getting started using adams/vibration

Overview

ADAMS/Vibration, part of the MSC.ADAMS® suite of software, performs frequency-domain analyses. ADAMS/Vibration is a plugin to the interface products ADAMS/Aircraft, ADAMS/Car, ADAMS/Engine, ADAMS/Rail, and ADAMS/View. It can also be used standalone with an ADAMS/Solver model.

Using ADAMS/Vibration, you can study forced vibrations within your MSC.ADAMS models. You can also use the results from ADAMS/Vibration in noise/vibration/harshness (NVH) studies to predict the impact of vibrations in automobiles, trains, planes, and so on.

ADAMS/Vibration can run in two modes: interactive and batch. This guide focuses on using ADAMS/Vibration in our MSC.ADAMS interface products, such as ADAMS/View (interactive mode). For information on batch mode analysis, refer to the ADAMS/Vibration online help.

This guide includes the following sections:

■ Introducing the Problem, 3

■ Building the Model, 9

■ Testing the Model, 19

■ Reviewing the Model, 23

■ Improving Your Design, 39

■ Optimizing the Model, 45

Getting Started Using ADAMS/Vibration

Getting Started Using ADAMS/VibrationCopyright2

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1 Introducing the Problem

OverviewThis tutorial teaches you how to use ADAMS/Vibration in ADAMS/View to perform a vibration analysis on an MSC.ADAMS model.

In this tutorial, you will investigate the operation of a satellite before the deployment of the solar panels and the separation of the satellite from the launch vehicle. You will investigate the launch vibration environment and its effect on the various components of the satellite.

This chapter provides details about the model you will use, and the problem you will address. It includes the following sections:

■ What You’ll Solve, 4

■ What You Will Learn, 5

■ What You Will Create, 7

This tutorial takes about two hours to complete.

Getting Started Using ADAMS/VibrationIntroducing the Problem4

About This TutorialWe assume that you will work through this tutorial in sequential order. Therefore, we give you more guidance in the beginning and less as you proceed through the tutorial. If you choose not to work through the tutorial in sequential order, you may have to reference the beginning chapters for some of the basic concepts.

We also assume the following:

■ You know how to run the MSC.ADAMS product to which ADAMS/Vibration plugs in (for example, you know how to run ADAMS/View).

■ You know how to use ADAMS/PostProcessor to view the results of the analyses.

■ ADAMS/Vibration is installed on your computer or network, and that your path variable contains the location where ADAMS/Vibration is installed and that you have permission to execute ADAMS/Vibration. If you do not know if ADAMS/Vibration is installed or where it is located, see your local ADAMS/Vibration expert or system administrator.

What You’ll SolveDuring launch, launch vehicles impart high loads into sensitive spacecraft components. Each spacecraft component and subsystem must be designed to withstand these launch loads. To make components strong enough to withstand these loads requires additional weight, which increases costs and reduces overall performance. A better option is to reduce the magnitude of the vibrations into the sensitive components by carefully designing the structure of the launch vehicle adapter.

In this tutorial, you will solve the problem of designing an isolation mount of the launch vehicle adapter such that the launch vibrations into sensitive components are minimized over a defined frequency range. The sensitive components you are concerned with are located on the solar panels. They are sensitive to inputs within the frequency range of 70 Hz to 100 Hz, especially in a direction normal to the panels.

Getting Started Using ADAMS/VibrationIntroducing the Problem 5

Three equally-spaced bushings connect the launch vehicle adapter to the launch vehicle. The stiffness and damping characteristics of these bushings affect the transmitted vibration loads within the 70 to 100 Hz frequency range. Therefore, the design problem is stated as:

Find the ideal values of stiffness and damping for the launch vehicle adapter system such that:

■ The vertical acceleration into the spacecraft is not amplified.

■ The transmitted lateral acceleration in the 70 to 100 Hz frequency range is minimized.

You must choose the stiffness and damping characteristics from a list of currently available, passive isolation bushings.

To simplify the problem, you will study this system as a simplified set of rigid bodies, undergoing one set of launch input forces. This will give you a conceptual design of the launch vehicle adapter isolation system that you can further refine.

What You Will LearnThe tutorial leads you through the design process steps outlined in Figure 1 on page 6. These are the basic steps you should follow whenever you use ADAMS/Vibration to build and test models. The Vibration menu in ADAMS/View is organized to facilitate the Build-Test-Review-Improve process.

■ Step 1 - Build: Add input channels and vibration actuators to an existing MSC.ADAMS model to vibrate the system. Add output channels to measure response.

■ Step 2 - Test: Define the input range and run a vibration analysis to obtain free and forced responses.

■ Step 3 - Review: For free response, look at mode shapes and transient response. For forced response, look at overall response animation, transfer function, frequency response function, and modal participation tables.

