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AUTOMOBILE INSTRUMENTATION
Technical Paper Presentation
Instrufiesta – 2006
By :
- Himanshu Madan
- Siddharth Shashidharan
C.O.E.P - T.Y (E&TC)
ABSTRACT
From the days of Henry Ford’s automated assembly production line, we
have come a long way into an era of intelligent automated cars that provide the
ultimate in security, comfort and functionality to the demanding empowered
customer.
A few years ago, instrumentation for the populace meant a few indicators
that told them the essential statistics of their vehicles, like the temperature, fuel
level, speed, mileage etc.
Things are far different today. People want vehicles that are capable of
driving themselves, that can park themselves and even warn of impending
collisions thereby reducing significantly the number of fatal crashes.
The car ought to be ‘intelligent’ enough to speed up on highways and slow
down in traffic (Adaptive cruise control). It also needs to provide the best drive
possible in terms of comfort, i.e automatically configuring its suspension systems
(Active body control), traction control on the wheels and advance lighting
systems (AHS) that account for curves and oncoming traffic as well as low
illumination.
This is being made possible thanks to recent developments in science and
technology and the seemingly effortless confluence of semiconductor electronics,
precision transducers and modern mechanical instrumentation systems. The
brain of the automobile, the microcontroller chip, is fed a continuous stream of
data via sensors that monitor virtually every aspect of the car’s functioning.
Pressure on accelerator and brake pedals, oxygen content in the fuel-air
mixture, engine temperature and friction etc. are sensed and the engine load is
varied. Electronic stability control (ESC), power steering assistance (EPS),
collapsible steering, auto-deployment airbags, keyless entry using biometrics and
RFIDs provide safety and security.
GPS, Bluetooth and WiFi connectivity is also being used for
communication between two vehicles for essential data-communication. Other
advances also include temperature and climate control, self-cleaning headlights
and windshields, tyre pressure monitors, external noise cancellation, auto-folding
anti-glare mirrors.
The good old car has indeed come a long way and thorough instrumentation of virtually every facet of the automobile has, in no insignificant way, helped to lay the foundations for the future; a future that promises efficiency, safety, functionality, ergodynamics, comfort, reliability, security and luxury.
Contents:
Performance enhancement: Instrumentation in cars used to enhance the performance and overall handling of the car.
Intelligent Light System Active Body Control Traction Control Electronic Stability Control
Engine instrumentation: Monitor and control the parameters and functions of the engine.
Engine Control Unit
Safety: Instrumentation to reduce fatalities and provide the ultimate in safety for the passengers.
Airbags, Seats and Seatbelts Anti-Lock Braking System Tyre Pressure Monitoring
Automation: Assistance and automated features that overcome common hassles.
Active Cruise Control Parking Assistance System Automatic Parking System Automated Highways
Smart features: Modern systems that are designed to make the vehicles more intelligent and further assist the passenger.
Rainfall Sensors Noise Cancellation Systems Global Positioning Satellite System
Other modern automobile instrumentation systems: Bluetooth and WiFi Automatic Headlight Wash Climate Control Keyless entry and RFIDs
Intelligent Light systems
The Intelligent Light System is
a new generation of adaptive
car headlamps which adjust to
suit prevailing driving and
weather conditions.
The optional active headlight
system uses intelligent
technology to enable a pair of
Bi-Xenon headlights to follow
the shape of the road through an arc of 15 degrees, providing drivers with up to
90 percent more visibility. The system is controlled by data provided by steering
angle and yaw rate input sensors as well as vehicle speed and GPS-fed road
data. Combined with bi-xenon headlamps, new lighting functions include country
road and motorway
light modes which
increase the driver’s
range of visibility by up
to 50 metres. The light
system also includes extended fog lamps which
illuminate the road edges and therefore provide even better orientation when
visibility is poor. The country road mode upgrades the low-beam lighting,
illuminating the driver's side edge of the road more widely and brightly, enlarging
the field of view by at least 10 metres. The motorway mode engages in two
stages once the vehicle reaches a speed of 90 km/h. In the first of these stages,
bi-xenon lighting output is increased from 35 to 38 watts. In stage two the range
of the driver's-side headlamp is increased when a speed of 110 km/h is reached,
extending the range of the low-beam lights by around 50 metres. With the
extended fog lamps, the left headlamp swivels outwards eight degrees and, at
the same time, lowers the cone of light. This illuminates the nearside of the road
more efficiently, while the wider beam reduces backglare in fog.
