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Part 1 of this feature discussed the four-year Challenge X tasks and selection of the hybrid power train architecture.
Part 2 detailed the power train Model-Based Design and simulation process used by the team.
Verification and validation
In order to ensure the simulation tools noted in Part 2 of this series were effective for Model-Based Design, verification and validation of the results obtained from these simulators was performed. The data shown below comes from the second year competition of Challenge X and individual experiments performed at the Center for Automotive Research (CAR) at The Ohio State University. At the present time, no verification of cX-TRAC has been accomplished as this simulator is still in the development stage.
cX-SIM
Using the data collected from competition, the acceleration performance and fuel economy predicted by cX-SIM is shown to yield a very reasonable match to reality.
Experimental testing at CAR led to the validation of the battery model used in cX-SIM as shown below. During an arbitrary driving cycle, voltage data from the battery is collected and then compared to the battery voltage reported by cX-SIM once the appropriate parameters are set.
In a similar fashion, the emissions model included in cX-SIM was validated and the results are shown below. The temperature of the lean-NOx trap and outlet NOx are of particular interest when using a diesel engine and are thus the primary metrics for validating the emissions predication of cX-SIM.
cX-Dyn
In a similar fashion to cX-SIM, the results of cX-Dyn are compared to results from actual vehicle testing for verification purposes. One of the competition events used accelerometers to evaluate drivability. Using the collected data from this event, the Ohio State team proved the accuracy of their dynamic simulator.
The plot below shows the vehicle speed as predicted by cX-Dyn (blue line) when the accelerator and brake pedal positions collected from the drive quality event are used as inputs. The actual vehicle speed collected from the same event is shown on the same plot as the red line.
The next plot shows the engine speed comparisons between the simulated results and acquired data from the event. Once again, a strong correlation between the prediction of cX-Dyn and reality was exhibited.
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