Electronic Control Units – Car

Cars, nowadays are getting more complicated by possessing 40 or more microprocessors in each. These processors are responsible for their internal working. Here are few reasons listed for increase of number of microprocessors,

• Engine control – to meet emissions and fuel-economy standards
• Diagnostics
• Simplification of cars design
• Reduction of wiring in cars
• Safety & Comfort features

Controlling the engine as desired is the most intensive job on your car which makes the way of arising engine control unit (ECU). which is the most powerful computer that monitors outputs of a system to control the inputs to a system, managing the emissions and fuel economy of the engine. Also, gathers data from different sensors, the ECU knows everything from the coolant temperature to the amount of oxygen in the exhaust. With this data, it performs millions of calculations each second and decide on the best spark timing and determining how long the fuel injector is open.

An ECU may contain a 32-bit, 40-MHz processor which we probably have in our PC’s. The code in each ECU takes up less than 1 megabyte (MB) of memory.

Components of ECU:

The ECU was a module with hundreds of components on a multi-layer circuit board. Some of the parts in the ECU are,

Analog-to-digital converters – These devices read the outputs of some of the sensors in the car, such as the oxygen sensor. The output of an oxygen sensor is an analog voltage. The processor only understands digital numbers, so the analog-to-digital converter changes this voltage into a 10-bit digital number.

High-level digital outputs – In many cars, the ECU fires the spark plugs, opens and closes the fuel injectors and turns the cooling fan on and off. These tasks require digital outputs (either on or off). For instance, an output for controlling the cooling fan might provide 12 V and 0.5 amps to the fan relay when it is ON, and 0 V when it is OFF. The small power that ECU can output energizes the transistor in the digital output, allowing it to supply a much larger amount of power to the cooling fan relay, which in turn provides a still larger amount of power to the cooling fan.

Digital-to-Analog converters – Sometimes, ECU should provide an analog voltage output to drive some engine components. Since it is a digital device, it needs a component that can convert the digital number into an analog voltage.

Signal Conditioners – In few cases, the inputs or outputs need to be adjusted before they are read. For instance, the analog-to-digital converter that reads the voltage from the oxygen sensor might be set up to read a 0V to 5V signal, but the oxygen sensor outputs a 0V to 1.1V signal. A signal conditioner is used here to multiply the voltage coming from the oxygen sensor by 4, to achieve 0V to 4.4V signal.

Communication circuits – Cars comprises of communication circuits with various communications standards. One of that dominates in-car communications is called CAN (controller-area networking). This communication standard allows for communication speeds of up to 500 Kbps.

Diagnostics of ECU:

A benefit of having a communications bus is that each module can communicate faults to one central module, which stores the faults and communicate them to an off-board diagnostic tool. This makes easier for technicians to diagnose few notorious problems in car, while it is given for repairs.

Design and Manufacture:

Communication standards in car has made designing and building them easier. Instrument cluster for instance, gathers and displays data from various parts of the vehicle. Most of this data is already used by other modules in the car. These modules transfer the data onto the communications bus with high speed.

Simplified Wiring:

Multiplexing is the method which can simplify the wiring in a car. A module containing at least one microprocessor consolidates inputs and outputs for an area of the car. Driver-door module for instance, have lots of controls on the door, windows etc., It would be impractical to run the thick bundle of wires that would come from a system like this out of the door. Instead, the driver’s-door module monitors all the switches.

Safety & Comfort:

All cars comprise safety systems such as ABS, Airbags, Traction and stability control systems etc. Each of these systems has their own module which contains multiple microprocessors. In coming years, there is chance of new convenience features and each of these requires more electronics modules.

To conclude, All the automakers are driving towards electric vehicles, which in turn may have significant increase of these control modules. However, this do not affect the consumers, but only in terms of cost and maintenance of their vehicle.