Cruise control (CC), function - GF30.30-P-0001CAM

MODEL 207.3/4 as of model year 2014

Fig 1: Cruise Control - Block Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

The units and values for the speed shown in the text should be assigned to the possible national versions. The details in "miles per hour (mph)" refer to vehicles with a miles indicator.

Engine running or drivetrain operational
Gear range "D" engaged (for transmission 722, 725)
Vehicle speed:
- v ≥30 to 250 km/h (v ≥ 20 to 150 mph) or up to the respective maximum speed according to the motorization of the vehicle (without code (233) DISTRONIC PLUS or for vehicles with code (233) DISTRONIC PLUS and deactivated distance control)
- v ≥30 up to 200 km/h (v ≥20 up to 120 mph) (for code (233) DISTRONIC PLUS and activated distance control)

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 CC function is implemented by the Electronic Stability Program control unit.

The vehicles with code (233) DISTRONIC PLUS transmits the radar sensors control unit function-relevant requests via the chassis FlexRay, chassis gateway control unit and chassis CAN 1 to the Electronic Stability Program control unit.

The Electronic Stability Program control unit processes these and prioritizes them according to the respective own evaluated parameters.

Operation of the CC function

Fig 2: Identifying Cruise Control Lever Adjustment Position

Courtesy of MERCEDES-BENZ USA

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.

Using the switches decelerate and fix in place and the switches accelerate and set, the set speed can be altered in Operation steps of v = 1 km/h (1 mph) or v = 10 km/h (5 mph).

Actuation up to the actuation point increases the set speed by v = 1 km/h (1 mph). If the switch is pressed beyond the actuation point then the set speed increases each time by v = 10 km/h (5 mph). If the switch is held at or beyond the over-center preload the set speed is altered every t = 0.6 s.

The following input factors are evaluated to implement the CC function:

Operating condition of engine/drivetrain (function requirements)
Engaged gear range (for transmission 722, 725) (function requirements)
Vehicle speed (function requirements)
Driver request via the cruise control lever
Accelerator pedal position

Operating condition for engine/drivetrain:

The CDI control unit or the ME-SFI [ME] control unit transmits the signal "electric motor runs" or "drivetrain operational" via the chassis CAN 1 to the Electronic Stability Program control unit.

For vehicles with code (233) DISTRONIC PLUS the CDI control unit or the ME-SFI [ME] control unit also transmits the signal via the chassis CAN 1, chassis gateway control unit and chassis FlexRay to the radar sensors control unit.

Engaged gear range (with transmission 722, 725):

The fully integrated transmission control unit sends the information about the gear range via drive train CAN, CDI control unit or ME-SFI [ME] control unit and chassis CAN 1 to the Electronic Stability Program control unit.

For vehicles with code (233) DISTRONIC PLUS the fully integrated transmission control unit also transmits the information via the drive train CAN, CDI control unit or ME-SFI [ME] control unit, chassis CAN 1, chassis gateway control unit and chassis FlexRay to the radar sensors control unit.

Vehicle speed:

The RPM sensors detect the wheel speeds and are read in directly by the Electronic Stability Program control unit. The vehicle speed is calculated by the Electronic Stability Program control unit from the wheel speeds.

The vehicles with code (233) DISTRONIC PLUS transmits the Electronic Stability Program control unit also transmits the wheel speed signals via the chassis CAN 1, chassis gateway control unit and chassis FlexRay to the radar sensors control unit. Driver request via the cruise control lever: The driver request over the CC lever are directly read in by the steering column tube module control unit. The steering column tube module control unit transmits the control signals from the CC lever via chassis CAN 1 to the Electronic Stability Program control unit. The vehicles with code (233) DISTRONIC PLUS the steering column tube module control unit also transmits the request the chassis CAN 1, chassis gateway control unit and chassis FlexRay to the radar sensors control unit.

Accelerator pedal position:

Operation of the accelerator pedal is registered by the accelerator pedal sensor.

The CDI control unit or the ME-SFI [ME] control unit directly reads in the signals from the accelerator pedal sensor and transmits these via chassis CAN 1 to the Electronic Stability Program control unit. For vehicles with code (233) DISTRONIC PLUS the CDI control unit or the ME-SFI [ME] control unit also transmits the signals via the chassis CAN 1, chassis gateway control unit and chassis FlexRay to the radar sensors control unit.

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

Increase/reduce engine torque
Engage targeted gear (downshift or upshift) (for transmission 722, 725)
Increase/reduce the braking torque

Raise/reduce engine torque:

The Electronic Stability Program control unit evaluates the input factors as well as further driving dynamics requests and transmits the request "increase/reduce engine torque" via the chassis CAN 1 to the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit implements this request.

For vehicles with code (233) DISTRONIC PLUS the radar sensors control unit transmits the request "increase/reduce drive torque" via the chassis FlexRay, chassis gateway control unit and chassis CAN 1 to the Electronic Stability Program control unit. The Electronic Stability Program control unit processes this, prioritizes this and transmits it according to its priority via chassis CAN 1 to the CDI control unit or the ME-SFI [ME] control unit.

Engage targeted gear (for transmission 722, 725):

The Electronic Stability Program control unit internally evaluates the input factors as well as further driving dynamics requests and transmits the request "Engage targeted gear" via chassis CAN 1, the CDI control unit or the ME-SFI [ME] control unit and drive train CAN to the fully integrated transmission control unit.

