UNIT V DIGITAL ENGINE CONTROL SYSTEM

1. Control algorithm for different operating modes of engine.

2. Pollution control devices.
3. Integrated engine control system,
4. Electromagnetic compatibility
5. EMI Suppression techniques
6. Electronic dash board instruments
7. On-board diagnosis system.
SI Engine Control system
 Hardware Development

• The specimens can be assigned as preliminary stages of the series-

production ECU to four categories. Each specimen category builds on

the preceding category and is suitable for the intended purpose in

each case.
A-specimen

• The A-specimen is built from an existing, if necessary modified ECU or

a development printed-circuit board.
• Its functional scope is limited.
• Its technical function is to a large extent guaranteed; however, the A-
specimen is not suitable for endurance testing.
• It is a function specimen which is used for preliminary tests and serves
to verify the design.
B-specimen
• The B-specimen contains all the circuit components.

• It is a test specimen, with which the entire functional scope and

technical requirements are tested in preliminary test.

• It is already suitable for endurance testing in motor-vehicle prototypes.

• The connection and installation dimensions correspond to series status.

However, it is possible that not all the vehicle manufacturer’s
specifications have been fulfilled, because, for example, other materials
have been used.
C-specimen

• The C-specimen is the release specimen, with which the vehicle

manufacturer’s tests are carried out for “Technical Release”.

• All the specifications are safely fulfilled with this ECU. The product
release concludes the development phase.

• Where possible, the C-specimens are manufactured with standard

tools and manufacturing processes closely approximating full-scale
production
D-specimen

• The D-specimen is the pilot-series specimen,on which the series type

plate showing the release number is incorporated.
• Pilot-series vehicles are equipped with D-specimens for large-scale
vehicle production trials.
• These ECUs are assembled and tested with standard manufacturing
processes and under series conditions.
• With these specimens, confirmation of manufacturing safety and
reliability is provided.
 Testing the equipped printed-circuit board

• Electrical testing
• Thermography
• Electromagnetic testing
 Electrical Testing

• The equipped and soldered printed-circuit board must be tested.

• Electrical test routines, which run on a computer, are drawn up for
this purpose.
• This automatic test checks the completeness of the equipped
components and the functional capability of the circuit.
 Thermography
• Thermographic pictures of the printed- circuit
board show the buildup of heat by the
components during operation.
• The different temperature ranges are shown
on the film in different colors. It is therefore
possible to identify components which become
too hot.
• The findings made here influence the change
list from the B- to the C-specimen.
• Layout changes (e.g., heat through hole plating)
can be used to reduce the buildup of heat.
 Electromagnetic testing

• The electromagnetic fields generated on the printed-circuit board can

be sampled with a magnetic-field probe.
• The results are then evaluated on a PC. Different field strengths are
identified by different colors.
• If necessary, layout changes must be made and additional
components provided which prevent electromagnetic fields from
being radiated.
• These tests are also carried out as early as on the B-specimen so that
the necessary changes can be taken into account in the C-specimen.
 EMC tests
• Tests conducted in an EMC test cell or EMC test chamber check the
behaviour of the ECU for electromagnetic irradiation and radiation.
• Tests are performed both on the installed ECU (vehicle tests) and in the
laboratory (e.g., stripline procedure).
• On the negative side, vehicle tests can only be carried out when the vehicle
and the electronics are already at an advanced stage of development.
• The possibilities for intervention in the event of unsatisfactory EMC
behaviour are therefore extremely limited at this stage. For this reason,
early laboratory tests are very important, because these allows tests at an
early stage with the hardware specimens.
• The EMC tests are carried out at different frequencies and different
electrical field strengths. The output signals (e.g., ignition signals, injection
signals) are analyzed to ascertain their immunity to interference from
irradiation and their radiation behaviour.
 Electromagnetic compatibility
• EMC stands for Electromagnetic compatibility, which means that a
device is compatible with (i.e., no interference is caused by) its
electromagnetic (EM) environment.
• It does not emit levels of EM energy that generate electromagnetic
interference (EMI) in other devices in the vicinity.

