1. ANTI - LOCK BRAKING and TRACTION CONTROL
SYSTEMS

2. Anti - Lock Braking Systems were first developed in
the aircraft industry to aid and further improve the
landing capabilities of the aircraft.

3. Anti - Lock Braking Systems were first developed in
the aircraft industry to aid and further improve the
landing capabilities of the aircraft.
This improved the following :
the stopping distance of
the plane.

4. Anti - Lock Braking Systems were first developed in
the aircraft industry to aid and further improve the
landing capabilities of the aircraft.
This improved the following :
the stopping distance of
the plane.
control of the plane on
landing.

5. Anti - Lock Braking Systems were first developed in
the aircraft industry to aid and further improve the
landing capabilities of the aircraft.
This improved the following :
the stopping distance of
the plane.
control of the plane on
landing.
safety in poor weather
conditions.

6. Anti - Lock Braking Systems were first developed in
the aircraft industry to aid and further improve the
landing capabilities of the aircraft.
This improved the following :
the stopping distance of
the plane.
control of the plane on
landing.
safety in poor weather
conditions.
directional stability.

7. Anti - lock braking systems on vehicles provide the same
advantages as with aircraft. Any system must fulfil the
following criteria :
maintenance of manoeuvrability (lateral guiding of the
front wheels).

8. Anti - lock braking systems on vehicles, provide the same
advantages as with aircraft. Any system must fulfil the
following criteria :
maintenance of manoeuvrability (lateral guiding of the
front wheels).
maintenance of directional stability (lateral guiding of
the rear wheels).

9. Anti - lock braking systems on vehicles, provide the same
advantages as with aircraft. Any system must fulfil the
following criteria :
maintenance of manoeuvrability (lateral guiding of the
front wheels).
maintenance of directional stability (lateral guiding of
the rear wheels).
reduction in braking distance in comparison with a
conventional system.

10. Anti - lock braking systems on vehicles provide the same
advantages as with aircraft. Any system must fulfil the
following criteria :
maintenance of manoeuvrability (lateral guiding of the
front wheels).
maintenance of directional stability (lateral guiding of
the rear wheels).
reduction in braking distance in comparison with a
conventional system.
Guarantee of low regulation amplitudes (pedal reactions
and comfort).
OVERALL IMPROVED SAFETY OF THE VEHICLE.

11. Brake Pressure Unit PUMP UNIT
This diagram shows an INTEGRATED ABS system.
Brake Pressure Unit
Brake Servo
ABS Unit
High Pressure
Pump
PUMP
UNIT

12. Brake Pressure Unit PUMP UNIT
This diagram shows an INTEGRATED ABS system.
Brake Pressure Unit
Brake Servo
ABS Unit
High Pressure
Pump
This system comprises of :
- a brake pressure unit : functional INTEGRATION of the master cylinder and brake servo with the ABS regulation unit.
PUMP
UNIT

13. Brake Pressure Unit PUMP UNIT
This diagram shows an INTEGRATED ABS system.
Brake Pressure Unit
Brake Servo
ABS Unit
High Pressure
Pump
This system comprises of :
- a brake pressure unit : functional INTEGRATION of the master cylinder and brake servo with the ABS regulation unit.
PUMP
UNIT
- a pump unit : source of high pressure (180 bars) for the hydraulic servo.

14. This diagram shows ADDITIONAL ABS system.
ADDITIONAL REGULATION UNIT (ABS)

15. This diagram shows ADDITIONAL ABS system.
ADDITIONAL REGULATION UNIT (ABS)
An additional ABS system comprises :
- a tandem master cylinder with servo (vacuum or hydraulic) which produces the brake pressure and distributes it to the callipers through the brake pipes.

16. This diagram shows ADDITIONAL ABS system.
ADDITIONAL REGULATION UNIT (ABS)
An additional ABS system comprises :
- a tandem master cylinder with servo (vacuum or hydraulic) which produces the brake pressure and distributes it to the callipers through the brake pipes.
- an additional regulation unit, modulating the brake pressure in each calliper independently of the effort applied to the brake pedal.

17. Schematic Diagram
Bosch 2SE system

18. Hydraulic Circuit A
The ABS system contains a :
- hydraulic circuit.
- electrical circuit. B
This circuit has 4 callipers (A) connected to the tandem master cylinder which generates the brake pressure.