■ Step 4 - Improve: Add force in the lateral direction and check the transmitted accelerations. Change the stiffness and damping characteristics for the bushing in the vibration fixture. Compare results to earlier results. Add a frequency-domain measure that you can use in further design studies and optimization.


Figure 1. Design Process Steps for the Satellite Model

Build

■ Create input channels and vibration actuators

■ Create output channels

Review

Test

Improve

■ Create and run forced vibration analysis

■ Review tabular results

■ Plot system modes

■ Animate normal modes analysis

■ Animate forced vibration analysis

■ Plot frequency response

■ Plot power spectral density

■ Plot modal coordinates

■ Run lateral forced vibration analysis

■ Animate normal modes analysis

■ Plot lateral frequency response

■ Inspect model parameterization and design variable

■ Create design objective

■ Run vibration design study

■ Plot frequency response in 3D

Getting Started Using ADAMS/VibrationIntroducing the Problem 7

What You Will CreateIn this tutorial, you will use a conceptual MSC.ADAMS model of a satellite. We developed this model using representative data for deployment devices and attachments to illustrate the effect of launch vibration on the structure.

The model includes a payload adapter between the satellite and the launch vehicle. Note that the solar panels are in the undeployed position. For other applications, the existing model can contain user-written subroutines, user-defined elements, hydraulic elements, and more.

You will create the vibration actuators, input channels, and output channels to study the vibration response of this system.

Figure 2 shows a model of the satellite.

Figure 2. Physical Model of Satellite Design

Launchvehicle

Payloadadapter

Satellite

2 Building the Model

OverviewIn this section, you start with a full nonlinear MSC.ADAMS model and add input channels, output channels, and vibration actuators to the model.

Completing this section involves the following:

■ Starting ADAMS/View and Importing the Model, 10

■ Loading ADAMS/Vibration, 12

■ Simulating the Satellite Model, 13

■ Creating Input Channels, 14

■ Creating Output Channels, 17

Getting Started Using ADAMS/VibrationBuilding the Model10

Starting ADAMS/View and Importing the ModelIn this section, you learn how to start ADAMS/Vibration from within ADAMS/View.

In the UNIX environment, you start ADAMS/View from the MSC.ADAMS Toolbar and then, from within ADAMS/View, you load the ADAMS/Vibration plugin.

In the Windows environment, you start ADAMS/View from the Start menu, and then load the ADAMS/Vibration plugin.

For information on starting MSC.ADAMS, see the Running and Configuring online help.

To start MSC.ADAMS and import your model:

1 Create a working directory, and copy the contents of install_dir/vibration/examples/tutorial_satellite to that directory (where install_dir is the directory where ADAMS/Vibration is installed).

Note: On Windows, you may need to set the permissions to Full Control to edit the tutorial files.

2 Do either of the following depending on the platform on which you are running ADAMS/View:

❖ In UNIX, type the command to start the MSC.ADAMS Toolbar at the

command prompt, and then press Enter. Select the ADAMS/View tool .

❖ In Windows, from the Start menu, point to Programs, point to MSC.Software, point to MSC.ADAMS 2005 r2, point to AView, and then select ADAMS - View.

The Welcome dialog box appears, in the ADAMS/View main window.

3 Select Import a File.

4 Select the Find Directory tool next to the Start in text box. This displays the Find Directory dialog box.

Note: The Start in text box specifies the working directory that ADAMS/Vibration uses as the default directory for reading and writing files.

5 Navigate to the working directory that you created in step 1.

Getting Started Using ADAMS/VibrationBuilding the Model 11

6 Select OK.

This ensures that all your work gets stored in the working directory you selected.

7 Select OK.

The File Import dialog box appears.

8 Right-click the File to Read text box, and select Browse.

9 Select the file satellite.cmd.

10 Select OK.

ADAMS/View opens the satellite model and displays it, as shown in Figure 3.

Figure 3. Satellite

Solarpanels

Bus

Payloadadapter

Testbase


Loading ADAMS/VibrationBecause ADAMS/Vibration is a plugin to ADAMS/Aircraft, ADAMS/Car, ADAMS/Engine, ADAMS/Rail, and ADAMS/View, you need to load ADAMS/Vibration when you use ADAMS/Vibration from within any of these products. If you’re creating a new model, or importing a model that has no ADAMS/Vibration data associated with it, you will need to load the ADAMS/Vibration plugin. If, however, you’re importing a model that already has ADAMS/Vibration data, the plugin automatically loads when you open the model.

To load ADAMS/Vibration:

1 From the Tools menu, select Plugin Manager.

2 Select the Load checkbox next to ADAMS/Vibration.

3 Select OK.

ADAMS/View loads the ADAMS/Vibration plugin and displays the Vibration menu. If you receive an error message, you might have a problem with your licensing. Contact your system administrator or local MSC.ADAMS expert.