Electromagnetic interference (EMI) is the interference

caused by one electrical or electronic device to another by
the electromagnetic fields set up by its operation.
 Example

• we notice that the tube light is flickering when a water pump or

motor device is on.
• This is because the motor draws more current, which causes a voltage
drop.
• The change of electrical current and voltage generates
electromagnetic interference (EMI).
• This interference must be within specific limits to avoid interference
in the other devices present within the range.
Types of EMC Tests
Types of Electromagnetic Interference (EMI)

Conducted Emission
• When the device emits an electromagnetic field and transmits it from
the conductor of a wire, it is called conducted emission.
• It can potentially cause problems in the entire power distribution
network, affecting other devices.
Radiated Emission

• When the device emits electromagnetic energy, it is released as

electromagnetic fields that propagate through the air and can also
interfere with other nearby devices.
Voltage Flicker Emission
• Voltage Flicker occurs by changing load current, which flickers both
frequency and amplitude.
• This can be illustrated by the change of a light bulb’s brightness or
changing the speed of the motor or fan.
Harmonic Current Emission
• When the device emits any harmonics and distorts the mains supply,
it is called harmonic current emission. It is associated with switch
mode power converters and other non-linear loads such as motor,
transformer, and lamp dimmers.
 Electromagnetic Susceptibility (EMS)
• Electromagnetic Susceptibility (EMI) means the device is capable or
has immunity to survive or works as expected in an environment
where other devices generate electromagnetic interference.
• Every device tends to emit electromagnetic interference, so the
victim device should not misbehave in these environments; these are
all noted in the EMS test standards of the country.
• Let’s take a real-life example to understand why is EMS test is
required. If a user hears any noise in their mobile while another
mobile or any home appliance is in use, it is because of the low
immunity of the device.
Types of Electromagnetic Susceptibility (EMS)
Conducted immunity
Radiated immunity
Electrostatic Discharge (ESD)
Electrical Fast Transient (EFT)
Surge
Magnetic Field
Voltage Dip and Short Interruption
Conducted immunity

In the conducted immunity test, the disturbance in cable or power

supply is created by an RF amplifier, and the device’s function should
not be affected by that distortion or interference in the power supply
 Radiated immunity
• In a radiated immunity test, the device creates an electric field
disturbance, noise, or magnetic field interference through the air. In
this scenario, the device should perform as expected.
 Electrostatic Discharge (ESD)

Electrostatic Discharge is the Discharge of the human body in

the metallic part of the device.
whenever the human body touches the device, they will get a
shock.
It could permanently damage the device, so that this test will
check the protection and immunity against ESD.
 Electrical Fast Transient (EFT)
• The EFT immunity test simulates the switching of inductive loads in
the real world.
• The inductive load switching creates a small spark, which is a bursting
of pulses. The device must be able to handle those pulses.
Surge

• ESD and EFT have similar rise times, pulse width, and energy levels.
With a surge, the pulse’s rise time is just 1.2us, and the duration is
longer.

• The pulse width is 50us so there should be protection in the circuit to

handle the surge.
Magnetic Field

The magnetic field is everywhere; a current passing through a wire can

generate a magnetic field around the wire. In this test magnetic field is
created to test the device’s behaviour and the functionality of the
device should not be affected.
 Voltage Dip and Short Interruption
• In this test, the power supply fluctuations are created in either AC or
DC, and then the device is observed under these conditions.
Global rules and regulations
Digital Instrumentation Panel
Instrumentation Control System
Electronic Speedometer
Electronic Coolant Temperature
Electronic Fuel Gauge
Electronic Oil Pressure Warning
Trip Computer
Vehicle Condition Monitoring System
Brake pad wear warning system
Light failure indication
Alternator condition monitoring
Voice warning system
Power Seat
On-Board Diagnostics
and Scan Tools
Troubleshoot
Objectives
After studying this chapter, you will be able to:

• Discuss the purpose and operation of onboard diagnostic systems.

• Explain the use of scan tools to simplify reading of trouble codes.

• Locate the data link connector on most makes and models of cars.

• Activate on-board diagnostics and read trouble codes with a scan tool.

• Erase diagnostic trouble codes.

 On-Board Diagnostic Systems
• On-board diagnostics
On-board diagnostics (OBD) is an automotive term referring to a vehicle's self-
diagnostic and reporting capability.

• Scan tool
– Communicates with vehicle computers

– Retrieves trouble codes,

– displays circuit and sensor values, runs tests, and gives hints for finding
problems
• On-board diagnostics check almost every electrical/electronic part in

