Simcenter Testing Solutions Combined Modes: Sine on Random (SoR), Random on Random (RoR), Sine on Random on Random (SoRoR)

2024-02-08T23:35:40.000-0500

Simcenter SCADAS Simcenter Testlab

Summary

Details

Direct YouTube link: https://youtu.be/BALLLL0avY0

When recreating vibration profiles on a shaker system, it is often desirable to recreate a “combined” environment. A “combined” vibration environment can consist of sine and random vibration, or random on random vibration.

Why might a combined environment need to be used? For example, physical components like electronics, structural members, etc might be subjected to vibration environments containing both random vibration and sinusoidal vibration. It is also possible that a component could be subject to two types of random vibration – narrowband random and broadband random at the same time.

These combined types of vibration environments (Figure 1) result from a number of different scenarios. Possibilities include propeller aircraft, jets, tracked vehicles, anti-lock brakes, helicopters, and more…

Figure 1: Example where a combined vibration environment (random and sine) would be reproduced on shaker table.

Instead of running traditional random vibration test, and then running a separate sine and/or random vibration test, the “combined” vibration control mode of Simcenter Testlab allows multiple types of vibration to be reproduced with a shaker system at the same time.

Many vibration guides specify combined mode testing. An example from the MIL-STD-810 vibration specifications is shown in Figure 2 below:

Figure 2: Example of a combined modes (sine and random) test from MIL-STD-810 Section 514.8 for a propeller aircraft. The specification consist of both random vibration (green and purple highlights) and sinusoidal vibration (orange and blue highlights).

MIL-STD-810 is a Department of Defense Test Method Standard. It describes how to manage and create vibration profiles to reproduce real-world vibration. Despite being developed for the qualification of military applications, it is often used for commercial products as well. Other standards include GAM EG13 and AIR 7306.

This article explains how to setup and create a combined mode test in Simcenter Testlab vibration control:

Getting Started
Sine-on-Random (SoR)
Random-on-Random (RoR)
Sine-on-Random-on-Random (SoRoR)

1. Getting Started

This article assumes the reader is familiar with random control testing and therefore only covers the additional combined modes setup. Combined modes add-ins are run on top of the base random control in Simcenter Testlab.

To run a combined mode test, start the Random Control workbook of Simcenter Testlab. Random control is started from the “Testlab Environmental” folder as shown in Figure 3:

Figure 3: Start Random Control from the Testlab Environmental folder.

If icons for Simcenter Testlab were not created during installation, Random Control can be started by searching for “Random Control” in the Windows search bar.

From the main menu, select “Tools -> Add-ins” to enable the combined modes on top of the base random control test as shown in Figure 4.

Figure 4: Combined mode add-ins are available in Random Control workbook.

When these add-ins are enabled, the reference profile editing tool is extended with multiple tabs to define the combined vibration environment as shown in Figure 5 below:

Figure 5: With the combined modes add-ins, additional tabs are added in the upper right of the profile definition area of the Random Control Setup worksheet.

More information about creating and running a random vibration control test can be found in these links:

The setup of the combine modes is covered in the next sections.

2. Sine-on-Random (SoR)

To perform a sine on random vibration test (a test with both random and sine combined), turn on “Sine-on-Random” add-in under “Tools -> Add-ins”. If using Simcenter Testlab token licensing, this add-in will occupy 25 tokens while it is turned on.

With the add-in turned on, two new tabs called “Fixed Sine Tones” and “Sweeping Sine Tones” appear in the Reference Profile editor next to the “Background PSD” tab of the Random Setup worksheet (Figure 6).

Figure 6: With “Sine-on-Random” add-in turned on, the reference profile is extended with “Sweeping Sine Tones” and “Fixed Sine Tones” tabs.

The “Background PSD” tab is used to setup the broad band random control part of the test, just like any random control test would be executed. The two tabs “Fixed Sine Tones” and “Sweeping Sine Tones” are in addition to the Random Control to make a combined mode test.

