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ADAPTIVE BRAKE Function - GF42.47-P-0002GW

Model 463 (except 463.342) as of model year 2013 up to model year 2019 

Model 463.342 

G13668470Courtesy of MERCEDES-BENZ USA

Block diagram 

Function requirements, general 

ADAPTIVE BRAKE, general 

ADAPTIVE BRAKE assists the driver in dangerous situations which occur suddenly, and thus enhances active safety.

To do so, the Electronic Stability Program control unit evaluates the following variables:

ADAPTIVE BRAKE is available in 2 variants:

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

The system is made up of the following subfunctions:

Additional function requirements for ESP® 

Function sequence for ESP® 

ESP® prevents the vehicle from breaking away when oversteering or understeering. It ensures that the vehicle does not deviate from the course specified by the driver (within physical limits). 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 control unit processes the following measured quantities to determine the vehicle behavior:

Differentiation 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 reduction in lateral force at the outer front wheel generates a yawing moment which counteracts the tendency of the vehicle to rotate inward. 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 arises which leads to the vehicle turning in with a simultaneous speed reduction, leading to a considerable stabilizing effect.

The Electronic Stability Program control unit sends the request to reduce the drive torque via chassis CAN 1 to the CDI control unit (engine 642) or to the ME-SFI control unit (engine 157, 273).

On vehicles with engine 176, the Electronic Stability Program control unit sends the request to reduce the drive torque via drive train CAN 1, the powertrain control unit and drive train CAN to the ME-SFI control unit.

The CDI control unit or the ME-SFI control unit then reduces the engine power accordingly.

A pending shift operation is suppressed for the duration of control intervention. For this purpose, the Electronic Stability Program control unit sends a corresponding signal over suspension CAN 1, the CDI control unit (engine 642) or ME-SFI [ME] control unit (engine 157, 273) or powertrain control unit (engine 176) and drive train CAN to the fully integrated transmission control unit. The fully integrated transmission control unit suppresses the shift operation.

EBD function sequence 

The EBD [EBV] function supports the driving stability of the vehicle. EBD [EBV] is active during mid and high level vehicle decelerations during the brake actuation. EBD is operational before the ABS becomes active, and prevents the rear axle from overbraking. This is achieved by brake pressure limitation at the rear axle as soon as the rpm sensors detect potential overbraking.

Function sequence of exhaust test, dynamometer test mode 

For vehicle test purposes, the ADAPTIVE BRAKE can be set to dynamometer test mode if the workshop menu is activated via the instrument cluster and the engine is then started. ESP®, ABS and ASR are then switched to passive. The Electronic Stability Program warning lamp and the antilock brake system indicator lamp in the instrument cluster light up. In addition a corresponding message is displayed on the multifunction display of the instrument cluster. The roller dynamometer mode can also be activated using the diagnostic unit.

The instrument cluster sends the status of the roller dynamometer mode via chassis CAN 2, the electronic ignition lock control unit and chassis CAN 1 to the Electronic Stability Program control unit. The Electronic Stability Program control unit then switches the ESP®, ABS and ASR to passive mode and sends the request to switch on the indicator lamps and to output a corresponding message via chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2 to the instrument cluster.

Additional function requirements for ABS 

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 the Electronic Stability Program control unit detects a locking wheel by evaluating the signals from the rpm sensors, the brake pressure at the corresponding wheel is reduced until the wheel begins to turn again.

Function sequence for Straight Line Control (as of 01.09.2015) 

The Straight Line Control function prevents the vehicle from pulling to one side when it is braked while traveling straight ahead. This ensures safe and stable vehicle handling. An increase in yaw rate during straight-ahead travel is detected using the signals from the yaw rate sensor for lateral and longitudinal acceleration. By reducing the pressure individually at each wheel, a corresponding counter torque is generated and the vehicle is stabilized.

Additional function requirements for ASR, electronic traction system 

Function sequence for ASR, electronic traction system 

ASR and the electronic traction system prevent the drive wheels from spinning when driving. ASR and the electronic traction system also serve to provide improved driving stability and road adhesion with increased traction potential over the entire vehicle speed range. If, as a result of evaluation of the signals from the rpm sensors, the Electronic Stability Program control unit detects spinning of the drive wheels, the drive torque is reduced.