every major system

• If any abnormal values are found

– Computer stores a trouble code

– Lights malfunction indicator light on instrument panel

Early On-Board Diagnostic Systems
• Early systems checked limited number of items
• Unable to detect weak circuits and components
• Little or no standardization between systems
OBD II Systems
• Environmental Protection Agency (EPA)
– Passed vehicle pollution laws that require on-board diagnostic
systems to detect problems before they produce harmful
exhaust emissions
– Standardize monitoring systems
OBD II Systems (Cont.)
• OBD II
– On-board diagnostics generation two
• More efficiently monitor hardware and software that
affect driveability emissions
• Designed to keep vehicle running efficiently for at least
100,000 miles
OBD II Systems (Cont.)
• Greater processing speed
• More memory
• More complex programming
• Standardized
– Data link connections
– Trouble codes
– Sensor and output device terminology
– Scan tool capabilities
OBD System Comparison
Malfunction Indicator Light (MIL)
• In OBD II systems, engine warning light is referred to as
malfunction indicator light (MIL)
• If MIL glows continuously, trouble is not critical but
should be repaired at owner’s convenience
• MIL light comes on and then goes out
– Problem may be intermittent
Malfunction Indicator Light (Cont.)
• A flashing MIL
• Means that trouble could damage catalytic converter
and is considered critical
• Trouble code chart
– Will state what each number code represents
• Trouble code conversion
– Scan tool converts number code into abbreviated words
Diagnostic Trouble Codes
• Diagnostic trouble codes (DTC)
– Digital signals produced and stored by computer
• Operating parameter
– Acceptable minimum and maximum value
Computer System Problems
• Loose electrical connection
• Corroded electrical connection
• Failed sensor
• Failed actuator
• Vacuum leak
• Electrical short
• Ignition system problems
• Fuel system problems
• Emission system problems
• Engine problems
Computer System Problems (Cont.)
• Computer malfunction
• Weak or lazy component
• Transmission problems
• Anti-lock brake system problems
• Air conditioning problems
• Air bag problems
• Hybrid electric drive train part and circuit malfunctions
Scan Tools
• Retrieve trouble codes from computer’s memory and
display these codes as numbers and words
• Basic scan tool
– Designed to read and erase vehicle trouble codes
• Advanced scan tool
– Troubleshooting guides
– More manufacturer specific tests and circuit readings
Data Link Connector
• Data link connector (DLC)
– Multipin terminal used to link scan tool to computer
• In the past, this connector was called
– Diagnostic connector
– Assembly line diagnostic link (ALDL)
Data Link Connector (Cont.)
• OBD I data link connectors
– Came in various shapes and sizes
– Equipped with varying number of pins or terminals
• OBD II, DLC is standardized 16-pin connector
Connecting the Scan Tool
• On late-model vehicles, data link connector mounts
under dash
– Easily accessible from driver’s seat
• In older vehicles, adapter is needed, so scan tool’s
connector will fit vehicle’s pre-OBD II pin configurations
Using Scan Tools
• Modern scan tools give prompts in display windows
• Scan tool may ask you to input VIN information
– Lets scan tool know which engine, transmission, and options
are installed on that car or truck
Using Scan Tools (Cont.)

(Snap-on Tool Corp.)

