Method for detecting the position of a child seat and associated detection system

Abstract

The invention relates to a method for detecting a so-called front position or a so-called rear position of a child seat arranged on a vehicle seat; the method further comprising the following steps: a) calculating (36) a first average value from the capacitive values ​​measured during a first period of the measurement phase, b) calculating (38) a second average value of the capacitive values ​​measured during a second period of the measurement phase, the second period being subsequent to the first period, c) calculating (40) a first variation between the second average value and the first average value, d) comparing (42) said first variation with a first threshold, e) transmitting (44) a first signal representative of a detection of a front position of the child seat, when the first variation is greater than said first threshold. The invention also relates to an associated detection system. Figure to be published with the abstract: Figure 7

Description

Title of the invention: Method for detecting the position of a child seat and associated detection system Technical field of the invention

[0001] The invention relates to a method for detecting a so-called front position or a so-called rear position of a child seat arranged on a vehicle seat and an associated detection system. State of the prior art

[0002] To increase the safety of passengers in motor vehicles, safety systems have become mandatory in the front of vehicles. These safety systems include, for example, a dashboard airbag and / or a door airbag.

[0003] Child seats can be attached to the front passenger seat of the motor vehicle either in a so-called "forward-facing" position illustrated in [Fig.l], or in a so-called "rear-facing" position illustrated in [Fig.2]. In the "rear-facing" position, also known as the rear position, the child faces the backrest. This position is safer for the child because the deployment of the airbag will not injure the child, but the driver has poor visibility of the child while driving. In the "forward-facing" position, also known as the front position, the child faces the dashboard of the vehicle. In this position, the driver can see and monitor the child while driving, but the deployment of an airbag can injure the child. This position is less safe for the child. There are devices and methods for automatically detecting the presence of a child seat on a motor vehicle seat.However, these devices and methods do not make it possible to know whether the child seat is in a “rear-facing” position or in a “forward-facing” position.

[0004] It would be desirable to know in which position the child seat has been fixed in order to be able to adapt the inflation strategy of the safety cushion, for example by blocking the inflation of the cushion or by adapting the injection speed or the quantity of air injected in order to reduce the impact between the cushion and the child, when the child seat is installed in the “forward-facing” position. Presentation of the invention

[0005] A first aim of the present invention is to propose a method and a system for detecting the position of a child seat, when the child seat is over 18 months old.

[0006] A second aim of the present invention is to detect whether the child seat installed on the seat is a seat for a child under 18 months. Summary of the invention

[0007] The present invention relates to a method for detecting a position known as before or of a so-called rear position of a child seat arranged on a vehicle seat; the method being implemented by a detection system comprising a vehicle seat comprising a seat and a backrest comprising a front face having two longitudinal edges, at least one first capacitive sensor with coplanar interdigital electrodes fixed on the backrest at a first distance from the seat, a detection device capable of detecting the presence of a child seat on the vehicle seat, and a processing unit connected to said at least one first capacitive sensor and to the detection device; the first distance being between 30 centimeters and 45 centimeters; the method comprising a measurement phase during which capacitive values ​​are measured at the electrodes of the at least one first capacitive sensor; upon detection of the presence of a child seat on the vehicle seat, the method further comprising the following steps: a) calculation of a first average value from the capacitive values ​​measured during a first period of the measurement phase, b) calculating a second average value of the capacitive values ​​measured during a second period of the measurement phase, the second period being subsequent to the first period, (c) calculation of a first variation between the second average value and the first average value, d) comparison of said first variation with a first threshold, e) transmission of a first signal representative of a detection of a front position of the child seat, when the first variation is greater than said first threshold.

