GF91.40-P-0001LE Pre-Safe Function

GF91.40-P-0001LE PRE-SAFE Function

Function requirements, general
^ Circuit 15 On
^ Vehicle speed v > 30 km/h
^ Engine running (circuit 61 ON)

The status of circuit 15 is sent by the EIS [EZS] control unit (N73) to the interior CAN (CAN B).

The CDI control unit (N3/9) (diesel engine) or ME control unit (N3/10) (gasoline engine) provides the status "Engine running" on the chassis CAN (CAN E).

PRE-SAFE, general
The PRE-SAFE system is activated in critical driving states, i.e. in a potential accident situation. The goal is to create the most favorable conditions possible for the occupants during the expected accident by activating the functions before the actual impact.

The data from the ESP control unit (N47-5) (except model 221.095/195) or the regenerative braking system control unit (N30/6) (model 221.095/195) is evaluated for actuation of the PRE-SAFE functions.

The PRE-SAFE function consists of the following subfunctions:
^ Function sequence for registering of activation criteria
^ Function sequence when Electronic Stability Program (ESP) is disabled
^ Function sequence for reversible emergency tensioning retraction for driver and front passenger (with model 221)
^ Function sequence for adjusting front passenger seat
^ Function sequence for adjustment of individual rear seats (with model 221 with code (223) Rear bench seat with electrically adjustable outer seats with PRE-SAFE positioning function for outer seats and outer head restraints)
^ Function sequence for closing all door windows
^ Function sequence for automatic closing of tilting/sliding roof (SR) (with model 221 with code (414) Power glass tilting/sliding sunroof or with model 216)
^ Function sequence for adjustment of seat contour (with code (409) Left/right front multicontour seat or with code (432) Left and right dynamic multicontour seat) or with model 221 with code (406) Rear multicontour seats)
^ Display of fault messages function sequence
^ Function sequence for ending the PRE-SAFE functions

Function sequence for registering of activation criteria
The activation criteria are registered using the following subfunctions:
^ Function sequence for registering the PRE-SAFE longitudinal dynamics
^ Function sequence for registering the PRE-SAFE lateral dynamics
^ Vehicle environment function sequence

Function sequence for registering the PRE-SAFE longitudinal dynamics
- Emergency stop:
The driver steps hard on the brake pedal

- Sustained panic braking:
The driver continues to push the brake pedal down to the maximum pedal travel

- On vehicles with code (233) DISTRONIC PLUS, the radar sensors control unit (SGR) (N62/1) applies the vehicle brakes (PRE-SAFE brake) on the basis of the information from the DTR control unit (A89).

Detailed information on this is given in the function description "DISTRONIC PLUS".

Function sequence for determining the PRE-SAFE lateral dynamics
- Excessive oversteer:
A large rear-axle slip angle that can no longer be stabilized by the ESP.

- Excessive understeer:
A large front-axle slip angle pending for an extended period that can no longer be stabilized by the ESP

- Critical steering movement:
Driver steering movement which is probably due to a startled reaction and which may lead to instability of the vehicle. Activation does not take place until speeds of v > 140 km/h have been reached. The activation characteristics become more sensible with increasing speeds

Function sequence, sensing of vehicle environment
Radar sensors are installed in the front bumpers to prevent possible collision with vehicles or obstacles. Driving situations during which a hazard of possible collisions could occur:
- Intersection situation:
Vehicle enters intersection unexpectedly

- Sudden lane change situation:
Vehicle suddenly changes lanes immediately in front of driver

- Curve situation:
Unexpected obstacle appears suddenly in curve

The distance between the vehicle and recognized object (vehicle, obstacle) is sensed by the outer left front bumper radar sensor (A86/1b1), inner left front bumper radar sensor (A86/1b2), inner right front bumper radar sensor (A86/1b3) and outer right front bumper radar sensor (A86/1b4) at the current approach speed. The radar sensors (short range sensors) detect obstacles at a short distance up to s = 30 m and at an angle of up to 140°.

This allows obstacles to be recognized at an early time and reversible passenger protection measures (e.g. passenger fixation) to be initiated. The data for determination of the collision severity and collision time is read in by the radar sensor control unit and provided to the strength system control unit (N2/7).

