ESP braking moment control circuit, function

CAN B

CAN C

CAN SBC

ESP, SPS [PML] and BAS control module (N47-5)

SBC right-side control unit (A7/4n1)

Engine control module

EGS control unit (N15/3)

Parking brake switch (S12)

Diagnostic interface (X11/4)

Instrument cluster (A1)

ESP and ABS warning lamp (A1e41)

ABS indicator lamp (A1e17)

multifunction display (A1p13)

VBF control unit (N72)

SAM control unit with driver-side fuse and relay module (N10/1)

EIS [EZS] control module (N73)

Jacket tube module

(N80)

Steering angle sensor

(N49)

Yaw rate and lateral acceleration sensor (B24/15)

Circuit 31, ground

Voltage terminal 87

ESP OFF switch (N72s14)

Left-side SBC control unit (A7/3n1)

The functions of the braking moment control circuit are controlled using the components of the electric/electronic system.

The Terminal 87 power supply for the ESP, PML and BAS control unit (N47-5) is provided by the SAM control unit with driver-side fuse and relay module (N10/1).

The ESP, PML and BAS control unit (N47-5) receives input signals from the following components:

 4 wheelspeed sensors (via SBC control units)

 Steering angle sensor over CAN data line

 Lateral acceleration sensor

 Yaw rate sensor

 SBC control units via CAN data wire

 AIRmatic control unit through CAN data wire

 DTR control unit via CAN data wire

 On-board electrical systems ECU through CAN data wire

 Engine control module over CAN data line

 ETC control module over CAN data line

 ESP OFF switch over CAN data line

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The input signals are processed in the ESP control module to form output signals for the following components:

 SBC control units through CAN data wire

 Engine control module over CAN data line

 ETC control module over CAN data line

 ESP and ABS warning lamps through CAN data wire

 ABS indicator lamp through CAN data wire

 Multifunction display over CAN data line

The ESP, PML and BAS control unit (N47-5) determines which of the 8 operating modes to activate based on the input signals

 Normal operation

 ABS control mode

 ASR control mode

 EBR control mode (see drive moment control circuit)

 ESP control mode

 ESP OFF mode

 BAS mode

 DTR control mode

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Normal operation

This is the case when the driving state requires no control mode. There is no closed-loop control during normal braking maneuvers.

This mode also exists when there is a malfunction in the ESP, BAS or ABS system. Drive torque control is not activated.

ABS control mode

Based on the wheelspeeds, the ESP, PML and BAS control unit (N47-5) determines that the criteria for initiating active closed-loop ABS control are present; the SBC control units respond by activating selected solenoid valves in the two hydraulic units.

The solenoid valves for the front and rear wheels in the SBC hydraulic units (A7/3, A7/4) are triggered individually (4-channel control).

ASR control mode

The ESP, PML and BAS control unit (N47-5) responds to incipient wheel slip in a drive wheel by activating the SBC control units, which then trigger selected solenoid valves for the rear wheels.

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ESP control mode

A status controller in the ESP, PML and BAS control unit (N47-5) receives and processes the signals for wheelspeeds, steering angle, vehicle yaw rate, lateral acceleration and braking at the individual wheels. Once the incoming signals have been processed, the SBC control units activate the necessary solenoid valves to modulate braking pressure at the individual wheels to the desired levels.

ESP OFF mode

Activation of the ESP OFF switch (N72n14) cancels the ESP system's drive torque regulation function as well as the stability enhancement feature during acceleration and coasting. The ESP stability function remains operational during braking. EBR control is deactivated.

With the switch in this position, braking force is applied to one spinning drive wheel via the braking moment control circuit at vehicle speeds of up to 40 km/h. If activation conditions continue to exist, brake intervention continues up to max. 60 km/h. The braking torque is, however, reduced continuously.

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BAS mode

Based on the rate at which the brake pedal is depressed, the ESP, PML and BAS control unit (N47-5) recognizes panic stops, to which it responds by initiating active BAS intervention (refer to BAS operation).

Distronic control mode

The Distronic (DTR) control unit transmits the signals for DTR control to the ESP control unit. This assigns priorities to the various demands before relaying the data to the engine-management ECU and, when indicated, initiating braking intervention.

The transmission display and warning function of the DTR is transmitted direct to the relevant receivers.