 103picoFrarads.

[0037] When a busy state is determined, the central processing unit 23 starts the clock 30 during a step 58. After the predefined time Tp has elapsed, the measuring unit 28 measures, during a step 60, a subsequent capacitance value Cu between the first electrode 18 and the second electrode 20. The preset time Tp is between 5 minutes and 60 minutes. Preferably, the preset time Tp is between 15 minutes and 25 minutes.

[0038] During a step 62, the central processing unit 23 calculates a new value T representative of a settling of the seat foam by subtracting the subsequent capacity value Cu from the initial capacity value Ci. During a step 64, the value T representative of a settlement recorded in the memory 32 is replaced by the new value T representative of a settlement calculated during the step 62. The new value T representative of a settlement calculated during the step 62 will therefore be used for the calculation of the first adjusted reference capacitance value CRAi and the second adjusted reference capacitance value C^ for the continuation of the detection method as well as the next time the starting contactor is engaged and the passage of current is authorized. Thus, the reference capacitance value is adjusted as the seat foam settles. This adjustment compensates for and corrects the drift in the measurements of the first and second capacitance values ​​generated by the settlement of the seat foam.

[0039] The detection method can continue with the steps described below.

[0040] During a step 66, the measurement unit 28 measures first values ​​of capacity Ci between the electrodes of the first interdigital electrode transducer 5 as well as the second first capacitance values ​​C2 between the electrodes of the second interdigital electrode transducer 6. It transmits these values ​​to the central processing unit 23. This measurement step 66 takes place in parallel and at the same time as steps 56 to 64 described above. During a step 68, the central processing unit 23 determines the occupancy status of the seat from the first capacity values ​​Ci and the second C2 capacitance values ​​measured during step 66.

[0041] For this purpose, the central processing unit 23 implements the instructions, the values ​​of the curves, the threshold values, the value of the determined deviation, the values ​​of the variation ranges and possibly the values ​​of the variation sub-domains described in the patent published under the number FR 2012255 with the exception of the fact that it replaces the first reference capacity value CRi and the second adjusted reference capacity value CR2, by the first adjusted reference capacity value Crai and the second adjusted reference capacity value Cra2.

[0042] Thus, if the seat occupant stands up and then sits back down on the seat, the occupancy detection method is implemented with the adjusted reference capacity values. Alternatively, the detection method described above is implemented with a single capacitive transducer with interdigital electrodes.

[0043] Alternatively, the detection method described above is implemented with more than two capacitive transducers with interdigital electrodes.

[0044] The invention also relates to a method for detecting a definitive settling of the foam of a vehicle seat. The detection method is implemented by a detection system identical to the detection system 2 described in connection with [Fig.l] except that the memory 32 further comprises a settling threshold ST and does not comprise a value T representative of a settling allowing compensation for drifts linked to this settling. This detection method has the sole purpose of warning the driver that the foam of the seat has reached a certain amount of sagging and settling.

[0045] The settlement threshold ST has been previously defined, for example by the seat manufacturer or by an authorized organization. It represents a certain amount of settlement of the seat beyond which it is considered that the seat foam is less comfortable and may cause back pain to the person sitting on the seat for a certain period of time. For example, a settlement threshold ST corresponding to a drift caused by a settlement of 11 millimeters of the foam could be chosen.

[0046] With reference to [Fig. 4], the method for detecting a definitive settling of the foam of a seat of a motor vehicle begins with a step 50 of energizing the first electrode 18 and an electrode of the first interdigital electrode transducer 5 and of the second interdigital electrode transducer. Step 50 continues with steps 52 and 54 identical to steps 52 and 54 of the occupancy detection method described above. These steps 52 and 54 will not be described again. During a step 57, the central processing unit 23 determines the state seat occupancy from the first capacitance values ​​Ci and the second capacitance values ​​C2 measured during step 54, the first reference capacitance value CRb of the second reference capacitance value CR2, the first detection range PDi of the second detection range PD2, the first threshold value Si and the second threshold value S2.

[0047] For this purpose, the central processing unit 23 implements the instructions, the values ​​of the curves, the threshold values, the value of the determined deviation, the values ​​of the variation ranges and possibly the values ​​of the variation sub-domains described in the patent published under number FR 2012255. When an occupied state is determined, the method continues with steps 58 to 62 identical to steps 58 to 62 of the occupancy detection method described above. These steps 58 to 62 will not be described again. During a step 69, the central processing unit 23 compares the value T representative of a settlement with the settlement threshold ST recorded in the memory. If the value T representative of a calculated settlement is greater than the settlement threshold ST, the central processing unit 23 generates, during a step 70, a warning signal representative of a certain quantity of definitive settlement of the seat foam. If the T value representative of a calculated settlement is lower than the settlement threshold ST, the detection process stops. Alternatively, the detection method described above is implemented with a single capacitive transducer with interdigital electrodes.

