Capacitive Sensor for Morphological Discrimination of a Motor Vehicle Seat Occupant

• US 20080211213A1
• Filed: 07/21/2006
• Published: 09/04/2008
• Est. Priority Date: 07/28/2005
• Status: Active Grant

• Current Assignee: Hitachi Computer Products (Europe) SAS (Hitachi, Ltd.)
• Original Assignee: Hitachi Computer Products (Europe) SAS (Hitachi, Ltd.)
• Inventors: Voisin, Florent, Launay, Claude, Da Silva, Joaquim
• Granted Patent: US 8,033,182 B2
• Time in Patent Office: Days
• US Class Current: 280/735
• CPC Class Codes: G01D 5/2405 by varying dielectric

Abstract

The invention concerns a detection set comprising in combination a sensor (100) comprising three electrodes: two main electrodes (110, 120) covering different zones of the space and the third auxiliary electrode (130), surrounding almost entirely the two main electrodes (110, 120) and processing means (200) connected to said electrodes(110, 120, 130) to power same through controlled voltage levels, operate the signals sampled therefrom as ratios between two signals and deliver partly binary data representing the overlap or non-overlap of one main electrode (110, 120) by comparing the signal sampled thereon with a predetermined threshold and partly analog data representing the percentage of overlap of at least one electrode.

Claims

1. A detection assembly comprising:

a sensor that comprises (i) first and second main electrodes covering different zones of the space, and (ii) a third auxiliary electrode almost entirely surrounding the first and second main electrodes, and

a processing means connected to the electrodes, wherein the processing means is for;

(i) powering the latter at controlled voltage levels,

(ii) making use of the signals taken therefrom in the form of ratios between two signals, and

(iii) delivering binary signals representing the covering or non covering of a main electrode by comparison of the signal taken therefrom with a predetermined threshold, and analog signals representing the percentage of covering of at least one electrode.

2. The assembly according to claim 1, wherein the first and second main electrodes include comprise main elements that extend in opposite directions in relation to a general plane of symmetry.

3. The assembly according to claim 1, wherein each of the main electrodes is “

L”

shaped, and the auxiliary electrode is “

T”

shaped with an upright and a head formed from an open loop that surrounds the main elements of the main electrodes.

4. The assembly according to claim 1, wherein each of the main electrodes is “

L”

shaped, and the auxiliary electrode is “

T”

shaped with an upright and a head formed from two open loops that respectively surround the main elements of the main electrodes.

5. The assembly according to claim 1, wherein the main electrodes comprise main elements that are rectilinear and aligned with each other.

6. The assembly according to claim 1, wherein the main electrodes include comprise main elements that are non-rectilinear.

7. The assembly according to claim 1, wherein the electrodes are positioned on a flexible support.

8. The assembly according to claim 1, wherein the electrodes are positioned on a support made from any thermoplastic material.

9. The assembly according to claim 1, wherein the electrodes are positioned on a support made from a material that is stable with temperature and humidity.

10. The assembly according to claim 1, wherein the electrodes are positioned on a support exhibiting a permittivity of ε

<

4.

11. The assembly according to claim 1, wherein the sensor is coated with a waterproof film, that is stable with temperature and humidity and of low permittivity.

12. The assembly according to claim 1, wherein the processing means is for applying an electric field to one or more of the electrodes by applying a ground potential or a voltage at a controlled level, typically equal to that of the electrode to be measured, on one or more other electrodes, and then measuring the charge on the electrode in question.

13. The assembly according to claim 1, wherein the processing means is for obtaining:

a first signal from a first pixel by applying an electric field between the first main electrode and the auxiliary electrode, and by measuring the electric charge on the first main electrode in relation to the auxiliary electrode with the pixel of the second main electrode connected to the ground,

a second signal from a second pixel by applying an electric field between the second main electrode and the auxiliary electrode, and by measuring the electric charge on this second main electrode in relation to the auxiliary electrode, with the pixel of the first main electrode connected to the ground,

a first analog signal by applying an electric field to the auxiliary electrode, in relation to the main electrodes, connected to the ground, and by measuring the electric charge on the auxiliary electrode,

a first pixel signal by applying an electric field between the first main electrode and the auxiliary electrode, and by measuring the electric charge on the first main electrode in relation to the auxiliary electrode, with the second main electrode connected to the electric field in order to neutralise its influence,

a second pixel signal by applying an electric field between the second main electrode and the auxiliary electrode, and by measuring the electric charge on the second main electrode in relation to the auxiliary electrode, with the first main electrode connected to the electric field in order to neutralise its influence,

a second analog signal by applying an electric field to the auxiliary electrode, in relation to the first main electrode, and by measuring the electric charge on the auxiliary electrode, with the second main electrode connected to the electric field in order to neutralise its influence,

a third analog signal by applying an electric field to the auxiliary electrode, in relation to the second main electrode, and by measuring the electric charge on the auxiliary electrode, with the first main electrode connected to the electric field in order to neutralise its influence,

a fourth analog signal by applying an electric field to the main and auxiliary electrodes, and by measuring the electric charge on the auxiliary electrode.

