METHOD FOR DETERMINING THE OCCUPIED STATUS OF A SEAT AND CORRESPONDING DETERMINATION SYSTEM

Description

technical field

[0001] This application concerns a method for determining the occupancy status of a seat and the corresponding determination system. Prior art

[0002] US patent 2006 / 033507 discloses a vehicle seat occupancy detection system comprising capacitive sensors 20 mounted on the seat. The capacitive sensors have two electrodes arranged on a conductive screen 22. The capacitance values ​​are measured by successively energizing one electrode, then the second electrode, and finally both electrodes, observing the capacitance variations between these measurements.

[0003] None of the capacitive sensors used in this system are interdigitated capacitive sensors. This document does not disclose or suggest calculating the difference between a resulting capacitance value and a reference capacitance value, nor does it compare the calculated difference to a threshold value.

[0004] US patent 6,392,550 describes a method for detecting a driver's level of alertness or drowsiness by measuring pressure variations on sensors placed on the seat. These pressure variations indicate whether the driver is slumped, leaning forward, or standing upright in the seat. This system uses a data processing technique based on a neural network.

[0005] Document WO 2019 / 172063 describes a method for performing gymnastic exercises (torso twists, leg movements, etc.) in a motor vehicle seat. For this purpose, the seat is equipped with pressure sensors. A mobile phone with a specific application is connected to the vehicle. The pressure sensors verify that the driver is correctly performing the required actions. To do this, the values ​​measured by the pressure sensors are compared to pre-recorded threshold values.

[0006] The methods described in US patent 6,392,550 and WO 2019 / 172063 do not implement any of the steps of the method claimed in the present invention. Furthermore, the sensors used to implement this method are not interdigitated capacitive sensors.

[0007] There is a growing demand for devices to determine the occupancy status of a motor vehicle seat, whether it is a driver or a passenger.

[0008] Generally, these detection devices use sensors such as a camera or a motion sensor located above the seat. However, the measurements obtained by such devices have a typically long response time, on the order of several seconds, which is unsuitable for providing sufficiently rapid data in certain situations, particularly in the event of an accident.

[0009] For example, there is a need to be able to adapt the properties of an airbag system designed to protect a vehicle seat occupant in the event of an accident. Thus, the operation of existing systems could be improved by adjusting the properties of a vehicle seat airbag and / or seat belt pretensioner based on real-time knowledge of parameters such as the occupant's exact position in the seat, their type, height, weight, etc.

[0010] Furthermore, measurements obtained with such devices often lack robustness because they are highly susceptible to disturbances. In addition, the measurements produced by these devices exhibit drift over time. Therefore, these devices are unsuitable for applications in the automotive sector, where a reliability period of at least ten years is required. Summary of the invention

[0011] In order to address the aforementioned drawbacks and this or these needs, this disclosure relates primarily to a method for determining the occupancy status of a seat in a motor vehicle, the method being implemented by a determination system comprising a seat, at least six interdigitated capacitive sensors carried by the seat, and a controller connected to the interdigitated capacitive sensors, said controller comprising a memory including a database, said database including at least one reference capacitance value and a threshold value for each interdigitated capacitive sensor, the method including a step of measuring at least three capacitance values ​​by each interdigitated capacitive sensor, the following steps being implemented by the controller for the capacitance values ​​measured by each interdigitated capacitive sensor: calculation of an average capacitance value from at least two measured capacitance values, calculation of the difference between the average capacitance value and the reference capacitance value, comparison of the calculated difference to the threshold value, determination of the seat occupancy status based on the result of said comparison.

[0012] According to one embodiment, the process further comprises a step of determining a minimum capacitance value and a maximum capacitance value from among the measured capacitance values, and in which the step of calculating the average capacitance value is a step of calculating an average capacitance value from the minimum capacitance value and the maximum capacitance value.

