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Adaptive Brake Function - GF42.47-S-0002TRA

Model 447 

Except Code XM0 (Facelift) 

Model 448 

G16501096Courtesy of MERCEDES-BENZ USA

Shown on model 447.8 without code ZG2 (4MATIC) 

G16501097Courtesy of MERCEDES-BENZ USA

Shown on model 447.6/7 

Function requirements, general 

ADAPTIVE BRAKE, general 

ADAPTIVE BRAKE uses various driver assistance systems to assist the driver in dangerous situations which occur suddenly, and thus enhances active safety.

For this purpose, the Electronic Stability Program (ESP) control unit (N30/4) evaluates the following signals:

IMPORTANT There are no differences between the versions with respect to the subfunctions described below.

The system is made up of the following subfunctions:

Function sequence for ESP® 

ESP® prevents the vehicle from breaking away when oversteered or understeered. Within physical limits it ensures that the vehicle does not deviate from the course specified by the driver.

Brake forces are produced selectively at the individual wheels to correct any deviations.

Furthermore, reduction of the drive torque takes place in order to increase driving stability.

The Electronic Stability Program (ESP) control unit (N30/4) processes the following measured quantities to determine the vehicle behavior:

The yaw rate (speed of vehicle rotation about vertical axis), the lateral acceleration and the steer angle of the front wheels (calculated from the steering wheel angle) are used to determine the lateral forces on the wheels. The longitudinal forces on the wheels are calculated using the engine torque, transmission shift stage and brake pressure at each wheel.

If the measured yaw rate does not match the specified value or if the determined side-slip angle (angle between vehicle longitudinal axis and direction of movement of the vehicle's center of gravity) is too large, the Electronic Stability Program (ESP) control unit (N30/4) generates a signal for brake force buildup or reduction for the relevant wheel. The resulting forces stabilize the vehicle.

A distinction is made between the following intervention types:

Intervention in the case of oversteer 

If the vehicle begins to oversteer, brake pressure is built up at the outer front wheel. The resulting forces cause a yawing moment which counteracts rotation of the vehicle. The vehicle speed decreases as a result of the brake force at the front wheel, which also enhances stability.

Intervention in the case of understeer 

If the vehicle understeers, the maximum possible lateral force at the front axle has been exceeded. In other words, the vehicle pushes via the front axle to the outer edge of the curve.

The resulting instability is counteracted by means of a reduction in drive torque and the following brake interventions at up to 3 wheels:

Depending on the brake force, a torque is generated which causes the vehicle to rotate with a simultaneous reduction in speed. This has a considerable stabilizing effect. The Electronic Stability Program (ESP) control unit (N30/4) sends a signal to reduce the drive torque via the chassis CAN (CAN E) to the CDI control unit (N3/33 or N3/36) or the ME-SFI control unit (N3/34), which then reduces the engine power accordingly.

On vehicles with transmission 722.9, an imminent shift operation is suppressed during the control intervention function. For this purpose, the Electronic Stability Program (ESP) control unit (N30/4) sends a signal via the chassis CAN (CAN E) and drive train CAN (CAN C) with the interface for the CDI control unit (N3/33 or N3/36) or ME-SFI control unit (N3/34), to the fully integrated transmission control (VGS) electric controller unit (N15/11). This controller unit suppresses the shift operation.

EBD function sequence 

The EBD provides assistance when the driver applies medium force to the brake pedal.

The EBD prevents overbraking at the rear axle and increases vehicle stability when braking on bends. To do so, the EBD selectively reduces the brake pressure at the rear wheels. The side-slip angle is determined using the yaw rate.

Function sequence of exhaust test, dynamometer test mode 

For vehicle test purposes, the ADAPTIVE BRAKE system can be set to roller dynamometer mode if the workshop menu is activated via the instrument cluster (IC) control unit (A1/1) and the engine is then started. ESP®, ABS, ASR and EBD are then switched to passive. The anti-lock braking system indicator lamp (A1/1e17), the Electronic Stability Program warning lamp (A1/1e41) and the brake system warning lamp (A1/1e51) in the instrument cluster (IC) control unit (A1/1) light up. Additionally, a corresponding message is shown in the instrument cluster (IC) control unit (A1/1).

When the dynamometer test mode is activated, the instrument cluster (IC) control unit (A1/1) sends the corresponding signal via chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4); on model 447.8 or model 448.8, additionally via user interface CAN (CAN HMI) with the interface for gateway for user interface CAN (N93/4).