[0008] The features set forth in the following paragraphs may optionally be implemented. They may be implemented independently of one another or in combination with one another: - The first threshold is between 15 picofarads and 50 picofarads. - The detection system comprises a second capacitive sensor with coplanar interdigital electrodes arranged on the backrest, the first and second capacitive sensors being arranged on either side of a longitudinal central plane; the longitudinal central plane extending vertically, between and midway between the two longitudinal edges; steps a) to d) being implemented by the processing unit from the capacitance values ​​measured at the electrodes of the second capacitive sensor, a first signal representative of a detection of a forward position of the child seat being transmitted only if the first variation calculated from the capacitive values ​​from the first capacitive sensor and the first variation calculated from the capacitive values ​​from the second capacitive sensor are each greater than said first threshold. - The detection system further comprises at least one capacitive sensor with additional coplanar interdigital electrodes arranged on the backrest; the additional capacitive sensor being located at a third distance from the seat, the third distance being between 20 centimeters and 30 centimeters; capacitive values ​​being measured at the electrodes of the at least one additional capacitive sensor during the measurement phase, and wherein when the at least one first variation is less than said first threshold, the method further comprises the following steps: - calculation of a third average value from the capacitive values ​​measured by the additional capacitive sensor during the first period, - calculation of a fourth average value from the capacitive values ​​measured by the additional capacitive sensor during the second period, - calculation of a second variation between the fourth average value and the third average value, - comparison of the second variation with the first threshold; - transmission of a second signal representing the fact that the child seat is a child seat intended for a child under eighteen months old.

[0009] The invention also relates to a system for detecting a front position or a rear position of a child seat arranged on a vehicle seat, said detection system comprising: - a vehicle seat comprising a seat and a backrest, the backrest comprising two longitudinal edges, - at least one first capacitive sensor with coplanar interdigital electrodes arranged on the backrest at a first distance from the seat, the first distance being between 30 centimeters and 45 centimeters from the seat, - a detection device capable of detecting the presence of a child seat on the vehicle seat, - a data processing unit connected to said at least one first capacitive sensor and to the detection device, the processing unit comprises a memory comprising instructions for implementing the method described above.

[0010] The features set out in the following paragraphs may optionally be implemented. They may be implemented independently of one another or in combination with one another:

[0011] - The at least one first capacitive sensor is arranged halfway between the edges longitudinal of the front face of the vehicle seat back. - The system further comprises a second coplanar interdigital electrode capacitive sensor arranged on the backrest, the first and second capacitive sensors being arranged on either side of a longitudinal central plane; the longitudinal central plane extending vertically, between and midway between the two longitudinal edges; the memory comprising instructions for implementing the steps of the method described above. - The first capacitive sensor and the second capacitive sensor are spaced from said longitudinal central plane by a second distance of between 1 centimeter and 5 centimeters. - The detection system further comprises at least one additional coplanar interdigital electrode capacitive sensor arranged on the backrest; the additional capacitive sensor being located at a third distance from the seat, the third distance being between 20 centimeters and 30 centimeters; the memory comprising instructions for implementing the steps of the method described above. - The additional capacitive sensor being arranged halfway between the longitudinal edges of the front face of the vehicle seat back. Brief description of the figures

[0012] [Fig-1] is a perspective view of a vehicle seat and a child seat arranged therein on the seat; the child seat being in a forward position;

[0013] [Fig.2] is a perspective view of a vehicle seat and a child seat arranged therein on the seat; the child seat being in a rear position;

[0014] [Fig.3] is a perspective view of a detection system according to a first mode of realization;

[0015] [Fig.4] is a perspective view of a detection system according to a second embodiment;

[0016] [Fig.5] is a perspective view of a detection system according to a third mode of realization;

[0017] [Fig.6] is a perspective view of a detection system according to a fourth embodiment;

[0018] [Fig.7] is a diagram representing the steps of a detection method according to a first embodiment;

[0019] [Fig.8] is a diagram representing the steps of a detection method according to a second embodiment; and

[0020] [Fig.9] is a diagram showing the steps of a method according to a third embodiment. Detailed description of the invention

[0021] In the following description, the spatial positioning indications such as front, rear, top, bottom, upper, lower, horizontal, vertical etc. are to be interpreted according to the usual position of use of a seat in a vehicle. The front direction being the direction of a vehicle moving forward. In particular, the front face of a backrest is the face on which the back of an occupant of the seat rests.

