ENGINE MANAGMENT SYSTEM Engine control systems play an important role in achieving legislated emission limits while at the same time providing a good driving experience for the driver. This is achieved in a dedicated robust controller hardware that goes u

Engine control systems play an important role in achieving legislated emission limits while at the same time providing a good driving experience for the driver. This is achieved in a dedicated robust controller hardware that goes under several names: Engine Management System (EMS), Engine Control Unit (ECU), or Powertrain Control Module (PCM).
The basic function of the EMS is to process sensor values and deliver control outputs to the actuators in real time, while simultaneously providing hardware protection and monitoring both hardware and software for safety critical engine control functions.
A self-contained custom-built computer which controls the running of an engine by monitoring the engine speed, the engine load, the engine temperature; providing the ignition spark at the right time for the prevailing conditions and metering the fuel to the engine in the exact quantity required.

1. 23-09-2025 Dr. Shrimantini 1 Engine Management System (EMS)

2. Engine control systems play an important role in achieving legislated emission limits while at the same time providing a good driving experience for the driver. This is achieved in a dedicated robust controller hardware that goes under several names: Engine Management System (EMS), Engine Control Unit (ECU), or Powertrain Control Module (PCM). The basic function of the EMS is to process sensor values and deliver control outputs to the actuators in real time, while simultaneously providing hardware protection and monitoring both hardware and software for safety critical engine control functions. A self-contained custom-built computer which controls the running of an engine by monitoring the engine speed, the engine load, the engine temperature; providing the ignition spark at the right time for the prevailing conditions and metering the fuel to the engine in the exact quantity required. 23-09-2025 Dr. Shrimantini 2 Engine Management Systems

3. 23-09-2025 Dr. Shrimantini 3

4. 23-09-2025 Dr. Shrimantini 4

5. 23-09-2025 Dr. Shrimantini 5 (Negative temp. coefficient)

6. 23-09-2025 Dr. Shrimantini 6

7. 23-09-2025 Dr. Shrimantini 7

8. It is already worth pointing out here that safety, monitoring, and diagnosis are crucial components in the EMS and make up a significant portion of the software. An EMS can also receive inputs from other sources and send signals to other systems than the engine. The EMS may, for example, for interface directly with an electronically-controlled automatic transmission or communicate with a transmission control unit. In-vehicle networks are used for communication and enable information exchange between different control modules. These often utilize the Controller Area Network (CAN), see lower left of Figure, bus which is a field-bus that is widely adopted by the automotive industry. 23-09-2025 Dr. Shrimantini 8

9. 23-09-2025 Dr. Shrimantini 9

10. EMS Building Blocks An EMS consists of several hardware components, for example one or more microcontrollers (CPU), memory (RAM, Flash, EEPROM), power circuits, communication system (CAN, FlexRay , TCP/IP), sensor input, output drivers, I/O circuitry, status indicators, and diagnostic systems. These are needed to process the information from inputs to outputs. Starting from the inputs, Figure shows that there are different types of inputs: Analog sensor values, read by analog to digital (A/D) converters. Digital inputs from on/off signals, pulses that mark engine events or pulse width modulated (PWM) signals for example an air mass flow sensor. These are either sampled on digital I/O pins or connected so they can generate interrupts in the microcontroller. Bi-directional data transfer to and from other units using, for example, CAN bus or FlexRay . Internally in the EMS there are one or more CPUs that do the majority of the calculations, the program and data is stored in the flash EPROM, enabling the new functions to be downloaded. The program code and data can also be encrypted to protect it from being modified by an unauthorized part. In the EMS there is often also a Timer Unit (TU) that generates wave forms an d supports crank angle referenced signals 23-09-2025 Dr. Shrimantini 10

11. Actuator Hardware Drivers An EMS also has output drivers for various types of actuators, with different power requirements, converting the low level CPU outputs to high power EMS outputs. Some actuators require less current, like the main relay, heaters for the 𝜆 sensors, and so on, while others require more, like the ignition coils, fuel injectors, and the electronic throttle valve motor. There is also a trend with intelligent actuators . For example, the VGT (Variable geometry turbocharger) actuator in the heavy duty diesel engine, used in Wahlström and Eriksson (2011b), has a separate control module with servo and integrated power electronics for the actuator. Set-point commands are sent from the EMS to the VGT module, via the CAN bus, which in its turn returns the current position to the EMS. 23-09-2025 Dr. Shrimantini 11

12. System for Crank and Time-Based Events There are events in the EMS that are executed with a fixed frequency, for example sampling of input signals and throttle servo controller, and events that are executed synchronously with the crankshaft rotation, such as ignition and injection. The first are called time based events and the latter crank angle-based events . To handle the time-based events there is a scheduler that executes different tasks periodically at a given frequency. Different frequencies, or time bases, are used for different functions depending on their need, where the fastest are executed at several 100 Hz or even higher, while the slowest are at about 1Hz or even slower. 23-09-2025 Dr. Shrimantini 12

