Importance Of Sensors In Automobile Vehicles

Sensors play an important role in automotives. These enable greater degrees of vehicle automation and futuristic designs. For example, at manufacturing units, sensorised robotic arms are used for painting car bodies and measuring the thickness of the coatings being applied. Manufacturers can simply monitor the thickness of the paint being sprayed on instruments, airbag claddings and various internal parts of the vehicles using sensors.

Fig. 1: Some sensors used in cars (Credit: www.digikey.com)

Electronic control unit

All sensors inside the vehicle are connected to the ECU, which contains the hardware and software (firmware). Hardware consists of electronic components on a printed circuit board (PCB) with a microcontroller (MCU) chip as the main component. The MCU processes the inputs obtained from various sensors in real time.

All mechanical and pneumatic controls have been replaced by electronic/electrical systems that are more flexible, easier to handle, lighter and cheaper. Moreover, the ECU has reduced the number of wires and emissions, and enabled diagnosing problems with ease. Controlling and monitoring in the modern vehicle is much easier with the ECU.

Communications and control

The ECU simplifies the communication between various components and devices, because long wires for each function are not required. It is installed in the vehicle and connected to the nearest vehicle bus, including controller area network (CAN), local interconnect network (LIN), FlexRay and BroadR-Reach, among others. A CAN bus standard is designed to allow MCUs, sensors and other devices to communicate with each other without a host computer.

Emission control

After sensing fuel level and calculating fuel quantity, the ECU sends signals to various relays and actuators, including ignition circuit, spark plugs, fuel injectors, engine idling air control valve and exhaust gas re-circulation (EGR) valve. Then, it extracts the best possible engine performance while keeping emissions as low as possible.

Engine fault diagnosis

ECU collects signals from various sensors, including faulty ones, and stores these in its memory. Sensors diagnose these faults either by reading ECU memory directly or engine diagnostic equipment supplied by the vehicle manufacturer.

Modern luxury cars contain hundreds of ECUs, but cheaper and smaller cars only a handful. The number of ECUs goes up with ever-increasing features.

Depending on the vehicle make and model, the ECU(s) can be found beneath the wiper, under the bonnet in engine bay, passenger front footwell under the carpet or near the glove compartment.

Some common vehicle sensors include ambient light, battery current, differential oil temperature, door open warning, anti-lock braking system (ABS), auto door lock position, battery temperature, brake power booster, camshaft position, crankshaft position, cylinder head temperature, diesel emissions fluid temperature, fuel cutoff, fuel temperature, headlight level, humidity, hybrid battery voltage, hybrid circuit breaker, ignition pass-lock, manifold absolute pressure (MAP), mass air flow (MAF), oil level, oxygen, power steering fluid level, speed, steering angle, temperature, throttle position, transmission oil pressure and windshield washer level.As a car owner, you do not have to know the functions of all sensors used in the vehicle, but knowing the basics can be helpful in case your car breaks down or something else goes wrong. Getting a replacement sensor demands attention to genuineness, quality and performance of the product. To understand these functions, a list of some popular sensors used in modern vehicles are listed in the table.

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