Drive control (FR) function

W30.35-1084-79

CAN bus systems involved:

1 Vehicle CAN bus

2 Engine CAN bus

3 Special equipment CAN bus

Indicator/warning lamps and fault indications requested by the drive control (FR):

4 Flame starting system indicator lamp
- Only for vehicles with code (M89) flame starting system

5 FLA fault display with fault code
- Only for vehicles with code (M89) flame starting system

6 FR/FMR fault display with fault code

7 Coolant level warning lamp

8 Charge indicator lamp

9 Air cleaner monitor sensor warning lamp

10 Wear-free brake indicator lamp

11 Oil level warning lamp in tank for automatic engine oil refill

12 Temperature indicator (on the display)

A20 Retarder control unit
- Only for vehicles with Code (BA9) Voith secondary-retarder R 115

A22 PSM control unit
- Only for vehicles with Code (ED5) parameterizable special module (PSM), Code (EM7) parameterizable special module with body CAN bus or Code (EM8) parameterizable special module with body and trailer CAN bus

A41 Torque converter clutch control unit
- Only for vehicles with Code (G02) torque converter clutch (WSK)

A42 WSP control unit

B1 Foot throttle actuator

B2 Clutch travel sensor

B3 Countershaft rpm sensor

B4 Outside temperature sensor

B5 Parking brake switch

B6 Coolant level switch

B7 Air cleaner monitoring sensor/switch

Components involved directly or indirectly:

A3 Drive control (FR) control unit

A4 Flame starting system (FLA) control unit
- Only for vehicles with code (M89) flame starting system

A6 MR/PLD control unit

A10 ABS control unit
- Vehicles with Code (B02) brake system, antilock brake system (ABS)

A11 BS/EPB control unit
- Vehicles with Code (BB1) brake system (BS) or with code (BB8) brake system (BS) with ASR

A15 Shift control unit, GS/EPS
- Only for vehicles with Code (GS2) gear control

A16 Control unit, GS/EPS
- Only for vehicles with Code (GS2) gear control

A18 Automatic gear determination/selection (AG/AGE) control unit
- Only for vehicles with Code (GE1) electronic drive control

B17 Speed sensor

B60 Gear sensor

B61 Gate sensor

G2 Generator

P1 Tachograph

P2 Instrument cluster

S1 Drive switch

S2 Engine control/permanent brake operating lever

S3 Splitter switch

S4 Stop lamp switch

S7 Reverse gear switch

a) Instrument cluster (INS)
- up to 31/12/1999

b) Instrument cluster (INS)
- from 01/01/2000

* Only for vehicles with Code (GS1) 'mechanical' gearshift or Code (GS3) 'hydraulic' gearshift

** Only for vehicles with Code (GS2) gear control

*** Only for vehicles with Code (B02) brake system, antilock brake system (ABS)

S8 Range position switch

S9 Neutral position switch

S23 PTO 1 indicator switch

S79 PTO 2 indicator switch

S80 PTO 3 indicator switch

X13 Diagnostic socket

Y1 Engine brake solenoid valve 1

Y2 Engine brake solenoid valve 2

Y29 GS/EPS valve block, solenoid valve MS2

Y30 GS/EPS valve block, solenoid valve MS1

Z1 CAN star point for cab dash support

General information

Like the engine control (MR), the drive control (FR) is an autonomous, electronic system and forms the interface between chassis and power train.

It regulates, controls, and monitors all vehicle-specific functions required in drive mode, and its main task is to calculate the specified torque for the driver intention and transfer this to the engine control (MR) system.

The central control and regulating unit is the FR control unit (A3), which is networked over the engine CAN bus (2) with the MR/PLD control unit (A6), and over the vehicle CAN bus (1) and CAN star point cab dash support (Z1) with the following control units (among others):

 Instrument cluster (P2),

 ABS control unit (A10) - for vehicles with Code (B02) brake system, antilock brake system (ABS),

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 BS/EPB control unit (A11) - for vehicles with Code (BB1) brake system (BS) or with Code (BB8) brake system (BS) mit ASR,

 GS/EPS control unit (A16) - only for vehicles with Code (GS2) gear control,

 Automatic gear determination/selection (AG/AGE) control unit (A18) - only for vehicles with code (GE1) electronic drive control,

 Retarder control unit (A20) - only for vehicles with Code (BA9) Voith secondary retarder R 115,

 PSM control unit (A22) - only for vehicles with Code (ED5) parameterizable special module (PSM), Code (EM7) parameterizable special module with body CAN bus, or Code (EM8) parameterizable special module with body and trailer CAN bus,

 Torque converter clutch control unit (A41) - only for vehicles with Code (G02) torque converter clutch (WSK).

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1 Base functions of the drive control (FR)

1.1 To calculate and transfer the specified enginge torque
The specified engine torque is determined by computer calculation only, from which the driver intention is deduced.
This value depends firstly on the position of the accelerator pedal, which is determined by the FR control unit (A3) through the foot throttle actuator (B1).
Depending on vehicle equipment, other variables may be sent by the GS/EPS sontrol unit (A16), the retarder control unit (A20), the PSM control unit (A22), the AG/AGE control unit (A18) or the torque converter clutch control unit (A41) over the vehicle CAN bus (1).

 The drive control (FR) can limit the specified engine torque in order to maintain the maximum speed required by law, or if there is a control intervention function by the antilock brake system (ABS) or acceleration slip regulation (ASR).

After the drive control (FR) has calculated the specified engine torque, it sends it over the engine CAN bus (2) to the engine control (MR).

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1.2 Control of the constant throttles and engine brake flap
The solenoid valves that supply compressed air to the constant throttles are actuated by the FR control unit (FR) (A3), which also (provided the vehicle is not equipped with Code (BA9) Voith secondary retarder R 115) detects the applied positions of the engine control/permanent brake operating lever (S2).