13. Crank angle events are often managed by a Timer Unit (TU) in the EMS, see Figure. The TU is a co-processor that combines special hardware and low-level microcode to make high-resolution timing measurements and to generate high-resolution pulse signals. It manages the critical timing associated with the EMS I/O and removes a very computation-intensive task from the CPU. There is a bi-directional communication between the CPU and TU, where the CPU can read and write information in the TU and the TU can trigger interrupts in the CPU. 23-09-2025 Dr. Shrimantini 13

14. TU tasks are organized in channels where a channel can, for example, be setup to provide the pulses to a fuel injector, an ignition coil, or a PWM signal. The TU channels process log and timer events and generate I/O signals and interrupts, that is they keep track of the engine position and generate injection and ignition events at the right crank angle positions. 23-09-2025 Dr. Shrimantini 14

15. In particular, the 58X wheel has a resolution of 6 degrees, but there is a need for controlling the ignition and injection timing with higher accuracy. To meet that requirement, the TU channels can lock on the crankshaft pulses and use the internal timer to increase the resolution, so that ignition and injection pulses can be generated with a resolution of fractions of a degree. 23-09-2025 Dr. Shrimantini 15 Fig:A Timer Unit (TU) in the EMS manages the timing of critical pulses and offloads timing of critical tasks from the CPU. It also generates wave form outputs, like injection and ignition pulses, with high precision in timing

16. Automatic Code Generation and Information Exchange Much of the control development, also called function development, is done in simulation environments. To increase quality and avoid manual errors there is a drive to generate the EMS code automatically from the simulation environments. This both speeds up the development process and avoids introducing errors in intermediate implementation steps There are also other initiatives for shortening the development time and improving the quality of the generation code and total software. One effort is directed to enabling exchange of code between OEMs (Original equipment manufacturer) and suppliers so that code from a supplier can easily be integrated in different platforms. An example of an initiative is AUTOSAR ( AUTomotive Open System ARchitecture ), which is a development partnership of major automotive industry OEMs and suppliers, as well as tool and software vendors worldwide. The goal of the partnership is to establish a global standard for common software architecture, application interfaces, and methodology of embedded software for vehicle electronics. 23-09-2025 Dr. Shrimantini 16

17. Calibration and Parameter Representation When the controllers have been designed and implemented there is still the step of calibration and tuning of the controller, for production release. This is an important part of the development process, where performance optimization and trade-offs are fine-tuned before the production. It is necessary because, at the time when the controller is developed, software and hardware, like engine, actuators, and so on, are not finished. Calibration of controller parameters and set points in the final stage for production is a time-consuming task as there can be about 30 000 parameters that need to be set in an EMS before production. Much of the calibration can be automatized with the support of automatic calibration tools that can run an engine day and night to parametrize the control system. Even though it can be automated, it is time and resource consuming, so designing a controller that is easy to calibrate is thus an important engineering task. Calibration data can be represented as scalar values or as matrices in lookup tables, often referred to as engine maps. 23-09-2025 Dr. Shrimantini 17

18. E ngine Maps Engine mapping is the term used by car manufacturers when relating engine inputs and outputs and it is essentially regression based. Possible inputs are SPARK(spark advance), FFR (fuel flow rate), AFR (air-fuel ratio),EGR (exhaust gas recycling) and RPM (engine speed); possible outputs are TQ (torque), exhaust emissions and exhaust temperature. Relationships between inputs and outputs are required for use in calibrating electronic engine controllers to give optimum performance-the methodology Is being redeveloped for the next generation of engines. The end point of the work is technical efficacy and cost effectiveness of the engine mapping activity. 23-09-2025 Dr. Shrimantini 18

19. The data stored in the individual cells of the computer’s memory can be represented graphically in the form of a characteristic map. Information for this map is found out by conducting a series of tests on the engine and the program for these tests is called engine mapping. These tests determine the perfor­mance and investigate the effects of each variable that has some bearing on the output of the engine.  When the effects are known, the settings that give the best perfor­mance can be determined and recorded. For engine mapping, the engine is connected to a dynamometer and operated throughout its entire speed and load range. 23-09-2025 Dr. Shrimantini 19

20. The engine is loaded by means of dynamometer and the torque, power output, economy, and emissions are measured against speed and other factors that have certain effect on the engine output  The performance curves derived from the tests are called engine maps. Some more impor­tant maps are discussed below. 23-09-2025 Dr. Shrimantini 20 Fig: Engine characteristics, full load test.