Active light at cornering Active light at high speed
Active body control
The hydraulic ABC chassis offers you supreme ride comfort at all times by
combining active control with passive damping to reconcile the two conflicting
objectives of dynamism and comfort. You are able to choose between a more
comfort-orientated and a sporty ride at the push of a switch. The system even
takes the load your vehicle is carrying into account to restrict vehicle body motion
as required when pulling away, cornering or braking, and to dampen such motion
as effectively as possible. ABC is the first suspension system in the world to be
actively controlled by computer. The super-fast computational unit teams up with
high-pressure hydraulics and a sophisticated system of sensors to automatically
adjust the position of the vehicle body. The ABC control unit is capable of
reacting to all manners of driving situations in an instant by directing a precisely
metered quantity of hydraulic fluid to each individual damper strut as the situation
dictates. This enables ABC Active
Body Control to all but eliminate the
pitching motion that would otherwise
occur at times when pulling away
from standstill or braking, as well as
the body's tendency to roll in
corners, translating into a palpable
improvement in ride comfort. ABC
incorporates load-sensitive self-levelling suspension front and rear, providing you
with the additional convenience of being able to raise the vehicle's ride height
when driving over rough roads or through snow. One can engage one of two
drive modes (+24 millimetres and +49 millimetres). If neither of these modes is
selected, the vehicle's ride height starts to drop automatically above a speed of
60 km/h to reduce drag, until reaching a point 15 mm below the standard ride
height at a speed of 140 km/h. If the speeds fall back below 140 km/h, the
vehicle will start to rise again accordingly. The upshot is a marked enhancement
of ride comfort, handling dynamics, motoring pleasure and safety in any situation
out on the road.
Variable hydraulic suspension
Traction control
Traction control deals specifically with lateral (front-to-back) loss of friction during
acceleration. In other words, when your car accelerates from a dead stop, or
speeds up while passing another vehicle, traction control works to ensure
maximum contact between the road surface and your tires, even under less-than-
ideal road conditions. For example, a wet or icy road surface will significantly
reduce the friction (traction) between your tires and the pavement. And since
your tires are the only part of your car that actually touches the ground, any
resulting loss of friction can have serious consequences. Traction control works
at the opposite end of the scale from ABS — dealing with acceleration rather
than deceleration. Still, since many of the same principles apply to both systems,
it might be best to visualize it as sort of ABS in reverse. ABS works by sensing
slippage at the wheels during braking, and continually adjusting braking pressure
to ensure maximum contact between the tires and the road.
Enter electronic traction control. In modern vehicles, traction-control systems
utilize the same wheel-speed sensors employed by the antilock braking system.
These sensors
measure differences
in rotational speed to
determine if the
wheels that are
receiving power have
lost traction. When
the traction-control system determines that one wheel is
spinning more quickly than the others, it automatically
"pumps" the brake to that wheel to reduce its speed and
lessen wheel slip. In most cases, individual wheel braking is
enough to control wheel slip. However, some traction-control
systems also reduce engine power to the slipping wheels.
Central microprocessor counters individual wheel slipping.
Pulsed braking.
Electronic stability control
ESC compares the driver's intended direction in steering and braking inputs, to
the vehicle's response, via lateral acceleration, rotation (yaw) and individual
wheel speeds. ESC then brakes individual front or rear wheels and/or reduces
excess engine power as needed to help correct understeer (plowing) or oversteer
(fishtailing). ESC combines anti-lock brakes, traction control and yaw control
(yaw is spin around a vertical axis). The system is fully independent of the
driver's actions. Even if the car is free-rolling (no acceleration or braking input
from the driver), the stability control system will kick in and perform its duty. Its
key component is a
yaw velocity sensor.