Accordingly, the restraint system control unit can be actuated earlier.

The sequence of the PRE-SAFE situations is coordinated by the PRE-SAFE master. This is integrated into the ESP control unit or regenerative braking system control unit. If the PRE-SAFE recognizes a critical situation, it actuates the following actuators:
- Reversible emergency tensioning retractors for driver and front passenger
- Adjustment of the front passenger seat
- Closing windows in all doors
- Closing of tilting/sliding roof (SR) (with model 221 with code (414) Power glass tilting/sliding sunroof or model 216)

The signal front the front close-in radar sensors is sent to the radar sensors control unit via the drive train sensor CAN (CAN I) and evaluated.

Function sequence when the ESP is switched off
The activation threshold for the PRE-SAFE functions is increased, if the ESP has been shut off manually via the ESP OFF switch (S6/2s11) (model 221 up to 31.5.09) in the cockpit switch group (S6/2). The signals from the cockpit switch group are read in by the upper control panel control unit (N72/1) via the instrument panel LIN (LIN 1). The upper control panel control unit transmits the signals via the interior CAN to the central gateway control unit (N93). The central gateway control unit sends the signals via the chassis CAN CAN E) to the ESP control unit or to the regenerative braking system control unit.

The ESP OFF switch is eliminated on model 221 as of 31.5.09. On model 221 as of 1.6.09, the ESP can then be switched off using the left multifunction steering wheel button group (S110). The message is shown in the multifunction display (A1p13) in the instrument cluster (A1).

Function sequence for reversible emergency tensioning retraction for driver and front passenger (with model 221)
The left front reversible emergency tensioning retractor (A76) and the right front reversible emergency tensioning retractor (A76/1) reduce the existing seat belt slack in dangerous situations. Thus, the occupants are secured in position in the seats at an early point in time in order to prevent displacement.

The occupants are therefore held in a favorable seat position in the event of an accident, allowing the conventional restraint systems to have their optimum protective effect.

The reversible emergency tensioning retractors receive the retraction signal via the chassis CAN from the ESP control unit or from the regenerative braking system control unit.

The reaction of the reversible emergency tensioning retractors varies depending on the recognized PRE-SAFE situation:
- in the event of a longitudinal dynamics situation, the belt is tensioned as quickly as possible (within approx. t = 120 ms) to a defined power level
- in the event of a lateral dynamics situation, the tensioning time is parameterizable

At the end of the tensioning request, the belt is released again. The reversible emergency tensioning retractors are activated only if the vehicle speed is v > 30 km/h and the latches of the seat belts are inserted into the seat belt buckles.

This is recognized via the driver seat belt buckle and seat belt warning switch (S68/1) and the front passenger seat belt buckle and seat belt warning switch (S68/2) by the restraint system control unit.

The restrain system control unit sends the status of the buckle emergency tensioning retractors via the chassis CAN to the ESP control unit or to the regenerative braking system control unit. If the speed drops below v = 30 km/h during a PRE-SAFE situation, all PRE-SAFE functions remain active until the speed has dropped below v = 3 km/h.

Additional function requirements for adjusting the front passenger seat
^ Normalized front passenger seat
^ Front passenger seat occupied
^ Front passenger seat set to an unfavorable position

Function sequence for adjusting front passenger seat
Adjustment of the front passenger seat is used to move the front passenger into a favorable position in the event of an imminent impact.

The front passenger seat is adjusted according to whether the front passenger is strapped in or not strapped in.

The status of the front passenger seat belt buckle and seat belt reminder warning switch is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This routes the status via the interior CAN to the right front seat control unit (N32/2).

The following adjustments can be made by the right front seat control unit according to the current setting:
- Seat fore/aft position
- by the right front seat fore/aft adjustment motor (M28/1)

- Seat backrest angle
- by the right front backrest angle adjustment motor (M28/5)

- Seat cushion inclination
- by the right front seat cushion inclination motor (M28/9)

- Seat height
- by the right front seat height adjustment motor (M28/10)

The automatic adjustment of the front passenger seat can be interrupted at any time by operating the right front seat operation switch group (S23).

If a PRE-SAFE situation continues to be present, the front passenger seat is adjusted again via PRE-SAFE after the manual adjustment has been completed.