[0013] According to one embodiment, the database further comprises first ranges of capacitance variation defined for the interdigitated capacitive sensors, each first range of variation being defined for an interdigitated capacitive sensor, the first ranges of variation being representative of a state occupied by a human person, and the method further comprises for each interdigitated capacitive sensor, a step of comparing the difference calculated to the first range of variation, the determined occupancy state being a state occupied by a human person, when the differences calculated for each interdigitated capacitive sensor are included in the first ranges of variation.

[0014] According to one embodiment, the database further comprises at least two capacitance variation subdomains defined for each interdigitated capacitive sensor, each capacitance variation subdomain being representative of a morphological type of a person, and the method comprises the following steps: comparison of the differences calculated at at least two subdomains of capacitance variation; and determination of a morphological type of the person sitting on the seat based on the result of said comparison.

[0015] According to one embodiment, the database further comprises second ranges of capacitance variation defined for the interdigitated capacitive sensors, each second range of variation being defined for a capacitance sensor, the second ranges of variation being representative of a state occupied by a thing, an animal or a child, and the method further comprises for each interdigitated capacitive sensor, a step of comparing the difference calculated to the second range of variation, the determined state of occupancy being a state occupied by a thing, an animal or a child, when the average capacitance values ​​calculated for each interdigitated capacitive sensor are within the second ranges of capacitance variation.

[0016] According to one embodiment, the database further comprises at least two capacitance variation subdomains defined for interdigitated capacitive sensors, each capacitance variation subdomain being representative of a range of child age values, and the method further comprises the following steps: comparison of the differences calculated at at least two subdomains of capacitance variation, and determination of a range of child age values ​​based on the result of the comparison.

[0017] According to one embodiment, the measurement step is implemented each time a door of the motor vehicle is opened or unlocked.

[0018] According to one embodiment, the measurement step is implemented each time a door of the motor vehicle is closed or locked.

[0019] According to one embodiment, the implementation of the measurement step lasts less than three seconds and preferably less than one second.

[0020] According to one embodiment, the memory comprises, for each interdigitated capacitive sensor, a curve representing average capacitance values ​​as a function of time, and a determined deviation, and wherein the method further comprises the following steps implemented, for each interdigitated capacitive sensor, after the step of determining a maximum capacitance value and a minimum capacitance value: selection of a determined number of last average capacitance values ​​of said curve, said determined number being between 5 and 20, and preferably equal to 10, calculation of the difference between the minimum capacitance value and the selected values, calculation of the difference between the maximum capacitance value and the selected values, if at least one of said differences is greater than said difference, the process returns to the measurement step, if said differences are less than said difference, the process continues with the step of calculating an average capacitance value.

[0021] According to one embodiment, when said differences are less than said deviation, the process includes a step of recording the average capacitance value in said curve.

[0022] According to one embodiment, the curve includes a capacitance value measured after the seat was manufactured and before it was fitted in the vehicle, a capacitance value measured after the seat was fitted in the motor vehicle and a capacitance value measured before first use.