The Electronic Stability Program control unit sends the request to reduce the drive torque via chassis CAN 1 to the CDI control unit (engine 642) or to the ME-SFI control unit (engine 157, 273).

On vehicles with engine 176, the Electronic Stability Program control unit sends the request to reduce the drive torque via drive train CAN 1, the powertrain control unit and drive train CAN to the ME-SFI control unit.

The CDI control unit or the ME-SFI control unit 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 sensor can be permitted again, e.g. due to an improvement in road surface adhesion. As a result of targeted brake intervention at the spinning wheel (without traction), the drive torque is transferred to the opposite drive wheel (with traction).

Additional function requirements for BAS 

BAS function sequence 

BAS detects emergency braking situations from rapid actuation of the brake pedal and, if necessary, increases the brake pressure in order to achieve maximum possible deceleration. To do so, the Electronic Stability Program control unit evaluates the increase in pressure in the brake system and initiates an emergency stop if a certain activation threshold is exceeded.

Function sequence for changing damper characteristics (with code A20 (Adjustable damping)) 

Changing the damper characteristics can enable a dynamic driving style and, at the same time, prevent the risk of tipping. Depending on the situation, the Electronic Stability Program control unit can request hard or soft damper characteristics from the adaptive damping system control unit via chassis CAN 1.

Additional function requirements for the Hill Start Assist 

Hill Start Assist function sequence 

When starting off, the Hill-Start Assist prevents the vehicle from rolling back opposite the travel direction of the engaged gear range during the time it takes for the driver to change from the brake pedal to the accelerator pedal. The function is automatically triggered when, with the vehicle at a standstill, an incline is detected which would cause the vehicle to roll contrary to the gear range engaged.

For this purpose, the Electronic Stability Program control unit evaluates the following variables:

The brake pressure applied by the driver is maintained in the brake system by the traction system hydraulic unit. Once the brake pedal is released, the brake pressure is modulated based on the downward torque due to slope, braking torque and 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 press the accelerator pedal, the pressure in the brake system is released after t = 1 s.

Function sequence for precharging dependent on accelerator pedal operation 

Upon detection of a possible emergency braking situation, the brake pads are brought into contact with the brake discs. The clearance between the brake lining and brake disc 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 p = 2 to 3 bar is requested.

The CDI control unit (engine 642) or the ME-SFI control unit (engine 157, 273) reads in the signals from the accelerator pedal sensor directly and sends them via chassis CAN 1 to the Electronic Stability Program control unit.

On vehicles with engine 176, the ME-SFI control unit reads in the signals from the accelerator pedal sensor directly and sends them via the drive train CAN, powertrain control unit and chassis CAN 1 to the Electronic Stability Program control unit.

Function sequence for HOLD function 

The HOLD function assists the driver when starting off on a hill or during waiting times in traffic. The HOLD function is activated by quickly pressing down hard on the actuated brake pedal after coming to a standstill. The adjusted brake pressure is held until the driver again starts off or depresses the brake pedal with a certain increased pressure.

Securing strategy: 

If the driver wants to leave the vehicle, the vehicle is secured by the security system of the intelligent servo module for DIRECT SELECT. To do so, the standstill control in the Electronic Stability Program control unit sends the request to engage the gear range "P" over suspension CAN 1, the CDI control unit (engine 642) or ME-SFI [ME] control unit (engine 157, 273) or powertrain control unit (engine 176) and drive train CAN to the intelligent servo module for DIRECT SELECT. The vehicle is secured after the P-request is carried out. A warning is issued on the instrument cluster.

Function sequence for ASR and ESP® passive switching 

The ASR and ESP® functions can be switched to passive mode using the ESP OFF button. The upper control panel control unit reads in the status of the ESP OFF button directly and sends the status via the battery sensor LIN, SAM control unit, interior CAN, electronic ignition lock control unit and chassis CAN 1 to the Electronic Stability Program control unit. If the system is switched passive, the Electronic Stability Program warning lamp lights up in the instrument cluster. The control thresholds are raised in the case of passive switching.