The adjustment process lasts until:
- The target area is reached (front passenger seat in ideal position)
- An impact occurs
- The PRE-SAFE situation ends

The front passenger seat does not automatically return to the position before the PRE-SAFE situation, but rather has to be adjusted via the right front seat operation switch group as necessary.

Additional function requirements for adjustment of individual rear seats (with model 221 with code (223) Rear seat bench with electrically adjustable outer seats with PRE-SAFE positioning function for outer seats and outer head restraints)
^ Seat adjustment normalized
^ Rear seats set to an unfavorable position

Function sequence for adjustment of individual rear seats (with model 221 with code (223) Rear seat bench with electrically adjustable outer seats with PRE-SAFE positioning function for outer seats and outer head restraints)
Rear seat adjustment is used to move the rear occupants into a favorable position in the event of an imminent impact. In this position, the restraint equipment can provide the best protective effect possible. Seat adjustment takes place depending upon whether the rear occupants are buckled up or no

The status of the left rear seat belt buckle switch (S68/11) and the right rear seat belt buckle switch (S68/12) is forwarded by the rear SAM control unit with fuse and relay module (N10/2) via the interior CAN to the central gateway control unit, and from there via the interior CAN to the rear seat control unit (N25/6).

The following adjustments can be made by the rear seat control unit according to the current setting:
- Inclination of head restraint
- by the left rear head restraint inclination adjustment motor (M18/15) and the right rear head restraint inclination adjustment motor (M18/16)

- Seat cushion inclination
- by the left rear seat cushion inclination adjustment motor (M18/19) and the right rear seat cushion inclination adjustment motor (M18/20)

- Seat fore/aft position
- by the left rear seat fore/aft adjustment motor (M18/17) and the right rear seat fore/aft adjustment motor (M18/18)

Seat adjustment if the occupants are buckled up Dependent upon how the rear seats are set, the:
- inclination of the head restraint is adjusted
- backrest is adjusted
- seat cushion inclination is adjusted

Seat adjustment if the occupants are not buckled up
The system moves the seat into a position that is suitable for situations that are unfavorable with regard to safety technology.

The adjustment process lasts until:
- The target area is reached (rear seats in ideal position)
- An impact occurs
- The PRE-SAFE situation ends

The PRE-SAFE function of the rear seats can be switched off via IS tester.

Function sequence for closing all door windows
The following control units receive the signal for the ESP control unit or regenerative braking system control unit to close the windows from the central gateway control unit via the interior CAN:
- Left door control unit (N69/1) (model 216)
- Left front door control unit (N69/1) (model 221)
- Right door control unit (N69/2) (model 216)
- Right front door control unit (N69/2) (model 221)
- Left rear door control unit (N69/3) (model 221)
- Right rear door control unit (N69/4) (model 221)

The windows are closed by the left front power window motor (M10/3), right front power window motor (M10/4), left rear power window motor (M10/5) and the right rear power window motor (M10/6) to a gap of s = 50 mm, to ensure that in the event of any subsequent impact the smoke particles generated by the pyrotechnical restraint equipment are then extracted.

The anti-pinch protection is active when the windows are closed via PRE-SAFE. If required, the closing process is reversed.

The closing process can be stopped at any time by a manual request from the following controls for the respective window:
- Driver power window outside mirror and trunk lid switch group (S20/1)
- Front passenger power window switch (S21/2)
- Left rear power window switch (S21/3) (model 221 without code (297) Roller sun blinds in rear doors, without code (413) Panoramic glass sunroof with top sliding sunroof, without code (540) Electric rear window roller blind)
- Right rear power window switch (S21/4) (model 221 without code (297) Roller sun blinds in rear doors, without code (413) Panoramic glass sunroof with top sliding sunroof, without code (540) Electric rear window roller blind)
- Power window/roller blind switch group, left rear door (S21/21) (model 221 with code (297) Roller sun blinds in rear doors, with code (413) Panoramic glass sunroof with top sliding sunroof or with code (540) Electric rear window roller blind)
- Power window/roller blind switch group, right rear door (S21/22) (model 221 with code (297) Roller sun blinds in rear doors, with code (413) Panoramic glass sunroof with top sliding sunroof or with code (540) Electric rear window roller blind)

If closing is activated via PRE-SAFE during an automatic lowering process, the automatic lowering process is aborted and closing is carried out via PRE-SAFE.

