Method for detecting a rotation of part of the trunk of an occupant seated on a seat
A method for detecting a rotation of part of the trunk of an occupant seated on a seat of a vehicle. The method includes: triggering a measurement of capacitance values; successively determining, from the measured capacitance values, a first stationary posture of the occupant during a first stationary period, a movement of part of the trunk of the occupant, and a second stationary posture of the occupant during a second stationary period; and calculating, for each capacitive sensor, the variation between the capacitance values measured during the first stationary period and the capacitance values measured during the second stationary period. If the variation calculated for the capacitive sensors is within ranges of capacitance values defined for the capacitive sensors, generating a detection signal.
1 . A method for detecting a rotation of at least part of the trunk of an occupant seated on a seat of a vehicle, the method being implemented by a detection system comprising the seat, at least a first interdigital capacitive sensor and a second interdigital capacitive sensor carried by the seat, and a controller connected to the first interdigital capacitive sensor and the second interdigital capacitive sensor, said controller comprising a memory containing at least a first range of variation of capacitance values that is defined for the first interdigital capacitive sensor and a second range of variation of capacitance values that is defined for the second interdigital capacitive sensor; the method comprising:
triggering a measurement phase comprising periods during which capacitance values are measured by the first interdigital capacitive sensor and the second capacitive sensor; the method further comprising, during the measurement phase successively,
determining a first stationary posture of the occupant from the measured capacitance values, the first stationary posture taking place during a first stationary period, determining a movement of at least part of the trunk of the occupant from the measured capacitance values, and
determining a second stationary posture of the occupant from the measured capacitance values, the second stationary posture taking place during a second stationary period;
calculating, for the first interdigital capacitive sensor, a first variation between a value representative of the capacitance values measured during the first stationary period and a value representative of the capacitance values measured during the second stationary period;
calculating, for the second interdigital capacitive sensor, a second variation between a value representative of the capacitance values measured during the first stationary period and a value representative of the capacitance values measured during the second stationary period;
comparing the first variation to said first range of variation of capacitance values defined for the first interdigital capacitive sensor;
comparing the second variation to said second range of variation of capacitance values defined for the second interdigital capacitive sensor; and
if the first variation is within said first range of variation of capacitance values defined for the first interdigital capacitive sensor and if the second variation is within said second range of variation of capacitance values defined for the second interdigital capacitive sensor, generating a detection signal.
2 . The method of claim 1 , wherein the value representative of the measured capacitance values is the average value of the measured capacitance values.
3 . The method of claim 1 , wherein determining a first stationary posture comprises:
for each capacitive sensor, calculating a maximum threshold and a minimum threshold based on the capacitance values measured during a previous period, and
for each capacitive sensor, comparing the capacitance values measured during a following period with the maximum threshold and with the minimum threshold; if the capacitance values are between the maximum threshold and the minimum threshold for the set of capacitive sensors, for a duration greater than one and a half seconds, then the first stationary posture is determined.
4 . The method of claim 3 , wherein the maximum threshold and/or the minimum threshold being calculated by adding and/or subtracting at least 2500 picofarads to/from an average value; the average value being calculated from the capacitance values measured during the previous period for each capacitive sensor.
5 . The method of claim 1 , wherein the second stationary period takes place at least two minutes after the first stationary period.
6 . The method of claim 5 , wherein the detection signal is generated only if the capacitance values measured during the second stationary period are between the maximum threshold and the minimum threshold for a duration of at least ten seconds.
7 . The method of claim 1 , further comprising alerting the occupant of the seat by the triggering of a sound, of a display, or a generation of a vibration.
8 . The method of claim 1 , wherein the seat comprises a seating portion and a backrest hinged to the seating portion about an axis extending in a transverse direction, and wherein the movement of the trunk of the occupant is a rotational movement about an axis parallel to the transverse axis.
9 . The method of claim 1 , wherein the generated detection signal is representative of at least one position of the occupant among the rotation of part of the trunk of the occupant, a rotation of the chest of the occupant, and a rotation of the pelvis of the occupant, and wherein the method further comprises a step of transmitting the detection signal to a device for managing the triggering of an airbag, the device being able to manage the triggering of the airbag according to the position of the occupant.
10 . The method of claim 3 , wherein the maximum threshold and/or the minimum threshold being calculated by adding and/or subtracting at least 3000 picofarads to/from an average value; the average value being calculated from the capacitance values measured during the previous period for each capacitive sensor.
11 . The method of claim 1 , wherein the second stationary period takes place at least three minutes after the first stationary period.
12 . A method for detecting a rotation of at least part of the trunk of an occupant seated on a seat of a vehicle, the method being implemented by a detection system comprising the seat, at least a first interdigital capacitive sensor and a second interdigital capacitive sensor carried by the seat, and a controller connected to the first interdigital capacitive sensor and the second interdigital capacitive sensor, said controller comprising a memory containing at least a first range of variation of capacitance values that is defined for the first interdigital capacitive sensor and a second range of variation of capacitance values that is defined for the second interdigital capacitive sensor; the method comprising:
triggering a measurement phase comprising periods during which capacitance values are measured by the first interdigital capacitive sensor and the second capacitive sensor;
the method further comprising, during the measurement phase successively
determining a first stationary posture of the occupant from the measured capacitance values, the first stationary posture taking place during a first stationary period, determining a movement of at least part of the trunk of the occupant from the measured capacitance values, and
determining a second stationary posture of the occupant from the measured capacitance values;
calculating, for the first interdigital capacitive sensor, a first variation between a value representative of the capacitance values measured during the first stationary period and a value representative of the capacitance values measured during the second stationary period calculating, for the second interdigital capacitive sensor, a second variation between a value representative of the capacitance values measured during the first stationary period and a value representative of the capacitance values measured during the second stationary period;
comparing the first variation to said first range of variation of capacitance values defined for the first interdigital capacitive sensor;
comparing the second variation to said second range of variation of capacitance values defined for the second interdigital capacitive sensor; and
if the first variation is within said first range of variation of capacitance values defined for the first interdigital capacitive sensor and if the second variation is within said second range of variation of capacitance values defined for the second interdigital capacitive sensor, generating a detection signal,
wherein determining a first stationary posture comprises:
for each capacitive sensor, calculating a maximum threshold and a minimum threshold based on the capacitance values measured during a previous period, and
for each capacitive sensor, comparing the capacitance values measured during a following period with the maximum threshold and with the minimum threshold; if the capacitance values are between the maximum threshold and the minimum threshold for the set of capacitive sensors, for a duration greater than one and a half seconds, then the first stationary posture is determined.