Information a Scan Tool Can Request
• Stored diagnostic trouble codes
• Fault description
• DataStream information
• Run tests
• Oxygen sensor monitoring
• Failure record
• Freeze frame
• Troubleshooting
Failure Record
• Failure record or failure recorder
– Stores information on number of times trouble code occurs
• OBD II systems
– Counts number of times engine reached operating
temperature since last trouble code occurred
Diagnostic Trouble Code Identification
• OBD II requires use of set of standardized alpha-numeric
trouble codes
• Each trouble code identifies same problem in all
vehicles, regardless of manufacturer
OBD II Codes
• Contain a letter and a four-digit number
• Letter indicates general function of affected system
• First digit indicates whether code is standard trouble
code or nonuniform code
OBD II Codes (Cont.)
• Standard trouble codes, or SAE codes
– Indicated by zero (0)
• Nonuniform codes
– Nonstandard codes assigned by manufacturers
– One (1) after system
• Second digit indicates specific system function where
fault is located
OBD II Codes (Cont.)
• Code’s last two digits
– Refer to specific fault designation
– Pinpoint exactly which component or circuit of system might
be at fault and problem type
OBD II Codes (Cont.)
Failure Types
• Hard failure
– Problem that is always present in a computer system
• Disconnected wire
• Soft failure or intermittent failure
– Problem only occurs under certain conditions
Computer System Failure Types
• General circuit failure
• Low-input failure
• High-input failure
• Improper range/performance failure
Datastream Values
• Datastream values or diagnostic scan values
– Produced by vehicle’s computer
– Give electrical operating values of sensors, actuators, and
circuits
– Values can be read on scan tool’s digital display
– Compared to known normal values in service manual
Key-On/Engine-Off Diagnostics
• Performed by triggering ECM’s on-board diagnostic
system with ignition key in on position but without
engine running
• Allows access to any stored trouble codes
• Usually performed before key-on/engine-on diagnostics
Wiggle Test
• Wiggle test or “flex” test
• Many computer system failures, especially intermittent
failures, caused by loose, dirty, or corroded connections
• If engine operation changes suddenly when connector
or wire is flexed, problem located at or near that point
Key-On/Engine-On Diagnostics
• Performed with engine running at full operating
temperature
• Check condition of sensors, actuators, computer, and
wiring while operating under normal conditions
Switch Diagnostic Test
• Involves activating various switches while using scan
tool
– To instruct which switch to move and monitor operation
– Quickly indicate if switch works normally
Actuator Diagnostic Test
• Uses scan tool to order vehicle’s computer to energize
specific output devices with engine on or off
• Lets you find out if actuators work
• Actuator diagnostic tests considered intrusive tests
Actuator Diagnostic Test (Cont.)
• Actuator diagnostic tests might
– Fire or prevent firing of ignition coil
– Open and close fuel injectors
– Cycle idle speed motor or solenoid
– Energize digital EGR valve solenoids
• Scan tool will give readouts showing whether there is
trouble with any actuators
Scanning during a Test-Drive
• With a scan tool
– Check for problems while
driving vehicle
– Simulate conditions
present when trouble
happens
Erasing Trouble Codes
• Erasing trouble codes or clearing diagnostic codes
– Clears stored codes from computer memory after system
repairs have been made
• In most cases, codes automatically erase after 30–50
engine starts or warm-ups
Erasing Trouble Codes (Cont.)
Various methods used to erase trouble codes
• Use a scan tool
• Disconnect battery ground cable or strap
• Unplug fuse to ECM
 EMC
• Electromagnetic Compatibility (EMC) refers to the ability of electronic
devices, systems, and equipment to operate in close proximity to each
other without experiencing or causing electromagnetic interference (EMI).
• EMC ensures that various electronic devices can coexist without negatively
impacting each other's performance.
• It involves designing and testing electronic systems to minimize the
generation of electromagnetic emissions (radiated and conducted) and to
enhance their immunity to external electromagnetic disturbances.
• In essence, EMC is crucial for maintaining the proper functioning and
reliability of electronic devices and systems in environments where
electromagnetic interference can be present, such as in industrial settings,
homes, and in the broader context of radio frequency and wireless
communications.
Anti-lock braking system
(ABS) is an automobile
safety system prevent the
wheels of a vehicle locking
as brake pedal pressure is
applied - often suddenly in
an emergency or short
stopping distance. This
enables the driver to have
steering control, preventing
skidding and loss of
traction.
History of ABS
1929 :- ABS was first developed for aircraft by the French automobile and
aircraft pioneer Gabriel Voisin, as threshold braking on airplanes is nearly
impossible.
1936: German company Bosch is awarded a patent an “Apparatus for
preventing lock-braking of wheels in a motor vehicle”.
1936-: Bosch and Mercedes-Benz partner - R&D into ABS.
1972: WABCO partners with Mercedes-Benz developing first ABS for trucks.
1978: First production-line installation of ABS into Mercedes and BMW
vehicles.
1981: 100,000 Bosch ABS installed. • 1985: First ABS installed on US vehicles
Objective of ABS Development
Under hard braking, an ideal braking system should:
• Provide the shortest stopping distances on all surfaces
• Maintain vehicle stability and steer ability
 ABS Working Principle
• When the brake pedal is depressed during driving, the wheel speed
decreases and the vehicle speed does as well.
• The decrease in the vehicle speed, however, is not always proportional
to the decrease in the wheel speed.
• The non-correspondence between the wheel speed and vehicle speed is
called “slip” and the magnitude of the slip is expressed by the “slip ratio”
which is defined as follows:
• Slip ratio = (Vehicle speed – Wheel speed)/Vehicle speed × 100%
• When the slip ratio is 0%, the vehicle speed corresponds exactly to the
wheel speed. When it is 100%, the wheels are completely locking
(rotating at a zero speed) while the vehicle is moving.
Relationship Between Braking coefficient and
wheel slip
• The best braking action occurs at between 10-20%.
•If vehicle speed and wheel speed is the same wheel slippage is 0%
•A lock-up wheel will have a wheel slippage of 100%
• ABS brake system are

– Integrated
• An integrated system has the master cylinder and control valve
assembly made together.

– Nonintegrated
• A nonintegrated has the master cylinder and control valve assembly
made separate.
ABS systems consist of 4 primary components:
• 1- ABS Controller; the brains of the system. ABS
Controllers are a computer that reads the inputs
and then controls the system to keep the wheels
from locking up and skidding.

