Control method for occupant restraint apparatus and occupant restraint apparatus

An occupant restraint apparatus comprising:

• an obstacle detecting device for detecting a position and relative speed of an obstacle with respect to a vehicle with the obstacle being in a travelling direction of the vehicle and potentially corning into collision with the vehicle;
• a collision predicting device for predicting a type of collision between the obstacle detected by the obstacle detecting device and the vehicle;
• a setting device for setting conditions for expanding an airbag of the vehicle based on the collision type predicted by the collision predicting device;
• and
• an expansion controlling device including a flap member for controlling both the expansion size of the airbag and gas discharge from the airbag according to the conditions set by the setting device, wherein the flap member has one end fixed to the airbag and another end releasably connected to an inflator device for the airbag and has smaller and larger vents with one or the other of the vents being overlapped with an opening in the airbag depending on whether the other end of the flap member is connected or released from the inflator device based on the conditions set by the setting device.