Remember, you only need to load ADAMS/Vibration when working with a new model. Once you have an ADAMS/Vibration model, you do not have to load the product. It automatically loads when you import your file.

Note: To automatically load ADAMS/Vibration each time ADAMS/View starts up, in the Plugin Manager, select the Load at Startup checkbox.


Simulating the Satellite ModelHere you simulate the model to verify that it works as expected. Before you simulate the model, you turn off gravity. The simulation shows the deployment of the solar panels in space.

To simulate the motion of your model:

1 To turn off gravity, from the Settings menu, select Gravity.

The Gravity Settings dialog box appears.

2 If not already cleared, clear the selection of Gravity.

3 Select OK.

4 From the Main Toolbox, select the Simulation tool .

5 Set up a simulation with a duration of 15 seconds and 500 output steps.

6 Select the Simulation Start tool .

The model simulates the deployment of the solar panels, and then remains in simulate mode.

7 To return to the initial model configuration, select the Reset tool .

8 To turn on gravity, from the Settings menu, select Gravity.

The Gravity Settings dialog box appears.

9 Select Gravity.

10 Select the -Y button .

The Y text box displays -9806.65, the earth’s normal gravity.

11 Select OK.

The model is now returned to the correct launch configuration for the vibration analysis.


Creating Input ChannelsHere you create two input channels at the center of the payload adapter (in the global x and y directions) and create vibration actuators for them.

Input channels provide ports into your system that you can use to:

■ Plot the frequency response.

■ Drive (vibrate) your system using a vibration actuator.

A vibration actuator applies force input or a displacement, velocity, or acceleration to vibrate the system.

A typical design specification may call for an input acceleration level of 0.2 g2/Hz when applied as a PSD. For this problem, we will use an equivalent force input normalized to a value of 1, since we are only interested in the relative accelerations at various frequencies.

You will create two vibration actuators that apply two orthogonal input forces that drive the system with sine waves over the range of specified frequencies. The y input will drive the satellite in the vertical direction. The x input will drive the satellite laterally.

Then, you will create a third actuator that applies a 1g vertical acceleration in the y-direction.

Finally, you will review the vibration actuator.

To create input channels and vibration actuators:

1 From the Vibration menu, point to Build, point to Input Channel, and then select New.

The Create Vibration Input Channel dialog box appears.

2 In the Input Channel Name text box, enter .satellite.input_x.

3 Leave the default Force.

4 Right-click the Input Marker text box, point to Marker, and then select Browse.

The Database Navigator appears.

5 Double-click payload_adapter.reference_point.

ADAMS/Vibration inserts this marker into the Input Marker text box.

6 Select Translational.


7 Set the Force Direction to Global X.

8 Select Actuator Parameters.

9 Select Swept Sine.

10 In the Force Magnitude text box, enter 1.

11 In the Phase Angle (deg) text box, enter 0.

12 Select Apply.

ADAMS/Vibration creates the input channel and vibration actuator, and leaves the dialog box open so you can create the second input channel and vibration actuator.

13 To create another input channel, in the Input Channel Name text box, enter .satellite.input_y.

14 Leave the default Force.

15 In the Input Marker text box, leave payload_adapter.reference_point.

16 Set Force Direction to Global Y.


18 In the Force Magnitude text box, enter 1.


20 Select OK.

ADAMS/Vibration creates another input channel and vibration actuator.

To create a kinematic input channel and vibration actuator:

1 From the Vibration menu, point to Build, point to Input Channel, and then select New.

The Create Vibration Input Channel dialog box appears.

2 In the Input Channel Name text box, enter .satellite.input_accel_y.

3 Set Force to Kinematic.

4 Right-click the Input Marker text box, point to Marker, and then select Browse.



5 Double-click payload_adapter.reference_point.

ADAMS/Vibration inserts this marker into the Input Marker text box.

6 Select Global.

7 Select Translational.

8 Select Acceleration and Y.


10 In Magnitude text box, enter 9806.65.


12 Select OK.

ADAMS/Vibration creates another input channel and vibration actuator.

To review the vibration actuator:

1 From the Vibration menu, point to Build, point to Input Channel, and then select Modify.


2 Double-click the model name to display the list of input channels.

3 Double-click .satellite.input_accel_y.

The Modify Vibration Input Channel dialog box appears.

4 Select Plot Actuator to open the Actuator Preview Plot dialog box.

5 Specify the following:

■ Begin: 0.1

■ End: 100

■ Steps: 1000

6 Leave all other default settings.

7 Select Generate Plot to plot the actuator.

8 Close the Actuator Preview Plot dialog box.

9 In the Modify Vibration Input Channel dialog box, select OK.


Creating Output ChannelsHere you create output channels. Output channels are output ports at which you examine the frequency response of the system. You can think of output channels as instrumentation ports where you can measure system response and report the results directly in the frequency domain.

To create output channels:

1 From the Vibration menu, point to Build, point to Output Channel, and then select New.

The Create Vibration Output Channel dialog box appears.

