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 forward or rearward position of a child seat mounted 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 from 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 the detection of a forward 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. Prior art

[0002] To increase the safety of motor vehicle passengers, 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 installed on the front passenger seat of a motor vehicle either in a "forward-facing" position, as illustrated in [Fig. 1], or in a "rear-facing" position, as illustrated in [Fig. 2]. In the "rear-facing" position, also known as the rear-facing position, the child faces the seat back. This position is safer for the child because the airbag deployment will not injure the child, but the driver has limited visibility of the child while driving. In the "forward-facing" position, also known as the forward-facing 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 could injure the child. This position is less safe for the child. Devices and methods exist for automatically detecting the presence of a child seat in a motor vehicle.However, these devices and methods do not allow one to know whether the child seat is in a "rear-facing" or "forward-facing" position.

[0004] It would be desirable to know in what 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 object 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 object of the present invention is to detect whether the child seat installed on the seat is a child seat for a child under 18 months. Summary of the invention

[0007] The present invention relates to a method for detecting a so-called forward 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 having a seat cushion and a backrest having a front face having two longitudinal edges, at least one first coplanar interdigitated electrode capacitive sensor fixed to the backrest at a first distance from the seat cushion, 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 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) calculation of 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 forward position of the child seat, when the first variation is greater than said first threshold.

[0008] The features described in the following paragraphs may optionally be implemented. They may be implemented independently of each other or in combination with each other: - The first threshold is between 15 picofarads and 50 picofarads. - The detection system includes a second coplanar interdigitated electrode capacitive sensor arranged on the backrest, the first and second capacitive sensors being arranged on either side of a central longitudinal plane; the central longitudinal 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 also includes at least one capacitive sensor additional coplanar interdigitated 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 at least one additional capacitive sensor during the measurement phase, and wherein, when at least a first variation is below 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 indicating 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 whether a child seat mounted on a vehicle seat is in a forward or rearward position, said detection system comprising: - a vehicle seat comprising a seat cushion and a backrest, the backrest having two longitudinal edges, - at least one first coplanar interdigitated electrode capacitive sensor 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 at least one first capacitive sensor and to the detection device, the processing unit includes a memory containing instructions to implement the process described above.

[0010] The features described in the following paragraphs may optionally be implemented. They may be implemented independently of each other or in combination with each other:

[0011] - At least one first capacitive sensor is arranged midway between the edges longitudinals of the front face of the vehicle seat backrest. The system further comprises a second coplanar interdigitated electrode capacitive sensor arranged on the backrest, the first and second capacitive sensors being arranged on either side of a central longitudinal plane; the central longitudinal plane extending vertically between and midway between the two longitudinal edges; the memory containing instructions for implementing the process steps described above. - The first capacitive sensor and the second capacitive sensor are separated from said longitudinal central plane by a second distance between 1 centimeter and 5 centimeters. - The detection system further comprises at least one additional coplanar interdigitated 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 containing instructions to implement the steps of the process described above. - The additional capacitive sensor is arranged midway between the longitudinal edges of the front face of the vehicle seat backrest. Brief description of the figures

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

[0013] [Fig.2] is a perspective view of a vehicle seat and an arranged child seat 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 method of implementation;

[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 method of implementation;

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

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

[0020] [Fig.9] is a diagram representing the steps of a process according to a third method of implementation. Detailed description of the invention

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

[0022] The invention is described in relation to the orthonormal coordinate system (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 for the back of a child and a rear face 26 opposite the receiving face. In [Fig. 1], the child seat 20 is positioned in a so-called "forward position" in which the rear face 26 of the child seat is opposite a backrest 13 of the passenger seat of the vehicle. In [Fig. 2], the child seat 20 is positioned in a so-called "rear position" in which the receiving face 24 of the child seat is opposite 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 between the so-called "forward position" and the so-called "rear position". The detection system 2 according to the first embodiment only works for child seats over 18 months of age.

[0025] Figure 3 shows 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 load-bearing structure, a layer of foam supported by the load-bearing structure, and an outer textile covering over the foam layer. The backrest 13 has a front face 14 designed to support the back of a seat occupant and a rear face 15 opposite the front face. The front face 14 of the backrest has two longitudinal edges 16 and 18 opposite each other.

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

[0029] The first capacitive sensor 6 is fixed to 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 shown 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 backrest.

[0031] The first capacitive sensor 6 is arranged between the foam layer and the outer covering of the backrest. The first capacitive sensor 6 can be fixed to a flexible support attached to 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 attached to the rod. The fingers extend perpendicularly to the rod. The fingers are spaced apart in a comb-like 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 the dimensions of the rods, fingers, and the spacing between the rods and fingers of the first capacitive sensor is described in patent application FR 3 126 776.

