Optimized Calibration

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Problem Definition Benefits of Automated Calibration

Problem Definition

This section describes the creation and optimization of calibration tables for the gasoline case study. The Model Browser section of this case study covers creating the design for the experiment and creating and evaluating models from the resulting data. You can export your models directly to CAGE; or to Simulink software or to a file, ready to be imported into CAGE for model-based calibration generation. An example file is provided.

The aim of this case study is to produce optimized tables for

• Intake cam phase

• Exhaust cam phase

• Spark timing schedules

  as a function of load and rpm, subject to the following constraints

  • Constrain solutions to lie within the boundary constraint model

  • Constrain cam phase solutions so they do not change by more than 10^o between table cells (that is, no more than 10^o per 500 RPM change and per 0.1 load change).

  • Constrain residual fraction <= 25% at each drive cycle point (to ensure stable combustion). Residual fraction is the percentage of burned gas mass in the cylinder at intake valve close, relative to the total mass in the cylinder at intake valve close. Constraining maximum residual fraction is a simple and reasonable way of ensuring stable combustion. Residual fraction = 100 * Burned Gas Mass from Last Cycle / (Burned Gas Mass From Last Cycle + Fresh Air Mass)

CAGE is intended for model-based calibration, although you can still create tables without reference to models if you want. For this case study, you use models produced in the Model Browser to generate calibrations in CAGE. You cover the following steps:

1. Load models of engine responses, decide on optimization strategy and define additional models. See Importing Models into CAGE.

2. Set up tables. See Setting Up Calibration Tables to Fill.

3. Define optimization objective and constraints. See Setting Up the Optimization.

4. Set up an operating point set for the optimization. See Defining Variable Values.

5. Run the optimization and view the results. See Running the Optimization

6. Duplicate and modify the optimization to create a sum optimization using the previous results as starting points. See Setting Up the Sum Optimization

7. Fill tables from optimization results. See Filling Tables with Optimization Results.

8. Use models and optimized tables to fill a spark estimator table. See MBT Spark Estimator Problem.

For guidance, you can look at the example finished project: Gasoline_optimization.cag.

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Benefits of Automated Calibration

• You can move the table-filling process away from the test bed.

• You can regenerate calibrations when objectives, constraints, or calibration table layouts change, without additional testing.

• You can explore tradeoff possibilities interactively.

• You can produce initial calibrations using engine simulation software, before hardware is available.

CAGE can provide both automatic and interactive calibration optimization. You can trade off multiple objectives, deal with multiple constraints, and you can examine optimizations point-by-point or drive-cycle-based. You can use built-in optimization routines or write your own. You can fill groups of tables simultaneously, and optimize table values and breakpoint settings. CAGE can provide solutions for these example applications:

• Control problems

  • Injection timing and duration

  • EGR valve

  • Spark timing

  • Dual-independent variable valve timing

  • Emissions-constrained BSFC optimization over drive cycles

• Estimation problems

  • Torque

  • Emissions

  • Air flow and manifold pressure

  • Intake valve temperature

  • Borderline spark

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Exporting the Models

Importing Models into CAGE

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