Abstract: An improved weight estimation apparatus in which an elastomeric bladder is supported on a semi-rigid backer board which is installed in a vehicle seat between the seat cushion and an underlying spring suspension. The bladder is secured onto the backer board, and the backer board is attached to the seat, enabling proper and consistent placement of the bladder relative to the seat surface. The backer board provides the reaction surface for the bladder, and masks non-uniformities of the seat structure. Additionally, the backer board will reduce or eliminate the effect of objects lying on the floor under the seat, which might otherwise pinch the bladder and produce weight estimation errors. Further, the board tends to protect the bladder from damage due to sharp objects, pinching by the suspension elements, and the effects of wires or cables routed through the seat.

Abstract: An improved occupant weight detection system measures the pressure in a fluid-filled bladder disposed in or under a foam seat cushion as an indication of occupant weight, and periodically adjusts the pressure vs. occupant weight relationship to compensate for changes due to aging and usage of the foam seat cushion. The system controller develops an aging adjustment value based on a measure of the cumulative aging and usage of the seat, and uses the developed adjustment value to compensate the operation of the system. The aging adjustment value is determined primarily as a function of occupant weight and time of seat occupancy, and the compensation is achieved by using the aging adjustment value to adjust either the estimated weight, or a threshold to which the measured pressure is compared for purposes of deciding if restraint deployment should be enabled.

Abstract: An improved occupant weight detection system measures the pressure in a fluid-filled bladder disposed in or under a foam seat cushion as an indication of occupant weight, and periodically adjusts the pressure vs. occupant weight relationship to compensate for changes due to aging and usage of the foam seat cushion. The system controller develops an aging adjustment value based on a measure of the cumulative aging and usage of the seat, and uses the developed adjustment value to compensate the operation of the system. The aging adjustment value is determined primarily as a function of occupant weight and time of seat occupancy, and the compensation is achieved by using the aging adjustment value to adjust either the estimated weight, or a threshold to which the measured pressure is compared for purposes of deciding if restraint deployment should be enabled.

Abstract: An improved method of producing a fluid filled elastomeric bladder for occupant weight sensing involves annealing the bladder material prior to its installation in a vehicle seat so as to quickly relieve initial stress due to stretching of the bladder material which occurs during fluid injection. In a preferred implementation, the initial stress is relieved by immersing the fluid-filled bladders in heated water for a time period on the order of 60 seconds or more. Alternatively, the bladder material may be heated with steam or radiant heat, by injecting heated fluid into the bladder, or by injecting heated air into an empty bladder before fluid injection. In each case the initial stress is quickly relieved, substantially eliminating a potential source of error in the sensed weight.

Abstract: An improved pressure-based weight estimation system that includes an adaptive technique for reliably and accurately determining the vacant, or unoccupied, seat pressure. The vacant seat pressure is initially determined by a factory calibration procedure, and is thereafter suitably updated by an adaptive learning algorithm based on temperature, time, and the measured pressure. If the seat temperature is within a normal range, and the measured pressure remains at least a predetermined amount below the calibrated vacant seat pressure for at least a predetermined time, a fraction of the difference between the measured and calibrated values is subtracted from the calibrated value to form a new calibration value. The predetermined difference amount determines the sensitivity of the control, and the predetermined time prevents adaptive correction of the calibration value due to transient pressure conditions.

Abstract: An improved weight estimation apparatus includes a closed elastomeric bladder filled with fluid and installed in the foam cushion of a vehicle seat bottom, with at least one pressure sensor installed in a closed exit port of the bladder. A temperature sensor disposed in proximity to the bladder provides a temperature signal, and a controller estimates the weight of the occupant based on the temperature and pressure signals. The pressure sensor is preferably configured to sense the gage pressure--that is, the differential pressure between the fluid and atmospheric pressure--at the center of gravity of the fluid in order to provide a stable output independent of changing atmospheric pressure and changing orientation of the bladder due to vehicle pitch and roll.