• 2- ABS Speed Sensors; there are generally one on

each wheel (sometimes they are located on the
differential). It detects a change in acceleration in
the longitudinal direction of the vehicle and
outputs it to the ABSCM as a voltage signal.
• 3 - ABS Modulator/Valves ; some system have
separate valves for each wheel with a modulator
to control them. Other systems they are
combined. In either case they work with the
controller and the pump to add or release
pressure from the individual wheels brakes to
control the braking.
• 4- ABS Pumps; since the ABS modulator/valves
can release pressure from the individual wheels
brakes there needs to be a way to restore the
pressure when required. That is what the ABS
pumps job is. When the pump is cycling, the
driver may experience a slight pedal vibration.
This cycling is happening many times per second
and this slight vibration is natural
We will discuss how one of the simpler system works.

• Sensors at each of the four --- sense the rotation of the wheel.
• Too much brake application --- wheel stop rotating
• Sensors—ECU--- releases brake line pressure ---- wheel turns again.
• then ECU applies pressure again--- stops the rotation of the wheel releases it
again and so on
• NB:
• This releasing and re-application or pulsing of brake pressure happens 20-30
times per second or more.
• This keeps the wheel just at the limit before locking up and skidding no
matter
• ABS system can maintain extremely high static pressure and must be
disabled before attempting repairs.
• ABS brakes are either
• 1 Channel,3 Channel ,4 Channel

One-channel, one-sensor ABS

This system is commonly found on pickup trucks with rear-wheel ABS. It has one
valve, which controls both rear wheels, and one speed sensor, located in the rear
axle.
Three-channel, three-sensor ABS
This scheme, commonly found on pickup trucks with four-wheel ABS, has a
speed sensor and a valve for each of the front wheels, with one valve and one
sensor for both rear wheels. The speed sensor for the rear wheels is located in
the rear axle.
Four-channel, four-sensor ABS
This is the best scheme. There is a speed sensor on all four wheels and a
separate valve for all four wheels. With this setup, the controller monitors each
wheel individually to make sure it is achieving maximum braking force.
Fuzzy control :

• Is Intelligent control systems can be used in ABS control to emulate

the qualitative aspects of human knowledge with several advantages

such as robustness, universal approximation theorem and rule-based

algorithms.
Advantages:
1. It allows the driver to maintain directional stability and control over
steering during braking
2. Safe and effective
3. Automatically changes the brake fluid pressure at each wheel to
maintain optimum brake performance.
4. ABS absorbs the unwanted turbulence shock waves and modulates
the pulses thus permitting the wheel to continue turning under
maximum braking pressure
Disadvantages
1. Stop Times - Anti -lock brakes are made to provide for surer braking
in slippery conditions. However, some drivers report that they find the
stopping distances for regular conditions are lengthened by their ABS
system, either because there may be errors in the system, or because
noise of the ABS may contribute to the driver not braking at the same
rate.
2. Delicate Systems - It's easy to cause a problem in an ABS system by
messing around with the brakes. Problems include disorientation of the
ABS system, where a compensating brake sensor causes the vehicle to
shudder, make loud noise or generally brake worse
• 3. Cost - An ABS can be expensive to maintain. Expensive sensors on
each wheel can cost Thousands of rupees to fix if they get out of
calibration or develop other problems.
For some, this is a big reason to decline an ABS in a vehicle .

• 4. System damage - A variety of factors can cause the system to be

less effective, and can present with everything from shuddering of the
vehicle to loud noises while trying to stop
Problems with ABS
The sensors on the wheels might get contaminated by
metallic dust. When this condition occurs the sensors
become less efficient in picking up problems.
In modern ABS systems, two more sensors are added to
help:
• wheel angle sensor
• gyroscopic sensor
TO Know
• The antilock braking system controls braking force
by controlling the hydraulic pressure of the braking
system, so that the wheels do not lock during
braking.
• The antilock braking system prevents wheels
locking or skidding, no matter how hard brakes are
applied, or how slippery the road surface. Steering
stays under control and stopping distances are
generally reduced .
Electronic control of Suspension
• An electronically controlled suspension system can help reduce body
roll and other reactions better than most conventional suspension
systems.
Basics of Electronic Suspensions

• Electronic suspension is essentially a computer-controlled system that

can adjust the ride characteristics and performance of your vehicle.
• Unlike air suspensions, an electronic suspension modifies the shocks
and/or struts electronically to ensure a smooth ride.
• Some electronic suspensions are also designed to automatically adapt
to changing road conditions for improved handling in all sorts of
terrain.
How Do Electronic Suspensions Work?