2 In the Output Channel Name text box, enter: .satellite.p1_center_x_dis.

3 Set Output Function Type to Predefined.

4 Right-click the Output Marker text box, point to Marker, and then select Browse.


5 Double-click .satellite.panel_1.center.

ADAMS/Vibration inserts the marker panel_1.center into the Output Marker text box.

6 Set Global Component to Displacement along X.

7 Select Apply.

ADAMS/Vibration creates an output channel.


8 Using the specifications in the following table, create the remaining output channels, selecting Apply after creating each channel, and selecting OK after you create the last output channel.

Table 1. Output Channel Options

Output Channel Name: Output Marker: Disp/vel/acc: Direction:

.satellite.p2_center_x_dis .satellite.panel_2.center Displacement x

.satellite.p1_corner_x_dis .satellite.panel_1.corner Displacement x

.satellite.p1_corner_x_vel .satellite.panel_1.corner Velocity x

.satellite.p1_corner_x_acc .satellite.panel_1.corner Acceleration x

.satellite.p1_corner_y_acc .satellite.panel_1.corner Acceleration y

.satellite.p1_corner_z_acc .satellite.panel_1.corner Acceleration z

.satellite.ref_x_acc .satellite.payload_adapter.cm Acceleration x

.satellite.ref_y_acc .satellite.payload_adapter.cm Acceleration y

.satellite.ref_z_acc .satellite.payload_adapter.cm Acceleration z

3 Testing the Model

OverviewIn this section, you run a vibration analysis in a particular configuration. Completing this section involves the following:

■ Creating and Running Vibration Analyses, 20

Getting Started Using ADAMS/VibrationTesting the Model20

Creating and Running Vibration AnalysesThe forced vibration analysis sets up the vibration reference configuration for your model. When you create a vibration analysis, ADAMS/Vibration designates input and output locations. These locations are used when you perform the vibration analysis. ADAMS/Vibration automatically performs a normal modes analysis before performing a forced vibration analysis.

To create and run a forced vibration analysis:

1 From the Vibration menu, point to Test, and then select Vibration Analysis.

The Perform Vibration Analysis dialog box appears.

2 Select New Vibration Analysis.

3 In the corresponding text box, enter .satellite.vertical.

4 For Operating Point, select Assembly.

This linearizes the model around an assembled configuration.

5 Select Forced Vibration Analysis.

6 Select Damping.

7 Right-click the Input Channels text box, point to Input_channel, point to Guesses, and then select input_y.

ADAMS/Vibration inserts input_y in the Input Channels text box.

8 Right-click the Output Channels text box, point to Output_channel, point to Guesses, and then select *.

ADAMS/Vibration inserts all the output channels you created earlier into the Output Channels text box.

9 Select Logarithmic Spacing of Steps.

10 Under Frequency Range (hz), in the Begin text box, enter 0.1.

11 In the End text box, enter 1000.

12 In the Steps text box, enter 400.

Getting Started Using ADAMS/VibrationTesting the Model 21

13 To specify parameters for modal energy, select Modal Energy Computation.

ADAMS/Vibration displays the Modal Energy Computation dialog box.

14 Select Compute Modal Energy and Kinetic Energy, and then select OK.

15 In the Perform Vibration Analysis dialog box, select OK.

ADAMS/Vibration performs a forced vibration analysis. The process runs quickly. If no error messages appear, you can assume the vibration analysis completed correctly. If you receive error messages, correct the problem, and rerun your analysis.

Getting Started Using ADAMS/VibrationTesting the Model22

4 Reviewing the Model

OverviewIn this section, you use ADAMS/PostProcessor to study the data from the vibration analysis you performed.


■ Reviewing Tabular Results, 24

■ Plotting System Modes, 26

■ Animating a Normal Modes Analysis, 29

■ Animating a Forced Vibration Analysis, 30

■ Plotting Frequency Response, 32

■ Plotting Power Spectral Density, 35

■ Plotting Modal Coordinates, 37

Getting Started Using ADAMS/VibrationReviewing the Model24

Reviewing Tabular ResultsIn this section, you will review tabular results of the vibration analysis you just performed.

To view the table of eigenvalues:

1 From the Vibration menu, point to Review, and then select Display Eigenvalue Table.

The following table appears:

Note that all modes of the model are stable. If the model had unstable modes, they would be highlighted in the table. If you had performed multiple vibration analyses, you could use the +/- buttons in the top right corner of the window to navigate between eigenvalue tables of successive analyses.

2 Select Close to close this table.

To view the table of modal coordinates:

1 From the Vibration menu, point to Review, and then select Display Modal Info Table.

Getting Started Using ADAMS/VibrationReviewing the Model 25

The following table of model coordinates at 0.1 Hz excitation appears:

This table displays how much the 16 modes in this model are excited at this forcing frequency for input input_y. You can review the modal coordinates at different excitation frequencies using the Frequency slider.

