Embedded Systems In Automobiles

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Fig. 5: A basic anti-lock brake system
Fig. 6: Functioning of a traction control system with brakes

Dynamic traction and stability control

The traction control system is required to prevent driver error from overloading any of the four wheels and causing a slip, through either throttle or brake application. When the drive wheels start losing traction, the dynamic stability control automatically begins stabilisation measures. The dynamic stability control system curbs engine output and stops slips on the wheels. In exceptional situations, however, a small amount of wheel slip can be an advantage.

The principle of the traction control system is the adaptation of wheel torque to the coefficient of friction between the wheel and the road surface.

When the traction control computer detects one or more driven wheels spinning significantly faster than another, it invokes the anti-lock braking system’s electronic control unit to apply brake friction to wheels spinning with lessened traction. Braking action on slipping wheel(s) cause power transfer to wheel axle(s) with traction due to the mechanical action within the differential. All-wheel drive vehicles often have an electronically-controlled coupling system in the transfer case to supply non-slipping wheels with torque.

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A traction control system has three main components: a sensor equipped in each wheel that senses changes in speed due to traction, an electronic control unit that receives the sensed speed from each wheel and an automatic traction control valve that supports in braking after the electronic control unit processes information from the wheels.


Embedded navigation system

The navigation system consists of an embedded circuitry built with a GPS receiver, gyroscope, DVD-ROM and display system. The GPS receiver receives current longitude and latitude values that are compared with the stored map. The gyroscope and other sensors provide road direction and speed. From all the information gathered at the main controller, the display system displays a navigation or route map of the destination on the display screen.

Fig. 7: Block diagram of an embedded navigation system

Embedded rain-sensing system

Fig. 8: An embedded rain-sensing system

In a rain-sensing system, an optical sensor is placed on a small area on the front windshield glass opposite to the rear-view mirror. This optical sensor emits infrared light and is placed at a 45-degree angle to the windshield. If the glass is dry, most of this light is reflected back into the sensor. If water droplets are on the glass, these reflect light in different directions. The wetter the glass, the lesser the light that makes back to the sensor.

The electronics and software in the sensor turn on the wipers when the amount of light reflected onto the sensor decreases to a preset level. The software sets the speed of the wipers based on how fast the moisture builds up between wipes. It can operate the wipers at any speed. The system adjusts the speed as often as necessary to match with the rate of moisture accumulation.

Embedded based automatic car parking system

This automatic car parking system is an independent car-manipulation system that moves a car from a traffic lane into a parking spot to perform parallel, perpendicular and angle parking.

The system mainly uses different methods to detect objects around the car. Sensors installed on the front of the vehicle and rear bumpers act as both a transmitter and a receiver. These send a signal that is replicated back when it meets an obstacle near the vehicle and then the car computer receives the time signal and the bumper uses the radar to decide the position of the obstacle. The car senses the parking space and distance from the side of the road and helps the driver drive the car into the parking place.

Fig. 9: Parking spotted by driver with distance mentioned between vehicle and parked vehicle
Fig. 10: Automatic car parking using sensors

Future prospects

With the ever-increasing use of embedded systems in automobiles, new technologies and enhancements are being developed to increase usability.

Intelligent adaptive cruise control.

By using this technology we can make driverless vehicle control a reality. Many automobile manufacturers are already engaged with this concept. This adaptive cruise control allows cars to keep safe distances from other vehicles on busy highways. The driver of the car can set the speed of the vehicle and the distance between his car and other vehicles. When traffic slows down, adaptive cruise control changes vehicle speed using moderate braking.

Each car has a laser transceiver or a microwave radar unit, which is fixed in front of the car to find out the speed and distance of the any other vehicle in the pathway. This works on the principle of Doppler Effect, which is basically change in the frequency of waves. It uses a forward-facing radar, installed behind the grill of a vehicle, to detect the speed and the vehicle ahead of it. It can automatically adjust speed in order to maintain proper distance between vehicles in the same lane.

It is hard to implement this system around a curve, when there are elevation changes, during cut-ins, during dense traffic and other situations.



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