Preventive Occupant Protection System, Basic Function - GF91.40-S-9900A

Model All (Light transporter) 

Overview 

This document contains the following information:

• General 
• PRE-SAFE® function requirements 
  • Function triggers 
• Preventive occupant protection measures 
  • Reversible emergency tensioning retraction 
  • Seat adjustment (vehicles with seat adjustment with memory function) 
  • Close sliding sunroof (vehicles with sliding sunroof or panoramic sliding sunroof). 
  • Close side window, leaving a small gap. 
  • Measures upon detecting a thermal event (vehicles with electric drive) 

General 

The approach of the preventive occupant protection system is to recognize potential risks of accident at their origin. For this purpose, various sensory capabilities are used, not least through the networking with driver assistance systems.

In hazard situations, different actuators are actuated according to the situation in order to deploy their protective effect before the actual impact.

If the accident fails to happen, the fully reversible systems can be restored to their default positions and are immediately ready for operation again.

Depending on the equipment installed, the preventive occupant protection system can be extended by the following functions:

• Measures upon detecting a thermal event of the high-voltage battery (electric vehicles)

PRE-SAFE® function requirements 

• Circuit 15 ON

Function triggers 

The preventive occupant protection system defines the driving state based on the following parameters:

• Vehicle deceleration
• Wheel speeds
• Natural dynamics of the vehicle (yaw rate, lateral acceleration)
• Steering angle
• Thermal event of the high-voltage battery (electric vehicles)

The following situations are classified as accident-critical:

• Emergency braking: Rapid brake pedal operation (startle response).
• Maximum full-stop braking: The driver's deceleration request is significantly greater than the vehicle deceleration that is physically possible (e.g. aquaplaning, ice, or snow). Strong interventions of the antilock braking system (ABS).
• Severe oversteer: Swerving of rear end, combined with strong ESP® stabilization interventions.
• Severe understeer: The vehicle pushes over the front wheels. Strong ESP® stabilization interventions.
• Side wind stabilization: Drifting from the lane, combined with strong ESP® stabilization interventions.
• Critical steering movements: Rapid steering at high speeds (startle response by the driver combined with excessive stress).
• Secondary accident: The occurrence of another crash after an accident.
• Vehicles with radar-assisted traffic area monitoring:
  • Strong brake force boosting by the Active Brake Assist: Risk of collision in linear or cross traffic.
  • Autonomous brake application by the Active Brake Assist: Risk of collision in linear traffic.
  • Autonomous course correction by the Blind Spot Assist: Course-correcting brake application when there is a risk of collision with vehicles to the side.
  • Collision object detection: Detection of an imminent impact.

The activation threshold for the preventive occupant protection measures is modified according to the following variables:

• ESP® mode
• Drive program (vehicles with automatic transmission)

Preventive occupant protection measures 

The preventive occupant protection system activates the following measures for occupant protection in critical driving situations:

• Reversible seat belt tensioning (driver and front passenger) 
• Seat adjustment 
• Close sliding sunroof (vehicles with sliding sunroof or panoramic sliding sunroof). 
• Close side window, leaving a small gap. 
• Measures upon detecting a thermal event (vehicles with electric drive) 

All measures are deactivated as soon as the prevailing situation is no longer evaluated as critical.

Reversible emergency tensioning retraction 

The reversible emergency tensioning retraction reduces the amount of seat belt slack by tensioning the front seat belts. The driver and front passenger are held better in the seats. Depending on the situation, the seat belt is tightened with varying force and speed.

As soon as the seat belt is fastened, the belt adjuster reduces the existing slack by tightening the seat belts. The function is available for the front seats. It can be switched on and off via the vehicle settings controls.

Seat adjustment 

To enable the best possible occupant protection, the preventive occupant protection system requests the adjustment of the front passenger seat.

Priority applies to manual adjustment, i.e.:

• If the seat is being adjusted manually when the PRE-SAFE® situation occurs, the seat follows this manual adjustment request. As soon as the switch is released, the seat follows the PRE-SAFE® request.
• Conversely, any manual operation of the seat adjustment switch will interrupt the PRE-SAFE® adjustment and the seat will remain stationary.

