Rear Axle Steering, Function - GF46.80-P-0007RR
Model 190
With Code 201 (Rear axle steering)
Function requirements, general
- Terminal 15 ON
Rear axle steering in general
The rear axle steering changes the toe angle on the rear wheels. The toe angle on the rear wheels is adjusted by a tie rod on each rear axle steering control unit. The toe angle change at the rear wheel is maximum 1.5 degrees.
The active rear axle steering assists the driver in unexpected driving situations such as, e.g. in the event of any evasive maneuvers thereby providing a major contribution to active safety.
The right rear axle steering control unit (master) and the left rear axle steering control unit (slave) also evaluates the following input factors to implement the function :
- Terminal status
- Terminal 15 ON and engine start OFF
- Vehicle speed
- Engine speed
- Engine running status
- Status of roller dynamometer mode
- Rear axle steering control mode request
- Toe angle change request
- Rear axle steering tie rod force request
Status of terminal 15 ON and engine start OFF :
The electronic ignition lock control unit sends the terminal status and the engine start OFF status over the chassis CAN 1, Electronic Stability Program control unit and the vehicle dynamics CAN to the rear axle steering control units.
Vehicle speed :
The Electronic Stability Program control unit sends the vehicle speed over the vehicle dynamics CAN to the rear axle steering control units.
Engine speed and engine running status :
The ME-SFI [ME] control unit sends the engine speed and engine running status over the drive CAN, AMG gateway control unit, chassis CAN 1, Electronic Stability Program control unit and the vehicle dynamics CAN to the rear axle steering control units.
Roller dynamometer mode status :
The Electronic Stability Program control unit sends the roller dynamometer mode status over the vehicle dynamics CAN to the rear axle steering control units.
Rear axle steering control mode request :
The Electronic Stability Program control unit sends the request from the corresponding mode of the rear axle steering over the vehicle dynamics CAN to the rear axle steering control units.
Toe angle change request :
The Electronic Stability Program control unit sends the toe angle change request over the vehicle dynamics CAN to the rear axle steering control units.
Rear axle steering tie rod force request :
The Electronic Stability Program control unit sends the rear axle steering tie rod force request over the vehicle dynamics CAN to the rear axle steering control units.
The right rear axle steering control unit and the left rear axle steering control unit operate according to the master-slave principle. In other words, the left rear axle steering control unit sends its status over the vehicle dynamics CAN to the right rear axle steering control unit, which evaluates the status and sends corresponding data over the vehicle dynamics CAN to the Electronic Stability Program control unit.
The rear axle steering includes the following subfunctions:
- Turn rear wheels to opposite direction of front wheels
- Turn rear wheels parallel to front wheels
- System and warning messages
Turn rear wheels to opposite direction of front wheels
At a vehicle speed up to 100 km/h the rear wheels are turned in the opposite direction to the front wheels. This virtual shortening of the wheelbase enables the vehicle to be even more agile when steering into corners and requires less force of the hand on the steering wheel, particularly on routes involving lots of changes in direction or ones that have a slalom character. The advantage in daily driving situations such as, e.g. when turning off a road or when parking lies in the reduced turning circle.
The rear axle steering control units evaluate the information of the Electronic Stability Program control unit and change the toe angle on the rear wheels to match. At the same time, the right rear axle steering control unit sends the request to change the toe angle over the vehicle dynamics CAN to the left rear axle steering control unit.
The right rear axle steering control unit sends the status and the steering position of the rear axle steering over the vehicle dynamics CAN to the Electronic Stability Program control unit.
Turn rear wheels parallel to front wheels
If the vehicle is moving at a speed faster than 100 km/h, the rear wheels are turned parallel to the front wheels. This is equivalent to a virtual extension of the wheelbase and thereby significantly improves driving stability. The faster build-up of lateral force on the rear wheels when changing direction results in a quicker response to steering commands.
The rear axle steering control units evaluate the information of the Electronic Stability Program control unit and change the toe angle on the rear wheels to match. At the same time, the right rear axle steering control unit sends the request to change the toe angle over the vehicle dynamics CAN to the left rear axle steering control unit.
The right rear axle steering control unit sends the status and the steering position of the rear axle steering over the vehicle dynamics CAN to the Electronic Stability Program control unit.
System and warning messages
The right rear axle steering control unit sends the requests to issue system or warning messages over the vehicle dynamics CAN, Electronic Stability Program control unit, chassis CAN 1, AMG gateway control unit and the user interface CAN to the instrument cluster. The corresponding system or warning messages are shown on the multifunction display.
| Electrical function schematic of rear axle steering | PE46.80-P-2050-97HBA | ||
| Overview of system components of rear axle steering | GF46.80-P-9998RR |