Cruise Control (Cc), Function - GF30.30-D-0001TSA

Model 907 

with code MS1 (Cruise control) 

Shown on model 907 

Function requirements, general 

• Engine running or drive train operational.
• Drive range "D" engaged.
• no undervoltage or overvoltage.
• Vehicle speed:
  • Vehicle speed v ≥ 30 to 250 km/h or maximum design speed.

Cruise control - general 

The cruise control regulates the vehicle speed constantly and automatically to the desired speed set by the driver. To do this, the cruise control evaluates the driver's commands and the current driving condition.

The cruise control is activated using the resume from memory switch.

Here the last stored or momentary vehicle speed is set as the set speed.

The target speed can be altered in steps of v = 1 km/h or v = 10 km/h using the "decelerate and set" switch and the "accelerate and set" switch.

Actuation up to the actuation point increases the set speed by v = 1 km/h. If the switch is pressed beyond the actuation point then the specified speed increases each time by v = 10 km/h. If the switch is held at or beyond the actuation point, the specified speed is changed every t = 0.6 s.

The following input factors are evaluated to implement the function: 

• Operating condition of engine/drivetrain (function requirements)
• Engaged gear range (function requirements)
• Vehicle speed
• Driver request via cruise control control panel in steering wheel
• Accelerator pedal position

Operating condition for engine/drivetrain: 

The CDI control unit or the ME-SFI control unit transmits the "engine running" or "powertrain operational" signal via the drive CAN, powertrain control unit, and suspension FlexRay to the ESP® control unit, also for vehicles with code ET4 (Active Distance Assist DISTRONIC) also to the Distance Pilot DISTRONIC controller unit.

The CDI control unit or the ME-SFI [ME] control unit, amongst other things, coordinates acceleration, deceleration or switching requirements. in doing so it prioritizes requests according to their relevance, while taking account of the additional variables such as the operating condition of the ancillaries or requests from the comfort systems such as the AAC.

Engaged gear range: 

The fully integrated transmission control unit transmits information on the engaged drive range via the drive CAN, powertrain control unit, and suspension FlexRay to the ESP® control unit.

Vehicle speed: 

The vehicle speed is calculated by the ESP® control unit based on the wheel speeds.

Driver request via the instrument cluster multifunction steering wheel button group: 

The cruise control ON driver requests, made via the instrument cluster multifunction steering wheel button group, are transmitted directly to the steering column tube module control unit by the steering wheel electronics. The steering column tube module control unit transmits the signal via suspension FlexRay to the ESP® control unit and for vehicles with code ET4 (Active Distance Assist DISTRONIC) additionally to the Distance Pilot DISTRONIC controller unit. Accelerator pedal position: 

The powertrain control unit transmits information on the accelerator pedal position via suspension FlexRay to the ESP® control unit and for vehicles with code ET4 (Active Distance Assist DISTRONIC) additionally to the Distance Pilot DISTRONIC controller unit.

The following initial parameters (requests) are issued to implement the function: 

• Increase/reduce drive torque.
• Engage requested gear (downshift or upshift).
• Increase/reduce braking torque.

Increase/reduce the drive torque: 

For vehicles except code ET4 (Active Distance Assist DISTRONIC), the ESP® control unit evaluates the input factors and additional driving dynamic requests and transmits the "increase/reduce drive torque" request via suspension FlexRay, powertrain control unit, and engine CAN to the CDI control unit or ME-SFI control unit.

For vehicles with code ET4 (Active Distance Assist DISTRONIC), the Distance Pilot DISTRONIC controller unit transmits the "increase/reduce drive torque" request via suspension FlexRay to the ESP® control unit. The ESP® control unit evaluates this and transmits it, according to its priority, via suspension FlexRay, powertrain control unit, and engine CAN to the CDI control unit or ME-SFI control unit.

The CDI control unit or the ME-SFI [ME] control unit implements this request.

Engage targeted gear (downshift or upshift): 

For vehicles except code ET4 (Active Distance Assist DISTRONIC), the ESP® control unit evaluates the input factors and additional driving dynamic requests and transmits the "engage requested gear" request via suspension FlexRay, powertrain control unit, and drive CAN to the fully integrated transmission control unit.

For vehicles with code ET4 (Active Distance Assist DISTRONIC), the Distance Pilot DISTRONIC controller unit transmits the "engage requested gear" request via suspension FlexRay to the ESP® control unit. The ESP® control unit evaluates this and transmits it, according to its priority, via suspension FlexRay, powertrain control unit, and drive CAN to the fully integrated transmission control unit.

This request is to be understood as a shift recommendation.

