Electronic Control Unit(ECU)

Ankul Gupta

Outline❖What is an ECU❖Hardware Design of an ECU❖Operation of an ECU❖AUTOSAR Architecture❖Applications❖ECU Challenges❖References

What is an ECUIn the Automobile industry an electronic control unit (ECU) is an embedded electronic device, basically a digital computer, that reads signals coming from sensors placed at various parts and in different components of the car and depending on this information controls various important units e.g. engine and other automated operations within the car among many.

ECU(Electronic Control Unit) and its mount location

Types of ECUECM - Engine Control ModuleEBCM - Electronic Brake Control ModulePCM - Powertrain Control ModuleVCM - Vehicle Control ModuleBCM - Body Control Module

Hardware Design of ECU

Components of ECUAn ECU consists of a number of functional blocks:1. Power Supply – digital and analog (power for analog sensors)2. MPU – microprocessor and memory (usually Flash and RAM)3. Communications Link – (e.g. CAN bus)4. Discrete Inputs – On/Off Switch type inputs5. Frequency Inputs – encoder type signals (e.g. crank or vehicle speed)6. Analog Inputs – feedback signals from sensors7. Switch Outputs – On/Off Switch type outputs8. PWM Outputs – variable frequency and duty cycle (e.g. injector or ignition)9. Frequency Outputs – constant duty cycle (e.g. stepper motor – idle speed control)

What an ECU doesThe ECU uses closed-loop control, a control scheme 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 host of other parameters).

Gathering data from dozens of different sensors, the ECU performs millions of calculations each second, including looking up values in tables, calculating the results of long equations to decide on the best spark timing or determining how long the fuel injector is open.

Number CrunchingA modern ECU might contain a 32-bit, 40-MHz processor, which may not sound fast compared to the processors we probably have in our PCs, but the processor in our car runs a much more efficient code. The code in an average ECU takes up less than 1 megabyte(MB) of memory. By comparison, we probably have at least 2 gigabytes (GB) of programs on our computers -- 2,000 times the amount in an ECU.

AUTOSAR ArchitectureThe software is structured according to AUTOSAR, with application layer, RTE and base software. The architecture is divided into four main parts:Application Layer: Containing the application functions, primarily modelbasedRun Time Environment (RTE): Abstraction of the ECU hardware, provid-ing a common runtime environmentBase Software: Basic services for communication, I/O, memory and systemfunctionalityFlash Loader: Standalone application allowing a flash update of the system

Need of AUTOSARWithout a proper software standard every company built its own software solution or utilised 3rd party software for the same. Integration of 3rd party software created implementation issues (e.g. wrapper software, interface components), issues with testing methodology etc. with several tool chains further required, to associate the hardware with the software. It piled up the issues for Tier-1 manufacturers who now had to integrate different software for each OEM.These integration problems proved difficult to identify and costly to debug in the long run.AUTOSAR provides different functional blocks for the integration of application layer with the micro-controller.

Implementation with AUTOSAR

Monaco Grand Prix Italian Grand Prix(Monza)

ApplicationsDepending upon the nature of the circuit the Engine mappings can change completely. On slower and twister tracks, the engine control system will help the driver have more control on the throttle input by making the first half of the pedal movement very sensitive.

At high speed circuits, the driver has to jump on the throttle more, rather than gradually applying full throttle. The accelerator will be set so that only a small movement will result in full engine acceleration.

This function has to be repeated every 20 milliseconds.Steps:− Read the data captured by the Analog-to-Digital Converter (ADC) on the Channel to which the Accelerator Pedal is Connected.− Using this data, look-up the value from a multi-dimensional Table (Map), which also contains the Engine RPM (Rotations per Minute), as another input axis.− Take the output value from the Map, multiply it by a correction factor (depending on, for e.g. Performance or Economy Mode).− The output of this calculation is the Torque to be generated by the Engine.− Repeat this sequence every 20 milliseconds.

Steps

Some other applications Anti Lock Braking System(ABS) Electronics Brake Distribution Force(EBD) Power Windows Climate Control Park Assist Collision Warning Heads-up Display(HUD) Cruise Control Airbag Control System(ACS) 4-Wheel drive and many more.

ECU ChallengesThe worse place in the world to put a sophisticated piece of electronics is under the bonnet of a car due to massive vibrations, constant heat variations and intense radio interference from the ignition system added to the fact that the manufacturers must produce on a huge scale, this causes so many problems and design flaws with modern day ECUs.

References auto.howstuffworks.com http://www.f1scarlet.com/tech&busin_aspectsf1.html http://vector.com/portal/medien/cmc/press/Vector/

AUTOSAR_ATZelektronik_200703_PressArticle_EN.pdf http://www.fujitsu-ten.com/business/technicaljournal/pdf/26-1.pdf http://www.autosec.org/pubs/cars-oakland2010.pdf en.wikipedia.org

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