[0022] The invention is described in connection with the orthonormal reference frame (X, Y, Z) illustrated in the Figures 1 and 2.

[0023] Figures 1 and 2 show a child seat 20 fixed to a seat 4 of a motor vehicle. The child seat 20 comprises a backrest 22 having a receiving face 24 intended to receive the back of a child and a rear face 26 opposite the receiving face. In [Fig.l], the child seat 20 is positioned in a position called the “front position” in which the rear face 26 of the child seat faces a backrest 13 of the passenger seat of the vehicle. In [Fig.2], the child seat 20 is positioned in a position called the “rear position” in which the receiving face 24 of the child seat faces the backrest 13 of the passenger seat of the vehicle.

[0024] The detection system 2 according to the present invention is configured to determine the position of the child seat 20 from among the position called “front position” and the position called “rear position”. The detection system 2 according to the first embodiment only works for child seats over 18 months old.

[0025] [Fig. 3] represents an example of a detection system 2 according to a first embodiment of the invention. This detection system 2 according to the first embodiment only works for child seats intended for children over 18 months old.

[0026] This detection system comprises a seat 4, a first capacitive sensor 6 with coplanar interdigitated electrodes, a detection device 8 and a processing unit 10 connected to the first capacitive sensor 6 and to the detection device.

[0027] The seat 4 comprises a seat 12 and a backrest 13 articulated to the seat. The backrest 13 comprises a supporting structure, a foam layer carried by the supporting structure and a textile-type outer covering covering the foam layer. The backrest 13 comprises a front face 14 intended to receive the back of an occupant of the seat and a rear face 15 opposite the front face. The front face 14 of the backrest comprises two longitudinal edges 16, 18 opposite one another.

[0028] For the purposes of this description, a longitudinal central plane (X, Z) is defined perpendicular to the seat back. The longitudinal central plane (X, Z) is vertical. The longitudinal central plane (X, Z) intersects the center of the width of the back. That is to say, it is located midway between the two longitudinal edges 16, 18 of the front face of the back.

[0029] The first capacitive sensor 6 is fixed on the backrest at a first distance DI from the seat. The first distance DI is between 30 centimeters and 45 centimeters. The first distance DI is measured substantially along the X axis. The first distance DI is measured between the rear part of the substantially horizontal face of the seat and the lower part of the capacitive sensor, as visible in [Fig.3]. The first distance is the smallest distance between the substantially horizontal part of the seat and the lower part of the capacitive sensor.

[0030] In the first embodiment, the first capacitive sensor 6 is arranged midway between the longitudinal edges 16, 18 of the vehicle seat back.

[0031] The first capacitive sensor 6 is arranged between the foam layer and the outer covering of the backrest. The first capacitive sensor 6 may be fixed to a flexible support fixed against the foam layer of the backrest. The flexible support is not shown in the figures.

[0032] The first capacitive sensor 6 comprises two electrodes. Each electrode comprises a rod and fingers secured to the rod. The fingers extend perpendicular to the rod. The fingers are spaced apart from each other in a comb-shaped configuration. The second electrode is positioned relative to the first electrode such that the fingers of the second electrode are interposed between the fingers of the first electrode. An example of dimensions of the rods, fingers and spacings between the rods and fingers of the first capacitive sensor is described in the patent application published under the number FR 3 126 776.

[0033] One electrode is connected to a voltage source via an electrical connection wire 21. The voltage source generates a voltage of, for example, 5 volts. The second electrode is connected to a ground via an electrical connection wire 21.

[0034] The detection device 8 is capable of detecting the presence of a child seat on the vehicle seat. The detection device 8 may be any device known for this purpose.