21. 23-09-2025 Dr. Shrimantini 21 Torque/Consumption Loop To plot this map the air-fuel ratio is varied and the fuel consumption and torque output are measured for each setting. Speed is kept constant during each test so that a series of tests is required to be conducted to cover the engine operating range. Figure shows a characteristic fish-hook shaped map, which is plotted for the engine operating under full-load. On the y-axis (vertical axis) the specific fuel consumption (SFC) is plotted and these values are obtained from the equation, SFC = fue l consumption (kg/h)/brake power (kW). The specific fuel consumption indicates the quantity of fuel necessary to produce one unit of power.

22. The map depicts that the engine develops low output torque but high fuel consumption i.e. high SFC when run on a weak mixture. As the mixture is enriched, the consumption falls to a point ‘E’ where maximum economy is attained. Enriching the mixture beyond this point causes an increase in torque but at the expense of fuel. Maximum torque and power occurs at point T’. It can be seen that the chemically correct ratio of 14.7:1 provides neither maximum torque nor maximum economy and to achieve these maximum results, the mixture must be slightly enriched and slightly weakened respectively. 23-09-2025 Dr. Shrimantini 22 Fig. Torque Vs consumption loop.

23. Exhaust Emission/Air-fuel Ratio Before exhaust emission regulation were introduced, the air-fuel mixture used was based on the ratios required for either maximum power or maximum economy. Unfortunately the 12 – 15% enrichment from the chemically correct ratio to provide maximum power also produces a high emission of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) in the exhaust gases. 23-09-2025 Dr. Shrimantini 23

24. This map illustrates that the operation of the engine on an enriched mixture should be avoided to minimize exhaust pollution. Comparing the results shown in Figs., it can be seen that lean-burn engines designed to operate with minimum exhaust pol­lution suffer a considerable increase in consumption and decrease in power if the air-fuel ratio is weakened beyond the economy point ‘E’. Since the tolerance is very small, a close control of fuel metering is required if satisfactory output, combined with reasonable service life of engine is to be achieved. 23-09-2025 Dr. Shrimantini 24 Fig. Exhaust emissions.

25. Spark Timing and Engine Performance Spark timing required to achieve a set power, depends on three main factors such as speed, load and air-fuel ratio. ( i ) Speed:  As the speed increases, the crank travels through a larger angle during the time taken for the gas to burn. (ii) Load:  As the load is increased, the opening of the throttle also increases to maintain a set speed. This in­creases the quantity of gas entering the cylinder, which causes the higher compression pressure, as a result the flame rate increases and the gas burns quicker. ( ii i) Air-fuel ratio:  A weaker mixture takes longer time to burn than the chemically correct mixture. The effects of these three factors can be determined by 23-09-2025 Dr. Shrimantini 25

26. Using a series of maps so that the optimum timing can be established. The spark timing advance is increased when the engine speed is increased and air-fuel ratio is weakened. The spark timing advance is decreased when the engine load is increased and exhaust emission of HC and/or NOx is too high. Fuel mixture requirements are related to engine load. When the engine is under light-load, or if the vehicle is cruising, a weaker mixture is supplied for better economy. During full-load condition high engine power is required; hence a less-weak mixture is supplied. Since the air-fuel ratio is mainly dictated by the load on the engine, the spark timing should only be responsive to load and speed, due to which most timing maps are based on these two variables. 23-09-2025 Dr. Shrimantini 26 Fig. Effect of varying ignition timing.

27. Three-dimensional Maps After determining the optimum angle of advance with respect to speed based on the results of a series of engine tests at different loads, a large number of maps can be drawn. However all these maps can be reduced to one by using the three-dimensional form (Fig.) The x, y and z three axes of the map represent speed, spark advance and load respectively. The number of tests used to construct the map detects the accuracy of spark timing obtained. A total of 60 timing settings are used in the simple map shown in the figure. 23-09-2025 Dr. Shrimantini 27 Fig: Typical spark advance map (simplified).

28. Components of a fuel injection system Figure shows a typical control layout for a fuel injection system. Depending on the sophistication of the system, idle speed and idle mixture adjustment can be either mechanically or electronically controlled. 23-09-2025 Dr. Shrimantini 28

29. Figure shows a block diagram of inputs and outputs common to most fuel injection systems. The basic fuelling requirement is determined from these inputs in a similar way to the determination of ignition timing. A three-dimensional cartographic map, shown in Figure ,is used to represent how the information on an engine’s fuelling requirements is stored. This information forms part of a read only memory (ROM) chip in the ECU. 23-09-2025 Dr. Shrimantini 29

30. When the ECU has determined the look-up value of the fuel required (injector open time), corrections to this figure can be added for battery voltage, temperature, throttle change or position and fuel cut off. Idle speed and fast idle are also generally controlled by the ECU and a suitable actuator. It is also possible to have a form of closed loop control with electronic fuel injection. This involves a lambda sensor to monitor exhaust gas oxygen content. This allows very accurate control of the mixture strength, as the oxygen content of the exhaust is proportional to the air–fuel ratio. The signal from the lambda sensor is used to adjust the injector open time . 23-09-2025 Dr. Shrimantini 30

