Longitudinal Dynamics Systems
By applying today's standard consideration aspects, subdividing the functions of driving
dynamics systems into the three co-ordinate axes results in the use of three different
systems that belong to longitudinal dynamics on the E70.
Longitudinal dynamics systems (effective direction mainly on the x-axis or longitudinal
axis):
• (ABS) Anti-lock braking system
• (DSC) Dynamic stability control
• (EMF) Electromechanical parking brake
• (DCC) Dynamic cruise control (cruise control with brake intervention)
ABS in DSC
The ABS prevents the wheels locking while braking and therefore ensures that the vehi-
cle stays on track and can be steered in critical situations.
ABS is constantly activated during vehicle operation and cannot be switched off by the
driver. The four wheel speed sensors send data to the DSC control unit that monitors the
speed of each wheel. If one or several wheels decelerate at a faster rate than permitted,
the DSC control unit activates the hydraulic unit, which in turn reduces the hydraulic
pressure in the corresponding brake line. The DSC control unit and the hydraulic unit
make up one assembly.
When the DSC control unit requests intervention of the antilock braking system, it acti-
vates the inlet and outlet solenoid valves in the hydraulic unit of the affected brake line
and switches on the return pump. The inlet valve closes in order to disconnect the brake
line(s) from the master brake cylinder and the outlet valve opens to allow the brake fluid
of the affected brake circuit to escape into the reservoir in order to reduce the pressure in
the circuit. Consequently, the braking effect is reduced and the wheel begins to turn.
The DSC control unit then opens and closes the inlet and outlet valves in such a way as
to ensure the optimum braking pressure is built up at each wheel without the wheels
locking.
The return pump conveys brake fluid from the equalizing reservoir of the master
brake cylinder, thus maintaining a constant brake fluid pressure downstream of the inlet
valves so that the pressure in the brake lines is immediately re-established when the inlet
valves are open again.
In the case of braking with ABS assistance, the driver normally obtains feedback in the
form of pedal vibration and the noise of solenoid valves or the pump. This is reduced to a
minimum by the high-performance hydraulic unit of the DSC E7x in the E70.
5
E70 Longitudinal Dynamics Systems
Introduction
Dynamic Stability Control (DSC)
The E70 is equipped with a new generation of the dynamic stability control system.
Note: To date, the DSC driving dynamics system on all-wheel drive vehicles
was referred to with the abbreviation "DXC".
Since this lead to confusion with the xDrive, in the future the dynamic stability control sys-
tem will be known as DSC also on all-wheel drive vehicles.
This new generation of the dynamic stability control (DSC E7x, supplied by Bosch) in the
BMW X5 is actually the only driving dynamics system that covers all three areas of longi-
tudinal, transverse and vertical dynamics with its control intervention functions and its
modular functional structure.
With its varied control strategies, the DSC ensures outstanding driving stability within
physical limits, active safety and excellent traction in all driving situations.
Electromechanical Parking Brake (EMF)
The electromechanical parking brake was used for the first time at BMW on the E65 (7
Series).
In principle, the task of the parking brake is to secure the stationary vehicle to prevent it
rolling away. The parking brake firmly holds the parked vehicle. In contrast to the parking
brake that to date was based on a pure mechanical hand brake and foot brake system,
the EMF is designed as an automated, comfort-oriented parking brake system where the
driver can apply and release the parking brake by the push of a button.
The design layout of the parking brake system is in keeping with typical BMW require-
ments:
• Exclusion of all safety-critical situations
• Optimum functionality
• Maximum system availability
• High degree of comfort and convenience
Besides complying with the legal requirement of mechanically holding the parked vehicle
and providing an independently operable parking brake in addition to the service brake,
one of
the main adv
antages of
the EMF is that it enables dynamic braking with DSC con-
trol.
Dynamic Cruise Control (DCC)
The dynamic cruise control is a conventional cruise control system (Tempomat) which
features additional functions including active brake intervention. Cruise control with brake
intervention (DCC) was introduced for the first time at BMW on the E90 (3 Series).
6
E70 Longitudinal Dynamics Systems
7
E70 Longitudinal Dynamics Systems
Bus Overview DSC
Index Explanation Index Explanation
CAS
Car Access System
DSC
Dynamic stability control
IHKA
A
utomatic climate control
DME
Digital motor electronics
KOMBI
Instrument cluster
DDE
Digital diesel electronics
JB
Junction box
EMF
Electromechanical parking brake
DSC SEN
DSC sensor
V
GSG
T
ransfer box control unit
SZL
Steering column switch cluster
GWS
Gear selector lever
8
E70 Longitudinal Dynamics Systems
D
SC Circuit Diagram
L
egend for DSC Circuit Diagram
DSC System Overview
9
E70 Longitudinal Dynamics Systems
Index Explanation Index Explanation
1
Wheel-speed sensor, front left
11
Brake light switch
2
Brake pad wear indicator, front left
12
Instrument cluster
3
Brake fluid level sensor
13
Center console switch cluster
4
Digital motor electronics
14
Automatic climate control
5
Dynamic stability control
15
Gear selector lever
6
Wheel-speed sensor, front right
16
DSC sensor
7
Junction-box ECU
17
Transfer box control unit
8
Wheel-speed sensor, rear right
18
Steering column switch cluster
9
Brake pad wear indicator, rear right
19
Car Access System
10
Wheel speed sensor, rear left
Index Explanation Index Explanation
1
Hy
dr
aulic unit with DSC control unit
5
Cent
er
console switch cluster
2
Wheel speed sensor (4x)
6
Steering column switch cluster
3
Master brake cylinder
7
Gear selector lever
4
DSC sensor
8
EMF actuating unit
10
E70 Longitudinal Dynamics Systems
E
MF Schematic Circuit Diagram
L
egend for EMF Schematic Circuit Diagram
EMF System Overview
11
E70 Longitudinal Dynamics Systems
I
ndex
E
xplanation
I
ndex
E
xplanation
1
Wheel-speed sensor, front left
5
Instrument cluster
2
Dynamic stability control
6
Gear selector lever
3
Digital motor electronics
7
EMF actuating unit
4
Junction-box ECU
Index Explanation Index Explanation
1
Dynamic stability control
4
EMF actuating unit
2
Master brake cylinder
5
Emergency release EMF
3
Gear
select
or
lever
New Features of the DSC E7x
The system supplier for the DSC E7x is Bosch. With its optimized control functions, the
new system design makes a significant contribution to increased driving dynamics.