[0035] According to a first example, the detection device 8 comprises, for example, several capacitive sensors arranged on the seat and connected to a processing unit capable of implementing a method for recognizing the presence of a child seat on the seat. A method of the same type as the method described in patent FR 20 12255 could for example be used by adding one or more sensors on the backrest and / or by receiving information from other sensors of the vehicle such as for example the belt tension sensor.

[0036] According to a second example, the detection device 8 is for example a camera capable of capturing images of the front passenger seat, a processing unit capable of implementing a child seat detection method based on the recognition of image contours from the images captured by the camera.

[0037] According to a third example, the detection device 8 can also be a control button capable of being actuated by an occupant of the vehicle.

[0038] The processing unit 10 periodically measures capacitance values ​​between the electrodes of the first capacitive sensor 6.

[0039] The data processing unit 10 may be a programmable device or a processor that uses software or a specific integrated circuit (ASIC). The processing unit 10 includes a memory 28 that stores executable code allowing implement the detection method described below from the capacitance values ​​received from the first capacitive sensor 6. The memory 28 comprises a random access memory, denoted RAM and a read only memory denoted ROM.

[0040] The memory 28 comprises instructions 30 for implementing the detection method according to the first embodiment of the invention described below.

[0041] With reference to [Fig.7], the detection method according to the first embodiment 31 of the invention comprises a measurement phase 32 during which capacitive values ​​are measured by the processing unit at the electrodes of the first capacitive sensor 6. The measurement phase 32 comprises several periods of the same duration. The measurement periods last between 1 second and 5 seconds. The measurements of the capacitive values ​​are carried out every 100 milliseconds.

[0042] During a step 34, the detection device 8 detects the presence of a child seat 20 on the seat 4. During a step 36, a first average value Ml is calculated from the capacitive values ​​measured during a first period. During a step 38, a second average value M2 is calculated from the capacitive values ​​measured during a second period subsequent to the first period. During a step 40, the difference between the second average value M2 and the first average value M1 is calculated. This difference is called a first variation AL During a step 42, the first variation Al is compared with a first threshold Sel. The first Sel threshold is between 15 picofarads and 50 picofarads. Preferably, the first Sel threshold is equal to 20 picofarads.

[0043] If the variation Al is greater than the first threshold Sel, a first signal Sigl representative of a detection of a front position of the child seat is transmitted by the processing unit, during a step 44.

[0044] If the variation Al is lower than the first threshold Sel, a signal Sig3, called third signal Sig3, representative of a detection of a rear position of the child seat is transmitted by the processing unit, during a step 46.

[0045] A detection system 48 according to a second embodiment is illustrated in [Fig. 4]. This detection system 48 according to the second embodiment only works for child seats intended for children over 18 months old. The detection system 48 according to this second embodiment is identical to the detection system 2 according to the first embodiment except that it comprises a second capacitive sensor 50 with coplanar interdigital electrodes arranged on the backrest 13 and that the processing unit implements a method according to a second embodiment.

[0046] The first capacitive sensor 6 and the second capacitive sensor 50 are arranged on either side of the longitudinal central plane (X, Z). The first capacitive sensor 6 and the second capacitive sensor 50 are each located at a first distance DI from the closest part of the seat, as illustrated in [Fig.4].

[0047] The first capacitive sensor 6 and the second capacitive sensor 50 are spaced from the longitudinal central plane (X, Z) by a second distance D2. The second distance is the smallest distance to the central plane. The second distance is between 1 centimeter and 5 centimeters. The second distance is measured along the Y axis.

[0048] The memory 28 comprises instructions 52 for implementing the steps of the detection method according to the second embodiment described below.

[0049] The other technical elements of the detection system 48 according to the second embodiment are identical to the technical elements of the detection system 2 according to the first embodiment, they bear the same references and will not be described a second time.

