Operation
The QMVH control unit receives a request from the ICM control unit to transfer a certain amount of torque to the left or right rear drive wheel. The control unit must convert this setpoint value into phase voltages for the electric motor to be actuated. The following calculation steps are required for this
- Deciding which superimposing gear unit needs to be activated. The side that should receive more of the available torque must be activated.
- Converting the torque to be transferred into a braking force at the superimposing gear unit.
- Determining the necessary adjustment path of the plates from the braking force that the plate assembly must generate.
- Calculating the motor rotation angle to achieve the required adjustment path of the plates.
- Determining the amplitude and progression of the three phase voltages.
During the adjustment process, the QMVH control unit uses the motor position sensor to measure whether and how far the electric motor has already moved. Once the calculated specified angle is reached, the actuation is changed so that the rotational angle achieved is maintained. A motor position regulation therefore takes place. The regulation principle is similar to that for Active Steering.
The QMVH control unit also carries out monitoring functions. This allows faults in the electronics and in the actuating elements to be detected which cause the function to be deactivated. In the event of a fault, the lines to the electric motors are disconnected. They are then de-energized and can no longer execute undesirable adjustment processes.
The multi-plate clutches also open, so that a previously active torque transfer is withdrawn.
The rear differential (and therefore the entire system) thus behaves like a conventional differential in the event of a fault.
As well as detecting faults, the QMVH control unit also monitors the signals from the temperature sensors on the rear differential. A protective function is thus implemented, which reduces the actuating element controls if the temperature is too high.
Classroom Exercise - Component Functions and Operation
Using the workbook material, please complete the following table
| Component or Function | Module responsible for Logic or Processing | Module responsible for Actuation or Output |
|---|---|---|
| EDC | ||
| AL/AFS | ||
| DPC/QMVH | ||
| XDrive | ||
| DSC | ||
| ASC | ||
| ABS | ||
| MSR | ||
| Automatic Hold | ||
| EVV | ||
| Servotronic | ||
| ARS | ||
| EHC | ||
| Total Steering Angle | N/A |
CLASSROOM EXERCISE - COMPONENT FUNCTIONS AND OPERATION CHART