This sensor
permanently tracks
the movement of
the vehicle around
its vertical axis,
comparing the
actual measured
reading with the
target value derived
from the driver's steering commands and the vehicle's speed. This information is
then fed into a microcomputer that correlates the data with wheel speed, steering
angle and accelerator position, and, if the system senses too much yaw, the
appropriate action to preempt the risk of skidding is taken. Fishtailing is actively
suppressed by applying the brakes at the front left and right wheels individually
and alternately. In the majority of cases, this is sufficient to eliminate the weaving
motion completely, and with it the threat of danger. If the snaking motion is
particularly severe, however, the engine's torque will also be throttled and the
towing vehicle's brakes applied at
all four wheels to bring the speed
below the critical range quickly.
Without ESC With ESC
Components of ESC
Engine Control Unit
Also known as Engine Management System (EMS), it is an electronic system,
fundamentally a computer, that controls an internal combustion engine by
reading several sensors in the engine and using the information to control its
ignition systems.
Because the ECU is dealing with actual measured engine performance from
millisecond to millisecond, it can compensate for many variables that traditional
systems cannot, such as ambient temperature, humidity, altitude (air density),
fuel octane rating, as well as the demands made on it by the driver.
Modern ECUs use a microprocessor which can process the inputs from
the engine sensors in real time. An electronic control unit contains the hardware
and software (firmware). The software is stored in the microcontroller or other
chips, typically in EPROMs or flash memory so the CPU can be re-programmed
by uploading updated code. This is also referred to as an (electronic) Engine
Management System (EMS).
It also communicates with
transmission control units or directly
interfaces electronically-controlled
automatic transmissions, traction control
systems, and the like. The Controller
Area Network or CAN bus automotive
network is often used to achieve communication between these devices.
Parameters that are mapped are:
Ignition: Defines when the spark plug should fire for a cylinder
Rev limit: Defines the max RPM that the engine is allowed to rev to. After this fuel
and/or ignition is cut.
Water temperature correction: Allows for additional fuel to be added when the
engine is cold (choke).
Transient fueling: Tells the ECU to add a specific amount of fuel when throttle is
applied.
Engine control unit
Low fuel pressure modifier: Tells the ECU to increase the injector fire time to
compensate for a loss of fuel pressure.
Closed loop lambda: Lets the ECU monitor a permanently installed lambda probe
and modify the fueling to achieve stoichiometric (ideal) combustion.
Some of the more advanced ECUs include functionality such as launch control,
limiting the power of
the engine in first
gear to avoid
burnouts.
Other examples of
advanced functions
are:
Waste gate control:
Sets up the
behavior of a turbo
waste gate,
controlling boost.
Banked injection:
Sets up the behavior of double injectors per cylinder, used to get a finer fuel
injection control and atomization over a wide RPM range.
Variable cam timing: Tells the CPU how to control variable intake and exhaust
cams.
Gear control: Tells the ECU to cut ignition during (sequential gearbox) upshifts or
blip the throttle during downshifts.
In order to communicate with the driver, an ECU can often be connected to a
"data stack", which is a simple dash board presenting the driver with the current
RPM, speed and other basic engine data. These stacks, which are almost always
digital, talk to the ECU using one of several proprietary protocols running over
RS232, CANbus or ethernet.
ECUs allow greater fuel efficiency, better power and responsiveness, and much
lower pollution levels than earlier generations of engines.
ECU schematic
Airbags, seats and seatbelts
Manufacturers today lay great emphasis on safety and comfort of the
passengers. Airbag deployment is now controlled by a number of factors.
The impact of a collision is sensed and
fed to the computer.