[0050] The detection method according to the second embodiment of the invention 49 is implemented by the detection system according to the second embodiment. The detection method according to the second embodiment is illustrated in [Fig.8]. It is identical to the detection method according to the first embodiment except that during the measurement phase 32, capacitive values ​​are measured by the processing unit at the electrodes of the first capacitive sensor 6 and at the electrodes of the second capacitive sensor 50.

[0051] After detecting the presence of a child seat 20 on the seat 4, steps 36 to 40 are implemented for the capacitance values ​​measured at the electrodes of the first capacitive sensor 6.

[0052] Then, during a step 54, the variation Al calculated during step 42 is compared to the first threshold Sel.

[0053] If the variation Al is greater than the first threshold Sel, the method returns to step 36 during a step 56 and steps 36 to 54 are again implemented from the capacitance values ​​measured at the electrodes of the second capacitive sensor 50.

[0054] During step 54, the first variation Al calculated from the capacitive values ​​from the second capacitive sensor 50 is compared to the first threshold Sel.

[0055] If the first variation Al calculated from the capacitive values ​​from the second capacitive sensor 50 is greater than the first threshold Sel, then a first representative signal Sigl of a detection of a front position of the child seat is transmitted during a step 58.

[0056] Thus, in this embodiment, a first representative signal Sigl of a detection of a front position of the child seat is transmitted only if the first variation Al calculated from the capacitive values ​​from the first capacitive sensor and the first variation Al calculated from the capacitive values ​​from the second capacitive sensor 50 are each greater than the first threshold Sel.

[0057] If the first variation Al calculated from the capacitive values ​​from the first capacitive sensor and / or the first variation Al calculated from the capacitive values ​​from the second capacitive sensor 50 is less than the first threshold Sel, then a third signal Sig3 representative of a detection of a rear position of the child seat is transmitted by the processing unit, during a step 60.

[0058] A detection system 62 according to a third embodiment is illustrated in [Fig.5].

[0059] Advantageously, the detection system 62 according to this third embodiment makes it possible not only to determine the front or rear position of a child seat 20 intended for a child over 18 months old but also to determine whether the child seat mounted on the passenger seat of the vehicle is a seat for children over 18 months old or a child seat for children under 18 months old.

[0060] The detection system 62 according to this third embodiment is identical to the detection system 2 according to the first embodiment except that it further comprises an additional capacitive sensor 64 arranged on the backrest and that the processing unit implements a method according to a third embodiment. The additional capacitive sensor 64 is a capacitive sensor 64 with coplanar interdigital electrodes. The additional capacitive sensor 64 is located at a third distance D3 from the seat. The third distance D3 is measured between the rear part of the substantially horizontal face of the seat and the lower part of the capacitive sensor, as visible in [Fig. 3]. The third distance is the smallest distance between the substantially horizontal part of the seat and the lower part of the capacitive sensor. The third distance D3 is measured along the X axis.

[0061] The third distance D3 is between 20 centimeters and 30 centimeters. The memory 28 comprises instructions 66 for implementing the steps of the detection method according to the third embodiment described below.

[0062] The other technical elements of the detection system 48 according to the third embodiment are identical to the technical elements of the detection system 2 according to the first embodiment, they bear the same references and will not be described a second time.

[0063] The detection method according to the third embodiment of the invention 63 is implemented by the detection system according to the third embodiment. The detection method according to the third embodiment is illustrated in [Fig.9]. It is identical to the detection method according to the first embodiment except that during the measurement phase 32, capacitive values ​​are measured by the processing unit at the electrodes of the first capacitive sensor 6 and at the electrodes of the additional capacitive sensor 64.

[0064] Then, steps 34 to 42 are implemented in the same way as in the detection method according to the first embodiment.

[0065] If, during step 42, the first variation Al is greater than the first threshold Sel, a first signal Sigl representative of a detection of a front position of the child seat is transmitted by the processing unit, during a step 44. If, during step 42, the first variation Al is lower than said first threshold Sel, the method returns to step 36, during a step 68.

