Dynamic multicontour seat, function - GF91.25-P-0003FL

MODEL 212 with CODE 432 (Left and right dynamic multicontour seat) 

Fig 1: Dynamic Multicontour Seat Block Diagram

Courtesy of MERCEDES-BENZ USA

In vehicles with code (494) USA version only the driver seat is a dynamic multicontour seat.

Function requirements, general 

• Circuit 15 or circuit 15R ON
• No overvoltage or undervoltage

The status of circuit 15 is sent by the electronic ignition lock control unit via interior CAN to the dynamic multicontour seat control unit.

Dynamic multicontour seat, general 

The dynamic multicontour seat combines the advantages of a comfortable multicontour seat with those of a sport seat. The contour and surface hardness of the backrest and the seat cushion of the driver and front passenger seat can be changed individually. This is done by air cushions that can be inflated independently of each other.

The air cushions are installed in the following areas:

• Lower lumbar area
• Upper lumbar area
• In the side bolsters of the backrest (lateral support)
• Front area of seat cushion (seat cushion length)

The lateral support in the driver and front passenger seat is made possible by a basic pressure in the lateral support air cushions. The dynamic function boosts the lateral support when cornering by automatically increasing the pressure in whichever lateral support air cushion is on the outside of the curve.

To prevent any tension in the back during long journeys, the multicontour seats are equipped with a massage function (pulse mode). As long as this is active, the contour of the seven-row massage insert is sequentially altered by building up, maintaining and relieving the pressure. The pulsation takes place in pressure jumps in the upward or downward direction. The dwell time can be set with the diagnostic tester.

The air supply required for inflating the air cushions is provided by the dynamic multicontour seat pneumatic pump. The relevant dynamic multicontour seat control unit sends the request to switch on over the interior CAN to the dynamic multicontour seat pneumatic pump. The status of the dynamic multicontour seat pneumatic pump is read in by the respective dynamic multicontour seat control unit via interior CAN.

PRE-SAFE:

In critical situations, the seat contour of the driver or front passenger seat is automatically changed to achieve a favorable seat position and securing of the occupant. Detailed information about this can be found in the "PRE-SAFE Function" function description.

The dynamic multicontour seat function comprises the following subfunctions:

• Function sequence for manual adjustment 
• Function sequence for position storage (with code (275) Electrically adjustable front seat memory package) 
• Function sequence for dynamic function 
• Function sequence for massage function 

Function sequence for manual adjustment 

Using the dynamic multicontour seat button groups, individual settings can be made at the driver or front passenger seat. The following seat areas can be adjusted:

• Lower lumbar area
• Upper lumbar area
• Side bolsters of the backrest (lateral support)
• Front area of seat cushion (seat cushion length)

The respective dynamic multicontour seat control unit reads in the control signals of the dynamic multicontour seat button group directly and evaluates them.

The inflation and deflation of the individual air cushions is controlled by the respective dynamic multicontour seat control unit by actuating the integrated piezo valves. The pressure values are recorded by integrated pressure sensors and stored by the relevant dynamic multicontour seat control unit.

Short-term and long-term control

The short-term control compensates for overpressure deviations in the air cushions. It activates following every adjustment and only remains active for a short, parameterizable period of time. The short-term control is used among others to compensate for sitting down or leaning back immediately and in a comfort-oriented fashion. After the short-term control, the long-term control becomes active. Here, the pressure supply is regulated such that the specified pressure is always achieved. It is regulated by the respective dynamic multicontour seat control unit.

The manual adjustment is aborted under the following conditions

• Overvoltage or undervoltage
• Inflation or deflation timeout
• Leak in one or more air cushions
• Dynamic multicontour seat button group has short circuit to ground or is jammed

The manual adjustment is blocked if the following faults occur:

• Inflation or deflation timeout
• Dynamic multicontour seat button group has short circuit to ground or is jammed

Function sequence for position storage (with code (275) Electrically adjustable front seat memory package) 

The set pressures in the air cushions of the driver and front passenger seat and the settings of the dynamic function can be saved and subsequently retrieved.

There are two options for saving the settings made:

• Press the respective front memory function switch and hold, then press the respective front memory 1 switch, front memory 2 switch or front memory 3 switch.
• Press respective front memory function switch for t > 100 ms and release, then press respective front memory 1 switch, front memory 2 switch or front memory 3 switch within t ≥ 0.2 to 3 s.

The respective front door control unit reads in the command requests of the individual switches at the corresponding front switch group, seat adjustment via front door LIN and sends this via interior CAN to the driver seat control unit or the front passenger seat control unit. The driver seat control unit or front passenger seat control unit sends the "Store memory position" request via interior CAN to the respective dynamic multicontour seat control unit.

When saving, the seat setting on the driver side, the steering column setting and the setting of the two outside mirrors are also saved.

Stored values can be overwritten at any time. The save process is canceled in the event of an active manual adjustment. Stored settings can be retrieved by pressing a memory switch. The respective front door control unit reads in the status of the memory switch via the front door LIN and sends it via interior CAN to the driver seat control unit or front passenger seat control unit. The driver seat control unit or front passenger seat control unit sends the "Adopt memory position" request over the interior CAN to the relevant dynamic multicontour seat control unit.