Modern systems like Jaguar’s Adaptive
Restraint Technology System (ARTS)
use ultrasonic sensors to identify not
only size and weight of occupants, but
also when they are out of the typical
seating position. The vehicle's computer then
determines the appropriate size and force of
airbag deployment. Furthermore, when an
impact is sensed, belt tensioners remove slack
and belt force
limiters regulate the restraining force with
flexibility. Airbags and seat belt systems are
increasingly operating "intelligently" in unison
with one another.
In an effort to improve comfort, The Active
Comfort Seat uses a sophisticated system of motors and hydraulic chambers to
move the seat up and down by 15 mm in a programmed fashion every 60
seconds imparting a gentle rocking movement of the pelvis that is almost
imperceptible, thus increasing blood circulation and making long drives more
comfortable. Many of tomorrow’s models will feature additional comfort features
like ergonomic self-adjusting seat
position sytems and user controlled
seating with memory settings that
remember the user’s preferred
seating position.
ANTI-LOCK BRAKING SYSTEM - ABS
ABS systems were introduced to the commercial vehicle market in the early
1970's to improve vehicle braking irrespective of road and weather conditions.
The four-wheel ABS or Anti-lock Braking System is designed to help the driver
maintain steering control during hard braking, especially in slippery conditions. It
prevents the wheels from locking up, helping you maintain steering control during
braking. In a similar situation, driving a car equipped with four-wheel ABS, it
would be easier for you to steer your vehicle while braking.
The four-wheel ABS system can help to slightly reduce the braking distance in
some situations. However, under certain conditions (e.g. on loose snow or
gravel), the braking distance may be longer.
How the actual ABS system works
Major components of the typical ABS
system include four speed sensors
(one at each wheel), an electronic
control unit (ABS computer) and a
hydraulic control unit (see the picture).
The ABS computer constantly monitors
the signal from each wheel speed
sensor. When it senses that any of the
wheels are approaching lock up during braking, the ABS computer sends the
signal to the hydraulic control unit, which modulates the braking pressure for a
corresponding wheel(s) preventing it from locking up. In modern systems, two
more sensors are added to help the system work: a wheel angle sensor, and a
gyroscopic sensor. When the gyroscopic sensor detects that the direction taken
by the car doesn't agree with what the wheel sensor says, the ABS software will
brake the necessary wheel(s) so that the car goes the way intended.
ABS hydraulic control unit
Braking on the snow without ABS
Tyre Pressure Monitoring
Tyre pressure monitoring detects even small pressure fluctuations, locates the
affected tires and informs the driver with warnings of varying urgency. Function:
A co-rotating wheel module with an integrated valve measures tire pressure and
temperature and transmits these data as an HF radio signal. Two functional
variants have been developed to receive and process the data:
TPMS A: 4 wheel modules, 4 antennas with HF coupler
The receiving antennas are located on the
connecting cables for the wheel speed
sensors. They send the data to the EBS-ECU,
which then analyzes them in an intelligent
warning strategy unit. We are the only supplier
that can offer this technology without any
additional cable, receiver and ECU.
TPMS B: 4 wheel modules, 1 central
antenna
This more economical solution with a central
receiver in the EBS control unit is used when
the maximum transmitting power is allowed for
the wheel modules. Through a combination
with DDS and intelligent data processing, this
system is able to assign the 4 received
pressures to the 4 wheels (autolocation
function) even with only one receiving antenna.
In case of failure of sensors, DDS is used as a
fallback solution.
Future generations of systems networked with TPMS, DDS and ESP will make
important contributions to active accident avoidance, such as ESP control
dependent of tire pressure and load-dependent tire pressure recommendation. A
sensor-transponder integrated in the tire without a battery will supply pressure
and temperature data as well as information about the tire itself.
Active cruise control
Much of everyday driving takes place in a
stream of traffic, one car following another.
Given the high incidence of rear end
collisions, Adaptive Cruise Control Systems
(ACCS), which control the vehicle speed in
a manner than will maintain a safe following distance, show great promise.