2 Select Modal Participation to display the modal participation table in the analysis.

3 Select Modal Energy to display the modal energy distribution table.

4 Select Close to complete your review of the Modal Info tables.


Plotting System ModesIn this section, you plot the system modes to determine which system modes in the sensitive frequency range contribute to amplification of launch loads.

To plot system modes:

1 From the Vibration menu, point to Review, and then select Postprocessing or press F8.

ADAMS/View launches ADAMS/PostProcessor, a postprocessing tool that lets you view the results of simulations you performed. Take a minute to familiarize yourself with ADAMS/PostProcessor. For more information about ADAMS/PostProcessor, see the ADAMS/PostProcessor online help.

Figure 4 shows the ADAMS/PostProcessor window.

Figure 4. ADAMS/PostProcessor Window

Menu bar

Menu toolbar

Treeview

Property editor

Status toolbar

Page

Dashboard


2 In the dashboard, set the Source to System Modes.

3 From the Simulation list, select vertical_analysis.

4 From the Eigen list, select EIGEN_1.

5 Select Add Scatters.

ADAMS/PostProcessor plots system modes. The scatter plot should look as shown in Figure 5.

Figure 5. Scatter Plot

6 On the Curve Manager toolbar, select the Plot Tracking tool . Move your cursor over one of the plotted modes. Notice how the real and imaginary values for the mode are displayed on top of the plot.

You can also zoom in on the scatter plot to view details for -5.0, 0.0 on the real axis and -15.0, 15.0 on the imaginary axis.

These lightly damped, low-frequency modes are the modes you are most concerned with for the payload_adapter design; they tend to influence the amount of energy transmitted from the launch vehicle into the satellite.

7 Turn off plot tracking by selecting the Plot Tracking tool again.


8 From the Vibration menu, point to Review, and then select Create Scatter Plot with Eigen Table.

The scatter is plotted with a table of eigenvalues as shown in Figure 6 below.

Figure 6. Scatter Plot with Table


Animating a Normal Modes AnalysisIn this section, you animate the model to inspect and relate mode numbers with mode shapes. Remember, doing a normal modes animation outside of ADAMS/Vibration is called a frequency-domain animation. So, if you’re referring to the ADAMS/PostProcessor online help for more information on normal modes animation, read the sections on frequency-domain animations.

To view a normal modes animation:

1 Create a new page by selecting the New Page tool .

2 Right-click the Page Layout tool , and select the 1 View tool .

3 Set the pull-down menu located in the menu bar below the File menu, to Animation.

ADAMS/PostProcessor switches to animation mode.

4 Right-click the animation window, and then select Load Vibration Animation.

The vertical animation appears in the animation window.

Note: The label on the animation is EIGEN_#, where # is the run number of the animation.

5 Select Normal Mode Animation.

6 Close the Information window.

7 Next to the Mode Number text box, use the tool to change modes.

8 Select the Play tool.

9 Study the mode shapes for modes 9 and 15.

These appear to have the greatest effect on the vertical motion. Other modes affect the lateral motion and we’ll discuss them later.

If you see excessive movement for a given mode, you can automatically rescale it

by entering 0.0 in the Scale Factor text box, or adjusting the scale with the tool.

Note: To view the animation from different angles, rotate the view by typing a lowercase r and then using the mouse to rotate the view.


Animating a Forced Vibration AnalysisNext you animate the mode to inspect the system response to a forced vibration of 2.5 Hz, a frequency close to the eigenvalue of system mode 9.

To view a forced vibration animation:

1 Select Forced Vibration Animation.

2 In the Frequency text box, enter 2.5, and then press Enter.

ADAMS/Vibration automatically selects the closer frequency value for the animation contained in the frequency response analysis (2.5119 Hz).

3 Select Automatically set time fields for one cycle.

ADAMS/Vibration sets the end time and steps for the forced vibration animation so that one cycle is always displayed.

4 Set Scale Factor to 0.0, and then press Enter.

ADAMS/Vibration calculates the scale factor.


6 Look at the response.

The satellite’s vertical motion is the main contributor to the vibration at this frequency.

7 In the Frequency text box, enter 10 and then press Enter.

ADAMS/Vibration automatically selects the closer frequency value for the animation contained in the frequency response analysis (10 Hz). This shows an amplification of the frequency response.

8 Select the Pause tool .

9 From the Vibration menu, point to Review, and then select Display Modal Info Table.

10 Select Modal Coordinates.


11 In the Modal Information window, set the Frequency to 10.0 Hz and then press Enter.

The Modal Information window appears as shown in Figure 7 on page 31. Note that mode 15 is the primary contributor to the system response at about 10 Hz.

12 Select Modal Participation and view the information.

This table indicates the level of participation of the systems modes in each of the output channels.