The following settings can be made:

• The front passenger seat is moved to a more favorable position in terms of safety. Depending on the current seat position, the following adjustments are made:
  • Backrest inclination
  • Seat fore-and-aft position
  • Seat cushion inclination
• The air cushions of the lumbar support are deflated. The occupant thus sits lower in the seat.

The adjustments are completed when the target seat position is reached. After completion or cancellation of the measure, the front passenger seat remains in the held position.

Close sliding sunroof (vehicles with sliding sunroof or panoramic sliding sunroof) 

The sliding sunroof is closed completely by the preventive occupant protection system if it was open in the tilt position previously. If the sliding sunroof was previously open in the sliding direction, it is closed leaving a small gap.

If the vehicle rolls over, for example, this makes it less likely that objects can enter the vehicle interior and that limbs of the occupants can protrude from the vehicle. After completion or cancellation of the measure, the sliding sunroof remains in the held position.

Close side windows, leaving a small gap 

The side windows are closed, provided that there is sufficient time, leaving a gap of approx. 50 mm. This prevents objects from entering the vehicle and limbs from protruding from the vehicle. Furthermore, it allows the smoke particles arising from the activation of the restraint equipment to disperse quickly.

Any active automatic sequence in the opening direction is aborted. However, manual adjustment (first notch of the switch) has priority and is carried out. When the side windows are closing, the automatic reversing function is active. If required, the closing process is reversed. After completion or cancellation of the measure, the side windows remain in the held position.

Function requirements upon detecting a thermal event (vehicles with electric drive) 

• Entire CAN bus system not in idle mode (e.g. during active charging process of a stationary vehicle).

Measures upon detecting a thermal event (vehicles with electric drive) 

In the event of an increase in the internal cell pressure or a drop in the insulation value or overheating of the high-voltage battery, appropriate measures are taken by the system. The measures are split up into 3 warning stages.

For warning level 1, the following measures are initiated:

• Wake-up of CAN bus system in charging mode
• Cancellation of an active charging process
• Sending of a push message (on vehicles with communications module)

If warning level 2 is reached or if the signal fails after previously receiving the signal of warning level 1, further functions are initiated:

• Warning message through the instrument cluster
• Emergency unlocking
• Automatic closing of side windows and sliding roof or panoramic sliding sunroof (except USA and Canada)
• Charging cable release (during charging process)
• Climate control; switchover to air recirculation mode
• Automatic emergency call (vehicles with HERMES communication module)
• Cancellation of autonomous driving functions or request for driver to take over (as from warning level 3 during driving operation)

If, after receiving warning level 1 or 2, warning level 0 is received again, the corresponding measures are suspended again.

	Function schematics
	Trigger preventive occupant protection system, function schematic	Model 447.8 with code XM0 (Facelift) except code M7E (Electric motor 150 kW/battery 60 kWh (usable)) except code ME4 (Electric motor 145 kW)	PE91.40-S-2500TRA
		Model 447.6 with code XM0 (Facelift) except code M8E (Electric motor 85 kW/battery 60 kWh (usable)) except code ME0 (Electric motor 85 kW) Model 447.7 with code XM0 (Facelift) except code M7E (Electric motor 150 kW/battery 60 kWh (usable)) except code ME0 (Electric motor 85 kW) except code ME4 (Electric motor 145 kW)	PE91.40-S-2500TRB
		Model 447.8 with code M7E (Electric motor 150 kW/battery 60 kWh (usable)) Model 447.8 with code ME4 (Electric motor 145 kW)	PE91.40-S-2500TRC
		Model 447.6 with code M8E (Electric motor 85 kW/battery 60 kWh (usable)) Model 447.6 with code ME0 (Electric motor 85 kW) Model 447.7 with code M7E (Electric motor 150 kW/battery 60 kWh (usable)) Model 447.7 with code ME4 (Electric motor 145 kW)	PE91.40-S-2500TRD
	Further basic functions
	Traffic area monitoring, basic function		GF54.71-S-1000A
	Speaker system, basic function		GF82.62-S-9900A
	Front seat electrical seat adjustment, basic function		GF91.10-S-9900A
	Control units
	Electronic Stability Program control unit, basic function		GF42.45-S-9890A
	Reversible belt tensioner, basic function		GF91.40-S-9890A