Radar headway sensors and newer
systems like rotating LASERs
detect other vehicles and obstacles
on the road ahead by their
reflections. The microcomputer in
the car then calculates the actual
distance and decides the optimum
seperation length and speed at
which to follow the car in front. This
option enables the driver to relinquish control partially to the car computer which
continues to follow the car ahead whilst maintaining a safe distance. It thus slows
down and speeds up automatically with the car in
front requiring minimal effort on the driver’s
part.
Advancements in
these systems
also include
lane departure warning systems and lateral/side
sensing control systems. A mounted camera
visualises the lane markings on the road and uses DSP to analyse it. The
software is incredibly sophisticated and is able to distinguish different types and
colors of lane markings in different lighting and weather conditions. Radars are
used to monitor blind spots.
Parking assistance systems
Position of front looking RADAR
RADAR Tx / Rx
Overhead camera
Computer monitors lane marking
Parking assistance systems automatically warn the driver of obstacles to the
front and rear of the vehicle when manoeuvring. Based on the echo-sounder
principle, the system has a total of ten sensors – six in the front bumper and four
in the rear bumper. These send out ultrasonic signals which are reflected by
other vehicles or obstacles. A microprocessor calculates the actual distance and
informs the driver by means of visual
displays on the dashboard as well as
by audible warning tones. The
system monitors an area extending
between 15 and 80 cm at the front of
the vehicle and between 20 and 120
cm at the rear. If an obstacle is detected within this area, the visual and audible
warnings are activated – the visual warning is triggered first and is
complemented by the audible warning when the obstacle is about 35 cm away.
Whereas only the front sensors are active when moving forwards, both the rear
and front sensors are active when reversing.
Automatic parking system
Linear or automated garage parking has been
a feature of high end cars for a while now.
Recently though, parallel automatic parking
systems, have been developed, which when
activated, uses ultrasonic sensors to scan for
empty parking spaces. When a spot suitable to
the length of the car is found, the car’s
computer takes over. The steering and acceleration is controlled by the car
computer and the driver simply watches as the car squeezes itself into tight
spots. This facility is already available in some BMW, Mercedes and Honda
variants. Commercially this facility is an eye-catching USP for modern vehicles
and therefore viable.
Automated highways
A vehicle that can “predict” the actions of neighboring vehicles is an important
step for safer highway transportation. This can be accomplished through multi-
sensor systems for adjacent vehicles and possibly inter-vehicle communications
to give an idea of what to expect beyond adjacent vehicles. Alternatively, the
roadside control may have knowledge of the positions of the vehicles relative to
fixed reference points. Roadside monitors will measure traffic flow and speed,
and vehicle paths will be calculated based on this information. Such
measurements are currently made with loop detectors, ultrasonic sensors, AVI
tags or vision systems. Information may be
communicated by infrared beacons, broadcast
and cellular radio, or using emerging ultra
wideband technologies. The vehicles need
longitudinal sensors to measure distance and
relative speed of the preceding vehicle, which
are based on radar, ultrasound, or vision. Microwave radar sensors perform very
well in fog and heavy rain, but they are very expensive. Laser radar systems are
low-cost, but cannot handle low visibility conditions. To facilitate lane changes at
a range of relative speeds, the vehicle must be
equipped with sensors that locate vehicles on the side
with a longitudinal range of about 30m. Infrared and
laser range finding techniques may prove to be useful
in this area. Besides headway and side sensor
information, longitudinal and lateral velocity and acceleration, yaw rate, front
steering angle, and lateral deviation data is needed to obtain a robust combined
lateral and longitudinal control. All of these except the last one can be obtained
using on-board accelerometers and encoders. For vehicle position sensing, there
are two alternatives: magnetic markers, and vision systems. An eight-vehicle
platoon demonstration at the National Automated Highway Systems Consortium
Technical Feasibility Demonstration, held in San Diego from August 7-10, 1997,
successfully demonstrated the technical feasibility of operating standard cars.
