By Aditya Rajendran (B.E ICE, 2014-18)

ab1If I told you, an invention made a century ago has single-handedly shaped our future, or the future of mankind, and this was the main force that essentially “drove” the future of innovation and technology, and this was the cut ribbon that opened the doors to the new century, it would be very appropriate.What started off as a self propelled, steam powered model toy for a Chinese emperor made by one Ferdinand Verbiest, accomplished mathematician and astronomer in the 17th century, made its way all the way to Karl Benz, generally regarded as the inventor of the modern day automobile powered by an internal combustion engine.This article will mainly deal with the Electronic Control Unit (ECU) and the many systems that control the various processes in the modern day automobile.

The Electronic Control Unit is basically an embedded system that controls and co-ordinates the various processes that are governed by it, through a series of data that is collected through strategically placed sensors that continuously give output data to the respective ECU.

The Output data received from the sensors by the ECU is processed and is constantly monitored to ensure the efficiency and the proper working of the respective system governed by the ECU.

There are a number of Electronic Control Units used, with the modern day automobiles having up to 80 ECUs. Each one of them are responsible for the working of the respective processes assigned to them. Taken together, these systems are sometimes referred to as the car’s computer. (Technically there is no single computer but multiple ones.)

An ECU is basically a mini-computer, featuring it’s own microcontrollers, RAM (Random Access Memory), and various external communication links such as USB (Universal Serial Bus), Serial ports , etc.

ab2A few of the most common and essential control units are listed-

Engine control module (ECM), Powertrain Control Module (PCM), Transmission Control Module (TCM), Brake Control Module (BCM or EBCM), Central Control Module (CCM), Central Timing Module (CTM), General Electronic Module (GEM), Body Control Module (BCM), Suspension Control Module (SCM), control unit, or control module.

The primary ECU responsible for the proper and efficient working of the engine of the automobile is the Engine Control Unit or Engine Control Module (ECM).

The Engine Control Unit governs the processes that the engine goes through, by means of controlling a series of actuators (essentially motors that control the various levels of pressure such as hydraulic fluid pressure, or pneumatic pressure, and many others). The Engine Control Unit reads values from a multitude of these actuators and sensors situated in the engine bay, interprets the data using multidimensional maps that then inform the ECU as to how much adjustment of the actuators is needed, and the ECU then does the same.

ab3A transmission control unit or TCU is a device that controls modern electronic automatic transmissions. A TCU generally uses sensors from the vehicle as well as data provided by the engine control unit (ECU) to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality, thereby increasing efficiency and minimizing human errors.ab4
The modern day automobile has a number of ECUs for user convenience and importantly, safety purposes. A few of them are listed below with their respective purposes.

-Airbag control unit (ACU)- To control the deployment of Airbags in case of accidents.

 -Body control module (BCU) controls door locks, electric windows, courtesy lights, etc.

– Convenience control unit (CCU) – Controls air conditioning and other comforts.

-Door control unit (DCU)- To warn the user when the door is ajar or not locked properly.

-Human Machine Interface (HMI) – To access the seamless interface between the user and the machine, and possibly control various options suited to his needs.

-Powertrain Control Module (PCM): Sometimes the functions of the Engine Control Unit and Transmission control unit (TCU) are combined into a single unit called the Powertrain Control Module.

-Seat Control Unit- To sense the occupancy of the seat and whether or not the seatbelt has been fastened and give the necessary warnings to the user.

-Speed Control Unit (SCU)- To monitor the rate of speed of the vehicle.

-Telematic Control Unit- An embedded system to monitor the location of a vehicle accurately using GPS or a number of other means.

-Brake Control Module (BCM; ABS )- To control and efficiently deploy brakes and provide enough braking power for the car to effectively come to a halt by assessing the various environmental conditions or surface conditions at the time.

-Battery Management System- To control the efficient and effective usage of the battery power and constantly monitor its output and recharging statistics.

The inculcation of the various convenience sensors are for the sole purpose of increasing the level of comfort and ease of use and most importantly, increasing the level of safety of the user.

Embedded software in ECUs continue to increase in the number of sensors and actuators governed by them, thereby increasing complexity and sophistication.

But an increase in these parameters ensure an increase in the level of user comfort, ease of use, and most importantly, safety of the user, thereby ensuring the progress in innovation and technology for generations to come.

Aditya RajendranADITYA RAJENDRAN (B.E ICE, 2014-18) is a unique individual with interests ranging from physics and electronics to astronomy and English literature. He is an accomplished gamer and also likes to be up to date with recent advances in prototype technologies.

For comments/feedback/suggestions, please write to