ABS function sequence 

The ABS prevents the wheels from blocking when braking and as a result maintains the steerability and driving stability during vehicle deceleration. If a locking wheel is detected by means of the signals from the rpm sensors (L6/1, L6/2, L6/3, L6/4) by the Electronic Stability Program (ESP) control unit (N30/4) via direct lines, the brake pressure is reduced at the corresponding wheel until the wheel begins to turn again.

Function sequence for acceleration skid control (ASR), electronic traction system (ETS) 

The ASR and ETS prevent the drive wheels from spinning excessively during vehicle operation, and also provide improved driving stability with increased traction potential across the entire vehicle speed range. Spinning of the drive wheels is detected by means of the signals from the rpm sensors (L6/1, L6/2, L6/3, L6/4) by the Electronic Stability Program (ESP) control unit (N30/4) via direct lines. Wheel spinning is countered by reduction of the drive torque.

For this purpose, the Electronic Stability Program (ESP) control unit (N30/4) sends a signal to reduce the drive torque via the chassis CAN (CAN E) to the CDI control unit (N3/33 or N3/36) or the ME-SFI control unit (N3/34), which then reduces the engine power accordingly. A check is continuously performed to establish whether the drive torque specified by the driver via the accelerator pedal module (B37/4) can be permitted again, e.g. due to an improvement in road surface adhesion. The specified drive torque is transmitted from the accelerator pedal module (B37/4) to the CDI control unit (N3/33 or N3/36) or the ME-SFI control unit (N3/34) via a direct line. Targeted interventions by the brake system at the spinning drive wheel transfer the drive torque to the opposite drive wheel.

BAS function sequence 

The BAS detects emergency braking situations based on rapid actuation of the brake pedal and, if necessary, increases the brake pressure in order to achieve maximum deceleration. For this purpose, the Electronic Stability Program (ESP) control unit (N30/4) evaluates the increase in pressure in the brake system and initiates an emergency stop if a certain triggering threshold is exceeded.

Hill Start Assist function sequence 

When starting off, the Hill-Start Assist prevents the vehicle from rolling back opposite the travel direction during the time it takes for the driver to change from the brake pedal to the accelerator pedal.

The function is released automatically if, when the vehicle is stationary, an uphill or downhill gradient which would cause the vehicle to roll opposite the direction of the engaged gear range is detected by the Electronic Stability Program (ESP) control unit (N30/4). The Electronic Stability Program (ESP) control unit (N30/4) reads in the status of the brake light switch (S9/3) directly and in this way detects the status of the brake pedal.

On model 447.8 or model 448.8, the electric parking brake (EFB) control unit (A13) sends the status of the electric parking brake via front end CAN (CAN G), electronic ignition lock (EIS) control unit (N73) and chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4).

Following release of the brake pedal and detection of a start-off request, reduction of the brake pressure is controlled by means of torque balancing system. This system takes into consideration the incline output torque, the total braking torque and the available drive torque.

When the start-off torque is high enough, the Hill-Start Assist is deactivated and the vehicle starts off without rolling in the undesired direction of travel.

If the driver does not depress the accelerator pedal, the pressure in the brake system is reduced after 2 s (with transmission 710.5 or 711.6) or 0.8 s (with transmission 722.9).

The Hill-Start Assist is terminated immediately in the following cases:

Additional function requirements for Downhill Speed Regulation (DSR) (With Code ZG2 (4MATIC) and without code MW1 (Engine run-on control (MWS)) and without code ZK2 (Taxi version with emergency alarm system) and without code ZK3 (Taxi version without emergency alarm system)) 

IMPORTANT The status of the Downhill Speed Regulation button (N74s6) is sent by the signal acquisition and actuation module (SAM) control unit (N10/1) via the interior CAN (CAN B), the electronic ignition lock (EIS) control unit (N73) and the chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4).

Function sequence for Downhill Speed Regulation (DSR) (With Code ZG2 (4MATIC) and without code MW1 (Engine run-on control (MWS)) and without code ZK2 (Taxi version with emergency alarm system) and without code ZK3 (Taxi version without emergency alarm system)) 

The downhill speed regulation function maintains the setting speed by means of specific intervention by the brake system. If the function requirements are fulfilled and the accelerator pedal, brake pedal or TEMPOMAT lever (S40/4) is actuated, the setting speed is then stored. This speed can be dropped below or exceeded at any time by braking or accelerating.