14. The assembly according to claim 1 wherein the processing means is for carrying out the addition of first and second pixel signals.

15. The assembly according to claim 12, wherein the assembly comprises several sensors and the processing means is for reiterating a measurement sequence successively on each sensor by bringing the other sensors to a measurement potential.

16. The assembly according to claim 1, wherein the processing means is for conducting measurement of pixelation by means of main electrodes that are generally rectilinear.

17. The assembly according to claim 1, wherein the processing means is designed to perform analog measurement by means of the auxiliary electrode.

18. A sensor for the creation of a detection assembly the sensor comprising:

(i) first and second main electrodes covering different zones of the space, and

(ii) a third auxiliary electrode almost entirely surrounding the first and second main electrodes,

wherein the assembly further comprises a processing means connected to the electrodes wherein the processing means is for;

(i) powering the latter at controlled voltage levels,

(ii) making use of the signals taken therefrom in the form of ratios between two signals, and

(iii) delivering binary signals representing the covering or non covering of a main electrode by comparison of the signal taken therefrom with a predetermined threshold, and analog signals representing the percentage of covering of at least one electrode.

19. A motor-vehicle seat, that comprises at least one detection assembly comprising:

a sensor that comprises (i) first and second main electrodes covering different zones of the space and (ii) a third auxiliary electrode almost entirely surrounding the first and second main electrodes and

a processing means connected to the electrodes wherein the processing means is for;

(i) powering the latter at controlled voltage levels,

(ii) making use of the signals taken therefrom in the form of ratios between two signals and

(iii) delivering binary signals representing the covering or non covering of a main electrode by comparison of the signal taken therefrom with a predetermined threshold, and analog signals representing the percentage of covering of at least one electrode.

20. The seat according to claim 19, wherein the at least one detection assembly comprises several sensors.

21. The seat according to claim 20, wherein the sensors are connected to common processing means.

22. The seat according to claim 19, wherein the seat comprises sensors on the seat bottom.

23. The seat according to claim 19, wherein the seat comprises sensors on the seat back.

24. The seat according to claim 19, wherein the seat comprises sensors on the lateral parts of at least one of the seat bottom and the seat back.

25. The seat according to claim 24, wherein the seat comprises sensors on the central part of at least one of the seat bottom and the seat back.

26. The seat according to claim 19, wherein the seat bottom comprises:

a first set of sensors, on each of the two lateral parts, perpendicular to the stitches and on the median axis of the seat between the front and the rear,

a second set of sensors, placed in the central part, on the other side of the stitches, that is toward the centre of the seat, with the second set of sensors offset toward the front, respectively in relation to the first set of sensors,

a first sensor whose length is equal to the width of the central part between the stitches, positioned toward the rear of the seat, at ⅔

of the way between the front and the rear, and

a second sensor whose length is equal to the width of the central part between the stitches, positioned toward the front of the seat bottom at ⅓

of the length thereof between the front and the rear.

27. The seat according to claim 19, wherein the seat back comprises:

a first set of sensors, on each of the two lateral parts, perpendicular to the stitches, and at substantially ⅔

of the back upwards,

a second set of sensors, positioned on the central part, on the other side of the stitches, that is toward the centre of the seat back, with the second set of sensors, offset downwards respectively in relation to the first set of sensors, or substantially on the median axis of the height of the seat back,

a first sensor whose length is equal to the width of the central part between the stitches positioned toward the bottom of the seat back, substantially at ⅓

the height thereof, and

a second sensor whose length is equal to the width of the central part between the stitches positioned toward the top of the back and substantially at ⅔

thereof.

28. The seat according to claim 19, wherein the seat comprises sensors positioned to measure the width of the thighs and the buttocks of a passenger.

29. The seat according to claim 19 wherein the seat comprises sensors positioned to measure the width of the shoulders and the buttock-shoulder distance of a passenger.