[0023] The present invention also relates to a system for determining the occupancy status of a seat in a motor vehicle, said system comprising: a motor vehicle seat comprising: a seat having a receiving face intended to accommodate a person, the receiving face being divided into a front zone and a rear zone, the front and rear zones being located on either side of a central transverse plane of the seat, a backrest having a receiving face intended to accommodate the back of a person, the backrest being articulated to the seat, the rear zone of the receiving face of the seat being adjacent to the backrest, only three interdigital capacitive sensors carried by the receiving face of the backrest, and only three interdigital capacitive sensors carried by the receiving face of the seat, a first interdigital capacitive sensor being located on an upper and lateral zone of said receiving face of the backrest, the second interdigital capacitive sensor being located on a lower or central zone of said receiving face of the backrest,the third interdigital capacitive sensor being located on a lateral area of ​​said receiving face of the backrest, the third interdigital capacitive sensor being located in a lower position relative to the second capacitive sensor, the second interdigital capacitive sensor being offset laterally towards the center relative to the first and third interdigital capacitive sensors, the fourth interdigital capacitive sensor being located on a lateral part of the rear area of ​​the receiving face of the seat, the fifth interdigital capacitive sensor being located on a rear or central area of ​​the receiving face of the seat, the sixth interdigital capacitive sensor being located on a lateral part of the front area of ​​the receiving face of the seat, the fifth interdigital capacitive sensor being offset laterally towards the center relative to the fourth and sixth interdigital capacitive sensors,The fifth interdigitated capacitive sensor is located longitudinally between the fourth and sixth interdigitated capacitive sensors, in a controller designed to implement the method for determining the occupancy status of a seat conforming to the characteristics mentioned above. According to one embodiment, the second interdigitated capacitive sensor is positioned laterally at the center of the seat's receiving face, and the fifth interdigitated capacitive sensor is positioned laterally at the center of the receiving face. Brief description of the figures

[0024] [ Fig. 1 ] is a schematic view of a first example of a determination system according to the present invention; [ Fig. 2 ] is a schematic view representing an example block diagram of the controller of the determination system illustrated on the figure 1 ; Fig. 3] is a diagram representing the variation of an average capacitance value of an interdigitated capacitive sensor of the determination system illustrated on the figure 1 , depending on the time; [ Fig. 4 ] is a schematic view of a second example of a determination system according to the present invention; [ Fig. 5 ] is a flowchart of the steps in the determination process according to the present invention.

[0025] Unless otherwise indicated, elements common or similar to several figures bear the same reference signs and have identical or similar characteristics, so that these common elements are generally not described again for the sake of simplicity. Detailed description of the invention

[0026] With reference to the figure 1, the determination system 2 according to this disclosure comprises a motor vehicle seat 4, six interdigitated capacitive sensors 6, 8, 10, 12, 14, 16 carried by the seat, and a controller 100 electrically connected to the interdigitated capacitive sensors.

[0027] Seat 4 has a seat 18 and a backrest 20 articulated to the seat.

[0028] In particular, the seat 18 includes a receiving face 22 intended to accommodate a person or an object. For the purposes of this description, the receiving face of the seat is said to be divided by a central transverse plane XX into a zone adjacent to the backrest, called the "rear zone" 24, and into a zone located on the side opposite the backrest, called the "front zone" 26.

[0029] The folder 20 also includes a receiving face 28 designed to accommodate the back of a human being or the face of an object. In this disclosure, the receiving face 28 of the folder carries three interdigitated capacitive sensors of the determination system. figure 1 This shows an advantageous example of interdigital capacitive sensor positioning. This positioning was chosen taking into account the pressure points of a human being seated on the seat.

[0030] A first interdigital capacitive sensor 6 is positioned on an upper and lateral area of ​​the receiving face of the backrest. Thus, the first interdigital capacitive sensor 6 is located at a position on the receiving face of the backrest that corresponds to a support area of ​​a shoulder blade of the person sitting on the seat and leaning against the backrest.

[0031] A second interdigital capacitive sensor 8 is located on a lower, laterally centered area of ​​the backrest's receiving surface. Alternatively, the second interdigital capacitive sensor 8 is located on the backrest's receiving surface at a point corresponding to the lumbar vertebrae of the individual. Alternatively, the second interdigital capacitive sensor 8 is located on a laterally and longitudinally centered area of ​​the backrest's receiving surface.

[0032] A third interdigital capacitive sensor 10 is located on a lower and lateral area of ​​the backrest's receiving surface. This third interdigital capacitive sensor 10 is positioned on the backrest's receiving surface in a location corresponding to a support area for the person's gluteal muscles.

[0033] The second interdigitated capacitive sensor 8 is located vertically between the first and third interdigitated capacitive sensors. The second interdigitated capacitive sensor is always located below the first interdigitated sensor 6.