Additional functions for active safety and additional comfort have been implemented in
the new system. The new system in the E70 offers the following advantages:
• Driving Dynamics
– DSC mode: Increased driving dynamics and maximum traction. Thanks to more
precise and faster control interventions, the driver can further extend the bound-
aries of driving dynamics while retaining vehicle safety.
– DTC mode: Compared to DSC mode, Dynamic Traction Control (DTC) allows for
increased slip at the drive wheels to provide maximum propulsion when driving off
in snow for instance. In addition, the stabilizing control interventions cut in later in
DTC mode thus allowing a more sport-oriented driving profile.
• Active Safety
– The additional functions of brake standby, dry braking and fading assistance short-
en the stopping distances.
– Increased DSC efficiency makes for more effective safety-relevant functions.
• Comfort
– Improved operating comfort (brake interventions are less audible, pedal vibration is
drastically reduced) through the use of a 6-piston pump in connection with a new
higher-frequency electrical actuation system.
– Additional functions such as start-off assistant and parking brake provide increased
driver assistance and comfort.
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E70 Longitudinal Dynamics Systems
Classic Brake Control Functions
• Antilock Braking System (ABS)
ABS prevents individual wheels from locking while braking by targeted modulation of
the braking pressures. The steerability of the vehicle through the front wheels is
largely retained. When braking on road surfaces with different coefficients of friction,
the straight-ahead position is stabilized in co-operation with the active steering
(option).
• Cornering Brake Control (CBC)
(CBC) keeps the vehicle under control when braking lightly in fast corners by asym-
metric control of the braking pressure, thus improving the cornering stability.
• Automatic Stability Control (ASC)
(ASC) prevents spinning of the drive wheels by way of specific brake application and
influencing the drive torque delivered by the combustion engine thus optimizing the
forward propulsion of the vehicle.
• Dynamic Brake Control (DBC)
If an emergency braking operation is initiated by the driver, the system assists the
driver by automatically applying the maximum braking pressure immediately in order
to optimize the braking effect.
• Automatic Differential Brake (ADB-X)
ADB-X replicates the function of the differential locks: if a wheel tends towards spin-
ning, it is automatically braked so that forward propulsion can still be achieved
through the other wheel on the axle.
• Dynamic Stability Control (DSC)
A vehicle which tends to understeer or oversteer is stabilized by specific brake inter-
vention on individual wheels. This function operates on the E70 together with the
active steering (option).
• Hill Descent Control (HDC)
HDC automatically applies the brakes at individual wheels when driving downhill at
lo
w speed, particularly on poor surfaces such as sand, gravel or snow. The function
is activated by means of a button in the center console.
• Trailer Stabilization Logic
This function automatically detects when a vehicle with a trailer begins to sway and it
stabilizes the vehicle-trailer combination by specific brake intervention thus reducing
the speed to belo
w the critical shear/swerve level.
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E70 Longitudinal Dynamics Systems
Additional Brake Control Functions
• Dynamic Traction Control (DTC)
DTC represents a special mode of DSC which, while interacting with (ASC), (ADB-X)
and xDrive, realizes maximum propulsion on loose surfaces such as snow, sand or
gravel, by extending the slip thresholds. The stabilization interventions in connection
with DTC cut in later than with DSC thus enabling a more sport-oriented driving pro-
file.
• Brake Standby
This function builds up a moderate braking pressure in the system when the driver
very quickly takes his/her foot off the accelerator pedal. The braking effect then cuts
in faster to assist the driver in emergency braking.
• Dry Braking
This function lightly applies the brake pads at specific intervals depending on the
operation of the windscreen wiper in order to dry the brake discs. This distinctly
improves the braking effect in braking operations.
• Fading Assistance
This function assists the driver in applying the braking force when the brake temper-
ature is very high due to an extreme driving profile which requires a higher braking
force in order to achieve the required braking effect.
• Start-off Assistant
The start-off assistant holds the vehicle on gradients for about. 1.5 seconds after
the driver has taken his/her foot from the brake. In this way, the driver can conve-
niently operate the accelerator pedal without the vehicle rolling back.
• Electromechanical Parking Brake (EMF)
The EMF is a parking brake that can be applied and released by means of a bidirec-
tional button. Depending on the respective vehicle operating situation, the holding
force is applied wither hydraulically via the DSC or mechanically via EMF.
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E70 Longitudinal Dynamics Systems
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