Modeling and Simulation of the Effect of Reversible Belt Pretensioners

The general task of a belt pretensioner is to reduce the slack in the seatbelt-system. While pretensioning the seat-belt is tightened to help to reduce seatbelt slack prior to occupant movement. In combinationwith other safety components like airbags this helps to reduce the potential for injuries to an occupant. A specific type of pretensioner is incorporated in the so called Active Control Retractor (ACR): A reversible pretensioner using the available time during the pre-crash phase. The ACR controls the seatbelt pretensioning and force with the help of a direct current motor (DC-motor). This pretensioning is reversible and carried out in certain driving situations. The ACR acts in combination with the Situation Management Algorithm (SMA). The SMA detects certain driving situations, using existing sensor technology in the car. This paper will show how the dynamic behavior of an occupant coupled with the ACR belt system can be simulated. The following models were developed for this study: 1. a model of the vehicle, which gives an input for the occupant, 2. an ACR-model which simulates the dynamic behavior of the belt-system, 3. an Occupant-Model which simulates the occupant dynamic and interaction to the ACR. Furthermore this paper will describe the modeling of the ACR, the vehicle and the occupant. To simulate the dynamic behavior of this system in the precrash phase Matlab/Simulink 1 is used.