[0034] The receiving face 22 of the seat also carries three interdigitated capacitive sensors of the determination system.

[0035] A fourth interdigital capacitive sensor 12 is located on a lateral part of the rear area 24 of the seat's receiving face. The fourth interdigital capacitive sensor 12 is located at a position on the seat's receiving face that corresponds to a support area for the buttocks of a person seated on the seat and leaning against the backrest.

[0036] A fifth interdigitated capacitive sensor 14 is located on a laterally centered portion of the rear area 24 of the seat's receiving face. Alternatively, the fifth interdigitated capacitive sensor is located on a longitudinally centered area of ​​the seat's receiving face.

[0037] A sixth interdigital capacitive sensor 16 is located on a lateral part of the front area 26 of the seat's receiving face. The sixth interdigital capacitive sensor 16 is positioned on the seat's receiving face that corresponds to a hamstring support area for that person. The fifth interdigital capacitive sensor 14 is located vertically between the fourth 12 and the sixth 16 interdigital capacitive sensors.

[0038] With reference to the figure 2The controller 100 of the determination system includes a communication bus connected, for example, to a central processing unit 101, such as a processor or a microprocessor, and denoted CPU. The controller 100 also includes a random access memory 102, denoted RAM, and / or a read-only memory, denoted ROM, for storing, in particular, a database 103 and executable code enabling the determination process to be implemented using the seat and the interdigitated capacitive sensors described above.

[0039] The controller 100 can be a programmable device that uses software, a specific integrated circuit (ASIC), or part of an engine control unit (ECU). The controller may include: a network interface 104 which is normally connected to a communication network on which digital data to be processed is transmitted or received; a user interface 105 for receiving input from a user or for displaying information to a user; an input / output module 107, denoted IO, for receiving and sending data from or to external devices such as hard drives, removable storage media, or others.

[0040] Database 103 contains the following for each interdigitated capacitive sensor: a reference capacitance value, a curve C representing the average capacitance values ​​as a function of time, and a determined gap E, at least one threshold value, a first range P1 of variation in capacitance values ​​representative of a seat occupied by a person, at least two subdomains D11, D12, D13 of capacitance variation defined for each interdigitated capacitive sensor, each subdomain of capacitance variation being representative of a morphological type of a person, subdomains D11, D12, D13 belonging to the first range of variation P1, a second range P2 of variation in capacitance values ​​representative of a state occupied by a child, a dog, or a thing, and at least two subdomains D21, D22 of capacitance variation defined for each interdigitated capacitive sensor, each subdomain of capacitance variation being representative of a morphological type of a person, subdomains D21,D22 belonging to the second beach P2.

[0041] The table below includes examples of threshold values, first range of variation P1 and second range of variation P2 for the six sensors of the determination system shown in the Figures 1 And 4 . Sensor Reference Average capacitance Threshold value Second First beach P2 beach P1 6 11 618 3 3 13 15 130 8 11 301 3 3 25 30 150 10 11 540 3 3 15 20 140 12 11 537 3 3 25 30 150 14 11 120 3 3 7,5 10 120 16 11 505 3 3 25 15 130

[0042] The values ​​in this table are given in 10 -3< picoFarad.

[0043] The table below includes examples of three subdomains D11, D12, D13 of the first variation range P1 and two subdomains D21, D22 of the second variation range P2 for the six sensors of the determination system shown on the Figures 1 And 4 . Sensor Reference D21 D22 D11 D12 D13 6 5-10 10-13 15- 20 25-60 60-90 8 5-10 10-13 30-40 45-90 15-90 10 5-10 10-13 15-20 40-80 15-90 12 5-10 10-13 15-20 40-60 15-90 14 5-10 10-13 10-20 25-35 40-90 16 5-10 10-13 15-30 30-50 50-90

[0044] The values ​​in this table are given in 10 -3< pico Farad.

