Seat foam humidity compensation for vehicle seat occupant weight detection system

Abstract

A vehicle seat occupant classification system uses a pressure responsive, fluid filled bladder and pressure sensor adapted for engagement with an underside of a foam seat cushion so as to generate a pressure signal corresponding to the weight of an occupant on an upper side of the foam seat cushion. A humidity sensor responds to relative humidity of air adjacent the pressure sensor and/or foam seat cushion to generate a humidity signal that is used to compensate at least one of the pressure signal, a stored reference pressure value and a stored threshold value, from which at least in part; an occupant classification is determined. The system preferably includes a time delay between the reading of a humidity value and the full use of that humidity value in compensation; and the time delay may be responsive to an activity factor derived from dynamic variations in the pressure signal associated with a pumping action on the foam tending to increase the rate of exchange of air between the foam and the atmosphere outside the foam. Preferably, the temperature adjacent the pressure sensor and/or foam seat cushion is also determined and used in conjunction with the humidity signal to provide au additional cross-correlation compensation.