Capacitive seat occupancy detection system operable at wet conditions
A vehicle seat occupancy detection system includes at least one capacitive sensor member having at least one sensing electrode, an impedance measurement circuit for determining a complex impedance or a complex admittance of the at least one sensing electrode, an evaluation unit for generating an output signal based on a determined complex admittance of the at least one sensing electrode and comparison of the determined complex admittance to at least one predetermined value, and at least one electrically conductive ground connecting member that is intentionally electrically connected to the reference electrode and that is arranged in close proximity to the at least one sensing electrode. The at least one ground connecting member and the at least one sensing electrode are galvanically separated such that, when the seat gets wet, the sensing electrode is directly electrically connected to the reference electrode by the at least one ground connecting member.
1. A capacitive seat occupancy detection system, comprising
at least one capacitive sensor member having at least one sensing electrode,
an impedance measurement circuit configured to determine a complex impedance or a complex admittance (Y) of the at least one sensing electrode relative to a reference electrode,
an evaluation unit that is configured to generate an output signal that is representative of at least one of detecting and classifying a seat occupancy, the output signal being based on a determined complex impedance or a determined complex admittance of the at least one sensing electrode and a comparison of the determined complex impedance or the determined complex admittance to at least one predetermined value for the determined complex impedance or the determined complex admittance, and
at least one electrically conductive ground connecting member that is electrically connected to the reference electrode and that is arranged in close proximity to the at least one sensing electrode, wherein the at least one ground connecting member and the at least one sensing electrode are galvanically separated.
2. The seat occupancy detection system as claimed in claim 1 , wherein the at least one sensing electrode is formed by at least one seat heater member that is configured for heating a heatable seat by a passage of electrical current through the at least one seat heater member.
3. The seat occupancy detection system as claimed in claim 1 , wherein the at least one electrically conductive ground connecting member is disposed coplanar to at least a portion of the at least one sensing electrode.
4. The seat occupancy detection system as claimed in claim 1 , wherein each at least one electrically conductive ground connecting member includes a single wire disposed in a plane and having a curved shape, and wherein the curved shape is arranged relative to the at least one sensing electrode such that a concave side of the curved shape faces an outer contour at least one sensing electrode.
5. The seat occupancy detection system as claimed in claim 1 , wherein each at least one electrically conductive ground connecting member includes a single wire disposed in a plane, and wherein the single wire comprises two legs forming a right angle, and is arranged relative to the at least one at least one sensing electrode such that an apex of the right angle is further away from an outer contour of the at least one sensing electrode than the legs.
6. The seat occupancy detection system as claimed as claimed in claim 1 , wherein each at least one electrically conductive ground connecting member includes a single wire disposed in a plane and being arranged with at least a part of its length of extension in parallel to an outer contour of the at least one sensing electrode.
7. The seat occupancy detection system as claimed in claim 1 , wherein the at least one electrically conductive ground connecting member comprises at least one resistor that is electrically connected in series to a balance of the at least one electrically conductive ground connecting member.
8. The seat occupancy detection system as claimed in claim 7 , wherein the at least one resistor comprises a thermistor that is configured to serve as a temperature sensor.
9. A vehicle seat, comprising
a seat structure for erecting the vehicle seat on a passenger cabin floor of the vehicle,
a seat base cushion,
at least one seat heater member that is configured for heating by a passage of electrical current through the at least one seat heater member,
a seat base supported by the seat structure and configured to receive the seat base cushion, the seat base and the seat base cushion being provided for supporting a bottom of a seat occupant,
a backrest configured to receive a backrest cushion provided for supporting a lumbar and back region of the seat occupant, and
a vehicle seat occupancy detection system as claimed in claim 1 , wherein the at least one sensing electrode is formed by the at least one seat heater member.
10. A seat occupancy detection method, comprising detecting occupancy of a vehicle seat using the capacitive seat occupancy detection system set forth in claim 1 .