The status of the accelerator pedal module (B37/4) is sent by the CDI control unit (N3/33 or N3/36) or the ME-SFI control unit (N3/34) via the chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4).

The status of the brake light switch (S9/3) is read in by the Electronic Stability Program (ESP) control unit (N30/4) via a direct line.

The status of the TEMPOMAT lever (S40/4) is sent by the steering column tube module control unit (N80) via the chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4).

The downhill speed regulation function can only be activated at a speed of ≤ 40 km/h. Above 40 km/h, the multifunction display (A1/1p13) shows the DSR symbol and the message "Drive at max. 40 km/h".

If the downhill speed regulation function is active, the indicator lamp of the Downhill Speed Regulation button (N74s6) lights up. Between 4 and 18 km/h, the multifunction display (A1/1p13) shows the DSR symbol and the stored setting speed. The corresponding request for this is sent by the Electronic Stability Program (ESP) control unit (N30/4) via chassis CAN (CAN E) with the interface for electronic ignition lock (EIS) control unit (N73); on model 447.8 or model 448.8, additionally via user interface CAN (CAN HMI) with the interface for gateway for user interface CAN (N93/4).

If, with downhill speed regulation active, the vehicle is accelerated to above 18 km/h, the downhill speed regulation function remains switched on but is no longer active. The DSR symbol disappears in the multifunction display (A1/1p13). If the vehicle then drops below 18 km/h, the downhill speed regulation function brakes the vehicle again to the stored setting speed.

The downhill speed regulation function can be switched off using the Downhill Speed Regulation button (N74s6) or by exceeding a speed of 45 km/h.

Additional function requirements - dry braking 

IMPORTANT The status of the windshield wiper system is sent by the signal acquisition and actuation module (SAM) control unit (N10/1) via the interior CAN (CAN B), the electronic ignition lock (EIS) control unit (N73) and the chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4).

Dry braking function sequence 

The dry braking function enhances the performance of the brakes on the front axle in wet driving conditions. The brake linings are applied cyclically for a short time (approx. 0.5 s) with a brake pressure of 1 bar to remove the film of water from the brake disks. This improves the response time of the brake.

Function sequence for precharging dependent on accelerator pedal operation 

When an emergency braking situation is detected, the brake linings are brought into contact with the brake disks. The clearance between the brake lining and brake disk is thus compensated before the driver operates the brake. The response time of the brake is improved and a shorter braking distance is achieved.

Emergency braking is detected on the basis of the release gradient of the accelerator pedal. If a rapid release of the accelerator pedal is detected, the system assumes that the driver intends to brake. The function is activated and a brake pressure of 2 to 3 bar is requested. For this purpose, the CDI control unit (N3/33 or N3/36) or the ME-SFI control unit (N3/34) reads in the corresponding signal from the accelerator pedal module (B37/4) via a direct line and sends this signal via the chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4).

IMPORTANT In order to adapt the calculated triggering threshold of the release gradient to the driver behavior, a learning algorithm is implemented which places the driver in the category "normal driver" or "hectic driver" on the basis of the average rate at which the accelerator pedal is released.

Function sequence for precharging depending on lateral acceleration 

During dynamic cornering, the brake linings are brought into contact with the front axle brake disks. This closes the air gap between the brake lining and brake disk in order to achieve the required braking power at the corresponding wheel as quickly as possible in the event of ESP® intervention.

Function sequence for ASR passive switching 

The ASR function can be switched to passive mode while the vehicle is in operation.

The Electronic Stability Program (ESP) control unit (N30/4) receives the corresponding request in the following way:

If ASR is switched to passive, the Electronic Stability Program warning lamp (A1/1e41) lights up in the instrument cluster (IC) control unit (A1/1).

IMPORTANT With the ASR switched to passive, only the control threshold for engine intervention is affected. The control thresholds are raised in the case of ASR switched to passive. ABS cannot be deactivated.

Function sequence for ESP® trailer stabilization (With Code Q22 (Trailer hitch with non-removable ball head) or With Code Q24 (NAFTA trailer crossmember, towing capacity 5000Ibs) or With Code Q50 (Trailer hitch with removable ball head)) 

The ESP® trailer stabilization detects rocking motion in the tractor/trailer combination based on the yawing vibrations caused in the tractor vehicle by the trailer. Instability of the tractor/trailer combination is detected by the Electronic Stability Program (ESP) control unit (N30/4).