The request "engage targeted gear" should be understood as a switching recommendation. Downshifting or upshifting of the A/T takes place autonomously itself by the fully integrated transmission control unit, dependent on the current operating condition.

For vehicles with code (233) DISTRONIC PLUS the radar sensors control unit transmits the request "Engage targeted gear" via the chassis FlexRay, chassis gateway control unit and chassis CAN 1 to the Electronic Stability Program control unit.

Raise/reduce braking torque:

The Electronic Stability Program control unit evaluates the input factors and actuates the traction system hydraulic unit appropriately. The traction system hydraulic unit reacts by increasing or reducing the braking torque.

For vehicles with code (233) DISTRONIC PLUS the radar sensors control unit transmits the request "increase/reduce braking torque" via the chassis FlexRay, chassis gateway control unit and chassis CAN 1 to the Electronic Stability Program control unit.

The cruise control function includes the following subfunctions:

Function sequence for automatic speed control
Function sequence for SPEEDTRONIC

Additional automatic speed control function requirements

Cruise control selected using SPEEDTRONIC switch (without code (494) USA version) (SPEEDTRONIC LED off)
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 set speed is displayed in the speedometer. To do this, the Electronic Stability Program control unit sends corresponding information via chassis CAN 1, front SAM control unit and chassis CAN 2 to the instrument cluster.

For vehicles with code (233) DISTRONIC PLUS the radar sensors control unit transmits this information via the chassis FlexRay, chassis gateway control unit and chassis CAN 2 to the IC.

The following events deactivate the automatic speed control:

Operation of the OFF switch
Depressing the brake pedal
Operation of parking brake
Active regulation of the ESP®
Speed v < 25 km/h (v < 17 mph)
Actuation of the clutch pedal for about t = 6 s (for transmission 711 or 716)
Gear range is not "D" (for transmission 722, 725)

The front SAM control unit detects the status of the parking brake indicator switch directly and sends this via the chassis CAN 1 to the Electronic Stability Program control unit. For vehicles with code (233) DISTRONIC PLUS the front SAM control unit also transmits the signal via chassis CAN 1, the chassis gateway control unit and chassis FlexRay to the radar sensors control unit.

For vehicles with transmission 711 or 716: The CDI control unit or ME-SFI [ME] control unit reads in the status of the clutch pedal switch directly and transmits it to the Electronic Stability Program control unit via chassis CAN 1.

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

Increase/reduce engine torque
Engage targeted gear (for transmission 722, 725):
Increase/reduce the braking torque

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).

Function sequence for SPEEDTRONIC

The SPEEDTRONIC comprises the following subfunctions:

Function sequence for variable SPEEDTRONIC (without code 494 (USA version))
Function sequence for permanent limiter

Additional function requirements for variable SPEEDTRONIC (without code 494 (USA version))

Variable SPEEDTRONIC selected with SPEEDTRONIC switch (SPEEDTRONIC LED on)
The steering column tube module control unit actuates the SPEEDTRONIC LED directly.
ESP® not switched passively
"Kickdown" not detected (for transmission 722, 725)

Function sequence for variable SPEEDTRONIC (without code 494 (USA version))

The maximum speed of the vehicle can be limited at any time to a freely selectable value (e.g. 50 km/h (31 mph) in urban traffic) via the variable SPEEDTRONIC. The driver can accelerate the vehicle up to the set limit.

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

Reduce engine torque
Engage targeted gear (for transmission 722, 725):
Raise braking torque

If switching takes place on the variable SPEEDTRONIC on the CC lever, the automatic speed control is deactivated.

The following events deactivate the variable SPEEDTRONIC:

Operation of the OFF switch
Kickdown (for transmission 722, 725) (accelerator pedal pressed by > 90% and vehicle speed v < 20 km/h (v < 12 mph) from the selected maximum speed)

Function sequence for permanent limiter

The maximum speed of the vehicle can be limited in operation steps of v = 10 km/h or 5 mph from v = 160 to 240 km/h or v = 100 mph to 150 mph. Adjustment of the maximum speed takes place in the menu "Settings", "Vehicle" and "Limitation (winter tires)" in the instrument cluster. The instrument cluster sends the set maximum speed via chassis CAN 2, front SAM control unit and chassis CAN 1 to the Electronic Stability Program control unit.

For vehicles with code (233) DISTRONIC PLUS the IC transmits the set maximum speed via chassis CAN 2, chassis gateway control unit and chassis FlexRay to the radar sensors control unit.

At about v = 10 km/h (v = 5 mph) before reaching the set maximum speed a message appears in the multifunction display which indicates limitation of the maximum speed.

For vehicles with code (233) DISTRONIC PLUS the radar sensors control unit transmits the respective request via the chassis FlexRay, chassis gateway control unit and chassis CAN 2 to the IC.

The driver can accelerate the vehicle up to the set maximum speed.

If the maximum speed was reached the following activities are started:

Reduce engine torque
Engage targeted gear (shift down) (for transmission 722, 725)
Reduce braking torque

Electrical function schematic for cruise control (CC)	MODEL 207.3/4 as of model year 2014 without CODE 233 (DISTRONIC PLUS)	PE30.30-P-2051-97EAC
Electrical function schematic for cruise control (CC)	MODEL 207.3/4 as of model year 2014 with CODE 233 (DISTRONIC PLUS)	PE30.30-P-2051-97EAD
Overview of system components for driver assistance systems		GF54.00-P-9998CAM