[0066] During this new step 36, the processing unit calculates a third average value M3 from the capacitive values ​​measured at the electrodes of the additional capacitive sensor 64 during the first period. During this new step 38, the processing unit calculates a fourth average value M4 from the capacitive values ​​measured at the electrodes of the additional capacitive sensor 64 during the second period. In a further step 40, the difference between the fourth mean value M4 and the third mean value M3 is calculated. This difference is called a second variation A2. Then, during step 70, the second variation A2 is compared with the first threshold Sel. If the second variation A2 is greater than the first threshold Sel, a second signal Sig2 is transmitted by the processing unit 10 during a step 72. This second signal Sig2 is representative of the fact that the child seat mounted on the passenger seat of the vehicle is a child seat intended for a child under eighteen months old.

[0067] If the second variation A2 is lower than the first threshold Sel, then a fourth signal Sig4 is transmitted by the processing unit 10 during a step 74.

[0068] This fourth signal Sig4 is representative of the fact that a child seat over 18 months old is arranged in a rear position.

[0069] A detection system 76 according to a fourth embodiment is illustrated in [Fig.6].

[0070] Just like the detection system according to the third embodiment, this detection system 76 also makes it possible to determine the position of a child seat 20 intended for a child over 18 months old among the position called "front position" and the position called "rear position" but also to determine whether the child seat mounted on the passenger seat of the vehicle is a seat for children over 18 months old or a child seat for children under 18 months old.

[0071] The detection system 76 according to this fourth embodiment is identical to the detection system 2 according to the second embodiment except for the fact that it further comprises an additional capacitive sensor 64 arranged on the backrest and that the processing unit implements a method comprising steps of the method 49 according to the second embodiment and steps of the method 63 according to the third embodiment. The additional capacitive sensor 64 is identical to the capacitive sensor 64 described in the detection system according to the third embodiment. The memory 28 comprises instructions 78 for implementing the steps of a method comprising steps of the method 49 according to the second embodiment and steps of the method 63 according to the third embodiment.

[0072] The other technical elements of the detection system 76 according to the fourth embodiment are identical to the technical elements of the detection systems according to the second embodiment and the third embodiment, they bear the same references and will not be described again.

Claims

Claims

1. Method for detecting (31, 49, 63) a so-called front position or a so-called rear position of a child seat (20) arranged on a vehicle seat (4); the method being implemented by a detection system (2, 48, 62) comprising a vehicle seat (4) comprising a seat (12) and a backrest (13) comprising a front face (14) having two longitudinal edges (16, 18), at least one first capacitive sensor (6) with coplanar interdigital electrodes fixed on the backrest at a first distance (Dl) from the seat, a detection device (8) capable of detecting the presence of a child seat (20) on the vehicle seat, and a processing unit (10) connected to said at least one first capacitive sensor (6) and to the detection device (8); the first distance being between 30 centimeters and 45 centimeters;the method comprising a measuring phase (32) during which capacitive values ​​are measured at the electrodes of the at least one first capacitive sensor (6);upon detection (34) of the presence of a child seat (20) on the vehicle seat, the method further comprising the following steps: a) calculation (36) of a first average value (Ml) from the capacitive values ​​measured during a first period of the measurement phase, b) calculation (38) of a second average value (M2) of the capacitive values ​​measured during a second period of the measurement phase, the second period being subsequent to the first period, c) calculation (40) of a first variation between the second average value (M2) and the first average value (Ml), d) comparison (42,54) of said first variation (Al) with a first threshold (Sel), e) transmission (44,58) of a first signal (Sigl) representative of a detection of a front position of the child seat, when the first variation (Al) is greater than said first threshold (Sel).;

2. Detection method (31, 49, 63) according to claim 1, wherein the first threshold (Sel) is between 15 picofarads and 50 picofarads.

