ADAMS/Vibration Release Notes

What's New
Changes
Issues Resolved
Known Issues

What's New

Plotting input actuators

You can now plot the magnitude and phase of existing vibration input actuators in the modeling environment. This is particularly useful when defining user actuators. You may access this feature from the Plot Actuator button in the lower-left corner of the Input Channel Modify dialog box. The plots you generate may optionally be saved for later viewing in the post-processing environment.

For an example, see Knowledge Base Article 1-KB12266.

Complex plane eigenvalues plot tracking

The plot tracking tool now works with the eigenvalue scatter plot. Access this feature from ADAMS/PostProcessor by displaying the System Modes scatter plot and then using the Plot Tracking tool.

For an example, see Knowledge Base Article 1-KB12268.

Modal table next to scatter plot

You can now automatically display the eigenmode table next to the scatter plot. This is useful when you are reviewing modes in the scatter plot that may be clustered together. You can readily view the real and imaginary values from the table. Access this feature in ADAMS/PostProcessor as follows: PlotCreate Scatter Plot with Eigen Table.

Frequency dependent modeling element

We have implemented 1- and 6-DOF frequency-dependent (FD) modeling elements that can be used in either interactive or batch analysis modes. The FD elements can be used in both time-domain and frequency-domain simulations, and accessed in ADAMS/View as follows:

Build -> ADAMS/Vibration -> FD Damper
Build -> ADAMS/Vibration -> FD 3D Damper

There are four bushing types available:

Pfeffer Linear
Simple FD
Simple FD-Bushing
General

You can enter up to three sets of damping and stiffness parameters and a single preload for each direction. A single component force (SFORCE) and general state equation (GSE) are created automatically for the 1-DOF element. A general force vector (GFORCE) and GSE are created for the 3D-damper element.

The methodology for deriving parameters for the FD elements is left to the user. However, we do offer an example which demonstrates one approach to parameter derivation. Refer to the guide, Getting Started Using ADAMS/Vibration.

For an example of using the 1D FD element, see Knowledge Base Article 1-KB12294.

More vibration design objectives

We have expanded our offering of vibration design objectives (several were pre-released in the 2003 service pack). The list now includes frequency response magnitude of sums, frequency response area, frequency response error, eigen natural frequency error, and modal energy. These objectives are useful for model correlation, system tuning, and more. See Knowledge Base article 1-KB10712 for a working example.

Saving vibration results in XML results file

Results from a Vibration analysis can now be saved for future use. The results file (.res) can be used to store the vibration results. This will enable you to plot vibration analysis data or perform vibration animation using data from a previously solved vibration run.

The new capabilities are:

You can import the results file, enabling you to generate vibration plots or animations without rerunning your vibration analysis. The .res file from a previously run vibration analysis will contain an EIGEN and linear state matrices, both of which are now used by the ADAMS/Vibration; this was not possible in previous releases. We have added support for importing a results file and attaching it to an existing vibration analysis object. This functionality is accessed as in ADAMS/PostProcessor as follows: FileImportVibration Results.
Vibration plots can now be preserved in an XML results file format. We now have macros which support the preservation and restoration of vibration plot data. Since menu buttons are not yet in place, use the following command language.
To write vibration plot curve data to an xml results file, use the following command:

mdi vibration save_plot_data &
vibration_analysis = YourVibrationAnalysisObject &
results_file_name = YourResFileName &
plots = ThePlotsOfInterest

Note: Your vibration analysis object must have an eigen and fva in place beneath the analysis that is associated with the VibrationAnalysis object.

To restore vibration plot data from an xml results file:

Make sure the vibration plugin is loaded

Read in the xml results file you have previously written the plot data: FileImportResults File.

Issue a command like this:
mdi vibration plots_from_vars analysis = TheAnalysis

A new plot on a new page will be created with one curve whose data comes the saved values. The plots will have the correct type (for example, Frequency Response) and an appropriate title. The curve legend will come from comment information that is stored in the .xml file.