The sine tones can be constant in frequency or vary in frequency:

Fixed Sine Tones: Enter a table of single frequencies with a fixed amplitude. Frequencies will not change during the test.
Sweeping Sine Tones: Define sine tones that vary in frequency, including the slew rate of variations.

2.1 Fixed Frequency Sine Tones

To enter the fixed frequency sine tones, in the “Fixed Sine Tones” tab, enter a profile name and click on the “Edit Fixed Sine Tones Profile” button as shown in Figure 7:

Figure 7: Use the “Edit Fixed Sine Tones Profile” button to create a table of fixed frequency sine tones to run in conjunction with the random vibration. The dots that appear in lower graph are the frequency, amplitudes, and abort limits of the individual frequencies.

In the resulting table, frequencies and their corresponding amplitudes are entered. Each sine frequency can have a different amplitude.

Scroll to the right in the table to enter a “On” duration for the sine tones (it can be less than the duration of the random vibration part of the test) as shown in Figure 8:

Figure 8: Scroll right in the “Fixed Sine Tone Editor” and make the “On” time greater than zero.

A time offset can also be entered. The offset is used so the sine tones will turn on after the specified delay after the random vibration test starts.

2.1 Sweeping Frequency Sine Tones

In some specifications, the sine tones vary in frequency and are not constant frequency. In this case, click on the “Sweeping Sine Tones” tab. Press the “Edit Sweeping Sine Tones Profile” button as shown in Figure 9.

Figure 9: Variable frequency sine tones are created in the “Sweeping Sine Sweep” tab.

On the left side of the “Sweeping Sine Tones Editor” the sweep definition field can be set to either “Global” or “Individual” as shown in Figure 10:

Figure 10: Choose “Global” or “Individual” in the Sweeping Sine Tones Editor. “Global” makes most sine sweep settings the same (except frequency range) while “Individual” gives complete control over the settings for each sweeping sine tone.

If set to Global, all sweeping sine tones that are defined will use common settings defined in the menu. For example, using the global settings, all sweeping sine tones could be set to have the same duration.

Possible global and individual settings include:

Sweep mode: Log or linear
Sweep strategy: Up, Down, or Up/Down
Total Sweep Time: Amount of time that the sweep will be active
Number of Sweeps: Number of times sweep will repeat
Time offset: Delay from reaching full random level that sweeping tones will be activated.

If global settings are not used, all of the above settings need to be set individually on each sweeping tone.

To add a sweeping sine tone, click on the “Add Sine Tone…” button in the Sweeping Sine Tones Editor.

The frequency range of sweeping tone is entered in the table shown in Figure 11:

Figure 11: Sweeping tone frequency range are set in the sweeping sine tone menu.

The frequency sweep range of each tone can always be entered, even if global settings are being used. If global settings are used, the other sweeping tone parameters in the menu are grayed out and insensitive. If local settings were selected, the other parameters may be edited.

After the sweeping tones are entered, a graphical summary is shown in the Editor menu (Figure 12):

Figure 12: With the sweeping tones entered, a graphical summary is shown in the lower area of the Editor menu. The lines show the frequency sweep range. The green line is the target amplitude, while the other lines are abort limits.

Sine on random is one type of combined mode vibration test. Random-on-random vibration is explained in the next section.

3. Random-on-Random (RoR)

Random-on-Random vibration tests involve broadband random combined with small bands or high amplitude vibration like those shown in Figure 13:

Figure 13: Random-on-Random vibration is used to reproduce vibration created in tracked vehicle applications.

A common cause of random on random vibration is tracked vehicles. In tracked vehicles, the slats of the track operate at a specific speed, but each slat creates a concentrated band of vibration around the frequency produced by the speed.

To perform random on random vibration test (a test with both narrowband random and a broad band random combined), turn on “Random-on-Random” add-in under “Tools -> Add-ins”. If using Simcenter Testlab token licensing, an additional 25 tokens will be occupied while the “Random-on-Random” add-in is turned on.