[0045] There figure 3 This illustrates an example of a curve C representing the average capacitance values ​​over time of the interdigitated capacitance sensor 6. This curve is different for each interdigitated capacitance sensor. The deviation E represents a variation in capacitance measurement that may be due to variations in temperature or humidity. The diagram of the figure 3 illustrates, by a first dashed curve, a positive deviation (of +E) from curve C, and by a second dashed curve, a negative deviation (of -E) from curve C. In the embodiment illustrated on the figure 1 The determination system 2 comprises a seat 4, a controller 100, and only six interdigitated capacitive sensors. According to a second embodiment illustrated in the figure 4A determination system 3 comprises, in addition to six interdigitated capacitive sensors, three resistive electrodes 30, 32, 34 mounted on the receiving face 22 of the seat and connected to the controller 100. The resistive electrodes are configured to determine the contact pressure of the user's body. One resistive electrode 30 may, for example, be located in the center of the rear area of ​​the receiving face of the seat. Two resistive electrodes 32, 34 may, for example, be located on either side of a longitudinal central plane of the seat. In this embodiment, the resistive electrodes are positioned at a distance from the interdigitated capacitive sensors of between 10 millimeters and 50 millimeters, and preferably on the order of 20 millimeters.

[0046] With reference to the figure 5The determination method according to the present invention will now be described. This method can be implemented using the determination system 2 illustrated in the figure 1 or by the determination system 3 illustrated on the figure 4 .

[0047] The process begins with a step 36 of measuring at least three capacitance values ​​using the first interdigitated capacitance sensor 6. The measurement step lasts less than three seconds and preferably less than one second. The measurement step is, for example, implemented each time a door of the motor vehicle is opened or unlocked.

[0048] Alternatively, the measurement step is implemented each time a door of the motor vehicle is closed or locked.

[0049] The measurement step 36 is also implemented for the second interdigitated capacitive sensor 8, the third interdigitated capacitive sensor 10, the fourth interdigitated capacitive sensor 12, the fifth interdigitated capacitive sensor 14 and the sixth interdigitated capacitive sensor 16.

[0050] Then, the process includes a step 38 of determining a minimum capacitance value and a maximum capacitance value among the capacitance values ​​measured by the first interdigitated capacitance sensor 6. The determination step 38 is also implemented for the second interdigitated capacitive sensor 8, the third interdigitated capacitive sensor 10, the fourth interdigitated capacitive sensor 12, the fifth interdigitated capacitive sensor 14 and the sixth interdigitated capacitive sensor 16.

[0051] The process includes a step 40 of selecting a predetermined number of the last average capacitance values ​​of the curve C defined for the first interdigitated capacitance sensor 6. This predetermined number is between 5 and 20. Preferably, this predetermined number is equal to 10.

[0052] The process further includes a step 42 of calculating the difference between the minimum capacitance value generated by the first interdigitated capacitance sensor 6 and the values ​​selected during step 40. Then, the differences between the maximum capacitance value generated by the first interdigitated capacitance sensor 6 and the selected values ​​are calculated.

[0053] If at least one of the said differences is greater than the deviation E stored for the first interdigitated capacitive sensor 6, the determination process returns to the measurement step during a step 44.

[0054] If the differences are less than the deviation E, the process continues with a step 46 of calculating an average capacitance value from the maximum capacitance value and the minimum capacitance value determined during step 38.

[0055] Alternatively, the average value is calculated directly from all the measured capacitance values.

[0056] In parallel, if the differences are less than the deviation E, the average capacitance value is recorded in the curve C during a step 47.

[0057] Steps 40, 42, 44 and 46 are also implemented for the second interdigitated capacitive sensor 8, the third interdigitated capacitive sensor 10, the fourth interdigitated capacitive sensor 12, the fifth interdigitated capacitive sensor 14 and the sixth interdigitated capacitive sensor 16.