13 Select Modal Energy.

If you opted to compute modal energy at the time the vibration analysis was run, ADAMS/Vibration displays the modal energy information.

The modal energy table displayed corresponds to the mode selected using the mode slider or to the mode number typed in the mode field.

14 Close the Modal Information window.

Figure 7. Modal Coordinates Table


Plotting Frequency ResponseNext, you plot the magnitude and phase of the frequency response. Magnitude is plotted in decibels (dB) against a logarithmic (log) scale for frequency. Phase is plotted in degrees using linear scale against a log scale for frequency. This plot will help you understand how the vertical vibration from the rocket affects the solar panel response.

To plot frequency response magnitude:

1 Select the New Page tool .

2 From the pull-down menu located below the File menu, select Plotting.

ADAMS/PostProcessor switches to plotting mode.

3 Set Source to Frequency Response.

4 From the Vibration Analysis list, select vertical.

5 From the Input Channels list, select input_y.

6 From the Output Channels list, select p1_corner_y_acc.

7 Select Magnitude.

8 Select Add Curves.

9 From the Output Channels list, select ref_y_acc.


ADAMS/PostProcessor plots the frequency response magnitude.

To display a horizontal, two-page layout:

■ Right-click the Page Layout tool , and select the Horizontal, 2-page tool .

The viewport now contains the frequency response function plot and a blank plot.


To plot frequency response phase:

1 Select the blank plot.




5 From the Output Channels list, select p1_corner_y_acc.

6 Select Phase.


8 From the Output Channels list, select ref_y_acc.


ADAMS/PostProcessor plots the frequency response phase (see Figure 8 on page 34).

From these plots you can determine the two primary modes that affect the vertical acceleration response. The first prominent mode is around 2.5 Hz. The second prominent mode is just above 10 Hz. These two modes contribute to an attenuation of accelerations about 4 Hz. This can be seen by comparing the input acceleration (ref_y_acc) directly with the output acceleration.


Figure 8. Frequency Response Plot


Plotting Power Spectral DensityHere you plot the power spectral density, or PSD. This plot shows the transmitted power from all inputs used in your analysis as a function of frequency.

To plot power spectral density:

1 Select the New Page tool.

2 Right-click the Page Layout tool, and then select the Page Layout: 1 View tool .

3 Set Source to PSD.


5 From the Output Channel list, select p1_corner_y_acc.


ADAMS/PostProcessor plots the power spectral density on a logarithmic scale.

7 Select the vertical axis of the plot.

8 Select dB from the list of scale options.

ADAMS/PostProcessor plots the transmitted acceleration in the units of

(mm/sec2)2/Hz, as shown in Figure 9 on page 36.

The resonance peak again corresponds to the frequency of about 2.5 Hz, as discussed above.


Figure 9. Power Spectral Density Plot


Plotting Modal CoordinatesHere you plot the modal coordinates to find out which modes participate more in the response.

To plot modal coordinates:


2 Set Source to Modal Coordinates.



5 Set Modal Coordinates By to Mode.

6 Set Mode to 9.


ADAMS/PostProcessor plots the modal coordinates.

8 Set Mode to 15.


ADAMS/PostProcessor plots the modal coordinates.

In Figure 10 on page 38, note the difference in the two curves to observe which modes are participating more in the response, especially near 2.5 Hz.


Figure 10. Modal Coordinates Plot

5 Improving Your Design

OverviewIn this section, you will investigate the lateral vibration environment. Different modes will influence the lateral acceleration at the panel corner than the vertical acceleration. You will identify the modes that influence the lateral acceleration and plot the frequency response function associated with the x direction of the panel.


■ Creating and Running a Forced-Vibration Analysis, 40

■ Animating a Normal-Modes Analysis, 41

■ Plotting Force Frequency Response, 42

Getting Started Using ADAMS/VibrationImproving Your Design40

Creating and Running a Forced-Vibration AnalysisHere you create and run a forced-vibration analysis called lateral.

To create and run a forced-vibration analysis:

1 Return to the modeling environment by pressing the ADAMS/View tool on the

ADAMS/PostProcessor toolbar.

2 From the Vibration menu, point to Test, and then select Vibration Analysis.

3 Select New Vibration Analysis.

4 In the corresponding text box, enter lateral_x.

5 For Operating Point, select Assembly.

6 Select Forced Vibration Analysis.

7 Accept the Damping default of On.

8 Right-click the Input Channels text box, point to Input_Channel, point to Guesses, and then select Input_x.

ADAMS/Vibration inserts input_x in the Input Channels text box.

9 Right-click the Output Channels text box, point to Output_channel, point to Guesses, and then select *.

ADAMS/Vibration inserts into the Output Channels text box all the output channels you created earlier.

