Seat Occupancy Detector (OC-3 Mat)
The purpose of the OC-3 mat is to monitor the presence of a person or object placed on the front passenger's seat and determine whether the passenger airbags should be deactivated. The OC-3 mat is capable of detecting a child seat that conforms to the relevant standard (NHTSA FMVSS 208) by virtue of the pattern of the impression it makes on the seat and deactivates the passenger airbags.
The previous SBE mat recognized a certain weight as proof that the seat is occupied. In order to meet legislative requirements, the seat occupancy detector (SBE) has been developed into an intelligent occupant classifier (OC). This was achieved by means of the following measures:
- By a larger number of sensor elements
- By sensing a larger area of the seat
- By an intelligent electronic analyzer
The OC-3 mat is capable of distinguishing between a one-year-old child in a child's seat and a light person.
The OC-3 mat is integrated into the seat area of the passenger seat. The OC-3 mat consists of conductors with pressure-dependent resistor elements (FSR, or Force Sensitive Resistance Elements). The conductors are connected to the electronic analyzer.
The FSR elements are wired in such a way that they can be sampled individually. When the mechanical load on a sensor element increases electrical resistance decreases and the measurement current changes accordingly.
By analyzing the signals from the individual sensors, the analyzer maps the occupancy of the seat surface and can identify the local concentrations of weight. The distances between the areas where pressure is applied and the concentrations of pressure reveal whether the seat is occupied by a person (A) or a child seat (B).
The analyzer of the OC-3 mat sends a message to the MRS5 control unit via the K-CAN. If the system detects that the seat is unoccupied or that a child seat for a child up to one year old is fitted, the airbags on the passenger side are deactivated. The MRS5 control unit switches on the airbag warning light. The airbag warning light indicates that the airbags on the passenger side are deactivated.