[0033] One electrode is connected to a voltage source via an electrical connecting wire 21. The voltage source generates a voltage of, for example, 5 volts. The second electrode is connected to ground via an electrical connecting 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 designed to implement a method for recognizing the presence of a child seat on the seat. A method of the same type as the method described in French patent FR 20 12255 could, for example, be used by adding one or more sensors to the seat back and / or by receiving information from other vehicle sensors, such as the seat belt tension sensor.

[0036] According to a second example, the detection device 8 is, for example, a camera suitable for capturing images of the front passenger seat, a processing unit suitable for implementing a child seat detection method based on image contour recognition 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 operated 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 can be a programmable device or a processor that uses specific software or an ASIC. The processing unit 10 includes a memory 28 that stores executable code enabling implement the detection process described below from the capacitance values ​​received from the first capacitive sensor 6. The memory 28 includes a random access memory, noted RAM and a read-only memory noted ROM.

[0040] The memory 28 includes instructions 30 to implement 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 equal duration. The measurement periods last between 1 second and 5 seconds. The capacitive values ​​are measured 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 step 40, the difference between the second mean value M2 and the first mean value M1 is calculated. This difference is called a first variation AL During 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 forward position of the child seat is transmitted by the processing unit, during a step 44.

[0044] If the variation Al is less than the first threshold Sel, a Sig3 signal, called the third Sig3 signal, representing 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 operates 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 coplanar interdigitated electrode capacitive sensor 50 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 central longitudinal plane (X, Z). The first capacitive sensor 6 and the second capacitive sensor 50 are each located at a first distance DI from the nearest part of the seat, as illustrated in [Fig.4].

[0047] The first capacitive sensor 6 and the second capacitive sensor 50 are separated 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] Memory 28 includes instructions 52 to implement the steps of the detection process 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 detection of 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 process 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 forward 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 forward 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 representing 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 but also to determine whether the child seat mounted on the passenger seat of the vehicle is a seat for children over 18 months or a child seat for children under 18 months.

[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 coplanar interdigitated electrode capacitive sensor. 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 shown 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 contains instructions 66 to implement the steps of the detection process 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 process 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 forward position of the child seat is transmitted by the processing unit, during a step 44. If, during step 42, the first variation Al is less than the first threshold Sel, the process 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 average value M4 and the third average 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 Sel threshold. 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.

[0067] If the second variation A2 is less 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 for children over 18 months is arranged in a rear-facing 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 among the so-called "front position" and the so-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 or a child seat for children under 18 months.

[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 It further comprises an additional capacitive sensor 64 arranged on the backrest, and the processing unit implements a process comprising steps of process 49 according to the second embodiment and steps of process 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 contains instructions 78 for implementing the steps of a process comprising steps of process 49 according to the second embodiment and steps of process 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

Demands

1. A method for detecting (31, 49, 63) a so-called forward or 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) having a seat (12) and a backrest (13) having a front face (14) having two longitudinal edges (16, 18), at least one first capacitive sensor (6) with coplanar interdigitated 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 process comprising a measurement phase (32) during which capacitive values ​​are measured at the electrodes of at least a 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 (M1) 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 (M1), d) comparison (42,54) of said first variation (A1) with a first threshold (Sel), e) transmission (44,58) of a first signal (Sigl) representative of a detection of a forward position of the child seat, when the first variation (A1) 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. A detection method (49) according to any one of claims 1 and 2, wherein the detection system (48) comprises a second coplanar interdigitated electrode capacitive sensor (50) 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 forward 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. A 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 at least one additional capacitive sensor (64) during the measurement phase, and wherein, when at least one first variation (Al) is below 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.

5. Detection system (2,48,62,76) for a forward or rear position of a child seat (20) arranged on a vehicle seat (4), said detection system comprising: - a vehicle seat (4) having a seat (12) and a backrest (13), the backrest (13) having two longitudinal edges (16, 18), - at least one first capacitive sensor (6) with coplanar interdigitated 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 having a memory (28) containing instructions (30) to implement the method according to claims 1 or 2.

6. Detection system (2,48,62,76) according to claim 5, wherein 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 backrest.

7. A detection system (48,76) according to claim 5, further comprising a second coplanar interdigitated electrode capacitive sensor (50) arranged on the back (13), the first (6) and 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 carrying out the steps of the process according to claim 3.

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

9. A detection system (62,76) according to claims 5 to 8, wherein the detection system further comprises at least one additional coplanar interdigitated 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 carrying out the steps of the process according to claim 4.

10. A 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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