Method for detecting a rotation of part of the trunk of an occupant seated on a seat

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.