412 Sensotronic brake control Purpose and function

Sensotronic brake control (SBC)

Sensotronic brake control (SBC) is an Basic functions
electrohydraulic brake system that com- As with a conventional braking system,
bines the functions of a brake servo unit sensotronic brake control must be capable of
and the ABS (antilock braking system) 쐌 reducing the speed of the vehicle,
equipment, including ESP (electronic 쐌 bringing the vehicle to a halt, and
stability program). The mechanical opera- 쐌 keeping the vehicle stationary when it is
tion of the brake pedal is redundantly mea- stopped.
sured by the actuator unit and transmitted
to the control unit. There, control com- As an active braking system, it also performs
mands are calculated according to specific the tasks of
algorithms and passed to the hydraulic 쐌 operating the brakes,
modulator where they are converted into 쐌 amplifying the brake force, and
pressure modulating operations for the 쐌 modulating the brake force.
brakes. If the electronics fail, a hydraulic
fallback system is automatically available. SBC is an electronic control system with
hydraulic actuators. Braking force distribu-
Purpose and function tion takes place electronically to each wheel
in response to driving conditions. A vacuum
By utilizing its “brake-by-wire” capabilities, source for the brake servo function is no
SBC can control the hydraulic pressure in longer required. The self-diagnosis capabil-
the wheel brake cylinders independently of ity enables an early warning function for
driver input. As a result, functions beyond detection of possible system faults.
those performed by ABS (antilock braking SBC uses hydraulic standard wheel
system), TCS (traction control system) and brakes. Because of the fully electronic pres-
ESP (electronic stability program) can be sure control, SBC can be easily networked
implemented. One example is the conve- with vehicle handling systems. It thus meets
nient method of brake application for ACC all the demands made of future braking
(adaptive cruise control). systems.

1 SBC components in the car

1 2 3 4 1 1

Fig. 1
1 Active wheel speed
Motr
C

onic
sensor with direction
A
N

sensing
2 Engine management SB
C
ECU
3 SBC ECU
4 Yaw rate and lateral
acceleration sensor
5 Hydraulic modulator
CA
N

(for SBC, ABS, TCS

æ UFB0704-2Y

and ESP)
6 Actuator unit with
pedal travel sensor
7 Steering angle
5 1 6 7
sensor

K. Reif (Ed.), Automotive Mechatronics, Bosch Professional Automotive Information,

DOI 10.1007/978-3-658-03975-2_19, © Springer Fachmedien Wiesbaden 2015
 Sensotronic brake control Purpose and function 413

By using a high-pressure accumulator, SBC optimum friction value is fully utilized. This
is capable of extremely rapid dynamic pres- results in a significant reduction of total
sure increases and thus offers the potential braking distance for hesitant drivers. The
for achieving short braking distances and highly dynamic braking force build-up of
excellent vehicle handling stability. Brake SBC exceeds that of conventional systems in
pressure modulation and active braking are this regard.
silent and produce no brake pedal feedback.
Consequently, SBC also satisfies demands Soft stop assist
for greater levels of comfort. SBC provides comfortable braking that stops
Braking characteristics can be adapted to the car with no jerking by automatically
the driving conditions (e.g. sharper response reducing the pressure just before the car
at high speeds or with more dynamic dri- comes to a complete stop. If more decelera-
ving styles). “Duller” pedal characteristics tion is desired, this function is not activated
allow the reduction of the braking effect, and SBC minimizes the braking distance.
which is necessitated by physics, to be
signaled to the driver before fading due Traffic jam assist
to overheating occurs. When traffic jam assist is activated, SBC
builds up a higher drag torque, which means
Additional SBC functions that the driver does not have to constantly
The auxiliary functions provided by SBC alternate between the accelerator and brake.
make a significant extra contribution to The vehicle is automatically braked and, if
safety and convenience. necessary, brought to a complete stop and
kept at a complete stop. This function can be
Hill hold control activated at speeds of 50 - 60 km/h.
After hill hold control is activated by a sig-
nificant increase in brake pressure while the Brake wiping
vehicle is stationary, the vehicle remains “Brake wiping” is an operation whereby the
braked without the need to keep the pedal film of water is regularly removed from the
down. The hill hold control is automatically brake disks in wet weather. It results in
released as soon as the driver has built up shorter stopping distances in wet conditions.
sufficient engine torque by depressing the You can take the information for activating
accelerator. This allows the driver to start the this function from the windshield wiper
car on a hill, for example, without activating signal, for example.
the parking brake system. Likewise, in other
situations in which the vehicle would roll
out of position if not braked, the driver does 2 Evolution of brake systems

not need to keep his or her foot on the brake

at all times once hill hold control has been
activated.
Brake-by-Wire- EMB electromechanical brake
Systems SBC electrohydraulic brake
Enhanced brake assist function EBS electronic braking system (trucks)
If the driver abruptly releases the accelerator, Electronic ESP electronic stability program
an automatically regulated brake pressure brake control TCS traction control system
build-up takes place that gently applies the systems
ABS antilock braking system
brake pads. If panic braking follows, this al- Unassisted
æ UFB0736-1E

Power-assisted brake Conventional

lows the brake to “grab” more quickly and brake
Externally powered brake braking systems
thus allows a shorter total braking distance.
If the system detects panic braking, the
brake pressure is briefly increased until the