Method for determining the morphology of an occupant in an automotive seat with capacitive sensors

• US 20090088929A1
• Filed: 05/15/2007
• Published: 04/02/2009
• Est. Priority Date: 05/17/2006
• Status: Active Grant

• Current Assignee: Hitachi Computer Products (Europe) SAS (Hitachi, Ltd.)
• Original Assignee: Hitachi Computer Products (Europe) SAS (Hitachi, Ltd.)
• Inventors: Ninomiya, Takanori, Maeda, Shunji, Voisin, Florent, Launay, Claude, Da Silva, Joaquim, Hirai, Tomoaki
• Granted Patent: US 7,987,033 B2
• Time in Patent Office: Days
• US Class Current: 701/49
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

The present invention relates to a method determining the morphology of the occupant of an automotive car, characterized in that it comprises the steps of collecting (200) the outputs of a plurality of capacitive sensors (100) provided on a seat, determining for each capacitive sensors (100) a first value representative of the distance (di) separating a target (10) from the sensor (100) and a second value (Sdi) representative of the surface of the sensor (100) covered by the target (10), applying (210) to the second values (Sdi) representative of the surface of the sensor (100) covered by the target (10) a respective weighting (Wi) based on the corresponding first value (di) representative of the distance separating the target (10) from the same sensor (100), and determining (240) the morphology of the target (10) on the basis of the collection of weighted second values (SdixWi).

Claims

1. A method for determining the morphology of the occupant of an automotive car, characterized in that it comprises the steps of collecting (200) the outputs of a plurality of capacitive sensors (100) provided on a seat, determining for each capacitive sensors (100) a first value representative of the distance (di) separating a target (10) from the sensor (100) and a second value (Sdi) representative of the surface of the sensor (100) covered by the target (10), applying (210) to the second values (Sdi) representative of the surface of the sensor (100) covered by the target (10) a respective weighting (Wi) based on the corresponding first value (di) representative of the distance separating the target (10) from the same sensor (100), and determining (240) the morphology of the target (10) on the basis of the collection of weighted second values (SdixWi).

2. The method of claim 1, characterized in that the respective weighting coefficient is determined by function Wi=(di−

dinf)/[ min(d1 to dp)−

dinf], wherein

di=distance calculated for each sensor i,

dinf=an estimated infinite distance, that is to mean when seat is considered empty

min(d1 to dp)=minimum distance calculated for all p sensors (100).

3. The method of one of claims 1 or 2, characterized in that the step of determining the morphology comprising counting up the number of sensors (100) covered by a passenger in order to define a corresponding class of morphology.

4. The method of one of claims 1 to 3, characterized in that the method comprises a step of filtering which eliminates all measured values (di, Sdi) for which the first value representative of the distance (di) separating a target (10) from the sensor (100) is above a threshold (d_inf).

5. The method of one of claims 1 to 4, characterized in that the method further comprises a step of coherence analysis (220) for eliminating all non coherent profile of morphology.

6. The method of one of claims 1 to 5, characterized in that the method further comprises a centre detection step to retain only signal issued by a sensor (100) which is considered as totally covered.

7. The method of claim 6, characterized in that the centre detection step retains signal issued by a sensor (100) only if a measured surface Si is included between value defined as 1−

α

=<

Si=<

1+α

, with for example α

=0.25.

8. The method of one of claims 1 to 7, characterized in that the method further comprises a step for analysing the slope progression from one sensor to another.

9. The method of one of claims 1 to 8, characterized in that the method further comprises a step for detecting an abnormal down slope between two adjacent sensors (100), representing for example a child with hand on a bolster.

10. The method of one of claims 1 to 9, characterized in that the method further comprises a step for detecting a “

hole”

, ie a detected distance which is greater than a threshold (dinf), so as to eliminate the next adjacent sensor from classification.

11. The method of one of claims 1 to 10, characterized in that the method further comprises a step of coherence analysis which involves at least one of the following items:

when two adjacent sensors (100S1 and 100S2 or 100S5 and 100S6) are detected empty, the corresponding signals are not taken into account,

when an external sensor (100S1 or 100S6) is empty, but only an adjacent part of the next sensor (100S2 and 100S5) is occupied, the corresponding signals are not taken into account,

when an external sensor (100S1 or 100S6) is empty, but the next sensor (100S2 and 100S5) is either fully occupied or occupied on its part opposite said external sensor, the signal obtained from the said next sensor (100S2 and/or sensor 100S5) is retained,

when an external sensor (100S1 or 100S6) is covered only on its external part, but the adjacent sensor (100S2 or 100S5) is empty, the signals considered as a hole detection are not retained,

when both an external sensor (100S1 or 100S6) and the adjacent sensor (100S2 or 100S5) are covered only on their external part, the are not taken into account,

when an external sensor (100S1 or 100S6) is covered only on its external part, while the adjacent sensor (100S2 or 100S5) is fully covered, the signal obtained from said next sensor (100S2 and/or sensor 100S5) is retained,

when an external sensor (100S1 or 100S6) is covered only on its external part, while the adjacent sensor (100S2 or 100S5) is covered on its opposite part, the signals obtained from said next sensor (100S2 and/or sensor 100S5) is retained,

when an external sensor (100S1 or 100S6) is fully covered, but the adjacent sensor (100S2 or 100S5) is empty, the signals considered as a hole detection are not retained,

