Vehicle occupant restraint system

A vehicle occupant restraint system comprising:

• a seatbelt device configured to be able to restrain an occupant seated on a vehicle seat by using a webbing of which one end is wound on a take-up device and the other end is fixed to the vehicle seat or a vehicle body and configured to be able to take up the webbing by driving a motor provided in the take-up device, the seatbelt device includes an emergency lock mechanism configured to, when a take-up shaft of the take-up device rotates at a predetermined rotation speed or higher, stop rotation of the take-up shaft;
• a road surface condition detection unit configured to detect a road surface condition ahead of a vehicle in a direction of travel;
• a vehicle status detection unit configured to detect a status of the vehicle;
• and
• a controller configured to compute an estimated acceleration that is estimated to be applied to the vehicle and a time that is taken from present time to acceleration occurrence time at which the estimated acceleration is anticipated to occur from the road surface condition detected by the road surface condition detection unit and the status of the vehicle, detected by the vehicle status detection unit, and, when the estimated acceleration is higher than or equal to a predetermined acceleration threshold and the time that is taken from present time to acceleration occurrence time at which the estimated acceleration is anticipated to occur becomes shorter than or equal to a predetermined value, take up the webbing by a predetermined amount by driving the motor,
• the controller is configured to be able to control the motor in a normal control stage in which the motor is driven at a normal driving force and a preliminary control stage in which the motor is driven at a driving force less than the normal driving force, and the controller is configured to, when the time that is taken from present time to acceleration occurrence time at which the estimated acceleration is anticipated to occur becomes shorter than or equal to the predetermined value, drive the motor in the preliminary control stage and then drive the motor in the normal control stage to activate the emergency lock mechanism, and
• the controller is configured to drive the motor such that the take-up shaft reaches the predetermined rotation speed in the normal control stage.