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## Testing a Wing Flutter Suppression System Design

This example illustrates use of the Simulink Report Generator to verify that a wing flutter suppression system design meets its design requirement. The example exploits the Report Generator's ability to run simulations and MATLAB scripts as part of report generation. This capability enables the Report Generator to serve as a system test manager, running simulations and scripts as necessary to collect and analyze the test data that it then reports.

This example requires the following products to run:

• Simscape

• Aerospace Blockset

• Curve Fitting Toolbox

• Signal Processing Toolbox

Overview

The example comprises the following elements:

• Simulink model of an aircraft wing flutter suppression system

• Excel spreadsheet containing a set of test vectors representing a range of flight conditions

• MATLAB script that analyzes the results of simulating the system

The report generator template runs the model for each flight condition specified by the test vector spreadsheet, analyzes the results, and generates a report summarizing and detailing the results.

System Design

Turbulence, especially near supersonic speeds, can cause an aircraft's wings to flutter, i.e., bend or twist rapidly, potentially leading to breakup of the aircraft. By reducing flutter, flutter suppression systems allow aircraft to fly safely at high speeds. The aircraft flutter suppression system that this example tests uses spoilers (wing control surfaces) to actively dampen flutter pitching moments, thereby allowing use of light and hence flexible wings to reduce the aircraft's overall weight.

System Model

The Simulink model used in this example is based on a mathematical model of an active flutter suppression system developed by Martin R. Waszak at NASA Langley Research Center in Hampton, Virginia. For a detailed description of the mathematical model, see

The Simulink model based on the NASA mathematical model represents a physical wind tunnel model of a wing, aerodynamic forces on the wing, and a flutter suppression system. The system's controller accepts as input a desired wing pitch and attempts to minimize deviations from the desired pitch angle.

```FlutterSuppressionSystem
```

System Design Requirement

The design requirement to be tested in this example is that the flutter suppression system damps out wing pitch oscillations caused by turbulence, i.e., momentary disturbances in the aerodynamic forces acting on the aircraft's wing over a range of flight conditions (speed, altitude, and desired wing pitch). For the purposes of for this system, success is determined by the system's damping ratio, a measure of how rapidly pitch oscillations decay as a result of the system's operation. A positive ratio is considered success; a negative ratio (i.e., the oscillations grow), failure.

Test Procedure

The example uses the following system test procedure:

2. For each flight condition, simulate the flutter suppression system, using the Simulink model (see System Model). The simulation computes the pitch flutter (oscillations) caused by a random disturbance (i.e., turbulence) in the aerodynamic forces acting on the wing.

3. Determine the positive peaks of the pitch oscillations from the pitch angle data generated by the simulation.

4. Fit an exponential curve to the peak data.

5. Compute the pitch damping ratio as a function of the positive(or negative) decay parameter of the exponential pitch angle curve.

Report Template

In this example, a report template implements the test procedure for a desired pitch angle of 0 degrees and for a set of flight conditions specified by the Excel spread sheet included in the example. Running the report template runs the test procedure and generates a report from the data produced by the test procedure.

The Test Report

The report produced by running the report template includes a summary of the test results, a description of the test procedure, detailed test results, and a description of the model used to generate test data.

The example includes a pregenerated test report:

Running the Test

To run the test and generate a report:

1. Change MATLAB's working directory to a writable directory on your system.

2. Click the "Run test" link below.