• There are two types of electronic suspensions:

• Adaptive and active.
• Each one works in a different way to improve performance.
 Adaptive Electronic Suspensions
• An adaptive electronic suspension is responsible for controlling the shock
absorbers and their dampening performance. Simply put, they adjust the shocks
as needed to deliver a smooth driving experience.
• Adaptive suspensions can adjust the shocks using a solenoid and valve that’s
placed on the strut.
• The solenoid connects to a computer in the system and monitors the road
conditions.
• When stiffness and overall suspension performance need to be adjusted, the
solenoid communicates this information to the system.
• Then it will activate the valves to open and close as needed to regulate the
amount of hydraulic fluid going into the shocks.
• An adaptive suspension may also use a magneto damper, or a damper filled with
fluid that contains metal particles. An electromagnet controls these little pieces
of metal to adjust the pressure and stiffness in each damper.
Active Electronic Suspensions
• An active electronic suspension changes the ride height for your vehicle to
improve performance and towing capabilities. This type of electronic
suspension uses hydraulics or electromagnets to operate.
• Active suspensions that adjust hydraulically use sensors to monitor the
vehicle’s movement and ride height.
• When performance or ride height needs to be regulated, the system
activates a hydraulic pump that pressurizes the liquid in the shocks.
• This will configure the stiffness of the suspension as well as the height of
the vehicle to your specific preferences.
• Electromagnetically controlled active suspensions work similarly to
hydraulically controlled systems. The only difference is that these systems
use electromagnet motors instead of pumps to adjust a car’s ride height.
This type of active electronic suspension is known to respond faster and
use less power than hydraulics.
• Input devices monitor conditions and provide information to the
electronic control module, which processes the information and
operates the actuators to control the movement of the suspension.
• A typical electronic suspension height sensor, which bolts to the
body and connects to the lower control arm through a control
link and lever.
• When suspension action moves the lever, it rotates the
slotted disc and varies how much of the photo transistor
is exposed to the LEDs, which vary the input signal.
• Typical suspension position sensor.
• A three-wire suspension position sensor schematic.
A suspension height sensor.
The steering wheel position (handwheel position) sensor wiring schematic and how the signal
varies with the direction that the steering wheel is turned.
The hand wheel position sensor is located at the base of
the steering column.
Steering wheel (handwheel) position sensor schematic.
The NS sensor information is transmitted to the EBTCM by Class
2 serial data.
An air pressure sensor.
A schematic showing the lateral acceleration sensor and the
EBCM.
TECH TIP:
Yaw rate sensor showing the typical location and
schematic.
A magnetic field is created whenever an electrical current flows
through a coil of wire wrapped around an iron core.
When magnets are near each other, like poles repel and
opposite poles attract.
When electrical current magnetizes the plunger in a solenoid, the magnetic field
moves the plunger against spring force. With no current, the spring pushes the
plunger back to its original position.
This air supply solenoid blocks pressurized air from the air spring valves when
off. The plunger pulls upward to allow airflow to the air spring valves when
the solenoid is energized.
An actuator motor uses a permanent magnet and four stator coils to drive
the air spring control rod.
The stator coils of the actuator are energized in three ways to provide
soft, medium, or firm ride from the air springs and shock absorbers.
Selectable Ride as used on Chevrolet and GMC pickup
trucks.
ALC maintains the same ride height either loaded or unloaded by
increasing or decreasing the air pressure in the rear air shocks.
A typical schematic showing the air suspension compressor assembly
and sensor.
The typical variable-rate air spring system uses three height sensors, two in the front
and one in the rear, to monitor trim height and to provide input signals to the ECM.
The air spring compressor assembly is usually mounted on rubber cushions to help isolate
it from the body of the vehicle. All of the air entering or leaving the air springs flows
through the regenerative air dryer.
A solenoid valve at the top of each spring regulates airflow into
and out of the air spring.
Schematic showing Computer Command Ride (CCR) system.
Schematic showing the shock control used in the RSS system.
Bi-state dampers (shocks) use a solenoid to control fluid flow
in the unit to control compression and rebound actions.
Solenoid valve controlled shock absorber circuit showing the left
front (LF) shock as an example.
A typical CCR module schematic.
The three dampening modes of a CCR shock absorber.
Integral shock solenoid.
A typical ZF Sachs self-leveling shock, as used on the rear of a Chrysler
minivan.
Schematic of the ALC system.
Air compressor assembly can be located at various locations
depending on the vehicle.
The exhaust solenoid is controlled by the rear integration module (RIM).
Schematic showing the rear integration module (RIM) and how it controls
the ALC compressor.
Vehicles that use magneto-rheological shock absorbers have a sensor
located near each wheel, as shown on this C6 Corvette.
controller for the magneto-
rheological suspension
system on a C6 Corvette is
located behind the right front
wheel.
FREQUENTLY ASKED QUESTION: Can Computer-
Controlled Shock Absorbers and Struts Be
Replaced with Conventional Units? Maybe. If the
vehicle was manufactured with or without electronic
or variable shock absorbers, it may be possible to
replace the originals with the standard replacement
units. The electrical connector must be disconnected,
and this may cause the control system to store a
diagnostic trouble code (DTC) and/or turn on a
suspension fault warning light on the dash. Some
service technicians have used a resistor equal in
resistance value of the solenoid or motor across the
terminals of the wiring connector to keep the
controller from setting a DTC. All repairs to a
suspension system should be done to restore the
vehicle to like-new condition, so care should be
exercised if replacing electronic shocks with
nonelectronic versions.
A cutaway of a magneto-rheological shock absorber as displayed at the
Corvette Museum in Bowling Green, Kentucky.
Most electronic level-control sensors can be adjusted, such as this
General Motors unit.
What are Airbags?
• Supplementary Restraint System for driver and/or
passenger safety in case of a crash.
• Basic Mechanism: A thin nylon bag in the steering wheel /
above glove compartment inflates in the event of an
impact and prevents the driver/passenger from hitting the
steering wheel/dashboard.
• 3 Main Components: 1) Airbag module
2) Diagnostic Unit
3) Crash sensors
Airbag Module
• Contains both inflator unit and light-weight fabric airbag and is located
either inside:
• 1) Steering wheel hub 2) Above glove compartment
• 3) Near side compartment (as separate/combined
head/side/window-curtain airbag)
• Airbag: Thin nylon fabric bag folded neatly into steering wheel that
inflates to the size of a large beach ball on impact.
• Inflator unit: Contains a number of sodium azide pellets which are
electrically ignited to produce N2 that then fills the airbag. This is
preferred to storing compressed gas in the unit (space, durability)
• Both airbag and inflator unit are for single deployment only – ie have
to be replaced after a crash
Diagnostic Unit
• Enables inflator unit and sensors when vehicle is turned on, performs
self check.
• Constantly monitors airbag readiness and indicates malfunctioning
through an indicator on dashboard
• Usually stores electricity to activate airbag in the event that a crash
damages the battery / link to battery