 On vehicles with Code (BA9) Voith-secondary-retarder
R 115, the applied positions of the engine control/ permanent brake operating lever (S2) are detected by the retarder control unit (A20), converted into messages and sent over the vehicle CAN bus (1) to the drive control (FR) control unit (A3).

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1.3 Determining and sending the vehicle speed
From the different input values, the drive control (FR) determines the momentary vehicle speed, on which the limitation of specified engine torque depends (among other things), and sends this to the other systems over the vehicle CAN bus (1).

1.4 Vehicle speed control
The drive control (FR) integrates comfort systems for speed control such as cruise control, Temposet and brakes/cruise control. The deceleration control (brakes/cruise control) is used to set a maximum speed, which is regulated (especially on sharp gradients) by almost continuous regulation of the braking torque. The required control values are calculated by the FR control unit (A3) and sent over the vehicle CAN bus (1) to the retarder control unit (A20).

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1.5 Generator preexcitation and charging current monitoring
Generator preexcitation is not performed by the charge indicator lamp (8), but by a circuit in the FR control unit (A3).
The FR control unit (A3) also monitors the charging current of the generator (G2) and, if the charging current is absent or too low, sends a request over the vehicle CAN bus (1), for actuation of the charge indicator lamp (8) by the instrument cluster (P2).

1.6 Actuation of the stop lamp
 Vehicles with Code (B02) brake system, antilock brake system (ABS):
Through the stop lamp switch (S4), the FR control unit (A3) detects the brake pedal position and actuates the stop lamp when the brake is operated (through a relay in the base module).

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 Vehicles with Code (BB1) brake system (BS) or with Code (BB8) brake system (BS) with ASR:
The FR control unit (A3) actuates the stop lamp if it receives the corresponding request (in the form of a message) from the BS/EPB control unit (A11) over the vehicle CAN bus (1).

1.7 Actuation of the backup lamp
 Vehicles with Code (GS1) 'mechanical' gearshift or Code (GS3) 'hydraulic' gearshift:
Through the reverse gear switch (S7), range position switch (S8) and neutral position switch (S9), the FR control unit (A3) detects the applied position of the transmission. If reverse gear is engaged, it actuates the backup lamp (through a relay in the base module).

 Vehicles with Code (GS2) gear control:
On vehicles with Code (GS2) gear control, the applied position of the transmission is detected by the GS/EPS control unit (A16) only.

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If the reverse gear is engaged, the GS/EPS control unit (A16) requests actuation of the backup lamp by the FR control unit (A3) over the vehicle CAN bus (1).

2 Additional functions of the drive control (FR)

2.1 Vehicles with Code (GS1) 'mechanical' gearshift or Code (GS3) 'hydraulisch' gearshift
On vehicles with Code (GS1) 'mechanical' gearshift or Code (GS3) 'hydraulisch' gearshift, the drive control (FR) detects the applied position of the transmission, through the information from the neutral position switch (S9) and reverse gear switch (S7). This is needed, for example if there is a start request, to be able to send a start enable to the engine control (MR).

 On vehicles with Code (GS2) gear control, the applied position of the transmission is detected by the GS/EPS control unit (A16) and sent over the vehicle CAN bus (1) to the FR control unit (A3).

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2.2 Vehicles with Code (ET5) adaptive cruise control
The other switches present with the engine control/ permanent brake operating lever (S2) on vehicles with Code (ET5) adaptive cruise control, are read in by the FR control unit (A3).
If the engine control/permanent brake operating lever (S2) is placed in the corresponding position, then the drive control (FR) activates or deactivates the adaptive cruise control (ART), or changes the desired vehicle speed or distance from the vehicle in front.
If the adaptive cruise control (ART) is active, then the drive control (FR) determines from various data whether the vehicle is to accelerate or decelerate. It then causes the vehicle to accelerate or decelerate accordingly, possibly by correcting the specified engine torque or by making a permanent brake (retarder) request, or by a request for a brake control intervention by the BS/EPB.

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2.3 Vehicles with Code (BA9) Voith secondary retarder R 115
From the retarder rpm, the retarder control unit (A20) determines the maximum retarder brake torque that can be implemented, and sends this to the FR control unit (A3).
At the same time, it detemines the position of the engine control/ permanent brake operating lever (S2) and sends this to the FR control unit (FR) (A3).
The FR control unit (A3) divides the specified torque that can be requested between the different lever positions or into different stages, and sends this back to the retarder control unit (A20).

2.4 Vehicles with power take-off
The working speed control for a power take-off can be performed by the drive control (FR).
The controller type, stationary speed limitation and torque limitation can be selected in the FR control unit (A3).

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2.5 Vehicles with Code (GE1) electronic drive control
On vehicles with Code (GE1) electronic drive control (EAS) with optional equipment electronics (for engine-clutch control/electromotive clutch control and automatic gear selection/automatic gear determination/selection), a special 0-load controller is installed for rpm adaptation when changing to automatic mode.

3 Diagnostic functions of the drive control (FR)
In the drive control (FR), the majority of connected components are monitored by the FR control unit (A3). Components that cannot be monitored (switches, etc.) can be fully tested using
measured and binary values. In certain cases, connected components can be measured in test mode (resistance measurement) or a test actuation performed (active test).

4 Special functions of the drive control (FR)
To be able to use the control units for the drive control (FR) with the various equipment in all vehicle models, more parameterization possibilities were required.
To be able to adapt the FR control unit to the individual equipment variants, outputs and inputs can be assigned to different functions and fault detection enabled/disabled at different outputs or inputs.