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Embedded Systems In Automobiles
Transcript of Embedded Systems In Automobiles
design by Dóri Sirály for Prezi
What is an Embedded System ??
An embedded system is a combination of hardware and software which creates a dedicated computer system that performs specific pre-defined tasks and which is encapsulated within the device it controls.
Embedded Sysem in Automobiles
ABS-Anti-Lock Braking System
An anti-lock braking system (ABS) (translated from German, Anti-Blockier System) is a safety system on motor vehicles which prevents the wheels from locking while braking.
A rotating road wheel allows the driver to maintain steering control under heavy braking, by preventing a locked wheel or skid, and allowing the wheel to continue to forward roll and create lateral control, as directed by driver steering inputs.
Components Of an ABS System
There are four main components to an ABS system:
It restrains the continous motion of the passenger by providing a soft surface to land on.
It is based on Newton's 2nd law of motion.
The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel
The sensor is the device that tells the bag to inflate. Inflation happens when there is a collision force equal to running into a brick wall at 10 to 15 miles per hour (16 to 24 km per hour).
The airbag's inflation system reacts sodium azide (NaN3) with potassium nitrate (KNO3) to produce nitrogen gas.
Hot blasts of the nitrogen inflate the air bursts from its storage site at up to 200 mph (322 kph) -- faster than the blink of an eye! A second later, the gas quickly dissipates through tiny holes in the bag, thus deflating the bag so you can move.
Cruise control is a system that automatically controls the speed of a motor vehicle. The system takes over the throttle of the car to maintain a steady speed as set by the driver.
Theory Of Operation
The driver sets the speed and the system takes over the throttle of the car to maintain the speed.
Most systems do not allow the use of the cruise control below a certain speed (normally around 40 km/h (25 mph))
Cruise control actuates the throttle valve by a cable connected to an actuator, instead of by pressing a pedal.
Adaptive Cruise Control
This new system can automatically adjust speed in order to maintain a proper distance between vehicles in the same lane. This is achieved through a radar headway sensor, digital signal processor and longitudinal controller.
It uses the 77-GHz Autocruise radar system made by TRW which has a forward-looking range of up to 492 feet (150 meters), and operates at vehicle speeds ranging from 18.6 miles per hour (30 kph) to 111 mph (180 kph).
Parking sensors are proximity sensors for road vehicles designed to alert the driver to obstacles while parking. These systems use either electromagnetic or ultrasonic sensors.
Ultrasonic sensors bounce sound waves off obstacles, using the ‘echo’ time to indicate how far away they are. A speaker in the car bleeps – increasingly frantically – as they get closer.
Working Of Sensors
Electromagnetic parking sensors create an invisible electromagnetic field around the car’s bumper; any objects entering it trigger a warning sound. Currently used by Audi, Citroën and Fiat, among others.
Rain sensing wipers uses optical sensors to detect the moisture. The sensor is mounted in contact with the inside of the windshield, near the rear view mirror.
The sensor projects infrared light into the windshield at a 45-degree angle. If the glass is dry, most of this light is reflected back into the sensor by the front of the windshield.
If water droplets are on the glass, they reflect the light in different directions -- the wetter the glass, the less light makes it back into the sensor.
The recent two decades has witnessed a trend in the automotive industry---a rapid growth in the percentage of cost of embedded electronic systems, more precisely the software components. As shown from in 2006, the electronic embedded system constituted at least 25% of the total cost of a car and more than 35% for a high-end model. Top-line cars today may contain up to 100 ECUs (Electronic Control Unit). Each controls one or more of the electrical systems or subsystems in a motor vehicle networked over standard communication buses.
Vehicle functions often have stringent real-time requirements, which means that only functional correctness cannot guarantee their correct behavior, but also their temporal correctness needs to be taken into account. That is, the right values (or right actions) have to be delivered (taken) at the right time
Unexpected problems may occur when integrating different individually developed functions on a single ECU. Due to interference from other software components, functions that work nicely when running on an ECU exclusively may exhibit incorrect
behavior when they have to share an ECU with other functions. The integration processes are in the late phases of the whole development process for a vehicle; any incorrectness in this phase may be very costly.