Occupant Classification System

Passenger Air Bag Deactivation Indicator 

The occupant classification system can determine if the front passenger seat is unoccupied, occupied by a small person, or occupied by a large person. The occupant classification system consists of:

• An occupancy sensor, installed under the cushion of the front passenger seat
• A safety belt tension sensor, integrated into the anchor point of the front passenger safety belt
• An occupancy sensor module, installed under the front passenger seat
• A PAD (passenger air bag deactivation) indicator, on the integrated control panel.

The occupancy sensor is a silicone filled bladder, which is connected to a pressure sensor. Any load on the pressure pad is detected by the pressure sensor.

The safety belt tension sensor is a strain gauge that measures the load applied by the safety belt anchor to the anchor bolt. The sensor is located in the lower safety belt anchor point.

The occupancy sensor module supplies a reference voltage to the pressure sensor and the safety belt tension sensor and, from the returned signals, measures the loads acting on the pressure pad and the safety belt tension sensor. The load measurement from the safety belt tension sensor is used to produce a correction factor for the load measurement from the pressure pad. The tightness of the safety belt affects the load acting on the pressure pad, so without the correction factor the occupant classification module cannot derive an accurate occupancy status.

The occupant classification module translates the load readings into a seat occupancy status and transmits the result to the RCM, on the high speed CAN bus. The occupancy sensor module incorporates two load limits for the seat cushion: When the load exceeds the lower limit, but is less than the upper limit, the occupant is classified as small; when the upper limit is exceeded, the occupant is classified as large.

The occupant classification system has four possible states, which are detailed in the following table.