Dept of IT, RVCE 1

AUTOMOTIVE COMPUTER CONTROLLED SYSTEMS

FAISAL AMEEN ZAMAN(1RV09IT017)

SIDDHARTH D.C.(1RV09IT043)

SIVA SUBRAMANIAN(1RV09IT045)

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WHY AUTOMOTIVE CONTROL SYSTEMS?

We see and use automobiles everyday, but most of us are not aware of the logic hidden underneath these systems.

While purchasing a vehicle, it is important you know the systems underneath to properly evaluate a vehicle and know whether you’re being cheated or not.

Over 50% of whoever is employed end up in the automotive sector in someway or the other.

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2nd SEM BASIC MECHANICAL ENGINEERING- A RECAP

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ECU THE “BRAIN” BEHIND THE “HEART”

What is an ECU?

Any embedded system that controls one or more electrical systems in a vehicle.

An ECU basically does 2 functions, ‘HOW MUCH OF FUEL TO BURN’ and ‘WHEN TO BURN IT’. Besides these functions it also does other

auxiliary functions such as controlling the radiator fan, instrument cluster and various safety systems (think ABS, Traction Control, Airbags etc.).

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THE ECU DEMYSTIFIED

How does the ECU does what it does?

The ECU determines the amount of fuel and ignition timing by collecting information from various sensors which convey the current operating status of the engine and other auxiliary systems on the car. The sensors used as inputs for the ECU can be

classified into:-• Position Sensors• Physical Condition Sensors(Temperature, Pressure)

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Sensors which tell when to burn the fuel

• Crank Angle SensorUsed to provide the position of the Crankshaft.

By this, the sensor will indirectly tell the ECU that the piston has almost reached the top position and it is time for the spark plug to provide the “spark”.

• Camshaft Position SensorUsed to provide the position of the camshaft

This sensor will tell the ECU that it the intake valve will now open and it is now time to spray the fuel and let the air-fuel mixture inside the cylinder

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Sensors which tell the Engine how much fuel to burn

Throttle Position Sensor

Nothing but a Rotary Potentiometer (4th sem ITDC)

Depending upon how much the accelerator is actuated, the throttle plate is turned by a certain angle.

More the actuation, more the air which enters, which means more fuel to burn, hence more power produced

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ALTERNATIVE SENSORS WHICH TELL HOW MUCH FUEL TO BURN

Intake Pressure Sensor

Is generally a piezoelectric sensor

Tells the suction pressure caused due to the suction created by the combustion chamber

More the suction pressure means more air is sucked and hence more fuel is needed, hence more power Air Mass Sensor

Provides an output proportional to the mass of air flowing into the cylinder

More air means more fuel sprayed, hence, yet again, greater power

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OTHER IMPORTANT SENSORS NEEDED FOR THE RUNNING OF THE ENGINE

Engine Temperature Sensor

Is generally a thermocouple

Used to input the engine temperature to the ECU

High temperature indicate engine overheating, which the ECU interprets and hence tells the radiator to start remove the heat from the engine via the coolant. Air Temperature Sensor

Provides the temperature of the ambient air.

This is essential since the temperature of the air lets us know about the density of the air which in turns lets us know about the pressure of atmospheric air. Used along with an Intake Pressure Sensor

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SO WHAT DOES THE ECU DO WITH ALL THESE INPUTS?

All the analog inputs are converted into digital inputs via ADC’s

The ECU has prewritten algorithms into it’s ROM

This algorithm generates a value of spark timing, amount and timing of fuel injection, and activates the cooling system based on inputs from the sensors.

This value is converted to analog form via DAC’s and provided to the respective output lines in the form of an analog voltage.

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OTHER COMPUTER CONTROLLED SYSTEMS ABS Airbags Speedometer Odometer Tachometer Traction Control Battery Management in Hybrid Vehicles

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SPEEDOMETER & ODOMETER

A speedometer is an instrument cluster which shows the driver how fast the vehicle is moving.

Inside the speedometer, the cable turns shaft with a small magnet on it.

The odometer records the total distance the vehicle has traveled.

The odometer operates by a pair of gears from the speedometer.

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Conti..

Some vehicles have an electronically-driven speedometer and odometer.

A vehicle speed sensor sends vehicle speed signal through wiring to the speedometer. This eliminates speedometer cable.

The odometer reading is not lost when battery is disconnected.

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SPEED CONTROL SYSTEM

This helps the vehicle to automatically maintain a speed selected by the driver.

An actuator motor or vacuum servo opens and closes the throttle, as and when needed, to maintain the speed.

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TACHOMETERS

They are used to indicate the RPM of the engine. This is useful when the driver wants to shift gears. An ideal RPM shift ensures the engine is working in the optimal condition.(No over-revving).

Traditionally, tachometers are dials with a needle pointing to the current speed in RPMs (revolutions per minute). However, with the onset of new reading systems, the use of digital tachometers has risen sharply

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Major parts of tachometer Dial :

The dial tells the driver the tachometer's reading. In a car, it is located on the dashboard.

The device is necessary in order to regulate how hard the engine is being worked.

Generators : Engines with ignition systems usually utilize a

small generator attached to the engine drive shaft. In this case, the tachometer is actually a voltage meter, meaning that it counts the pulsations of voltage in the ignition system.

The output voltage is proportional to the shaft's speed so measuring voltage is converted into an accurate measurement in RPMs.

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ABS-ANTI-LOCK BRAKE CONTROLLER

Most ABS works on PASCAL’s law A typical ABS includes a central

electronic control unit (ECU), wheel speed sensors, and at least one hydraulic actuator.

There is one speed sensor mounted on each wheel.

This sensors supply the speed of each wheel to the microcontroller, and this MC calculates the braking force to be applied on each wheel.

This ensures that the tires do not skid due to uneven braking force.

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ABS >>

Some anti-lock system can apply or release braking pressure 16 times per second

The ABS equipment may also be used to implement a traction control system(TCS) on acceleration of the vehicle

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Air bag

There are two types - frontal and the various types of side-impact airbags.

There are four crash sensors deployed for its working

The system is powered by the battery of car

Propellant used in airbag is sodium azide The deployment time from impact to

inflation is about 50 ms

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Traction control

Designed to prevent loss of traction(Grip) of driven road wheels

Reduces or suppress spark sequence to one or more cylinders(shuts of some cylinders temporarily)

Reduce fuel supply to one or more cylindersBrake force applied at one or more wheelsElectronic throttle control system serves as a

mechanical link between the accelerator pedal and the throttle In turbo-charged vehicles,

A boost control solenoid can be actuated to reduce boost and therefore engine power.

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HYBRID CARS

A car which combines a internal combustion engine propulsion system with an electric propulsion system.

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Components

Conventional car engine – It can be a petrol or diesel engine. They will be smaller with greater efficiency and lesser emissions.

Fuel Tank – For storing the fuel needed to run the car’s IC engine.

Batteries – Batteries are needed to store and release energy as required by the car. The energy from the battery is taken by the motor.

Electric Motor and generator – Though motors can act as generators, both of them are needed for this car. A motor will be needed to take energy from the batteries and accelerate the car. Generators, on the other hand, are needed to produce the electrical power.

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AdvantagesBetter mileage. More reliable and comfortable. Very clean cars due to less emissions. Batteries need not be charged by an external

source

Disadvantages The initial cost will be very high – higher than other

cars.Spare parts will be very costly and rare.The Hybrid car battery also has a limited life spanAs there is electrical components there is a risk of

shock during an accident

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Famous Hybrid Cars

Ford Escape Hybrid Toyota Prius