Downshifting or upshifting of the automatic transmission takes place autonomously by the fully integrated transmission control unit dependent on the current operating condition.

Raise/reduce braking torque: 

For vehicles except code ET4 (Active Distance Assist DISTRONIC), the ESP® control unit evaluates the input factors and actuates the traction system hydraulic unit accordingly.

For vehicles with code ET4 (Active Distance Assist DISTRONIC), the Distance Pilot DISTRONIC controller unit transmits the "increase/reduce braking torque" request via suspension FlexRay to the ESP® control unit. The ESP® control unit evaluates this and actuates the traction system hydraulic unit accordingly.

The traction system hydraulic unit reacts by increasing or reducing the braking torque.

For model the kinetic energy is converted within defined limits into electrical energy (regenerative braking). If the requested braking torque exceeds the deceleration through recuperative braking, the ESP® control unit also actuates the traction system hydraulic unit and therefore the service brake.

Cruise control encompasses the following subfunctions:

• Function sequence for automatic speed control
• Function sequence, variable speed limiter

Additional automatic speed control function requirements 

• Cruise control selected via limiter switch (limiter light-emitting diode does not light up)
• Electronic Stability Program (ESP®) not switched to passive mode

Function sequence for automatic speed control 

Through actuation of the "Resume from memory" switch the last set speed stored is applied, provided a set speed was stored since the last engine start. If no set speed was stored, the current vehicle speed is set as the set speed. The target speed is displayed in the IC.

For vehicles except code ET4 (Active Distance Assist DISTRONIC), the ESP® control unit transmits the speed setting (specified speed) via suspension FlexRay, electronic ignition lock control unit, and the user interface CAN to the instrument cluster.

For vehicles with code ET4 (Active Distance Assist DISTRONIC), the Distance Pilot DISTRONIC controller unit transmits the speed setting (specified speed) via suspension FlexRay, electronic ignition lock control unit, and user interface CAN to the instrument cluster.

The driver also has the option to accelerate beyond the set target speed through actuation of the accelerator pedal (for example when overtaking). The set speed is regulated again after removal of the acceleration request (releasing the accelerator pedal).

The following events deactivate the automatic speed control:

• Operation of the off switch.
• Switchover to the variable limiter.
• Actuation of the brake pedal.
• Active regulation of the ESP® or ESP® is switched off.
• Speed v < 25 km/h.
• Drive range not "D".

The following activities are started in order to reach or maintain the set speed:

• Increase/reduce drive torque.
• Engage requested gear (downshift or upshift).
• Increase/reduce braking torque.

Function sequence, variable speed limiter 

The DTCO has the following subfunctions:

• Function sequence of variable speed limiter
• Function sequence for permanent limiter

Additional function requirements of variable speed limiter 

• Variable speed limiter selected over variable speed limiter switch (variable speed limiter LED lights up):

The steering column tube module control unit actuates the variable speed limiter LED directly.

Function sequence of variable speed limiter 

The variable speed limiter can be used to limit the vehicle's maximum speed to a freely selectable value (e. g. v = 50 km/h in urban traffic).

The driver can accelerate the vehicle up to the set limit.

If the set limit was reached, the following activities are started:

• Reduce drive torque.
• Engage requested gear (downshift).
• Raise braking torque.

If the driver switches to the variable limiter on the instrument cluster multifunction steering wheel button group, the automatic speed control is deactivated.

The following events deactivate the variable speed limiter:

• Operation of the OFF switch
• Changeover to CC
• Kickdown (accelerator pedal pressed by > 90 % and driven speed v < 20 km/h removed from the set maximum permissible speed)
• ESP switched to passive mode

Function sequence for permanent limiter 

The maximum permissible speed of the vehicle can be limited in steps of v = 10 km/h from v = 160 to 240 km/h. Setting of the maximum permissible speed takes place in the menu "Settings", "Vehicle", and "Limitation (winter tire)" in the head unit.

Approx. v = 10 km/h before reaching the set maximum permissible speed, a message appears in the multifunction display of the instrument cluster, which indicates the limitation of the maximum permissible speed. The driver can accelerate the vehicle up to the set maximum permissible speed. The head unit transmits the set maximum permissible speed via the user interface CAN to the instrument cluster.

If the set permissible maximum speed was reached, the following activities are started:

• Reduce drive torque.
• Engage requested gear (downshift).
• Raise braking torque.

The permanent limiter also remains active for a switched off variable speed limiter.

Electrical function schematic for cruise control (CC)	Model 907	PE30.30-D-2051-97TSA
Overview of system components for driver assistance systems		GF54.00-D-9998TSA