31. 1. Engine speed sensor An engine speed sensor is attached to crankshaft of cars engine and it indicate the speed that crankshaft is spinning. This information is beneficial to control the ignition timing and EMS 2. Temperature sensor include analog and digital Ics designed for temp. monitoring of a system. A simple thermistor provides engine coolant temperature information. 3. Air temperature sensor: It helps to measure the air density for fuel mixture control and trim the air flow ratio according to the airflow density. 23-09-2025 Dr. Shrimantini 31

32. 4. Throttle position sensor: This sensor is used to monitor the throttle position of a car. This sensor moves with the throttle and sends a voltage signal to the computer indicating throttle angle and speed of movement. The computer uses this data to measure engine load, adjust timing , fuel delivery etc. 5. Map Sensor: (Manifold Absolute Pressure Sensor) This sensor measures air pressure which tells engine the current altitude of a vehicle 23-09-2025 Dr. Shrimantini 32

33. 6. Lambda sensor This device provides information to the ECU on exhaust gas oxygen content. From this information, corrections can be applied to ensure the engine is kept at or very near to stoichiometry. 7. Idle or fast idle control actuator Bimetal or stepper motor actuators are used. The air that it allows through is set by its open/close ratio. 8. Air Flow Sensor: Measures actual speed of air flowing through the engine in different segments. 23-09-2025 Dr. Shrimantini 33

34. 9. Fuel injector(s) They are simple solenoid-operated valves designed to operate very quickly and produce a finely atomized spray pattern. 10. Injector resistors These resistors were used on some systems when the injector coil resistance was very low. A lower inductive reactance in the circuit allows faster operation of the injectors. Most systems now limit injector maximum current in the ECU in much the same way as for low resistance ignition on coils 23-09-2025 Dr. Shrimantini 34

35. 11. Fuel pump The pump ensures a constant supply of fuel to the fuel rail. The volume in the rail acts as a swamp to prevent pressure fluctuations as the injectors operate. The pump must be able to maintain a pressure of about 3 bar. 12. Fuel pressure regulator This device ensures a constant differential pressure across the injectors. It is a mechanical device and has a connection to the inlet manifold. 13. Cold start injector and thermo time switch An extra injector was used on earlier systems as a form of choke. This worked in conjunction with the thermo-time switch to control the amount of cold enrichment. Both engine temperature and a heating winding heat it. This technique has been replaced on newer systems, which enrich the mixture by increasing the number of injector pulses or the pulse length. 23-09-2025 Dr. Shrimantini 35

36. 14. Combination relay This takes many forms on different systems but is basically two relays, one to control the fuel pump and one to power the rest of the injection system. The relay is often controlled by the ECU or will only operate when ignition pulses are sensed as a safety feature. This will only allow the fuel pump to operate when the engine is being cranked or is running. 15. Electronic control unit Earlier ECUs were analogue in operation. All ECUs now in use employ digital processing 23-09-2025 Dr. Shrimantini 36

37. Stoichiometry and air-fuel ratio 23-09-2025 Dr. Shrimantini 37

38. The theoretical air required to complete combustion of fuel results from the equation of stoichiometry of oxygen/fuel reaction. Stoichiometric air means the minimum air in stoichiometric mixture. The stoichiometric air/fuel ratio (AFR) can be calculated from the reaction equation (g/g). For gas AFR is usually determined in m 3 /m 3 . The actual combustion air depends also on the assumed air excess (equivalence ratio or stoichiometric ratio). 23-09-2025 Dr. Shrimantini 38

39. THE STOICHIOMETRIC RATIO ( λ ) 23-09-2025 Dr. Shrimantini 39 AN EQUIVALENCE RATIO φ

40. 23-09-2025 Dr. Shrimantini 40

41. AIR EXCESS ( n ) 23-09-2025 Dr. Shrimantini 41

42. 23-09-2025 Dr. Shrimantini 42

43. 23-09-2025 Dr. Shrimantini 43

44. 23-09-2025 Dr. Shrimantini 44

45. Design an electric powertrain for a small city car having the following characteristics: curb mass = 840 kg, payload = 2 · 75 kg, tires: 155/65/14T, cd · Af = 1.85 m2, rolling resistance coefficient = 0.009, to meet the following performance criteria: ( i ) max speed = 65 km/h, (ii) max grade = 16%, (iii) 100 km range. Assume perfect recuperation, overall efficiency of 0.6, and 85% SoC window. Choose motor size in a class with a maximum speed of 6000 rpm and the number of battery modules having a capacity of 1.2 kWh each. 23-09-2025 Dr. Shrimantini 45

46. 23-09-2025 Dr. Shrimantini 46