GF91.29-P-0008LE Lumbar Adjustment Function

GF91.29-P-0008LE Lumbar Adjustment Function
- except CODE (409) Left/right front multicontour seat
- except CODE (432) Left and right dynamic multicontour seat

Function requirements, general
On vehicles with code (275) Memory package for electrically adjustable front seats with memory adjustment:
^ No on-board electrical system limp-home mode
^ Pressure supply active (no timeout)

Additional function requirements for adjusting via the front central operating unit (A40/9)
^ Circuit 15R ON

Lumbar adjustment function description, general
The lumbar adjustment is described on the driver seat for left-hand vehicles by way of an example, but this also applies for the passenger seat.

In order to provide optimum support for the vertebral column, the backrests on the driver and front passenger seats each contain a lumbar support. Each lumbar support unit comprises an air cushion and the driver lumbar support regulator control unit (N32/23) or the front passenger lumbar support regulator control unit (N32/24).

The compressed air production is ensured by the lumbar support pump (M25/1) in the trunk. Adjustment can be performed menu-guided with the front central operating unit and indicated on the COMAND display (A40/8) (without code (867) SPLITVIEW) or SPLITVIEW display (A40/10) (model as of YoM 09 with code (867) SPLITVIEW) Adherence to the set pressure values as well as the specified pressures of the individual cushion areas is continuously being regulated.

The contours of the driver seat or front passenger seat lumbar support cushion can be adjusted manually via the front central operating unit, actuated by the left front seat control unit (N32/1) or by the right front seat control unit (N32/2), by inflating and deflating.

On vehicles as of model year 2010 / YoM 09 and with code (867) SPLITVIEW, the SPLITVIEW display (A40/10) is installed instead of the COMAND display (A40/8).

The 4-way lumbar support permits the following subfunctions:
^ +/- adjustment of the lumbar support
^ Storing and calling lumbar support (on model 221 with code (275) Memory package for electrically adjustable front seats or on model 216)

Additional functions also run in the background:
^ Initializing
^ Target pressure regulation
^ Long-term control

+/- adjustment of the lumbar support
By actuating the multicontour seat quick select button (A40/9s4) in the front central operating unit, the submenu "Seats" is activated on the COMAND display (without code (867) SPLITVIEW) or SPLITVIEW display (model 216 as of YoM 09 with code (867) SPLITVIEW). After the option for the driver seat, use the rotary pushbutton (A40/9s11) of the front central operating unit to select the "Lumbar support" setting in the submenu.

Pressing the rotary pushbutton of the central operating unit to the right or to the left in the submenu changes the backrest contour of the lumbar support air cushion manually in 10 steps by inflating or deflating. Pressing towards "0" causes the lumbar support cushions to be deflated to a minimum pressure.

The rotary pushbutton on the central operating unit can also be actuated by turning to the right or left instead of up or down in the submenu. Pressing the rotary pushbutton down confirms the particular setting.

Storing and calling lumbar support adjustment (on model 221 with code (275) Memory package for electrically adjustable front seats or on model 216)

Additional function requirements
^ Status of door control unit on interior CAN (CAN B) OK

The set pressure in the driver seat's lumbar support cushion can be saved in a non-volatile memory of the left front seat control unit and retrieved again. The stored positions are saved and retrieved via the memory switch (S22s6) and memory 1 switch (S22s7), memory 2 switch (S22s8), or memory 3 switch (S22s9) of the left front seat operation switch group (S22).

The position saving function is described for the driver seat for left-hand drive vehicles of model 221 by way of an example, but this also applies for the front passenger seat and model 216.

While saving, not only the seat cushion contour but also the position of the seat adjustment for the driver seat, the steering column, and the two outside mirrors are stored.

The status of the switch is read in via the front door LIN (LIN B1) by the left front door control unit (N69/1) and transmitted to the left front seat control unit () via the interior CAN. The left front seat control unit then saves the currently set position or, when a position is retrieved, adjusts the requested lumbar support contour via the driver lumbar support regulator control unit by inflating or deflating.

Abort conditions
- Adjustment request from left front seat control unit

The position saving function has the following structure:
^ Saving a lumbar support contour
^ Retrieving a lumbar support contour

Saving a lumbar support contour
The seat contour is stored using the memory switch and memory 1 switch, memory 2 switch or memory 3 switch of the left front seat operation switch group.

There are two possibilities for storing the lumbar support contour:
- The memory switch is held pressed and then memory 1 switch, memory 2 switch, or memory 3 switch is pressed for the particular memory.
- The memory switch is pressed for t > 100 ms and then released. The memory 1 switch, memory 2 switch or memory 3 switch has to be pressed within a period of 0.2 to 3 seconds.

It is possible to overwrite the stored values at any time, the cushion contour currently set is saved. No cushion contour has been saved at the factory (cushion at minimum pressure).

Retrieving a lumbar support contour
A stored seat contour can be restored at a later time by pressing memory 1 switch, memory 2 switch or memory 3 switch.

A memory request issued via memory 1 switch, memory 2 switch or memory 3 switch during the "Massage program" function will cancel this function. The requested memory position is then adjusted by the left front seat control unit via the driver lumbar support regulator control unit.

Initializing
After switching on or waking up the seat control unit and the COMAND control unit (A40/3), the actual value of the COMAND control unit is taken over as the nominal value for the left front seat control.

Comparison of actual values and specified values does not result in any adjustment; pressure surges are not visible over the actual value on the COMAND display (without code (867) SPLITVIEW) or SPLITVIEW display (as of YoM 09 with code (867) SPLITVIEW) of the COMAND control unit.

Target pressure regulation
For the precise adjustment of specified pressure values, the line length between the pressure sensor and the lumbar support bladder, the response times of the control valve as well as other variables, such as the flow characteristics and the actual pressure in the lumbar support cushion, are taken into account. At the same time the various flow characteristics over the possible pressure range are also taken into account by correction parameters. Damping factors due to the flow characteristics are corrected via filters.

Long-term control

Additional function requirements
^ Circuit 15R ON

The current specified air pressure of the lumbar support is regulated so as to be unnoticeable by the customer, provided the function conditions for lumbar support adjustment are met. This function is used among others to compensate for sitting down or leaning back immediately and in a comfort-oriented fashion.

The long-term regulation is active for the following pressure deviations:
- Leakage in the seat inflators
- Temperature changes due to seat heater, solar radiation, air conditioning, heat from user (change in pressure up to ± 40 mbar)
- Ambient pressure changes, e.g. due to change in weather or altitude The long-term regulation is started after the assembly has been woken, and also after every lumbar support adjustment.