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Active Modeling

Active Modeling. ENGI9496 – Proper Modeling Spring 2011. Motivation. Proper model may vary throughout a simulation maneuver e.g., truck mobility model with varying terrain Element activity hierarchy in a model changes with time Can we adjust model complexity “on the fly”?.

melissa-stephens
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Active Modeling

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  1. Active Modeling ENGI9496 – Proper Modeling Spring 2011

  2. Motivation • Proper model may vary throughout a simulation maneuver • e.g., truck mobility model with varying terrain • Element activity hierarchy in a model changes with time • Can we adjust model complexity “on the fly”?

  3. Example – Half-Car Truck Model • Kypuros, J.A., and Longoria, R.G. (2002) “Variable fidelity modeling of vehicle ride dynamics using an element activity metric.” Proc. ASME IMECE 2002, New Orleans, LA, pp. 525-534.

  4. Road Input and Activity Indices

  5. Variable Proper Model Structure

  6. Variable Proper Model Structure

  7. Variable Proper Model Structure

  8. Simulation Results

  9. Simulation Time

  10. Limitations of Prior Work • Switching between successive proper models was not automated • Knowledge of the input stage time window required for calculating activity • Limitation partially addressed by using moving average of power

  11. New Approach • Turning off elements that become low-activity • easy • Turning on elements that would have significant activity if they were in the model • hard • We need a means of calculating activity of an element that does not provide a casual input to the system

  12. Non-Power Conserving Transformer • Example – spring element

  13. Application to Causally Weak Elements

  14. Application to Causally Strong Elements Switching off element sets junction power variable to zero

  15. Case Study – Quarter Car Road amplitude is 1.5 m/s at a frequency of 100 rad/s for t = 0 to 2 seconds; 10 rad/s from 2 to 4 seconds, and 100 rad/s thereafter

  16. Quarter Car Results

  17. Case Study – Half Car Nonlinear model Bilinear rear shock Nonlinear hydraulic front shock

  18. Model Element Switching

  19. Simulation Results

  20. Conclusions • Active modeling using MAPI and non-power conserving transformers allows the modeler to: • predict proper model at any instant, without prior knowledge of input changes • synthesize a sequence of proper models and determine the time windows in which to use them • save time by running the models sequentially • predict simulation discrepancies from variable-complexity models • Reference: Rideout, D.G., and Haq, K.T. (2010) "Active Modelling: A Method for Creating and Simulating Variable-Complexity Models." ASME Paper DS-08-1290, Journal of Dynamic Systems, Measurement and Control Special Issue on Physical System Modeling, 132(6), November 2010. ASME, New York, NY.

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