Automotive computer controlled systems


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Automotive computer controlled systems

  2. 2. WHY AUTOMOTIVE CONTROL SYSTEMS?2  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. Dept of IT, RVCE
  4. 4. ECU THE “BRAIN” BEHIND THE “HEART”4  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.). Dept of IT, RVCE
  5. 5. THE ECU DEMYSTIFIED5  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) Dept of IT, RVCE
  6. 6. Sensors which tell when to burn the fuel6 • Crank Angle Sensor Used 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 Sensor Used 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 Dept of IT, RVCE
  7. 7. Sensors which tell the Engine how7 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 Dept of IT, RVCE
  8. 8. ALTERNATIVE SENSORS WHICH TELL HOW MUCH FUEL TO BURN8  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 Dept of IT, RVCE
  9. 9. OTHER IMPORTANT SENSORS NEEDED FOR THE RUNNING OF THE ENGINE9  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 of IT, RVCE Dept
  10. 10. SO WHAT DOES THE ECU DO WITH ALL THESE INPUTS?10  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. of IT, RVCE Dept
  11. 11. OTHER COMPUTER CONTROLLED SYSTEMS11  ABS  Airbags  Speedometer  Odometer  Tachometer  Traction Control  Battery Management in Hybrid Vehicles Dept of IT, RVCE
  12. 12. SPEEDOMETER &12 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. Dept of IT, RVCE
  13. 13. Conti..13  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. Dept of IT, RVCE
  14. 14. SPEED CONTROL14 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. Dept of IT, RVCE
  15. 15. TACHOMETERS15  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 Dept of IT, RVCE
  16. 16. Major parts of tachometer16  Dial :  The dial tells the driver the tachometers 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 shafts speed so measuring voltage is converted into an accurate measurement in RPMs. Dept of IT, RVCE
  17. 17. ABS-ANTI-LOCK BRAKE CONTROLLER17  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 Dept of tires do not skid due the IT, RVCE
  18. 18. ABS >>18  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 Dept of IT, RVCE
  19. 19. Air bag19  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 50Dept of IT, RVCE ms
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  22. 22. Traction control23  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 cylinders  Brake force applied at one or more wheels  Electronic 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. Dept of IT, RVCE
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  27. 27. HYBRID CARS28  A car which combines a internal combustion engine propulsion system with an electric propulsion system. Dept of IT, RVCE
  28. 28. Components29  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 theDept of IT, RVCE power. electrical
  29. 29. 30 Dept of IT, RVCE
  30. 30. 31 Advantages  Better 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 span  As there is electrical components there is a risk of shock during an accident Dept of IT, RVCE
  31. 31. Famous Hybrid Cars32 Ford Escape Hybrid Toyota Prius Dept of IT, RVCE