when an external sensor (100S1 or 100S6) is fully covered, but the adjacent sensor (100S2 or 100S5) is only covered on a part adjacent said external sensor, a summation of the signal obtained from these couples of sensors (100S1 and 100S2 or 100S5 and 100S6) is operated only if the opposite internal sensor (ie respectively 100S5 and 100S2) is empty,

when both the sensors (100S1 and 100S2 or 100S5 and 100S6) are fully covered, the signals are retained,

when an external sensor (100S1 or 100S6) is fully covered, but the adjacent sensor (100S2 or 100S5) is only covered on a part opposite this external sensor, the signal issued from the internal sensor (100S2 and/or 100S5) is retained, but the signal issued from the external sensor (100S1 and/or 100S6) is retained only if a condition is applied, for example if S1<

S2+β

or S6>

S5−

β

,

when an external sensor (100S1 or 100S6) is covered only on its internal part, and the adjacent sensor (100S2 or 100S5) is empty, the signals considered as a hole detection are not retained,

when an external sensor (100S1 or 100S6) is covered only on its internal part, and the adjacent sensor (100S2 or 100S5) is only covered on a part adjacent said external sensor, a summation of the signal obtained from these couples of sensors (100S1 and 100S2 or 100S5 and 100S6) is operated only if the opposite internal sensor (ie respectively 100S5 and 100S2) is empty.

when an external sensor (100S1 or 100S6) is covered only on its internal part, and the adjacent sensor (100S2 or 100S5) is fully covered, the signals are summed.

when an external sensor (100S1 or 100S6), as well as the adjacent sensor (100S2 or 100S5) are covered only on their internal part, the signal issued from the internal sensor (100S2 and/or 100S5) is retained, but the signal issued from the external sensor (100S1 and/or 100S6) is retained only if a condition is applied, for example if S1<

S2+β

or S6>

S5−

β

.

12. The method of one of claims 1 to 11, characterized in that the method further comprises a step of confidence test.

13. The method of one of claims 1 to 12, characterized in that the method further comprises a step of confidence test which is based on distance detection.

14. The method of one of claims 1 to 13, characterized in that the method implements a capacitive sensor (100) comprising at least two electrodes (110, 120) covering complementary respective areas of a sensed zone so as to form two balanced pixel sensors.

15. The method of one of claims 1 to 14, characterized in that the method implements a capacitive sensor (100) comprising three electrodes:

two main electrodes (110, 120) covering complementary respective areas of a sensed zone and a third auxiliary electrode (130) covering both said complementary respective areas.

16. The method of claim 15, characterized in that the method implements a capacitive sensor wherein said third auxiliary electrode (130) surrounds the two main electrodes (110, 120).

17. The method of one of claims 1 to 16, characterized in that the method implements at least four sensors (100S1, 100S2, 100S5, 100S6) substantially aligned from left to right on a seat.

18. The method of claim 17, characterized in that the method implements at least an additional sensor (100S3, 100S4) provided onward or backward in regard of the four sensors (100S1, 100S2, 100S5, 100S6) substantially aligned.

19. The method of one of claims 1 to 18, characterized in that the method implements sensors (100S1, 100S6) provided on bolster of a seat.

20. The method of one of claims 1 to 19, characterized in that the method comprises the steps of applying respective controlled electric potentials upon electrodes (110, 120, 130) and subsequently, after breaking said electrical potentials, measuring the electric charges upon at least one selected electrode so as to generate an electrical output.

21. The method of one of claims 1 to 20, characterized in that the method implements a step of selecting a value representative of the distance (di) separating the target (10) from the sensor (100), from a look up table, using as input for this selection a combination of the outputs issued by the capacitive sensor and selecting a value representative of the amount (Sdi) of the surface of the sensor (100) covered by said target (10), from another look up table, using also as input for this selection a combination of the outputs issued by the capacitive sensor.

22. The method of one of claims 1 to 21, characterized in that the method implements look up tables which contain values representative of the distance (di) separating the target (10) from the sensor (100) and/or values representative of the amount (Sdi) of the surface of the sensor (100) covered by said target (10), for a plurality of temperature and humidity values, and the method comprises the step of selecting in the look up tables an output value depending on a combination of the outputs issued by the capacitive sensor which represents real temperature and humidity.

23. The method of one of claims 1 to 22, characterized in that it comprises a step of positioning different threshold on a statistical distribution of morphological classes corresponding to predetermined number of pixels.

24. A system for implementing the method in accordance with one of claims 1 to 23, so as to determe the morphology of the occupant of an automotive car, characterized in that it comprises means for collecting (200) the outputs of a plurality of capacitive sensors (100) provided on a seat, means for determining for each capacitive sensors (100) a first value representative of the distance (di) separating a target (10) from the sensor (100) and a second value (Sdi) representative of the surface of the sensor (100) covered by the target (10), means for applying (210) to the second values (Sdi) representative of the surface of the sensor (100) covered by the target (10) a respective weighting (Wi) based on the corresponding first value (di) representative of the distance separating the target (10) from the same sensor (100), and means for determining (240) the morphology of the target (10) on the basis of the collection of weighted second values (SdixWi).

25. Seat for an automotive car characterized in that it comprises means for implementing the method in accordance with one of claims 1 to 24.