19. Hydraulic Circuit C
A load sensitive compensator (C) modifies the braking pressure to the rear callipers according to body movement.

20. Hydraulic Circuit D
The Additional Regulator Unit (D), modifies the brake pressure in the callipers in such a way as to prevent the wheel locking.

21. Electrical Circuit
This circuit comprises of :
- 4 wheel speed sensors (E) which generate electrical impulses whose frequency depends on the speed of rotation of the wheel. E E E E

22. Electrical Circuit F
An electronic control unit (F) which uses the signals from the wheel sensors and controls the solenoid valve in the regulation unit.

23. H
Electrical Circuit
A warning lamp (G) located in the instrument panel and a connector (H) enabling fault diagnosis. G

24. Electrical Circuit - The Wheel Sensor
Nearly all modern ABS systems have four
channel operation. That is to say that there
is a wheel sensor fitted on each of the road
wheels.
The ECU can monitor up to 8000 sensor signals
per second and can take action within a few
milliseconds.

25. Electrical Circuit - The Wheel Sensor
Nearly all modern ABS systems have four
channel operation. That is to say that there
is a wheel sensor fitted on each of the road
wheels.
The ECU can monitor up to 8000 sensor signals
per second and can take action within a few
milliseconds.
PERMANENT
MAGNET

26. Electrical Circuit - The Wheel Sensor
Nearly all modern ABS systems have four
channel operation. That is to say that there
is a wheel sensor fitted on each of the road
wheels.
The ECU can monitor up to 8000 sensor signals
per second and can take action within a few
milliseconds.
PERMANENT
MAGNET
SOFT IRON CORE

27. Electrical Circuit - The Wheel Sensor
Nearly all modern ABS systems have four
channel operation. That is to say that there
is a wheel sensor fitted on each of the road
wheels.
The ECU can monitor up to 8000 sensor signals
per second and can take action within a few
milliseconds.
PERMANENT
MAGNET
SOFT IRON CORE
WINDING

28. Electrical Circuit - The Wheel Sensor
The wheel sensor is known as a PASSIVE sensor.

29. Electrical Circuit - The Wheel Sensor
Reluctor tooth on driveshaft
Pick up coil in wheel
sensor with permanent
magnet

30. + 0.3v Electrical Circuit - The Wheel Sensor
As the reluctor tooth approaches the pick up coil tooth, a magnetic field increases in strength, thus generating a voltage in the pick up coil.
+ 0.3v
Amp
Volt
Ohm
Farad
VOLTAGE

31. + 0.7v Electrical Circuit - The Wheel Sensor
Just before the tooth is in line with the pick up coil tooth, maximum voltage
is generated.
+ 0.7v
Amp
Volt
Ohm
Farad
MAXIMUM VOLTAGE

32. 0.0v Electrical Circuit - The Wheel Sensor ZERO VOLTAGE
Amp
Volt
Ohm
Farad
ZERO VOLTAGE
The reluctor tooth is now in line with the pick up coil tooth, the magnetic field is longer growing (moving) thus no voltage is generated in the pick up coil.

33. - 0.7v Electrical Circuit - The Wheel Sensor
Amp
Volt
Ohm
Farad
NEGATIVE
VOLTAGE
The reluctor tooth is now moving away from the pick up coil tooth and the magnetic field is collapsing (moving in the opposite direction). The voltage has become negative.

34. Electrical Circuit - The Wheel Sensor
ZERO
VOLTAGE
The reluctor tooth has moved some distance from the pick up coil tooth and the voltage generated voltage has dropped back to ZERO.

35. Electrical Circuit - The Wheel Sensor
With an oscilloscope an AC waveform should be
produced with the wheel rotating.

36. Electrical Circuit - The Wheel Sensor
Experiment :
Using the computer program Crocodile Clips
produce a simple ABS layout with wheel sensors.
Use the oscilloscope to test the wheel sensors.
You must carry out the following tests :
1. Set the motor speed to 50 rpm and the wheel
sensor to 1 Hz.
2. Using the oscilloscope test each wheel sensor
for operation.
3. Does the polarity of the waveform change.
If so why?
4. Set the motor speed to 100 rpm and the sine
wave generator to 3Hz. What do you notice about
the waveform signal?
One the next screen is an example.