Additional function requirements for the dynamic function 

• Vehicle speed v > 10 km/h
• Steering wheel angle change > 9°
• Seat occupancy detected or seat belt buckle inserted (front passenger seat)

Function sequence for dynamic function 

The dynamic function boosts the lateral support when cornering by increasing the pressure in whichever lateral support air cushion is on the outside of the curve. The intensity of the lateral support can be adjusted in two stages.

The dynamic function is selected by pressing the Dynamics button:

• Pressed once, stage 2 (sport, both LEDs on)
• Pressed twice, stage 1 (standard, one LED on)
• Pressed three times, dynamic function OFF (both LEDs off)

The selected stage is indicated by one or both LEDs in the corresponding dynamics button lighting up. The respective dynamic multicontour seat control unit reads in the status of the Dynamics button and activates the LEDs in the Dynamics button directly according to the selected stage.

Depending on the vehicle speed and the vehicle's motion (lateral acceleration), the relevant dynamic multicontour seat control unit briefly increases the air pressure in the outside lateral support air cushion. The instrument cluster sends the vehicle speed via interior CAN to the respective dynamic multicontour seat control unit.

Information on the vehicle's self-movement is sent by the Electronic Stability Program control unit or the regenerative braking system control unit via chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13), front SAM control unit and interior CAN to the respective dynamic multicontour seat control unit.

The motion of the steering wheel is also evaluated. The steering wheel angle is recorded by the steering wheel sensor. The steering column tube module control unit reads in the signals of the steering angle sensor directly and sends them to the respective dynamic multicontour seat control unit via chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13), front SAM control unit and interior CAN.

The dynamic function is interrupted under the following conditions:

• Overvoltage or undervoltage
• Inflation or deflation timeout
• Leak in one or both lateral support air cushions
• On-board electrical system emergency running mode
• No information about the vehicle's self-movement
• Memory adjustment (with code (275) Electrically adjustable front seat memory package)
• Dynamic multicontour seat button group has short circuit to ground or is jammed

If the following faults occur, the dynamic function is blocked but the LEDs in the dynamics button remain switched on:

• Inflation or deflation timeout
• Dynamic multicontour seat button group has short circuit to ground or is jammed

Function sequence for massage function 

The massage function is a convenience function and lets the driver or front passenger relax, in particular during longer trips. Intensity can be adjusted in two stages. The respective dynamic multicontour seat control unit moves a slide valve in a cylinder with seven air outlets. By moving the slide valve, the air outlets to the rows of air cushions for the massage insert are opened or closed. The respective dynamic multicontour seat control unit can move the slide valve in a total of 23 slider positions and hold it there. The individual positions are compared to a reference position (limit switch). The front seat massage function actuator motor is actuated directly by the respective dynamic multicontour seat control unit. The status of the limit switch is read in directly by the respective dynamic multicontour seat control unit.

The massage function is selected by pressing the massage function button:

• Pressed once, massage program 1 (undulating, both LEDs on)
• Pressed twice, massage program 2 (rolling, one LED on)
• Pressed three times, massage function OFF (both LEDs off)

The selected massage program is indicated by one or both LEDs in the corresponding massage function button lighting up. The respective dynamic multicontour seat control unit directly reads in the status of the massage function button and directly actuates the LED in the massage function button according to the selected stage.

Massage program 1 (undulating):

• Manual lumbar support adjustment
• Manual adjustment of lateral support
• Memory adjustment (with code (275) Electrically adjustable front seat memory package)

The massage function is interrupted under the following conditions:

• Overvoltage or undervoltage
• Reference position in the seat massage function actuator motor not OK
• Target position in seat massage function actuator motor not reached
• Overloading of the dynamic multicontour seat pneumatic pump
• Adjustment request by PRE-SAFE
• Dynamic multicontour seat button group has short circuit to ground or is jammed

The massage function is blocked if the following faults occur:

• Reference position in the seat massage function actuator motor not OK
• Dynamic multicontour seat button group has short circuit to ground or is jammed

After pressing the massage function button, the respective dynamic multicontour seat control unit opens the air supply via the main valve to the front seat massage function actuator motor. Starting with the lower massage air cushion row (row 1), the contour changes sequentially through inflation, maintenance of the pressure and deflation. After a defined waiting time the cycle for the next massage air cushion row (row 2) is started on the same pattern. When the waiting time for inflating the last massage air cushion row (row 7) has elapsed, the cycle continues with the bottom massage air cushion row (row 1). The front seat massage function actuator motor has a total of 23 slide positions which it can moved to during a massage cycle. The pressure difference between the deflated and the inflated massage cushion is approx. p = 100 mbar. A wave motion is created by alternately deflating and inflating the rows of massage air cushions. After approx. t = 8 min, massage program 1 ends automatically.

Massage program 2 (rolling):

Starting with the lower massage air cushion row (row 1), the contour changes sequentially through inflation, maintenance of the pressure and deflation. After a defined waiting time the cycle for the next massage air cushion row (row 2) is started on the same pattern. When the waiting time for inflating the last massage air cushion row (row 7) has elapsed, the cycle continues with the next massage air cushion row (row 6). The remaining massage air cushion rows are then activated successively in the reverse order. After approx. t = 12 min, massage program 2 ends automatically.

In both programs the massage function can be performed with two characteristics (weak or strong). This results in four massage programs that can be assigned via the variant coding.

The active massage program is interrupted under the following conditions: