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Internal Combustion Engine Test Bench Control, Data Acquisition, andEngine Control Unit Calibration

"Thanks to National Instruments PXI hardware and LabVIEW softwaresolutions, we used the engine test bench to calibrate ECU controlparameters within one programming environment, which successfullyintegrates data acquisition and control as well as CAN and LANcommunication."- Predrag Mrdja, MSc, PhD student, Internal Combustion Engines Department, Faculty of Mechanical Engineering, University of Belgrade,Serbia

Author(s):Predrag Mrdja, MSc, PhD student - Internal Combustion Engines Department, Faculty of Mechanical Engineering, University ofBelgrade, Serbia Nenad Miljic, MSc, Teaching Assistant - Internal Combustion Engines Department, Faculty of Mechanical Engineering,University of Belgrade, SerbiaSlobodan Popovic, MSc, Teaching Assistant - Internal Combustion Engines Department, Faculty of Mechanical Engineering,University of Belgrade, SerbiaMarko Kitanovic, MSc, PhD student - Internal Combustion Engines Department, Faculty of Mechanical Engineering, Universityof Belgrade, Serbia

The Internal Combustion Engines Department (ICED) at the University of Belgrade, Faculty of Mechanical Engineering is thelargest and oldest institution devoted to IC engine research in Serbia (including former Yugoslavia). Dealing with one of themost dynamic objects in mechanical engineering, our research requires intensive lab work and cutting-edge acquisitionsystems. Our in-house-developed, VME Bus-based engine test lab data acquisition and measurement systems date back to theearly 1980s and we started to use NI solutions almost a decade ago.

IC Engine Development Background and TrendsObserving IC engine development reveals two major trends: increased engine performance and harmful pollutant emissionreduction requirements. Staying on both trends requires implementing complex engine control algorithms from a series of inputparameters. IC engines are complex, dynamic systems affected by many control parameters (aside from environmentalconditions and geometric characteristics) such as air-to-fuel ratio, throttle position, spark advance, intake- and exhaust-valvetiming, and exhaust gas recirculation (EGR) valve position. Engine torque, fuel consumption, and pollutant emission parametersmust be optimized to obtain peak performance throughout the entire operating range of the engine. It is impossible to haveoptimal ECU look-up tables without performing extensive engine testing, no matter how reliable and advanced IC enginesimulation software packages are.

ECU Hardware and Software TestingStudents have shown great interest in engine management problems and have devoted themselves to developing an open ECUto use in our IC engine test labs. Students built all the componentsfrom engine wiring harnesses, to injection and ignitionsystem power driver modules, to signal conditioning modules. Because the system, based on a Freescale MPC565microcontroller, is inherently modular, we can easily modify it to use in both lab and testing conditions.

While prototyping the ECU, we performed hardware-in-the-loop (HIL) testing to verify the developed ECU software prior to usingit on a real engine. We found NI hardware and ideal for this task. We used the NI and LabVIEW PXI-6123 PXI-6229multifunction data acquisition devices for simultaneous engine sensor signal simulation and verification. While the 32-bit NIPXI-5401 function generator features, such as direct digital synthesis mode, and the NI digital multimeter modules suitPXI-4070the ECU validation process, it is easier to generate engine signals using NI field-programmable gate array (FPGA) hardware,which is the next step in upgrading our HIL system.

ECU Parameter Calibration and Data MeasurementThe automotive industry typically uses a controller area network (CAN) for in-vehicle data transmission and communication. OneCAN communication protocol devoted to ECU calibration is the CAN Calibration Protocol (CCP). We easily established two-waycommunication using a high-speed NI PXI CAN interface card and the (see FigureNI ECU Measurement and Calibration Toolkit1).

We used the CCP to fetch data from the ECU software and to calibrate tuneable parameters defined in the ECU developmentstage. The CCP also read numerous engine sensors (engine speed; intake collector pressure and temperature; throttle position;air mass flow; intake air temperature; and wide-band lambda). Through parameter tuning, we can modify the air-to-fuel ratio orinfluence ignition timing in real time while the engine is running. This gave us complete insight to optimize the developed ECUsoftware and its basic environment.

The Challenge:Developing and building internal combustion (IC) engine test bench submodules for test bench control, digital data acquisition, andonline look-up table calibration on the engine control unit (ECU).

The Solution:Using off-the-shelf NI LabVIEW software and PXI hardware with modular instruments to rapidly solve numerous challenging dataacquisition and control problems on the IC engine test bench.

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Engine Test Bench Control and Data MonitoringTesting an IC engine involves acquiring data from various engine-mounted sensors, as well as the test bench system and ICengine control. We used LabVIEW to develop the entire engine test bench monitor and control system. We relied on NI PXIhardware and PXI modular instruments to comfortably control the engine load, cooling, and fuel supply system. With thissystem, we can clearly visualize sensor information regarding the following:Brake torqueEngine speedEngine powerExhaust gas temperatureIntake air pressure and temperatureCoolant temperatureOil pressure and temperatureFuel and air mass flowAir-to-fuel ratio

Because these readings come from sensors mounted in parallel with the engines original automotive sensors accessed by theECU, we can use this application to test ECU signal conditioning capabilities and software functionality.

In-Depth Work Cycle Monitoring and AnalysisOptimizing certain parameters requires a detailed engine work-cycle analysis based on angle-resolved, in-cylinder pressuremeasurement (engine-indicating). To do this, we use an encoder-triggered NI PXI-6123 module. To reduce the PXI system CPUload, we implemented network-published shared variables to transfer acquired data to another PC with a specially developedLabVIEW application devoted to analyzing and executing indicated parameters. This analysis application relies on

in-house-developed script nodes implemented using MathWorks, Inc. MATLAB software. The nodes saved time and helped us

achieve fast analysis. For example, we implemented online calculation of the mass fraction burned (MFB) and rapiddetermination of its 50 percent angle position. Because this position is strongly related to engine efficiency and is mostlyinfluenced by ignition-timing parameters, we immediately used it to calibrate the ECU.

ConclusionThanks to NI PXI hardware and LabVIEW software, we used the engine test bench to calibrate ECU control parameters withinone programming environment, which successfully integrates data acquisition and control as well as CAN and LANcommunication. The versatility of LabVIEW also helps us easily visualize the acquired data and analysis results. This concept isespecially valuable for student engineers building their IC engine testing and development skills.

MATLAB is a registered trademark of MathWorks, Inc.

Author Information:

Predrag Mrdja, MSc, PhD student

Nenad Miljic, MSc, Teaching Assistant

Slobodan Popovic, MSc, Teaching Assistant

Marko Kitanovic, MSc, PhD student

Internal Combustion Engines Department, Faculty of Mechanical Engineering, University of Belgrade

Kraljice Marije 16, 11120 Belgrade 35, Serbia

Tel.: +381 11 3302 416

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Figure 1. Measurement and Calibration Application

Figure 2. Monitor Application

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Figure 3. In-Cylinder Combustion Process Analysis

Next StepsLearn More About NI CAN Hardware and Software

Configure Your Own PXI System

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