[0058] The process further includes a step 48 of calculating the difference between the average capacitance value and the reference capacitance value.

[0059] Then, during a step 49, the difference calculated during step 48 is compared to the threshold value V s6 recorded in database 103 and associated with the first interdigitated capacitance sensor 6.

[0060] The steps for calculating the difference 48 and comparison 49 are implemented with 1) the average capacitance value of the second interdigitated capacitive sensor 8 and the threshold value V s8 associated with the second interdigitated capacitance sensor, 2) the average capacitance value of the third interdigitated capacitive sensor 10 and the threshold value V s10 associated with the third interdigitated capacitance sensor, 3) the average capacitance value of the fourth interdigitated capacitive sensor 12 and the threshold value V s12 associated with the fourth interdigitated capacitive sensor, 4) the average capacitance value of the fifth interdigitated capacitive sensor 14 and the threshold capacitance value V s14 associated with the fifth interdigitated capacitive sensor, 5) the average capacitance value of the sixth interdigitated capacitive sensor 16 and the threshold capacitance value V s16 associated with the sixth interdigitated capacitive sensor.

[0061] If the total calculated differences are less than the threshold values, the process includes a step 50 to determine that seat 4 is unoccupied, i.e., empty. The control then transmits a signal indicating that the seat is empty. This signal can, for example, be displayed on a dashboard display or transmitted to a vehicle safety system.

[0062] If the set of average capacitance values ​​is greater than the threshold values, the process includes a step 52 of determining whether seat 4 is occupied by an object, an animal or a person.

[0063] When the process has determined that the seat is occupied, the process further includes a new step 54 of comparing the difference calculated during step 48 with the first range P1 of capacitance variation defined for the first capacitance sensor 6.

[0064] Step 54 is implemented with the differences calculated for the second interdigitated capacitive sensor 8, the third interdigitated capacitive sensor 10, the fourth interdigitated capacitive sensor 12, the fifth interdigitated capacitive sensor 14 and the sixth interdigitated capacitive sensor 16, with the first ranges of variation P1 defined for these sensors each time.

[0065] When the differences calculated for each interdigitated capacitive sensor are within the first P1 ranges of capacitance variation defined for each of these sensors, the process determines an occupied state of the seat by a human person, during a step 56.

[0066] The process continues with a step 58 of comparing the differences calculated during step 48 to the three subdomains of capacitance values ​​D11, D12, D13 defined for each sensor.

[0067] The process includes a step 60 for determining the morphological type of the person seated in the seat based on the results of the comparisons (step 58). Morphological types define a weight range and a height range for an individual. For example, the entire European population constitutes the domain of all morphological types.

[0068] Within this domain, subdomains are defined by classifying the total population, specifically according to percentiles of height and weight within the domain. An example of subdomain D11 includes some of the population's morphological types that meet the following condition: height is less than or equal to the 5th percentile of the European population's height, and / or weight is less than or equal to the 5th percentile of the European population's weight. An example of subdomain D12 includes some of the European population's morphological types that meet the following condition: height is less than or equal to the 50th percentile of the population's height, and / or weight is less than or equal to the 50th percentile of the population's weight.An example of subdomain D13 includes a portion of the morphological types of the European population, meeting the following condition: height is greater than or equal to the 95th percentile of population height and / or weight is greater than or equal to the 95th percentile of population weight.

[0069] The Asian population can be considered another example of a domain within the set of morphological types. The American population can be considered another example of a domain within the set of morphological types. Each domain within the set of these morphological types comprises subdomains. These preceding examples are independent of one another; other examples could be given.

[0070] During step 62, the difference calculated during step 48 is compared with the second P2 range of capacitance variation defined for the first capacitance sensor 6.

[0071] Step 62 is implemented with the differences calculated for the second interdigitated capacitive sensor 8, the third interdigitated capacitive sensor 10, the fourth interdigitated capacitive sensor 12, the fifth interdigitated capacitive sensor 14 and the sixth interdigitated capacitive sensor 16, with each time the second ranges of variation P2 defined for these sensors.