Rainfall sensors
Magnetic loops for lane ID
Ceramic magnets
The rain sensor controls the windscreen
wipers autonomously. The electronics control
the wipers to give you an optimum view
through the windscreen whilst ensuring that
the windscreen wipers do not run over a dry
windscreen. The sensors make allowances
for the sensitivity of the human eye at night-
time and the frequency of the intermittent
wipe varies according to the vehicle's speed. Invisible beams of infrared light
transmitted by two light-emitting diodes scan an area of the windscreen on a
level with the rear-view mirror. The light beams are
reflected with varying intensity depending on how heavy
the rainfall is or how wet the windscreen is. A sensor
responds to the reading by adjusting the wiper interval
appropriately. If a few drops suddenly turn into a downpour, the system switches
from intermittent to continuous wipe, smoothly increasing the wiper speed in the
process as required. The reverse applies when the rain eases off again.
Noise cancellation system
Microphones located in the front and rear of the car’s interior on the ceiling listen
to the low-frequency wind and engine (road) noise inside
the car. It processes this and inverts the signal, feeding a
sample of it to the car’s stereo which then
plays an anti-noise signal that is 180 out of
phase with the original noise. This results in
destructive interference which effectively
blanks out the said noise. The noise
cancellation system also ensures that it doesn’t
cancel out the music on stereo output by
effectively matching the digital audio content.
Global Positioning Satellite Systems
Rain sensor
Rainfall monitored wiper system
A GPS unit consists of a space segment, a control segment, and a user
segment. The space segment is a constellation of two dozen satellites orbiting
the earth twice every 24 hours, at approximately 10,900 nautical miles above the
earth's surface, funded and controlled by the U.S. Department of Defense. The
control segment is a series of monitoring stations located at different sites on
earth that update and correct errors in the navigational message of the satellites.
The user segment is a receiver that receives radio waves from the satellites in
orbit and can determine how far away it is from each satellite by keeping track of
the time it takes for a radio wave to travel from the satellite to the receiver.
Four satellites are used
simultaneously to pinpoint the
precise position of the receiver on
the earth. Information from the first
three satellites narrows down the
range of possible locations to two
points; one of these is usually
illogical and indicates a point not on the earth. A fourth satellite is used to confirm
the target location. When installed in a car, a GPS unit can provide useful
information about the car's position and the best travel routes to a given
destination by linking itself to a built-in digital map. A monitor in the car shows the
relevant portion of the map. The driver can enter the target location, and the
computer will calculate the optimal route and display it instantly. It can respond to
user preferences and map a route that avoids highways or avoids local roads. If
the map is detailed enough, it will also provide the locations of the nearest gas
station, supermarket, restaurant, hotel, and ATM machine.
GPS also tracks the distance traveled on a particular trip, vehicle mileage,
and speed. It can keep a record of driving activity, including the address of each
destination, names of streets traveled, and how long the vehicle remained at
each location. GPS can also issue warnings when the car is speeding, aid in
recovery of a stolen car.
Other Modern Automobile Instrumentation Systems
Bluetooth and WiFi connectivity
Modern cars will feature
Bluetooth and WiFi connectivity
for entertainment, internet access
as well as exchange of important
information from one car to the
next viz. speed, traffic conditions,
accident warning and other
practical data.
Self-cleaning Headlights
Sensors in the car sense the
reflection off the protection
glass when the headlights
are turned on. It is thus able
to judge if the glass is dirty,
and automatically shoots a
jet of water to clean it.
Climate Control
Sensors monitor the temperature,
humidity, air quality etc. and
accordingly activate the climate
control system to provide ideal
climate conditions. It also makes
efficient use of re-circulated air and
enhances passenger comfort.
Keyless Entry and RFIDs
It eliminates the need for keys in the car. The car comes equipped with a
unique radio frequency tag which only the corresponding wireless key can
open. Starting the car in these cars is a simple push-button.