10 Select Logarithmic Spacing of Steps.

11 Under Frequency Range (hz), in the Begin text box, enter 0.1.

12 In the End text box, enter 1000.

13 In the Steps text box, enter 400.

14 Select OK.

ADAMS/Vibration performs a forced-vibration analysis.

Getting Started Using ADAMS/VibrationImproving Your Design 41

Animating a Normal-Modes AnalysisIn this section, you animate the model to inspect and relate mode numbers with mode shapes.

To view a normal-modes animation:

1 From the Vibration menu, point to Review, and then select Postprocessing or press F8.


3 From the pull-down menu located below the File menu, select Animation.

ADAMS/PostProcessor switches to animation mode.

4 Right-click the animation window, and then select Load Vibration Animation.

5 Select lateral_x from the list.

The lateral animation appears in the animation window. Note that the label on the animation is EIGEN_#, where # is the run number of the animation.

6 Select Normal Mode Animation.

7 In the Mode Number text box, use the tool to select different modes.


9 Look at the mode shape for mode numbers 8, 11, and 14.

Mode 8 is a symmetric rocking mode. Modes 11 and 14 are asymmetric rocking modes. These three modes will affect the lateral acceleration.

10 Select the Pause tool.


Plotting Force Frequency ResponseIn this section you plot the frequency response from the lateral force input.

To plot frequency response magnitude in dB and log scale:


2 From the pull-down menu located below the File menu, select Plotting.

ADAMS/PostProcessor switches to plotting mode.


4 From the Vibration Analysis list, select lateral_x.

5 From the Input Channels list, select input_x.

6 From the Output Channels list, select p1_corner_x_acc.

7 Select Magnitude.


9 From the Output Channels list, select ref_x_acc.


ADAMS/PostProcessor plots the frequency response magnitude (see Figure 11 on page 43).

Note that there is an amplification of the input around .76 Hz and between 3.5 Hz and about 5.8 Hz, but an attenuation of the input for frequencies above 5.8 Hz. You can check this by comparing the reference input with the output.

Getting Started Using ADAMS/VibrationImproving Your Design 43

Figure 11. Frequency Response Plot

From the frequency response functions, it is clear that the input becomes attenuated above about 5.8 Hz (see Figure 11). Therefore, any accelerations that come through the test base into the payload adapter will be sharply attenuated by the bushings connecting the payload adapter with the satellite bus.

6 Optimizing the Model

OverviewIn this section, you modify an existing design variable so that you can determine what value of damping is optimal for reducing vibration for a given frequency range.


■ Performing an ADAMS/View Automatic Design Study Analysis, 46

■ Conclusion, 54

Getting Started Using ADAMS/VibrationOptimizing the Model46

Performing an ADAMS/View Automatic Design Study AnalysisYou will now perform a design study with the help of the ADAMS/View design study tool. In this exercise, you will look for the effect of the translational damping value on the absolute maximum of the frequency response measured between the input channel input_x and the output channel p1_corner_x_acc. To do this you will learn:

■ Reviewing Parameterization, 46

■ To define the ADAMS/View objective for the use with an ADAMS/Vibration analysis:, 48

■ To create a simulation script:, 49

■ To specify that the results from each run are to be stored:, 50

■ To run a design evaluation analysis based on an ADAMS/Vibration simulation event:, 52

■ To evaluate results of the design study:, 53

■ To plot the frequency response in a three-dimensional plot:, 53

Reviewing Parameterization

In this section, you’ll investigate the parameterization set up for the bushing damping. You’ll then define the range over which the design variable will be varied.

To review parameterization of the model:

1 Return to the modeling mode by selecting the ADAMS/View tool.

2 From the Tools menu, select Database Navigator.

3 In the pull-down menu next to Filter, select Forces.

4 Select Satellite to display all forces in the model.

5 Select BUSHING_1, and then select OK.

The Information window displays information about BUSHING_1. Notice the parameterization of the bushing damping using the design variable trans_damp.

6 Return to the Database Navigator and filter on Variables.

Getting Started Using ADAMS/VibrationOptimizing the Model 47

7 Select trans_damp, and then select OK to display information on this design variable.

8 In the Information window, double-click percent_damping in the expression for trans_damp.

Information on the design variable appears in the information window.

9 In the Information window toolbar, select Modify.

The Modify dialog box appears as shown in next.

Figure 12. Design Variable Settings


10 To define the range over which the design variable will be varied, specify the following:

■ Standard value: 1.0

■ Min. Value: 1.0

■ Max. Value: 20.0

11 To save your selection, select OK.

12 Close the Information Window and the Database Navigator (if it is still open).

Defining the ADAMS/View Objective

In this section, you’ll define a return value to track the value of the objective for each simulation.

To define the ADAMS/View objective for the use with an ADAMS/Vibration analysis:

1 From the Vibration menu, point to Improve, point to Vibration Design Objective, and then select New.

The Create Vibration Design Objective Macro and the Create Design Objective dialog boxes appear.