3. Detection method (49) according to any one of claims 1 and 2, in which the detection system (48) comprises a second capacitive sensor (50) with coplanar interdigitated electrodes arranged on the backrest (13), the first and second capacitive sensors being arranged on either side of a longitudinal central plane (X,Z); the central plane longitudinal (X,Z) extending vertically, between and midway between the two longitudinal edges (16, 18); steps a) to d) being implemented by the processing unit (10) from the capacitance values ​​measured at the electrodes of the second capacitive sensor (50), a first signal (Sigl) representative of a detection of a front position of the child seat being transmitted (58) only if the first variation (Al) calculated from the capacitive values ​​from the first capacitive sensor and the first variation (Al) calculated from the capacitive values ​​from the second capacitive sensor (50) are each greater than said first threshold (Sel).

4. Detection method (63) according to any one of claims 1 to 3, wherein the detection system (62) further comprises at least one additional coplanar interdigitated electrode capacitive sensor (50) (64) arranged on the backrest (13); the additional capacitive sensor (64) being located at a third distance (D3) from the seat, the third distance (D3) being between 20 centimeters and 30 centimeters; capacitive values ​​being measured at the electrodes of the at least one additional capacitive sensor (64) during the measurement phase, and wherein when the at least one first variation (Al) is less than said first threshold (Sel), the method further comprises the following steps: - calculation (36) of a third average value (M3) from the capacitive values ​​measured by the additional capacitive sensor during the first period, - calculation (38) of a fourth average value (M4) from the capacitive values ​​measured by the additional capacitive sensor during the second period, - calculation (40) of a second variation (A2) between the fourth average value (M4) and the third average value (M3), - comparison (70) of the second variation (A2) with the first threshold (Sel); - transmission (72) of a second signal (Sig2) representative of the fact that the child seat is a child seat intended for a child under eighteen months old.

5. Detection system (2,48,62,76) of a front position or a rear position of a child seat (20) arranged on a vehicle seat (4), said detection system comprising: - a vehicle seat (4) comprising a seat (12) and a backrest (13), the backrest (13) comprising two longitudinal edges (16, 18), - at least one first capacitive sensor (6) with coplanar interdigital electrodes arranged on the backrest at a first distance (Dl) from the seat (12), the first distance (Dl) being between 30 centimeters and 45 centimeters from the seat (12), - a detection device (8) capable of detecting the presence of a child seat (20) on the vehicle seat, - a data processing unit (10) connected to said at least one first capacitive sensor (6) and to the detection device (8), the processing unit comprises a memory (28) comprising instructions (30) for implementing the method according to claims 1 or 2.

6. Detection system (2,48,62,76) according to claim 5, wherein the at least one first capacitive sensor (6) is arranged midway between the longitudinal edges (16, 18) of the front face (14) of the vehicle seat back.

7. A detection system (48,76) according to claim 5, which further comprises a second capacitive sensor (50) with coplanar interdigital electrodes arranged on the backrest (13), the first (6) and the second (50) capacitive sensors being arranged on either side of a longitudinal central plane (X, Z); the longitudinal central plane (X, Z) extending vertically, between and midway between the two longitudinal edges (16, 18); the memory (28) comprising instructions (52) for implementing the steps of the method according to claim 3.

8. Detection system (48,76) according to claim 7, wherein the first capacitive sensor (6) and the second capacitive sensor (50) are spaced from said longitudinal central plane (X, Z) by a second distance (D2) of between 1 centimeter and 5 centimeters.

9. Detection system (62,76) according to claims 5 to 8, wherein the detection system further comprises at least one additional coplanar interdigital electrode capacitive sensor (64) arranged on the backrest (13); the additional capacitive sensor (64) being located at a third distance (D3) from the seat, the third distance (D3) being between 20 centimeters and 30 centimeters; the memory (28) comprising instructions for implementing the steps of the method according to claim 4.

10. Detection system (62,76) according to claim 9, wherein said additional capacitive sensor (64) is arranged midway between the longitudinal edges (16,18) of the front face (14) of the seat back. of vehicle.

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