Pos. | spare part no | Name |
1 | - | Belt tension sensor |
2 | - | Passenger presence sensor |
3 | - | Passenger Presence Sensor Module |
In North American countries where seat belts are not frequently used, additional technology is used to classify the passenger in the front seat. The occupant classification system transmits seat load information to the occupant protection control unit (RCM).
The passenger classification system includes the following components:
- Pressure pad mounted under the front seat cushion connected to a pressure sensor.
- Seat belt tension sensor located at the front passenger's seat belt attachment point.
- Passenger Classification Module installed under the front passenger seat.
The pressure pad is an analogue of a heating pad filled with silicone fluid. Any load on the pressure pad is registered by a pressure sensor. The seat belt tension sensor is a strain gauge that detects the load on the seat belt anchor bolt. The sensor is located at the bottom anchor point of the seat belt.
The passenger presence sensor responds to changes in the weight on the passenger seat and sends a corresponding signal to the passenger presence detection module. In addition, the seat belt tension sensor provides a separate input to the passenger presence module. The module processes the signals from the sensors and transmits the corresponding signal to the RCM via the high speed CAN bus.
The RCM monitors and processes data from these and other sensors before making the decision to deploy the airbag. In addition to weight, the system is able to take into account several other variables: the slope of the car and the exact position and structure of the weight on the seat.
This helps to prevent accidental deployment of the airbag, for example, if there is a small child in a child seat on the seat, or an unfastened, but very light adult passenger; in both cases, the airbag will be disabled. The occupant classification system forms an important part of the airbag deployment control strategy based on the type of occupant.
The classification system can give four possible definitions:
Seat not occupied: passenger airbag, passenger side airbag and seat belt and pretensioner are deactivated; The passenger's airbag deactivation indicator does not come on.
Busy, blocked: seat occupied by a small passenger, passenger airbag, passenger side airbag and seat belt and pretensioner are deactivated; the passenger airbag deactivation indicator is on.
seat occupied: the seat is occupied by a large passenger; passenger airbag, passenger side airbag and seat belt and pretensioner are on, passenger airbag off indicator is off. The condition of the passenger's seat belt and pretensioner depends on the condition of the seat belt buckle:
- active for buttoned
- inactive for unbuttoned
- active for buttoned
- inactive for unbuttoned
Passenger Presence Sensor Module
The passenger presence sensor module is installed under the front passenger seat. The module supplies power to the passenger occupancy sensor and monitors the reverse voltage signal to detect seat occupancy. The result is transmitted to the RCM via the high speed CAN bus. The passenger occupancy sensor module also monitors the occupancy sensor circuits for shorts or open circuits. If a malfunction is detected, the occupant occupancy sensor module sends a malfunction message to the RCM.
Belt tension sensor
The seat belt tension sensor is a strain gauge built into the passenger seat belt anchorage. The sensor converts the force applied to the seat belt into an electrical signal. If a child seat is installed on the front passenger seat, the force applied to the passenger's seat belt is reflected in the sensor output, which provides data that supplements the passenger presence sensor information.
The occupant occupancy sensor module processes the incoming data and passes it on to the occupant protection control unit, which then evaluates whether the passenger airbag should deploy.
Comments on this article