[0072] Step 62 can be implemented directly after step 52 or after step 54 when at least one of the differences calculated during step 48 is not included in the first P1 ranges.

[0073] When the differences calculated for each interdigitated capacitive sensor are within the second P2 ranges of capacitance variation defined for each of these sensors, the process determines an occupied state of the seat by a thing, an animal or a child, during a step 64.

[0074] The process continues with a step 66 of comparing the differences calculated during step 48 to the three subdomains of capacitance values ​​D11, D12, D13 defined for each sensor.

[0075] The process includes a step 68 of determining a range of values ​​for the age of a child sitting on the seat based on the result of the comparison (step 66). The age ranges are, for example, 0 to 1 year and 1 to 6 years.

Claims

1. A method of determining the occupancy status of a seat (4) in a motor vehicle, the method being carried out by a determination system (2) including a seat (4), at least six interdigital capacitive sensors (6, 8, 10, 12, 14, 16) carried by the seat, and a controller (100) connected to the interdigital capacitive sensors, said controller including a memory (102) comprising a database (103), said database comprising at least one reference capacitance value and a threshold value for each interdigital capacitive sensor, the method comprising a step of measuring (36) at least three capacitance values for each interdigital capacitive sensor (6, 8, 10, 12, 14, 16), the following steps being carried out by the controller for the capacitance values measured by each interdigital capacitive sensor: - calculating (46) an average capacitance value from at least two measured capacitance values, - calculating (48) the difference between the average capacitance value and the reference capacitance value, - comparing (49) the calculated difference with the threshold value, - determining (50, 52, 56) the occupancy status of the seat on the basis of the result of said comparison.

2. The determination method according to claim 1, which further comprises a step of determining (38) a minimum capacitance value and a maximum capacitance value from the measured capacitance values, and wherein the step of calculating the average capacitance value is a step of calculating (46) an average capacitance value from the minimum capacitance value and the maximum capacitance value.

3. The determination method according to any of claims 1 and 2, wherein the database (103) further comprises first capacitance variation ranges (P1) defined for the interdigital capacitive sensors, each first variation range (P1) being defined for an interdigital capacitive sensor, the first variation ranges being representative of a status occupied by a human person, and wherein the method further comprises for each interdigital capacitive sensor, a step of comparing (54) the calculated difference with the first variation range (P1), the determined occupancy status (56) being a status occupied by a human person, when the differences calculated for each interdigital capacitive sensor lie within the first variation ranges (P1).

4. The determination method according to claim 3, wherein the database (103) further comprises at least two capacitance variation subdomains (D11, D12) defined for each interdigital capacitive sensor, each capacitance variation subdomain being representative of a morphological type of a person, and wherein the method comprises the following steps: - comparing (58) the calculated differences with the at least two capacitance variation subdomains (D11, D12); and - determining (60) a morphological type of the person sitting on the seat on the basis of the result of said comparison.

5. The determination method according to one of claims 1 and 2, wherein the database further comprises second capacitance variation ranges (P2) defined for the interdigital capacitive sensors, each second variation range (P2) being defined for a capacitance sensor, the second variation ranges (P2) being representative of a status occupied by a thing, an animal or a child, and wherein the method further comprises, for each interdigital capacitive sensor, a step of comparing (62) the calculated difference with the second variation range (P2), the determined status of occupancy (64) being a status occupied by a thing, an animal or a child, when the average capacitance values calculated for each interdigital capacitive sensor lie within the second capacitance variation ranges.

6. The determination method according to claim 5, wherein the database further comprises at least two capacitance variation subdomains (D21, D22) defined for the interdigital capacitive sensors and respectively, each capacitance variation subdomain (D21, D22) being representative of a range of child age values, and wherein the method further comprises the following steps: - comparing (66) the calculated differences with the at least two capacitance variation subdomains, and - determining (68) a range of child age values on the basis of the result of the comparison.