Sensors
• Several crash sensors located in the front of vehicle and in the
passenger compartment
• Each senses the sudden deceleration or impact in the event of a crash
and flips a mechanical switch to indicate a crash.
Airbag Deployment
• Frontal crash scenario: Car crashes into an
obstacle (wall) at 20+ mph
• Sensors detect the deceleration and inflator
unit activated
• Deployment sensitivity: To guard against
accidental inflation on hard braking, sensors
detect collisions into a solid barrier at speeds greater than 8-14 mph only
as impacts
• An electric current is used to heat a filament wire that ignites the NaN3
capsules, producing N2:
2NaN3  2Na + 3N2
10Na + 2KNO3 K2O + 5Na2O+ N2
K2O + Na2O SiO2 alkaline glass (safe, unignitable)
130 g of NaN3 produces 67 ltrs of N2
 Airbag Deployment
• The airbag then inflates fully at speeds > 320mph within 35 to 45ms of
crash. For maximum safety, occupant must have seat belt on and sit with
chest 10” from steering wheel
• Immediately after full inflation, the airbag deflates through tiny pores on
the surface within 0.3s
 Additional Features

• An on/off switch
• Combination with seat-belt pre-
tensioners and other safety systems
• Inflation in the event of fire (high
temp.) to prevent explosion of solid
compound
• Depowering and differential
powering
• Small rapid deployment airbags for
side impact at roof-rail or door or
seat back.
eg: 1) Beltline Head/Torso Side
Airbag 2) Inflatable Tubular
Structure
Electromechanical Crash Sensors
 Smart Restraint System
• Is one that adapts its geometry, • ie, a smart restraint system must
performance or behavior to suit be able to update itself on the
varying impact types and/or following:
occupants & occ. posns. • Occ. characterisation
• Must be able to distinguish • Occ. location
between: • Accordingly decides:
• RFIS & child seat • Which airbags to deploy when
• Child • Full blown / supressed
• Adult • Seat belt pre-tensioning,
• Empty retraction/collapse of parts
• Subsets of possible seating • Direction of deployment
posns. for above (< / >10”) • Sequencing & Timing
• Belted / non-belted • Post deployment action
• Crash severity
• Crash direction
 • Advance meth. (complex, high
Smart Restraints computing power reqd.)
• Passive Infra-red
• Detection types: • Video systems
• mechanical • Biometric sensing
• spatial
• other
• Systems must:
• Means of detection: • Sequence & time appropriately
• Weight & distribution (3) • Extremely reliable
• Seat belt (webbing , rotation • Work within varying auto
ctr & buckle) interior atmosphere and
• Active Infra-red (OOP sense) lighting
• Ultrasonic • Differentiate camouflage
• Radar/Microwave • Low cost
• Capacitive
• tags for RFIS & smart keys
• Height sensors in seat / belt
Smart Restraints
• Components • Sensor types:
• Side/Variable/dual-stage • Electromechanical
airbags • Accelerometers
• Seat-belt pre-tensioners • Pressure
• Side/Central/Satellite/Safing • Stress-wave
crash sensors • Pre-crash
• Occupant sensors
• Pre-crash sensing
• Central ECU
• More details read from sensors
• Pre-crash sensors
• Advantage: Enables early decision
• Driving states: and pre-tensioning
• Normal • Disadv: imprecise object
• Collision avoidable classification & cost
• Collision imminent • Same sensors as those for ACC,
CW/CA
• Post-crash
Collision Avoidance radar warning system
• It is also known as pre-collision system.
• It is designed to reduce the severity of an accident.
• It uses a radar to detect an imminent crash.