IMPORTANT The ESP® trailer stabilization only functions if a trailer hitch was installed at the factory. The status of the trailer recognition control unit (N28/1) is sent via the interior CAN (CAN B) and chassis CAN (CAN E) with the interface for the electronic ignition lock (EIS) control unit (N73), to the Electronic Stability Program (ESP) control unit (N30/4). ESP® trailer stabilization is deactivated on retrofitted trailer hitches.

The ESP® trailer stabilization stabilizes the tractor/trailer combination by means of brake pressure requests on alternating sides of the front axle and, if necessary, slows down the tractor/trailer combination by reducing engine torque and by building up pressure at all wheels. This does not change the critical speed.

Function sequence for PRE-SAFE® (With Code JP1 (PRE-SAFE)) 

PRE-SAFE® is activated in critical driving conditions, 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.

PRE-SAFE® is integrated in the Electronic Stability Program (ESP) control unit (N30/4). If the Electronic Stability Program (ESP) control unit (N30/4) detects one of the following situations, PRE-SAFE® is activated:

The PRE-SAFE® system is described in a separate function description.

Additional requirements for standstill control (SSC) (with transmission 722.9 and With Code ET4 (DISTRONIC PLUS) or With Code EZ7 (Active Parking Assist)) 

Function sequence for standstill control (SSC) (with transmission 722.9 and With Code ET4 (DISTRONIC PLUS) or With Code EZ7 (Active Parking Assist)) 

The standstill control monitors the DISTRONIC PLUS driver assistance system below a speed of 3 km/h until the vehicle has come to a safe standstill. Within this vehicle speed range, the SSC is responsible for the transfer to a safe standstill when a securing event occurs.

When the vehicle is at a safe standstill, the rolling monitoring function of the SSC is requested by the driver assistance system. If vehicle rolling is detected, the brake pressure is increased until the vehicle is stationary again. Furthermore, leakage compensation is additionally active when the vehicle is at a safe standstill. If the brake pressure measured by means of the circuit pressure sensors drops relative to the specified pressure request of the SSC, the specified pressure of the SSC is restored by means of an active pressure buildup.

Securing the vehicle by means of the SSC is necessary if the following events occur:

IMPORTANT The status of the driver seat belt buckle switch is detected by the driver seat belt buckle restraint system switch (S68/1) and read in by the Supplemental Restraint System (SRS) control unit (N2/18). The Supplemental Restraint System (SRS) control unit (N2/18) sends the status via the chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4) and, on model 477.8, additionally to the gateway for the user interface CAN (N93/4).

Door contact plausibility check 

The plausibility check detects a fault along the signal path from the left front door control unit (N69/3), via the interior CAN (CAN B) and chassis CAN (CAN E), with the interface for the electronic ignition lock (EIS) control unit (N73), to the Electronic Stability Program (ESP) control unit (N30/4). If, as the result of an electrical or mechanical fault, "Driver door closed" is wrongly detected although the driver door is open, this is detected by the door contact plausibility check in the SSC and a corresponding fault is stored in the Electronic Stability Program (ESP) control unit (N30/4).

SSK deactivation 

Deactivation of the SSC is signaled to the connected control units via the chassis CAN (CAN E). Activation of the driver assistance system is no longer possible. Securing of the vehicle is additionally requested immediately if the SSC is deactivated.

Safety strategy, request engage "P" or Emergency-P path (with transmission 722.9) 

The safety strategy is implemented via the intelligent servo module (ISM) for DIRECT SELECT control unit (A80). The Electronic Stability Program (ESP) control unit (N30/4) sends a request to engage gear range "P" via the chassis CAN (CAN E), electronic ignition lock (EIS) control unit (N73), CDI control unit (N3/33 or N3/36) or ME-SFI control unit (N3/34) and drive train CAN (CAN C) to the intelligent servo module (ISM) for DIRECT SELECT control unit (A80). The vehicle is secured after gear range "P" has been engaged and after the intelligent servo module (ISM) for DIRECT SELECT control unit (A80) has sent a corresponding feedback signal to the Electronic Stability Program (ESP) control unit (N30/4). The existing brake pressure at the wheels is reduced and the SSC becomes inactive.

