Transcript No Slide Title

ANTI - LOCK BRAKING and TRACTION CONTROL
SYSTEMS
Anti - Lock Braking Systems were first developed in
the aircraft industry to aid and further improve the
landing capabilities of the aircraft.
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.
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.
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.
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.
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).
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).
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.
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.
Brake Pressure Unit
This diagram shows an INTEGRATED ABS
system.
Brake
Servo
ABS Unit
High Pressure
Pump
PUMP
UNIT
Brake Pressure Unit
This diagram shows an INTEGRATED ABS
system.
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
Brake Pressure Unit
This diagram shows an INTEGRATED ABS
system.
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.
- a pump unit : source of high pressure (180
bars) for the hydraulic servo.
PUMP
UNIT
This diagram shows ADDITIONAL ABS
system.
ADDITIONAL
REGULATION UNIT
(ABS)
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.
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.
Schematic Diagram
Bosch 2SE system
Hydraulic Circuit
A
The ABS system
contains a :
- hydraulic circuit.
B
- electrical circuit.
This circuit has 4
callipers (A) connected
to the tandem master
cylinder which generates
the brake pressure.
Hydraulic Circuit
C
A load sensitive
compensator (C)
modifies the braking
pressure to the rear
callipers according to
body movement.
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.
Electrical Circuit
E
E
E
E
This circuit
comprises of :
- 4 wheel speed
sensors (E) which
generate electrical
impulses whose
frequency depends
on the speed of
rotation of the
wheel.
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.
Electrical Circuit
H
G
A warning lamp (G)
located in the
instrument panel and
a connector (H)
enabling fault
diagnosis.
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.
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
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
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
WINDING
SOFT IRON CORE
Electrical Circuit - The Wheel Sensor
The wheel sensor is known as a PASSIVE sensor.
Electrical Circuit - The Wheel Sensor
Reluctor tooth on driveshaft
Pick up coil in wheel
sensor with permanen
magnet
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
Volt
Farad
VOLTAGE
Amp
Ohm
Electrical Circuit - The Wheel Sensor
Just before the tooth is in line
with the pick up coil tooth,
maximum voltage
is generated.
+ 0.7v
Volt
Farad
MAXIMUM VOLTAGE
Amp
Ohm
Electrical Circuit - The Wheel Sensor
0.0v
Volt
Farad
ZERO VOLTAGE
Amp
Ohm
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.
Electrical Circuit - The Wheel Sensor
- 0.7v
Volt
Farad
Amp
Ohm
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
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.
Electrical Circuit - The Wheel Sensor
With an oscilloscope an AC waveform should be
produced with the wheel rotating.
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.
Electrical Circuit - The Wheel Sensor
250ohms
Volt
Farad
Amp
Ohm
Electrical Circuit - The Wheel Sensor
Resistance/continuity check
250ohms
Volt
Farad
Amp
Ohm
Control System - Modulator.
Solenoid Valve
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.
Master Cylinder
Pump OFF
Solenoid Winding
Solenoid Plunger
Solenoid
Current
0A
ABS
ECU
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.
Master Cylinder
Pump ON
Solenoid Winding
Solenoid Plunger
Solenoid
Current
5A
ABS
ECU
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
Master Cylinder
Pump ON
Solenoid Winding
Solenoid Plunger
Solenoid
Current
2A
ABS
ECU
Brake Calliper
Wheel Sensor
The weaker magnetic flux
produced by 2A holds the
plunger half way. The ECU
will increase pressure again
until a skid is detected.
Hydraulic Accumulator
Hydraulic Modulator - Pressure Being Held Steady.
Master Cylinder
Hydraulic Modulator
Control System (closed loop).
brake
pressure
control
unit
Master Cylinder
Hydraulic Modulator
Control System (closed loop).
computes
change of
speed
U
brake
pressure
control
unit
Master Cylinder
Hydraulic Modulator
Control System (closed loop).
controls
pressure
C
brake
pressure
control
unit
Master Cylinder
Hydraulic Modulator
Control System (closed loop).
computes
change of
speed
U
monitors
system
E
controls
pressure
C
brake
pressure
control
unit
Master Cylinder
Hydraulic Modulator
Control System (closed loop).
computes
change of
speed
U
ABS SYSTEMS - DELCO VI - GM Latest System
Block Diagram
30
K200
15
F43
30
F20
15 -Ignition ON
30 - Battery Positive
31 - Ground
A 205 - 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
X13 - Diagnose
P17
F38
Y205.1
Y205.2
Y205.3
Y205.4
P18
P19
A 205
P20
K61
M205
S8
K50
WEG
H5
31
H26
X13
Y205.1 - Solenoid valve FR
Y205.2 - Solenoid valve FL
Y205.3 - Solenoid valve RL
Y205.4 - Solenoid valve RR
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.
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.
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.
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.
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.
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.
Throttle and Pedal Position Potentiometer
1 volt
Volt
Farad
Amp
Ohm
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.
Throttle and Pedal Position Potentiometer
3 volts
Volt
Farad
Amp
Ohm
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.
Throttle and Pedal Position Potentiometer
5 volts
Volt
Farad
Amp
Ohm
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.
Throttle and Pedal Position Potentiometer
5 volts
Volt
Farad
Amp
Ohm
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.
Throttle and Pedal Position Potentiometer
5 volts
Volt
Farad
Amp
Ohm
Wth the multi plug connected, check the following:
- power supply, normally 5 volts.
Throttle and Pedal Position Potentiometer
0 volts
Volt
Farad
Amp
Ohm
Wth the multi plug connected, check the following:
- power supply, normally 5 volts.
- zero volts on earth path (accept up to 0.1 volts).
Throttle and Pedal Position Potentiometer
3 volts
Volt
Farad
Amp
Ohm
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.
Throttle and Pedal Position Potentiometer
3 volts
Volt
Farad
Amp
Ohm
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.
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).
ROTARY ACTUATOR - Throttle Control
M
ECU controls rotary actuator clockwise / anti-clockwise
to control engine rpm/power.
ROTARY ACTUATOR - Throttle Control
M
Vehicle near full throttle ECU detects spin and activates
actuator to close throttle.
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.
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.