37. Electrical Circuit - The Wheel Sensor
250ohms
Volt
Farad
Amp
Ohm

38. 250ohms Electrical Circuit - The Wheel Sensor
Resistance/continuity check
250ohms
Volt
Farad
Amp
Ohm

39. Control System - Modulator.
Over the next few screens you will
see the operation of the hydraulic
modulator. The solenoid drawn
only represents 1 of the 4 in the
system. There is 1 solenoid plunger
for each separate wheel.
Fluid flow through the solenoid valve
is determined by the solenoid plunger,
the position of which is determined by
current supplied by the ECU to the
energising coil.
The 3 plunger positions needed to
control the system are obtained in
response to ECU outputs of 0A, 2A and
5A.
Solenoid Valve

40. Hydraulic Modulator - Normal operation ABS not activated.
Master Cylinder
Pump OFF
Solenoid Winding
Solenoid Plunger
ABS
ECU
Solenoid
Current 0A
Brake Calliper
When the output from the
ECU is 0A the return spring
holds the plunger into position.
Wheel Sensor
Hydraulic Accumulator
Hydraulic Modulator - Normal operation ABS not activated.

41. Hydraulic Modulator - Skid Sensed Pressure Reduction
Master Cylinder
Pump ON
Solenoid Winding
Solenoid Plunger
ABS
ECU
Solenoid
Current 5A
Brake Calliper
When 5A is applied from the
ECU it is forced to the upper
end of its travel.
ABS is in use.
Wheel Sensor
Hydraulic Accumulator
Hydraulic Modulator - Skid Sensed Pressure Reduction

42. Hydraulic Modulator - Pressure Being Held Steady.
Master Cylinder
Pump ON
Solenoid Winding
Solenoid Plunger
ABS
ECU
Solenoid
Current 2A
Brake Calliper
The weaker magnetic flux
produced by 2A holds the
plunger half way. The ECU
will increase pressure again
until a skid is detected.
Wheel Sensor
Hydraulic Accumulator
Hydraulic Modulator - Pressure Being Held Steady.

43. Control System (closed loop).
Hydraulic Modulator
Master Cylinder
Control System (closed loop).

44. Control System (closed loop).
brake
pressure
control
unit
Hydraulic Modulator
Master Cylinder
Control System (closed loop).

45. Control System (closed loop).
computes
change of
speed U
brake
pressure
control
unit
Hydraulic Modulator
Master Cylinder
Control System (closed loop).

46. Control System (closed loop).
pressure
computes
change of
speed U C
brake
pressure
control
unit
Hydraulic Modulator
Master Cylinder
Control System (closed loop).

47. Control System (closed loop).
monitors
system E
controls
pressure
computes
change of
speed U C
brake
pressure
control
unit
Hydraulic Modulator
Master Cylinder
Control System (closed loop).

48. ABS SYSTEMS - DELCO VI - GM Latest System Block Diagram30
K200
F38 15
F43 30
F20
15 -Ignition ON
30 - Battery Positive
31 - Ground
A Brake modulation
F20 - Fuse
F38 - Fuse
F43 - Fuse
H5 - Tell brake system
H26 - tell tale ABS
K50 - ABS ECU
K61 -Engine ECU
K200 ABS relay
M205 - ABS motor pack
P17 - Wheel sensor FL
P18 - Wheel sensor FR
P19 - Wheel sensor RL
P20 - Wheel sensor RR
S8 - Brake light switch
WEG -Odometer signal Y Solenoid valve FR Y Solenoid valve RL
X13 - Diagnose Y Solenoid valve FL Y Solenoid valve RR
P17
K50
Y205.1
Y205.2
Y205.3
Y205.4
P18
P19
A 205
P20
M205
K61 S8
WEG H5 31
H26
X13

49. TRACTION CONTROL
It has long been known that safety and vehicle performance is improved if spinning of the road wheels could be prevented under driving conditions. When a wheel spins, traction is lost and vehicle control is jeopardised. This control problem arises because spinning of a rear wheel causes the back of the vehicle to move sideways and loss of adhesion at the front results in loss of steering control.
Since many vehicles are now fitted with ABS, the speed sensors on each wheel can also be used to signal when a wheel starts to spin. The existence on the vehicle of this sensing equipment means that it is a comparatively small step to fit a TCS.