2 In the Create Design Objective dialog box, enter Max_FRF in the Name text box.

3 In the Create Vibration Design Objective Macro dialog box, right-click the Return Value Variable text box, point to Variable, and then select Create.

The Create Design Variable dialog box appears.

4 Set Standard Value to 0.0.

5 Accept the remaining defaults of the Create Design Variable dialog box, and then select OK.

This variable will be used as the return variable to track the value of the objective for each simulation.

6 From the Target Vibration Data list, select Frequency Response: 1 input, 1 output.

7 Right-click the Input Channel text box, point to Input_Channel, point to Guesses, and then select input_x.


8 Right-click the Output Channel text box, point to Output_Channel, point to Guesses, and then select p1_corner_x_acc.

9 Set Value Type to Maximum.

10 Set Frequency Range to All Frequencies.

11 Select OK to create the vibration design objective macro.

ADAMS/Vibration automatically fills in the text boxes in the Create Design Objective dialog box with the reference to the return variable DV_1 and the macro MACRO_1, created by ADAMS/View, to calculate the design objective for every simulation as specified.

12 Select OK in the Create Design Objective dialog box.

Creating a Simulation Script

Here you create the simulation script for the model.

To create a simulation script:

1 From the Vibration menu, point to Test, and then select Create Multi-Run Script.

The Create Vibration Multi-Run Script dialog box appears.

2 Complete the dialog box as shown in Figure 13, and then select OK.


Figure 13. Create Vibration Multi-Run Script Dialog Box

Storing Results

Here you tell ADAMS/View where to store the results.

To specify that the results from each run are to be stored:

1 From the Settings menu, point to Solver, and then select Output.

2 Complete the dialog box as shown in Figure 14. Be sure to select More to expand the dialog box to the form shown.

3 Select Close.


Figure 14. Solver Output Settings


Running a Design Evaluation Analysis

Now that you’ve defined the objective, the design variable values, and the script, you can run a design evaluation analysis.

To run a design evaluation analysis based on an ADAMS/Vibration simulation event:

1 From the Vibration menu, point to Improve, and then select Design Evaluation.

2 Right-click the Simulation Script text box, point to Simulation Script, point to Guesses, and then select .multirun_vib.

3 Set Study a to Objective.

4 Right-click the Objective text box, point to Objective, point to Guesses, and then select max_FRF.

5 Accept the default setting of Design Study.

6 Right-click the Design Variable text box, point to Variable, point to Browse, and then select percent_damping.

7 Confirm that Default Levels is set to 5.

8 Select Start to initiate the design study.

After the design study analysis runs, ADAMS/Vibration generates a plot indicating the maximum of the selected FRF for the five different cases.

Figure 15. Design Objective Strip Chart


Evaluating the Results of the Design Study

To evaluate results of the design study:

1 In ADAMS/PostProcessor, select the New Page tool.

2 In the Vibration analysis text box, select all analyses from lateral_x_1 to lateral_x_5.

3 Set Input Channel to Input_x.

4 Set Output Channels to p1_corner_x_acc.

5 Select Add Curves to create the plot.

A multi-curve plot appears as shown in Figure 16.

Figure 16. Response for Design Study

To plot the frequency response in a three-dimensional plot:


2 From the pull-down menu located below the File menu, select Plot3D.

3 In the Vibration Analysis text box, select all analyses from lateral_x_1 to lateral_x_5.

4 Set Input Channels to Input_x.


5 Set Output Channels to p1_corner_x_acc.

6 Select Add Surface to create the three-dimensional plot.

7 To shade the 3D plot, select the Wireframe/Shaded tool .

8 Click on the legend, and in the property editor, set Placement to Left.

The plot appears as shown in Figure 17.

Figure 17. Three-Dimensional Plot of Design Study

ConclusionFrom the frequency response plot, it is clear that 5% damping is best for attenuating vibration for the 5 to 10 Hz range. This damping gives the steepest roll-off for the acceleration frequency response. This low damping, however, has the highest peak response at 2.5 Hz. On the other hand, setting percent_damping to 12.5% gives the lowest peak response, but it does not roll off as rapidly in the 100 to 400 Hz range as it does for 5% damping.

You have designed the concept of a vibration isolation system for a satellite. You first checked the payload adapter frequency response in the vertical direction, finding two modes which affected the transmitted vibration.


Next, you checked the frequency response in the lateral direction. You investigated the effect of damping on the transmitted vibration and selected an optimal damping ratio.

Further design investigations could include the effects of flexible bodies to represent the solar panels. You could further improve the vibration isolation characteristics by replacing linear bushings with frequency dependent bushings. See Knowledge Base article 12433 at http://support.adams.com/kb/faq.asp?ID=kb12433.dasp for more information.

http://support.adams.com/kb/faq.asp?ID=kb12433.dasp

getting started using adams/vibration

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