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Explore the NASA HL-20 Model

Introduction

This section introduces a NASA HL-20 lifting body airframe model that uses blocks from the Aerospace Blockset™ software to simulate the airframe of a NASA HL-20 lifting body, in conjunction with other Simulink® blocks.

The model simulates the NASA HL-20 lifting body airframe approach and landing flight phases using an automatic-landing controller.

For more information on this model, see NASA HL-20 Lifting Body Airframe.

What This Example Illustrates

The NASA HL-20 lifting body airframe example illustrates the following features of the blockset:

  • Representing bodies and their degrees of freedom with the Equations of Motion library blocks

  • Using the Aerospace Blockset blocks with other Simulink blocks

  • Feeding Simulink signals to and from Aerospace Blockset blocks with Actuator and Sensor blocks

  • Encapsulating groups of blocks into subsystems

  • Visualizing an aircraft with Simulink 3D Animation™ and Aerospace Blockset Flight Instrument library blocks.

Open the Model

To open the NASA HL-20 airframe example, type the example name, aeroblk_HL20, at the MATLAB® command line. The model opens.

The visualization subsystem, four scopes, and a Simulink 3D Animation viewer for the airframe might also appear.

Key Subsystems

The model implements the airframe using the following subsystems:

  • The 6DOF (Euler Angles) subsystem implements the 6DOF (Euler Angles) block along with other Simulink blocks.

  • The Environment Models subsystem implements the WGS84 Gravity Model and COESA Atmosphere Model blocks. It also contains a Wind Models subsystem that implements a number of wind blocks.

  • The Alpha, Beta, Mach subsystem implements the Incidence, Sideslip & Airspeed, Mach Number, and Dynamic Pressure blocks. These blocks calculate aerodynamic coefficient values and lookup functionality.

  • The Forces and Moments subsystem implements the Aerodynamic Forces and Moments block. This subsystem calculates body forces and body moments.

  • The Aerodynamic Coefficients subsystem implements several subsystems to calculate six aerodynamic coefficients.

NASA HL-20 Example

Running an example lets you observe the model simulation in real time. After you run the example, you can examine the resulting data in plots, graphs, and other visualization tools. To run this model, follow these steps:

  1. If it is not already open, open the aeroblk_HL20 example.

  2. From the Simulation menu, select Start. On Microsoft® Windows® systems, you can also click the Start button in the model window toolbar.

    The simulation proceeds until the aircraft lands:

    View of the landed airframe

    Plot that Measures Guidance Performance

    Plot that Measures Altitude Accelerations Mach

    Plot that Measures Inertial Position

    Plot that Measures Demand Data Against Achieved Data

Modify the Model

You can adjust the airframe model settings and examine the effects on simulation performance. Here is one modification that you can try. It changes the camera point of view for the landing animation.

Change the Animation Point of View

By default, the airframe animation viewpoint is Rear position, which means the view tracks with the airframe flight path from the rear. You can change the animation point of view by selecting another viewpoint from the Simulink 3D Animation viewer:

  1. Open the aeroblk_HL20 model, and click the Simulink 3D Animation viewer.

  2. From the list of existing viewpoints, change the viewpoint to Fixed Position.

    The airframe view changes to a fixed position.

  3. Start the model again. Notice the different airframe viewpoint when the airframe lands.

You can experiment with different viewpoints to watch the animation from different perspectives.

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