The time is 7.30pm and you have just managed to end your business meeting. However, you still have more tasks to complete. Your travel time back to your home is about an hour and you would like to get moving at the earliest. You take some deep breaths to relax from the grilling meeting, fish out your mobile phone on which rests an app that will have the nearest cab sent to you. Within seconds of sending the request you receive a text confirmation and in the next few minutes—the cab.

Fig. 1: Dashboard view of Google self-driving car (Source: www.slashgear.com)
Fig. 1: Dashboard view of Google self-driving car (Source: www.slashgear.com)

“Home,” you say, as you start initiating a video call with a prospect in New York. The car first checks road conditions and then glides into the self-drive lane, checking and flashing a message that you are likely to reach home in the next 45 minutes. During this time, you will have closed a business deal with the New York prospect, apprised a subordinate, answered a few calls from your office and yes, also set your pick-up time for tomorrow morning. You reach home relaxed and ready to spend some quality time with your family. As you get off the car, it glides away to pick up its next guest. No one wishes you good night—as there is no driver in the car!

This technology is enabled by equipping cars with a host of sensors, cameras and radar systems. Artificial intelligence (AI) then guides the cars as to where to drive. It is important that the automobiles collect a vast quantity of data about nearby obstacles, compute risks and make micro-second decisions.

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How it all began
Modern solid-state control systems made their way into automobiles only in the early seventies with the proliferation of transistor technology and affordable solid-state products. The transistor served a very good purpose to incorporate aspects like the ignition’s mechanical points into electronic ignition modules. This was maintenance-free, more reliable and cost-effective. The growing need of being able to control automobiles with higher accuracy in order to meet the tightening emissions and fuel economy standards catalysed the automotive computer systems’ evolution.

Fig. 2: Early automotive computer systems used in 1979 Chrysler cars (Source: www.allpar.com)
Fig. 2: Early automotive computer systems used in 1979 Chrysler cars (Source: www.allpar.com)
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Fig. 3: ECM from a 1996 Chevrolet Beretta (Source: http://en.wikipedia.org/wiki/Engine_control_unit)
Fig. 4: A master diagnostic technician using a laptop computer to diagnose and repair the brake system (Source: http://www.cbsnews.com)
Fig. 4: A master diagnostic technician using a laptop computer to diagnose and repair the brake system (Source: http://www.cbsnews.com)

Modern automotive computer systems came into the picture only by early 1980s when almost every car manufactured in the US had a check-engine light and a primitive computer. The onboard computer was indeed a bit ancient, given its huge tin box with edge-board connectors which had a propensity to oxidise and result in drivability issues. Stricter emission laws saw the advent of microprocessors in car engines, since sophisticated control processes were needed to regulate the air and fuel mixture so that the catalytic converter could eliminate most of the pollution from the exhaust.

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An ECM manages the key engine operations, such as spark timing, fuel delivery, emissions and, in some cases, the automatic transmission too. The computer gets electrical signals from sensors and input devices associated with the engine on a regular basis. It analyses this information and sends control signals to valves, controllers and other output devices, to balance the requirements of power, fuel economy and emission control.

The ECM uses closed-loop control, a control method that monitors outputs of a system to control the inputs to a system, managing the emissions and fuel economy of the engine (as well as a number of other variables). Collecting data from a number of different sensors, the ECM keeps track of everything from the coolant temperature to the quantity of oxygen in the exhaust. Using this data, it performs millions of calculations per second, which include looking up values in tables, calculating the results of long equations to decide on the optimal spark timing and determining how long the fuel injector is open. The ECM works with the objective of achieving the lowest emission levels and highest mileage.

A contemporary ECM could even have a 64-bit, 100MHz processor. While this processing power may seem insignificant (considering the levels to which today’s computers have reached), actually your car computer is more efficient than your PC. The programming memory needed by a typical ECM is approximately 1MB to 2MB. Whereas, generally, we need about 2GB of programming space on our PC. The microprocessor is packaged with several other components on a multi-layer circuit board. Besides, there are several other components in the ECM that support the processor. Some of these are mentioned below.

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Analogue-to-digital converters. These read the outputs of certain sensors in the car. The output of a sensor is an analogue voltage. Since the processor understands only digital numbers, the analogue-to-digital converter transforms this voltage into a 10-bit digital number.

Digital-to-analogue converters. Sometimes the ECM has to give an analogue voltage output to certain engine components. As the processor on the ECM is a digital device, it requires an element that can convert the digital number into an analogue voltage.

High-level digital outputs. In some of the recently launched cars, the ECM fires the spark plugs, opens and closes the fuel injectors and switches the cooling fan on and off. Such computerised tasks need digital outputs. For example, an output for controlling the cooling fan might supply 12V and 0.5A to the fan relay when it is on, and 0V when it is off. The minute amount of power that the processor supplies energises the transistor in the digital output, allowing it to supply a considerably higher amount of power to the cooling fan relay, which in turn provides an even higher amount of power to the cooling fan.

Communication chips. These chips carry out various communication standards that are used on cars. There are several standards used, but the most popular one is called controller-area networking (CAN).

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