For information on using these features, see the example in Knowledge Base Article 1-KB12312.

Phase on PSD actuator (46349)

The phase angle for the PSD actuator may now be defined by a spline. In prior releases you were limited to using a constant phase angle.

Extended support for Python-based vibration analysis

A Python-based interface was introduced in the 2003 release to enable batch processing of vibration models. Now we have extended the support to include model building, and enhanced the analysis and post-processing capabilities as described below.

New transfer functions

You now have access to transmissibility and other transfer functions. You can also store your results in an XML results file, which can be readily imported into ADAMS/View for post-processing.

The new transfer functions available in batch mode are:

Dynamic stiffness
Compliance
Impedance
Mobility
Dynamic inertia
Accelerance
Force transmissibility
Motion transmissibility
Nibble

For more information see the MechanicalTransferFunctions subdirectory in the vibration/examples directory. For an example of using the new transfer function, see Knowledge Base Article 1-KB12267.

Simplified creation of rotating mass inputs

Instead of separately creating a leading and lagging input channel, you can now create the pair of inputs simultaneously using the Python interface. This is useful when building wheel unbalance events, such as nibble.

Python Vibration analysis at multiple operating points (46505, 46365)

Previously, vibration analysis could only be performed at a single operating point. In some applications it would be useful to be able to perform vibration analysis at several operating points, for example, along a trajectory that is being solved during dynamic analysis. This capability also allows you to perform compliance matrix calculations at various operating points.

This multi-operating point solution has been implemented in the vibration Python environment only.

For more information see the MultiPointAnalysis subdirectory in the vibration/examples directory.

Python plotting

Rudimentary post-processing of vibration results may be performed with PyQt. We provide a working example which demonstrates some of the possibilities of using the Python environment. This may give you ideas of how to use Python to better streamline your NVH analysis process.

Flexible body modal energy shading

The primary purpose of this feature is to allow visualization of modal energy distribution in a flexible body during forced vibration animation. Through the use of contour plots, you can now identify regions of energy concentration in a flexible body at a given frequency.

We have implemented the following sets of functions for energy shading:

Kinetic energy: Requires nodal masses to be in the MNF file.
Strain energy: Uses the nodal masses and eigen vectors to solve for nodal stiffness. Requires nodal masses to be in the MNF file.
Strain energy SS: Uses stress and strain solution to solve for nodal strain. Requires stress and strain to be in the MNF file.

To use this feature, instrument a flexible body model and run a vibration analysis. Then from ADAMS/PostProcessor, load the vibration animation, select the Contour Plots tab, and then choose the energy you want to display. Sometimes it is easier to view the model energy animation with Auto Scale turned off and using a scale factor of 1.0.

For an example, see Knowledge Base Article 1-KB12266).

User-specified frequencies (41810)

By customer request, we have now made it possible to perform a vibration analysis for a list of user-specified frequencies, instead of being limited to a given frequency range. This is useful when you are validating your ADAMS/Vibration results with experimental data that is only available at certain frequency values. The frequencies can be entered manually in the dialog box or you may reference values in an external text file.

Documentation Enhancements

ADAMS/Vibration Documentation Improvements

Improved documentation as follows:

Added information on the following:
- Changes to ADAMS/Vibration plotting options
- Changes to the Python API
- New Actuator Preview Plot dialog box
- New FD damper dialog box
- New design objectives
- New Vibration Analysis Attach Results dialog box (in ADAMS/PostProcessor)
Updated the online help and the guide, Getting Started Using ADAMS/Vibration to reflect other changes made to the product.

