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
•
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 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.
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 Central microprocessor counters individual wheel slipping. Pulsed braking.
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.
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
Without ESC With ESC Components of ESC
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.
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.
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.
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 ABS hydraulic control unit
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.
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
Position of front looking RADAR
RADAR Tx / Rx
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
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
Magnetic loops for lane ID
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
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
Rain sensor
Rainfall monitored wiper system
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
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.
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.