After it is turned on, two new tabs called “Fixed Narrow Bands” and “Sweeping Narrow Bands” appear in the Reference Profile editor of the Random Setup worksheet (Figure 14).

Figure 14: “Fixed Narrow Bands” and “Sweeping Narrow Bands” are added to the Reference Profile editor when the “Random-on-Random” add-on is turned on.

The random bands of vibration can be defined at fixed frequencies or with sweeping (i.e., changing) frequencies.

3.1 Fixed Narrow Bands

To define bands of random data, choose the “Fixed Narrow Bands” tab, enter a profile name, and click on the “Edit Fixed Narrow Bands Profile” button as shown in Figure 15.

Figure 15: To create fixed frequency bands of random data, choose the “Edit Fixed Narrow Band Profile” button in the “Fixed Narrow Bands” tab of Random Setup.

At a minimum, the following must be entered:

Frequency: The center frequency of narrow random band.
Level: The vibration level, expressed in g2/Hz. This is based on Power Spectral Density.
Bandwidth: The total frequency range of the band. A 50 Hertz bandwidth will be +/- 25 Hertz to each side of the center frequency.
On: The amount of time that the band will be active. This can be set independent of the test duration.

The “On” time is located on the right side of the “Fixed Narrow Bands Editor. Scroll right as shown in Figure 16.

Figure 16: Scroll to the right in the “Fixed Narrow Bands Editor” and enter a “On” time duration.

The profile cannot be fully entered without setting the “On” time higher than the default of zero (0:00:00.00).

In the next section, defining narrow bands of random data that change in frequency is covered.

3.2 Sweeping Narrow Bands

In the Sweeping Narrow Bands tab, a profile with varying frequency narrow bands can be entered. After clicking on the “Edit Sweeping Narrow Bands” button, the interface in Figure 17 is displayed.

Figure 17: Sweeping Narrow Bands Editor.

Before entering the desired narrow band random sweeps, on the left side of the Editor, choose either “Global” or “Individual” as shown in Figure 18 below.

Figure 18: Set Sweep Definition to either “Global” or “Individual”.

If set to “Global”, all sweeping narrow random bands that are defined will use common settings defined in the menu. For example, this setting could be used to set the sweep time the same for all bands. If individual bands need unique settings, select “Individual”.

Possible global and individual settings include:

Sweep mode: Log or linear
Sweep strategy: Up, Down, or Up/Down
Total Sweep Time: Amount of time that the sweep will be active
Number of Sweeps: Number of times sweep will repeat
Time offset: Delay from reaching full random level that sweeping tones will be activated.

If global settings are not used, all the above settings need to be set individually on each sweeping random band.

To add a sweeping narrow band, click on the “Add Band…” button in the Sweeping Narrow Bands Editor.

3. Sine-on-Random-on-Random (SoRoR)

Need to do it all? Wideband random, with narrow band random, with sine tones? Then turn on both the “Random on Random” add-in and “Sine on Random” add-in under “Tools -> Add-ins”.

There will be five separate tabs in the Reference Profile definition! (Figure 19)

Figure 19: Reference Profile Definition of Random Control with both the “Sine on Random” and “Random on Random” add-ins on.

With both add-ins turned on, 50 tokens will be occupied.

Now all these different modes can be run at the same time!

Hope this helps! Questions? Email chris.sensor@siemens.com.

Related Links

KB Article ID# KB000129586_EN_US

Summary Details

Associated Components

SCADAS Durability SCADAS III SCADAS Lab SCADAS Mobile SCADAS PBN SCADAS RS Configuration App SCADAS RS Hardware SCADAS RS Recorder App SCADAS Recorder SCADAS XS

Simcenter Testing Solutions Combined Modes: Sine on Random (SoR), Random on Random (RoR), Sine on Random on Random (SoRoR)

Summary

Details

KB Article ID# KB000129586_EN_US

Contents

Associated Components