Overall Documentation Improvements

For MSC.ADAMS 2005, we've made improvements to the MSC.ADAMS help:

Added global search so you can search across the entire set of MSC.ADAMS help. To access the global search, do one of the following:
- At the top of the help, select Switch Products, and then select the Search tab.
- In any product, select the Search tab, and then in the window that appears, select Global Search.
Note that the global search does not include any .pdfs (including getting started guides and ADAMS/Driver).
Removed any hardcoding of font sizes so you can scale the text of the help to any size. Please note that many of the equations do not scale because they are images, and the help looks the best when viewed with medium (or 100%). In addition, your browser will print the text the same size as it is displayed.
Documented many of the environment variables for the products to help customize your session. The environment variables are for ADAMS/Controls, ADAMS/Durability, ADAMS/Flex, ADAMS/Solver, ADAMS/View, and the template-based products (ADAMS/Aircraft, ADAMS/Car, ADAMS/Driveline, ADAMS/Rail). For more information, see the Running and Configuring help.

Changes

Python script language changes

For those using the Python-based batch analysis, note that there have been some Python script language changes that will affect your upgrade to the 2005 release.

Below are the required changes to convert python scripts from ADAMS/Vibration 2003 to 2005.

Path to the vibration interface (new location):
- 2003:
  /from AvInputChannel import */
- 2005:
  /from msc.ADAMS.Vibration.AvOutputChannel import */
Input channel and output channel no longer take the marker name (now using amd name no longer required):
- 2003:
  /InCh4 = AvInputChannelMarker("Input 4", 4160, "Marker/4160", "Translational", "Global", .../
- 2005:
  /InCh4 = AvInputChannelMarker("Input 4", 4160, "Translational", "Global", .../
- 2003:
  /outCh6 = AvOutputChannelPredefined("Output 6", 10040, "Marker/10400", "Acceleration", "Z")/
- 2005:
  /outCh6 = AvOutputChannelPredefined("Output 6", 10040, "Acceleration", "Z")/
Frequency parameter is now a 1D vector:
- 2003:
  /Freq = AvAPI_Matrix(20, 1, f)/
- 2005:
  /Freq = AvAPI_Matrix(20, f)/

Results files saved when using external solver (47175)

The vibration solve dialog box now ensures that results file output is enabled when the external solver is used. The results file contains the eigensolution that is needed, so that the ADAMS/View database can be populated with the vibration results. If you did not enable results file saving, an alert box displays notifying you that the saving of results files has been turned on.

Utility macro for removal of vibration objects (31601)

A new utility macro has been added that can clean out all vibration entities from a model. This is useful when you want to share your model with other MSC.ADAMS users who will not be using the model for ADAMS/Vibration analysis, allowing them to start from a clean slate.

The command associated with the macro can be issued from the command line. For example:

mdi vibration model cleanup model=YourModel retain_fd_dampers=no

The optional parameter retain_fd_dampers will keep any FD damper elements in the model if it is set to yes, but remove all other vibration entities, such as input or output channels.

Issues Resolved

The 2005 release of ADAMS/Vibration includes all of the fixes and enhancements that were provided in the 2003 Service Pack. See ADAMS/Vibration 2003 Service Pack, APN-130-260. The resolved items are:

22639

Scatter plots were plotted in Hz regardless of the frequency units setting. This problem has been fixed. Complex scatter plots now plot the correct frequency units and update when units are changed.

30248, 40408, 40339

The acceleration frequency response for flexible bodies was calculated incorrectly. The error was present when using flexible bodies and "rigidized" flexible bodies. Prior to the service pack, the workaround for obtaining correct acceleration frequency responses was to derive the velocity frequency responses using the curve editor tools, or to create an output channel on a dummy part (constrained with a fixed joint to the flexible body at the point of interest). This problem has been corrected and the workaround is no longer necessary. Note that the problem did not extend to displacement or velocity responses; these outputs were not in error.

37621

Logarithmic plots have been enhanced so that the minor divisions are spaced logarithmically, instead of linearly.

42087

It was discovered that for some larger models the vibration analysis could fail due to inaccuracies in eigenvector computation. This problem has been corrected by improving the accuracy of eigenvectors and thereby improving the stability of vibration analysis.