If the intelligent servo module (ISM) for DIRECT SELECT control unit (A80) does not signal engagement of gear range "P" within a defined time, the Emergency-P function of the electronic ignition lock (EIS) control unit (N73) forces gear range "P" to be engaged.

To do so, the electronic ignition lock (EIS) control unit (N73) also receives the request to engage gear range "P" from the Electronic Stability Program (EPS) control unit (N30/4) via the chassis CAN (CAN E) and sends this request to the intelligent servo module (ISM) for DIRECT SELECT control unit (A80). If the electronic ignition lock (EIS) control unit (N73) does not receive feedback from the intelligent servo module (ISM) for DIRECT SELECT control unit (A80) within a defined time, the Emergency-P path is energized via a direct line by the electronic ignition lock (EIS) control unit (N73) after being enabled by the intelligent servo module (ISM) for DIRECT SELECT control unit (A80), and engagement of gear range "P" is forced by a spring mechanism in the intelligent servo module (ISM) for DIRECT SELECT control unit (A80).

Additional function requirements for HOLD function (model 447.8 or model 448.8 with transmission 722.9 and With Code ET4 (DISTRONIC PLUS) or With Code EZ7 (Active Parking Assist)) 

Function sequence for HOLD function (model 447.8 or model 448.8 with transmission 722.9 and With Code ET4 (DISTRONIC PLUS) or With Code EZ7 (Active Parking Assist)) 

The HOLD function assists the driver when driving off and maneuvering on a hill as well as during waiting times in traffic. It maintains the brake pressure for max. 20 min without the brake pedal being depressed. The SSC function is used to detect when the vehicle is at a standstill.

If the function requirements are fulfilled, the HOLD function can be activated by depressing the brake pedal followed by quickly and fully depressing the brake pedal. The HOLD symbol then appears in the multifunction display (A1/1p13).

The HOLD function is deactivated in the following cases:

With the HOLD function activated, gear range "P" is engaged automatically in the following cases:

Additional function requirements for Crosswind Assist 

Function sequence for Crosswind Assist 

The Crosswind Assist function assists the driver in the event of strong crosswinds and minimizes the vehicle's yaw response and the track offset. The Electronic Stability Program (ESP) control unit (N30/4) detects the movement of the vehicle when it encounters strong gusts of wind. For this purpose, the steering column tube module control unit (N80) sends the steering wheel angle signal via chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4); on model 447.8 or model 448.8, additionally via the interface for the gateway for user interface CAN (N93/4). Furthermore, the Electronic Stability Program (ESP) control unit (N30/4) receives the wheel speed signals from the rpm sensors (L6/1, L6/2, L6/3, L6/4).

System fault display function sequence 

The driver is informed about the system status and about faults by the following displays in the instrument cluster (IC) control unit (A1/1):

If the Electronic Stability Program (ESP) control unit (N30/4) fails, basic braking without ABS is always available.

IMPORTANT

Model 447.8

except code XM0 (Facelift)

Model 448.8

The status of the brake fluid level switch (S11) is read in by the signal acquisition and actuation module (SAM) control unit (N10/1) and sent via the interior CAN (CAN B), electronic ignition lock (EIS) control unit (N73) and chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4) and to the instrument cluster (IC) control unit (A1/1).

IMPORTANT

Model 447.8

except code XM0 (Facelift)

Model 448.8

The status of the brake fluid level switch (S11) is read in by the signal acquisition and actuation module (SAM) control unit (N10/1). The latter sends the corresponding signal via the interior CAN (CAN B), electronic ignition lock (EIS) control unit (N73) and chassis CAN (CAN E) to the Electronic Stability Program (ESP) control unit (N30/4) as well as via the interior CAN (CAN B), gateway for user interface CAN (N93/4) and user interface CAN (CAN HMI) to the instrument cluster (IC) control unit (A1/1).

  Electrical function schematic for ADAPTIVE BRAKE Model 447.6/7 except code XM0 (Facelift) PE42.47-S-2051-97TRB
    Model 448.7 PE42.47-S-2051-97TRA
    Model 448.7 PE42.47-S-2051-97VDB
    Model 448.8 PE42.47-S-2051-97VDA
  Overview of system components of ADAPTIVE BRAKE   GF42.47-S-9996TRA 
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