Once the PRE-SAFE situation has ended, the windows must be manually moved back into the desired position.

Functional sequence for automatic closing of tilting/sliding roof (SR) (on model 221 with code (414) Power glass tilting/sliding sunroof or on model 216)
Closing the tilting/sliding roof via PRE-SAFE is intended to prevent objects from penetrating the vehicle interior and stop the occupants' body parts (such as arms) from protruding from the vehicle if an accident occurs.

The overhead control panel control unit (N70) receives the ESP control unit request or regenerative braking system control unit from the central gateway control unit via the interior CAN and triggers the closure of the tilting/sliding roof.

The tilting/sliding roof is closed leaving a gap of s = 50 mm in order to ensure that, in the event of a possible subsequent impact, smoke particles generated by the pyrotechnical restraint systems can escape.

Closing can be aborted at any time by manually operating the roof switch (N70s1).

The anti-pinch protection is active when the tilting/sliding roof is being closed. If required, the closing process is reversed. If closing is activated via PRE-SAFE during a manual adjustment, the manual adjustment request is completed first and then closing via PRE-SAFE.

If closing is activated via PRE-SAFE during an automatic process, the automatic process is aborted and closing is carried out via PRE-SAFE.

Once the PRE-SAFE situation has ended, the tilting/sliding roof must be manually moved back into the desired position.

The PRE-SAFE function of the SR can be switched off via IS tester.

Function sequence for adjustment of the seat contour (with code (409) Left/right front multicontour seat or with code (432) Left and right dynamic multicontour seat) or with model 221 with code (406) Rear multicontour seats)
The purpose of inflating the side inserts in the seats is to centrally secure the occupants in position in the seats. In this position, the restraint equipment can provide the best protective effect possible. The following control units receive the signal for the ESP control unit or regenerative braking system control unit to close the windows from the central gateway control unit via the interior CAN:

With code (409) Left/right front multicontour seats:
- Left front multicontour backrest control unit (N32/15)
- Right front multicontour backrest control unit (N32/16)

With code (432) Left and right dynamic multicontour seat:
- Left front dynamic seat control unit (N32/19)
- Right front dynamic seat control unit (N32/22)

For model 221 with code (406) Rear multicontour seats:
- Left rear multicontour backrest control unit (N32/20)
- Right rear multicontour backrest control unit (N32/21)

The seat contour is adjusted until the PRE-SAFE specified pressure is reached or until the end of the PRE-SAFE situation. Once the PRE-SAFE situation has ended, the filling status of the side inserts is returned to the respective initial status it had before PRE-SAFE was activated.

The adjustment of the seat contour can be aborted at any time via a manual adjustment or by means of a memory request.

Display of fault messages function sequence
If a fault is detected in the reversible emergency tensioning retractors, this is indicated on the multifunction display in the instrument cluster. Faults of other components that are part o PRE-SAFE are not displayed as PRE-SAFE faults.

Function sequence for ending the PRE-SAFE functions
PRE-SAFE is deactivated as soon as a PRE-SAFE longitudinal dynamics situation or lateral dynamics situation is no longer present.

The ESP control unit or regenerative braking system control unit sends a signal to switch off the PRE-SAFE functions via the chassis CAN.
The signal is transmitted to the control units involved through the central gateway control unit via the interior CAN.

The adjustment of the front passenger seat and the individual rear seats is canceled if the PRE-SAFE position has not yet been reached.

Closing of the windows and the tilting/sliding roof is not aborted. The automatic closing function continues until the PRE-SAFE position has been reached.

The reversible emergency tensioning retraction is released as soon as the vehicle acceleration has dropped below a value of a = 0.3 g.

The reversible emergency tensioning retractors are equipped with a mechanical acceleration sensor, which locks the belt extension in the event of any vehicle acceleration of a > 0.3 g. For this reason, the belt may remain mechanically locked even when the reversible tensioning retraction has been completed.

In the event of an impact that is detected by the restraint systems control unit, all adjustments are stopped immediately.