IMPORTANT ABS cannot be deactivated. ESP® is always active during a brake application.

Function sequence for ESP® trailer stabilization (except model 463.242) 

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. If vehicle/trailer instability occurs, this is detected by means of the signals from the yaw rate sensor for lateral and longitudinal acceleration.

The ESP® trailer stabilization function 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 drive torque and by building up pressure at all wheels. Active vehicle/trailer stabilization does not change the critical vehicle speed.

Additional function requirements for adaptive brake lights, flashing 

Function sequence for adaptive brake lights flashing 

In the event of emergency braking, the Electronic Stability Program control unit sends a corresponding signal via chassis CAN 1, the electronic ignition lock control unit and interior CAN to the SAM control unit.

The SAM control unit actuates all the brake lights for the duration of the signal (at least for t = 1 s) with a flashing frequency of f = 5 Hz. If the vehicle decelerates from a speed of v > 70 km/h (not in urban traffic) to standstill, the brake light are permanently actuated again. In addition, the hazard warning flasher function is automatically activated. If the vehicle then exceeds a speed of 10 km/h, the hazard warning system is automatically switched off again.

Additional function requirements for dry braking (as of 01.09.2015) 

IMPORTANT The SAM control unit sends the status of the windshield wiper system via the interior CAN, electronic ignition lock control unit and chassis CAN 1 to the Electronic Stability Program control unit.

Function sequence for dry braking (as of 01.09.2015) 

The dry braking function enhances the performance of the brakes on the front axle in wet driving conditions. Cyclical application of the brake pads for a brief period (approx. t = 0.5 s) at a brake pressure of p = 1 bar, ejects the water film from the brake disc. This improves the response time of the brake.

Function sequence - Fail boost 

The fail boost function ensures brake boosting. It is activated if the pneumatic brake booster cannot adequately support driver braking because of a system error in the vacuum supply. The system error in the vacuum supply is displayed in the instrument cluster by the brake force distribution warning lamp.

The failure of the pneumatic brake booster is detected via the brake vacuum sensor, which is integrated in the pneumatic brake booster. The Electronic Stability Program control unit reads in the signals from the brake vacuum sensor directly.

The fail boost function performs hydraulic brake boosting using a suitable boost factor and for this purpose actuates the corresponding components in the traction system hydraulic unit.

Function sequence - Over boost 

Like the fail boost function, the over boost function ensures brake boosting. The over boost function is activated if the pneumatic brake booster can no longer adequately support driver braking because of a brief sub-optimal vacuum level.

Unlike fail boost, over boost represents a normal operating state.

There is no system error in the vacuum supply.

This briefly reduced vacuum level operating state can occur, for example, in the following cases:

The over boost function performs hydraulic brake boosting using a suitable boost factor and for this purpose actuates the corresponding components in the traction system hydraulic unit.

Function sequence for standstill control (SSC) 

The standstill control (SSC) monitors the braking driver assistance system DISTRONIC PLUS (with ADAPTIVE BRAKE premium system (with code EZ9 (DISTRONIC PLUS))) and the HOLD function at a vehicle speed of v < 3 km/h until the vehicle comes to a safe standstill. Within this vehicle speed range, the SSC is responsible for the transfer to a safe state 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 systems. If vehicle rolling is detected, the brake pressure is increased until the vehicle is stationary again.

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

The driver is deemed as absent if the driver door is open and the belt lock tongue of the driver seat belt is not inserted into the seat belt buckle. Insertion of the belt lock tongue into the seat belt buckle is detected by the driver seat belt buckle restraint system switch. The supplemental restraint system control unit reads in the status of the driver seat belt buckle restraint system switch directly and transmits the status via chassis CAN 1 to the Electronic Stability Program control unit. The driver assistance systems cannot be operated.

System fault display function sequence 

The driver is informed about the system status and about faults by the following displays:

If the Electronic Stability Program control unit fails, basic braking without ABS is always available.

IMPORTANT The status of the brake fluid level switch is read in by the SAM control unit. The SAM control unit sends the request to switch on the corresponding indicator lamp via the interior CAN to the instrument cluster.

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