43319

The vibration deformation scale for models containing flexible bodies was computed incorrectly. This problem with forced vibration animation has been corrected.

43320

The total percentage distribution of strain and dissipative energy was substantially less than 100% for models containing MSC.ADAMS Beam/Bushing/Field elements. This error has been corrected.

43483

Models having switch (or dummy) parts may fail to produce the correct frequency response. An error was found in the handling of zero mass parts. The service pack corrects that error.

43851

Errors were not being handled properly for those situations where solver linearization would fail, such as memory overflow due to insufficient memory model size. The vibration analysis macro has been improved so that this error condition is detected, the user is alerted, and macro is exited cleanly.

43854

The wrong units were being specified for the generalized mass listed in modal energy table when phase was included. Now the unit label agrees with the mass units used in the model.

43892

The algorithm for vibration animation of flexible bodies has been optimized for improved performance. Modes that contribute very negligibly to the animation (that is, those likely to be imperceptible on the screen) are now ignored. The new algorithm finds the largest modal coordinate and ignores any other coordinate that is less than 10% of that value. This is done for system modes and flex body modes as well. 10% is the default, but you can control the value using the following two environment variables:

ADAMS_VIBRATION_MIN_PARTICIPATION (for system modes)
ADAMS_VIBRATION_MIN_FLEX_PARTICIPATION (for flex modes)

For some models containing only rigid bodies, this default value results in a number of meaningful modes being removed from the animation. This can be rectified by having all system modes included in the animation (that is, set the value of ADAMS_VIBRATION_MIN_PARTICIPATION to 0.0). To use 5% on system modes and all the flex modes:

On Windows:

set ADAMS_VIBRATION_MIN_PARTICIPATION=0.05
set ADAMS_VIBRATION_MIN_FLEX_PARTICIPATION=0.0

On UNIX:

setenv ADAMS_VIBRATION_MIN_PARTICIPATION 0.05
setenv ADAMS_VIBRATION_MIN_FLEX_PARTICIPATION 0.0

Alternatively, these can be set from within the ADAMS/View command window using the PUTENV function. Refer to Knowledge Base Article #10713 for details.

43904

When post-processing an ADAMS/Vibration simulation, and selecting normal mode and showing undeformed, the undeformed part was drawn in the wrong location. The misbehavior related to the use of eigen scale (which should not be used) when retrieving transforms for the undeformed configuration. Undeformed parts that appeared to be at maximum deformation (or off by 90 degrees) will now be drawn properly.

44057

Selecting the vibration animation Automatically set time fields for one cycle checkbox failed to convert the time units for models using the milliseconds time unit. This problem, which would lead to improper animations, has been corrected.

44270

Flexible body models containing parameterized marker locations would encounter an application crash during vibration animation with icons on. This issue has been resolved in the prerequisite ADAMS/View service pack.

44431, 44272

Corrected the problem that was preventing the ADAMS_VIBRATION_SOLVER license from being released after first simulation using internal solver. The workaround for the problem, which was to use the external solver, is no longer necessary.

Additional items resolved

44378

Removed performance bottleneck due to solver compatibility checking that was affecting design studies, DOE, and optimization. The problem (duration between runs becoming progressively longer) was most noticeable when several successive simulations were run and the analysis results from the individual runs were being saved.

44686

Corrected problem that was causing an application crash when trying to delete a model containing vibration entities.

44937

The wrong frequency units were being used in kinetic energy computation. The net modal kinetic energy should use frequency in radians/unit_time rather than cycles/second; this has been fixed.

46347

Fixed problem that caused the settings in the scale factor text box to be ignored during mode-shape animation.

47506

Corrected security problem in the management of the vibration plugin which was causing an application crash when Load at Startup was used and a binary containing vibration entities was opened.

46521, 46572

Corrected flexible body animation scaling problem that was causing rigid bodies to appear as if they were disconnected from the flexible body to which they were attached.

Revised: 09/06/05