7. The determination method according to any of claims 1 to 6, wherein the step of measuring (36) is carried out each time a motor vehicle door is opened or unlocked.

8. The determination method according to any of claims 1 to 6, wherein the step of measuring (36) is carried out each time a motor vehicle door is closed or locked.

9. The determination method according to any of claims 1 to 8, wherein the step of measuring (36) takes less than three seconds and preferably less than one second.

10. The determination method according to any of claims 1 to 9, wherein the memory comprises, for each interdigital capacitive sensor, a curve (C) representing average capacitance values as a function of time, and a determined deviation (E), and wherein the method further comprises the following steps carried out, for each interdigital capacitive sensor, after the step of determining (38) a maximum capacitance value and a minimum capacitance value: - selecting (40) a given number of last average capacitance values of said curve, said given number being between 5 and 20, and preferably equal to 10, - calculating (42) the difference between the minimum capacitance value and the selected values, - calculating (42) the difference between the maximum capacitance value and the selected values, - if at least one of said differences is greater than said deviation (E), the method returns to the step of measuring (36), - if said differences are less than said deviation (E), the method continues with the step of calculating (46) an average capacitance value.

11. The determination method according to claim 10, wherein if said differences are less than said deviation (E), the method comprises a step of recording (47) the average capacitance value in said curve (C).

12. The determination method according to any of claims 10 and 11, wherein the curve includes a capacitance value measured after manufacture of the seat and before installation in the vehicle, a capacitance value measured after installation of the seat in the motor vehicle and a capacitance value measured before first use.

13. A system (2) for determining the occupancy status of a seat (4) in a motor vehicle, said system comprising: - a seat (4) for a motor vehicle including: - a seating portion (18) having a receiving face (22) for accommodating a person, the receiving face (22) being divided into a front zone (26) and a rear zone (24), the front zone and the rear zone being located on either side of a transverse central plane (X-X) of the seating portion, - a backrest (20) having a receiving face (28) for accommodating the back of a person, the backrest (20) being hinged to the seating portion (18), the rear zone (24) of the receiving face of the seating portion being adjacent to the backrest (20), - only three interdigital capacitive sensors (6, 8, 10) carried by the backrest receiving face (28), and only three interdigital capacitive sensors (12, 14, 16) carried by the seating portion receiving face (22), a first interdigital capacitive sensor (6) being located on an upper and lateral zone of said backrest receiving face (28), the second interdigital capacitive sensor (8) being located on a lower zone or a central zone of said backrest receiving face, the third interdigital capacitive sensor (10) being located on a lateral zone of said backrest receiving face, the third interdigital capacitive sensor (10) being located at a lower position relative to the second capacitive sensor, the second interdigital capacitive sensor (8) being offset laterally toward the center relative to the first and third interdigital capacitive sensors, the fourth (12) interdigital capacitive sensor being located on a lateral part of the rear zone (24) of the seating portion receiving face, the fifth interdigital capacitive sensor (14) being located on a rear or central zone of the seating portion receiving face, the sixth interdigital capacitive sensor (16) being located on a lateral part of the front zone of the seating portion receiving face, the fifth interdigital capacitive sensor (14) being offset laterally toward the center relative to the fourth and sixth interdigital capacitive sensors, the fifth interdigital capacitive sensor (14) being located longitudinally between the fourth (12) and the sixth (16) interdigital capacitive sensors, - a controller (100) suitable for carrying out the method of determining the occupancy status of a seat according to any of claims 1 to 12.

14. The determination system (2) according to claim 13, wherein the second interdigital capacitive sensor (8) is positioned laterally at the center of the seat receiving face, and wherein the fifth interdigital capacitive sensor (14) is positioned laterally at the center of the receiving face.