Power Seat Control Module: Description and Operation

GF91.25-P-5201RI Multicontour Seat Control Unit (MCS), Component Description
- with CODE (404) Driver seat multicontour backrest
- with CODE (405) Front passenger seat multicontour backrest as of Model Year 09/YoM 08 model refinement package

Component Identification:

Location
The left front multicontour backrest control unit (N32/15) and the right front multicontour backrest control unit (N32/16) are centrally located in the backrest frame of the driver seat or front passenger seat.

Tasks
- Inflating and deflating the multicontour backrest in accordance with the requests read in by the left front multicontour backrest switch group (S109) or right front multicontour backrest switch group (S108).
- Control of the dynamic lumbar support (massage function), activated by the dynamic lumbar support adjustment switch (S108s1) or (S109s1).
- Reading in the voltage-coded left front multicontour backrest switch group (S109) or right front multicontour backrest switch group (S108).
- Adjusting the stored pressure values when calling up the memory function and storing the actual contours.
- Shutoff of the respective function if the pressure valve responsible has overheated
- Creating status data records on cushion inflation and transmission of these records via a bidirectional, serial interface to the left front seat adjustment control unit with memory (N32/1) or right front seat adjustment control unit with memory (N32/2).

These are grouped as follows:
^ Reading in of sensors and signals
^ Evaluation of input factors
^ Actuation of components

Reading in of sensors and signals
These input factors are read in via the following connections:
^ Direct line
^ Bidirectional serial interface

Direct line
- Circuit 30
- Circuit 31

The following sensors are read in via direct lines:
- Left front multicontour backrest switch group (S109)
- Right front multicontour backrest switch group (S108)

Bidirectional serial interface (private bus)
The left or right front multicontour backrest control unit communicates via the bidirectional serial interface with the following:
- The left front seat adjustment control unit with memory (N32/1) for adjustment and storage of the seat contours on the driver seat
- The right front seat adjustment control unit with memory (N32/2) for adjustment and storage of the seat contours on the front passenger seat

Evaluation of input factors
The read in input factors are evaluated by the front multicontour backrest control unit. The air cushions in the seat are actuated via the valves integrated into the front multicontour backrest control unit.

Actuation of components
The actuation of the components takes place via the following connections:
^ Direct line
^ Bidirectional serial interface

Direct line
The following components are actuated via direct lines:
- Status LED in the left front multicontour backrest switch group (S109) or right front multicontour backrest switch group (S108) for display of the pulse program (massage program, dynamic lumbar support).

The air cushions in the seat are actuated via valves integrated into the multicontour backrest control unit.

Bidirectional serial interface
The left or right front multicontour backrest control unit communicates via a serial interface with the following:
- The left front seat adjustment control unit with memory (N32/1) for acknowledgment of the adjustment and storage of the seat contours on the driver seat
- The right front seat adjustment control unit with memory (N32/2) for acknowledgment of the adjustment and storage of the seat contours on the front passenger seat

Design
In addition to the intelligent circuit, piezo-resistive pressure sensors are located in the front multicontour backrest control unit. These sensors are used to measure and monitor the pressure. The air pressures in the cushions are adjusted by the valves integrated into the front multicontour backrest control unit. The front multicontour backrest control unit is connected to the left front multicontour backrest switch group or right front multicontour backrest switch group at the seat via the 8-pin connector.

This connector is also to connect it to the left front seat adjustment control unit with memory or right front seat adjustment control unit with memory via the bidirectional serial interface. The power is also supplied via the particular front seat adjustment control unit with memory.

Function

Short-term control
The short-term control is actuated following each adjustment process (manual adjustment, memory request, initialization) for a certain period of time. It compensates for excess pressure deviations from the specified pressure of each air cushion (cushion areas, connected to a pressure sensor, are jointly in the temporary control phase) within a parameterized time period. Vacuum deviations during this phase are not compensated for. This phase is used to compensate for large pressure jumps when sitting down and leaning back immediately and in a comfort-oriented fashion.

Long-term control
After the short-term control, the long-term control becomes active for the active cushions, until it is reset by events with a higher priority. Almost without the customer noticing, the lumbar support is regulated in the specified time frame such that the mean value of the actual pressure adjusts to the specified pressure within the repeatability over a certain period of time.

If an adjustment to the specified pressure cannot be achieved in several consecutive steps, a "gross leak" is detected. The affected cushion area is deactivated completely until the malfunction is no longer present.

Non-active air cushions are deflated in increments to a pressure less than the minimum pressure.

Variants
There are no variants for the hardware of the front multicontour backrest control unit.