2004-01-1240 An Overview of Hardware-In-the-Loop ... - dSPACE

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Figure 10 Closed Loop PCM Application Testing.Figure 11 Closed Loop Plant Model.SYSTEM LEVEL TESTING USING CLTThe components of system level testing using CLT areillustrated in Figure 10. The fundamental differencebetween the OLT and CLT is the presence of dynamicplant model in the CLT system running in real timesimulation. The plant models represent the bahavior ofthe actual plant and provide appropriate feedbackresponse. The response of the plant model influencesthe input to the system, thus providing a completedynamic system simulation with controller feedback looppreserved. Figure 11 shows a block diagramrepresentation of Open and Closed loop testinginterfaces of the HIL system with the PCM. The“Ambient_and_Environment” block contains static inputssuch as atmospheric pressure and temperature; the“Driver_Inputs” block contains a manual and automaticdriver model. The automatic driver model compares thevehicle speed feedback with the speed stimulus anddecides the required throttle and brake inputs to theplant model, while manual driver provides the hooks tocontrol the brake and throttle pedal input from externalsource under simulation environment.The “PCM_Interface” block contains the routing of I/Osignals between a specific family of PCM and the HILsystem hardware. The "Vehicle Model" contains theactual plant model representing the dynamic behavior ofthe plant, for our application it is a combination of andengine and transmission model. We have implementeda complete set of sensors, actuators and plant models inthis system. In order to be able to simulate in real time,we used a regression based engine model, usingmapping data for the same engine from a Dynamometer.Simplified transmission, driveline and vehicle modelswere also implemented. After successful simulation ofKey On Engine Off (KOEO) and Key On Engine Running(KOER) conditions, the system was successfully testedand simulated for idle conditions, followed by manualand automatic drive cycle simulation implementation.Prior to integration of the plant models with the HILsystems, the plant models were simulated and validatedon the desktop. After validation of the plant model in thedesktop environment the models were integrated withthe HIL system. In order to validate the plant models theresults obtained from a real engine drive cycle testconducted on a Dynamometer were compared with thesimulation results. In drive cycle exercise the vehicle isdriven through a known speed profile (e.g. FTP UDDS).The target speed is input to the automatic driver model.The automatic driver receives the actual speed of thevehicle as a feed back from the complete vehicle plantmodel. The automatic driver manipulates the brake andthrottle to keep the vehicle in targeted speed. Thevehicle speed profile from the Dynamometer test cellrecording (using calibration tool, ATI Vision 1.9) 3wasused as the input stimulus for the automatic driver forthe simulation. Engine torque, engine speed and vehiclespeed from the simulation are recorded usingControlDesk, the HIL user interface software, and thedata was compared. The comparison (not presented inthis paper) of the vehicle and engine speed profile andengine torque values along with other variables showeda very good correlation with minimal error. Themaximum errors in these comparisons were less than 10percent. Although final software verification andvalidation can be done only on a real vehicle, thecomplete closed loop simulation can easily be used forvalidating software at a system level during the earlydesign stages of software development with less than 10percent error margin to validate the PCM software.There are certain limitations in using HIL for validationand verification of PCM software due to high3ATI is trademark of Accurate Technologies Inc.
computational requirements for a real-time simulation.For example the emission related testing and validationis not feasible in the current HIL environment. A betterplant model (e.g. complete detail combustion basedmodel), however, can provide better correlation ofengine variables as well engine performance. However,a detailed combustion based model may not be suitablefor real time execution with the present computingtechnology.Future advancement, both in real-time computing andplant modeling will close this gap of complete bench topsimulation and may make the HIL an absolutereplacement for a real vehicle for software validation andverification.CONCLUSIONA brief discussion of on the implementation and usagescenario of HIL systems at Visteon Corporation for PCMsoftware verification and validation is presented in thispaper. The Powertrain Software development group inVisteon uses HIL systems in every step of the softwaredevelopmental phase.Using HIL in integrated EIO software, Unit Testing, andclosed loop testing of the system software significantlyreduced the testing time and improved software quality.Software quality is improved by identifying potentialerrors and/or discrepancies between the requirement,specification and software very early in the developmentphase.The successful implementation of closed loop simulationhas proved to be useful in validating several features atthe system level. However, further improvements in realtime computing technology and implementation will berequired for simulating features such as emissionrequirements.REFERENCES1. H. Hanselmann, "Hardware-in-the-Loop SimulationTesting and its Integration into a CACSD Toolset",IEEE International Symposium on Computer-AidedControl System Design 1996.2. Hanselmann, H.: Advances in Desktop Hardware-Inthe-LoopSimulation. SAE Paper 970932, 1997.3. S. Nabi, "Development of an Integrated TestEnvironment for ECU Software Validation," dSPACEUser Conference 2002,4. Eckel, B.; "Design Patterns In Python", 2002Software Development West conference, San Jose,CA, USA.5. Lamberg, K.; Richert, J.; Rasche, R.; A NewEnvironment for Integrated Development andManagement of ECU Tests, SAE 2003-01-1024,Detroit, USA.6. Gehring, J.; Schuette, H.; A Hardware-in-the-LoopTest Bench for the Validation of Complex ECUNetworks, SAE 2002-01-0801, Detroit, USACONTACTSyed NabiVisteon CorporationVisteon Technical Center17000 Rotunda Dr.Dearborn, MI 48121Phone: (313) 755-1881E-mail: snabi@visteon.comMahesh Balike, PhDVisteon CorporationVisteon Technical Center17000 Rotunda Dr.Dearborn, MI 48121Phone: (313) 755-3804E-mail: mbalike@visteon.comJace AllenSenior Project EngineerApplications GroupdSPACE, Inc.28700 Cabot DriveSuite 1100Novi, MI 48377Phone: (248) 567-1265Fax: (248) 567-0130E-mail: jallen@dspaceinc.comKevin RzemienSupervisorApplications GroupdSPACE, Inc.28700 Cabot DriveSuite 1100Novi, MI 48377Phone: (248) 567-1265Fax: (248) 567-0130E-mail: krzemien@dspaceinc.comADDITIONAL SOURCES1. R.W. Weeks and J.J. Moskwa, "Automotive EngineModeling for Real-Time Control UsingMATLAB/SIMULINK", SAE paper 950417.2. H. Hanselmann, "Hardware-in-the-Loop SimulationTesting and its Integration into a CACSD Toolset",
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