• Once the detection is done, these system give warning to the driver
or take action autonomously without any driver input.(by applying
bake and steering control)
Layout of Collision avoidance
• With the use of radar, lasers and cameras, collision avoidance alert systems include:

• Forward-collision Warning (FCW): Visual and/or audible warning to alert driver of

collision risk. The Insurance Institute of Highway safety (IIHS) has already observed a
27% reduction in front-to-rear crashes through this technology.
• Blind-spot Warning (BSW): Visual and/or audible notification that a vehicle is in the
driver’s blind spot in a neighboring lane; an additional warning may sound if a turn
indicator is used when a vehicle is in the blind spot. IIHS studies have shown a 14%
reduction in lane-change crashes and a 23% reduction in lane-change crashes with
injuries in vehicles with this capability.
• Cross Traffic Warning: A visual, audible, or haptic alert if an object is currently out of
camera range, but appears to be moving into it. Studies show a 22% reduction in
reverse crashes.
• Lane Departure Warning (LDW): A visual, audible, or haptic alert that a driver is
crossing lane markings. This technology has provided a 11% drop in sideswipe and
head-on crashes, with a 21% reduction of injuries in the crashes of those types that
occur.
Vehicle Tracking system
• Vehicle tracking system is software and hardware system enabling the
vehicle owner to track the position of their vehicle.
• VTS module is attached to each vehicle
Advantages of VTS
• Fuel and Power Saving
• Effective Fleet Control
• Instantaneous Fuel Level Monitoring
• Decreasing the Accident Risk
• Driver and Load Security
• Evaluation of Drivers Performance
• Monitoring the Delivery Time
Purpose
• Instantaneous Location Targeting
• Positioning with the help of GPS Satellite
• Acknowledging the Position - via GSM, SMS or Data Line
• Monitoring the Vehicle Online
• Tracking the position of the vehicle on digital maps via an online
monitoring program
1.Car-alarm Door Sensors
2.Car-alarm Shock Sensors
3.Car-alarm Window and
Pressure Sensors
4.Car-alarm Motion and Tilt
Sensors
5.Car-alarm Alerts
6.Car-alarm Transmitters
 Car-alarm Door Sensors

The most basic element in a car alarm system is the door alarm. When you open the front hood,
trunk or any door on a fully protected car, the brain triggers the alarm system.

Car-alarm Window and Pressure Sensors

A lot of the time, car thieves who are in a hurry don't mess around with disabling locks to get into a car:
They just bust a window. A fully equipped car alarm system has a device that senses this intrusion.
• Car-alarm Motion and Tilt Sensors
There are several good ways for a security system to keep tabs on
what's going on outside the car. Some alarm systems
include perimeter scanners, devices that monitor what happens
immediately around the car. The most common perimeter scanner is
a basic radar system, consisting of a radio transmitter and receiver.
The transmitter sends out radio signals and the receiver monitors the
signal reflections that come back. Based on this information, the
radar device can determine the proximity of any surrounding object.
Car-alarm Alerts

• An alarm system must trigger some response that will deter thieves
from stealing your car.

At the minimum, most car alarm systems will honk the

horn and flash the headlights when a sensor indicates an
intruder. They may also be wired to shut off the ignition starter,
cut off the gas supply to the engine or disable the car by other
means.
Car-alarm Transmitters
• Most car alarm systems come with some sort of portable keychain
transmitter. With this device, you can send instructions to the brain
to control the alarm system remotely. This works in basically the same
way as radio-controlled toys. It uses radio-wave pulse modulation to
send specific messages (to see how this works, check out How Radio
Controlled Toys Work)