50. TRACTION CONTROL - TCS
There are 2 main additional requirements of a tractive
control system:
throttle controller - varies the output of the engine.
ECU - detects spin at any wheel and overcomes it by
applying the brake on that wheel and simultaneously
reduces engine power. Vehicles with an ABS system have a
dual ABS traction control ECU.

51. TRACTION CONTROL
Throttle Controller
Engine torque is controlled either by fitting an additional
throttle (electronically controlled) or using an actuator on
the main throttle.
When an electronic actuator controls the position of the
throttle the traditional mechanical linkage becomes redundant
so a drive by wire system is employed.
Vehicles fitted with this electronic throttle control have the
accelerator pedal connected to a potentiometer.

52. Throttle and Pedal Position Potentiometer
Operation
The position sensor contains a potentiometer or
variable resistor. The variable resistor has a power supply
from the ECU (5 volts), connected at one end of the resistor
track, the other end connected to earth via the ECU.

53. Throttle and Pedal Position Potentiometer
Operation
The throttle/pedal position sensor contains a potentiometer or
variable resistor. The variable resistor has a power supply
from the ECU (5 volts), connected at one end of the resistor
track, the other end connected to earth via the ECU.

54. Throttle and Pedal Position Potentiometer
Operation
A third terminal on the sensor connects to “wiper” contact.
The wiper sweeps backwards and forwards along the
resistance track when the throttle/pedal is opened and closed.

55. 1 volt Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
Depending on the wiper position the voltage at the wiper
contact will vary. On most systems, the voltage will rise
as the throttle/pedal is opened.

56. 3 volts Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
Depending on the wiper position the voltage at the wiper
contact will vary. On most systems, the voltage will rise
as the throttle is opened.

57. 5 volts Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
Depending on the wiper position the voltage at the wiper
contact will vary. On most systems, the voltage will rise
as the throttle is opened.

58. 5 volts Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
The ECU monitors the signal voltage from the third terminal
and therefore has an exact indication of throttle position. The
ECU also requires an indication that the throttle is at idle.
This may be achieved by having a set voltage range of 0.5 to
0.7 volts when the throttle is closed.

59. 5 volts Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
Wth the multi plug connected, check the following:
- power supply, normally 5 volts.

60. 0 volts Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
Wth the multi plug connected, check the following:
- power supply, normally 5 volts.
- zero volts on earth path (accept up to 0.1 volts).

61. 3 volts Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
Wth the multi plug connected, check the following:
- power supply, normally 5 volts.
- zero volts on earth path (accept up to 0.1 volts).
- check signal voltage at centre terminal. It should rise
smoothly as throttle is opened.

62. 3 volts Throttle and Pedal Position Potentiometer
Amp
Volt
Ohm
Farad
If there is no power supply availiable or the supply voltage
is incorrect, then check wiring from the sensor to the ECU.
If the voltage on the earth circuit is greater than 0.1 v, then
check for a high resistance or poor connection.
If the signal from the centre terminal jumps at all, suspect a
sensor fault and replace potentiometer.

63. Experiment : Below is an example of a potentiometer circuit.
Task
Using Crocodile Clips construct a circuit that would represent
both the throttle and pedal position sensors. The ECU is
represented by the 5 volt battery (both supply and earth).

64. M ROTARY ACTUATOR - Throttle Control
ECU controls rotary actuator clockwise / anti-clockwise
to control engine rpm/power.

65. M ROTARY ACTUATOR - Throttle Control
Vehicle near full throttle ECU detects spin and activates
actuator to close throttle.

66. M ROTARY ACTUATOR - Throttle Control
Vehicle near full throttle ECU detects spin and activates
actuator to close throttle and simultaneously applies the
brake/s ant the spinning wheel.

67. ELECTRICAL CIRCUIT - TASK
Using Crocodile Clips, design a simplified circuit to show and
ABS system and Traction control system. Your design should
function correctly. It should include the following:
4 wheel sensors (sine wave generator).
1 ECU to be represented by a 5 volt battery.
2 potentiometers (1 throttle and 1 pedal).
4 solenoid valves.
1 rotary actuator (use a motor).
1 diagnostic light.
TCS ON light and OFF light.
Where necessary use switches to simulate ECU outputs.