[0048] Alternatively, the detection method described above is implemented with more than two capacitive transducers with interdigital electrodes.

Claims

Claims

1. Method for detecting the occupancy of a seat of a vehicle, in particular of a motor vehicle, the detection method being implemented by a detection system (2) comprising at least one capacitive transducer with interdigital electrodes (5, 6), at least one first electrode (18) and one second electrode (20), a voltage source (8) connected to the first electrode and to an electrode of the at least one capacitive transducer with interdigital electrodes, a controller (22) comprising a capacitance measuring unit (28), a clock (30) and a memory (32) comprising a predefined time (Tp), as well as at least one reference capacitance value (CRi, CR2), at least one threshold value (Si, S2) and at least one detection range (PD1> PD2) associated with said at least one capacitive transducer with interdigital electrodes as well as a value (T) representative of a settlement, the method comprising the following steps: a) calculation (48) of an adjusted reference capacitance value (CRAi, Cra2) by subtracting said value (T) representative of a settlement from the reference capacitance value (CRi, CR2), b) energizing (50) the first electrode (18) and an electrode of the at least one capacitive transducer with interdigital electrodes (5, 6), c) measuring (52) an initial capacitance value (Ci) between the first electrode (18) and the second electrode (20), d) measuring (54) several capacitance values ​​(Ci, C2) between the electrodes of the at least one capacitive transducer with interdigital electrodes (5, 6), e) determining (56) the occupancy state of the seat from the measured capacity values ​​(Ci, C2), the at least one adjusted reference capacity value (CRAi, CRA2), the at least one detection range (P di, Pd2) and the at least one threshold value (Sb S2), f) when an occupied state is determined, starting (58) the clock (30), g) after the predefined time (Tp), measurement (60) of a subsequent capacitance value (Cu) between the first electrode (18) and the second electrode (20), h) calculation (62) of a value representative of a settlement by subtracting the subsequent capacitance value (Cu) from the capacitance value

2.

3.

4.

5. initial (Ci), i) replacement (64) of the representative value of a settlement recorded in the memory (24) by the representative value of a settlement calculated during step h). Occupancy detection method according to claim 1, wherein the memory (32) comprises at least a first capacity variation range (PI), a second capacity variation range (P2), the method further comprising the following steps: - measurement (66) of several capacitance values ​​between the electrodes of the at least one interdigital electrode transducer (5, 6), - determination (70) of the seat occupancy status from the values ​​of the measured capacity values ​​(Cb C2), the adjusted reference capacity value (CRAi, CRA2), the first variation range (PI), the second variation range (P2) and the threshold value (Si, S2). Detection method according to one of claims 1 and 2, in which the predefined time (Tp) is between 5 minutes and 60 minutes. Detection method according to one of claims 1 and 2, in which the predefined time (Tp) is between 15 minutes and 25 minutes.Method for detecting a definitive settlement of the foam of a seat of a vehicle, in particular of a motor vehicle, the detection method being implemented by a detection system (2) comprising at least one capacitive transducer with interdigital electrodes (5, 6), at least one first electrode (18) and one second electrode (20), a voltage source (8) connected to the first electrode and to an electrode of the at least one capacitive transducer with interdigital electrodes, a controller (22) comprising a capacitance measuring unit (28), a clock (30) and a memory (32) comprising a settlement threshold (ST), predefined time (Tp), as well as at least one threshold value (Si, S2), at least one reference capacitance value (Cri, CR2) and at least one detection range (PD1> PD2) associated with said at least one capacitive transducer with interdigital electrodes, the method comprising the following steps:. - energizing (50) the first electrode (18) and an electrode of the at least one interdigital electrode transducer (5, 6), - measurement (52) of an initial capacitance value (Ci) between the first electrode (18) and the second electrode (20), - measurement (54) of several capacitance values ​​(Ci, C2) between the electrodes of the at least one interdigital electrode transducer (5,6), - determination (57) of the seat occupancy status from the measured capacity values ​​(Cb C2), the at least one reference capacity value (CRi, CR2), the at least one detection range (PD1> PD2) and the at least one threshold value (Sb S2), - when an occupied state is determined, triggering (58) of a clock, - after said predefined time (Tp), measurement (60) of a subsequent capacitance value (Cu) between the first electrode (18) and the second electrode (20), - calculation (62) of a value (T) representative of a settlement by subtraction of the subsequent capacity value (Cu) from the initial capacity value (Ci), - comparison (69) of the value (T) representative of a settlement at the settlement threshold (ST), and if said value (T) representative of a settlement is greater than the settlement threshold, generation (70) of a warning signal representative of a certain quantity of definitive settlement of the seat foam.

6. The detection method according to claim 5, wherein the predefined time is between 5 minutes and 60 minutes.

7. The detection method according to claim 5, wherein the predefined time is between 15 minutes and 25 minutes.

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