Simcenter Testing Solutions Single Axis Waveform Replication (SAWR)
Summary
Details
Direct YouTube Link: https://youtu.be/Pj_srqdVPaU
This article is an introductory guide to perform a test in the Simcenter Testlab Single Axis Waveform Replication (SAWR) Workbook. The article covers the minimum requirements to set up and execute a test. The SAWR test mode plays an imported time domain signal, either from field data or lab created data, on a shaker.
Contents include:
1. Shaker, Amplifier, and Controller Setup
2. Starting Simcenter Testlab Single Axis Waveform Replication Control
2.1 Setting the Shaker Definition
2.2 Saving the SAWR Workbook Project File
2.3 Worksheet Ribbon
3. Channel Setup Worksheet
4. SAWR Setup Worksheet
4.1 The Control Pane
4.2 The SAWR Profiles Pane
4.3 The Schedule Pane
4.4 Status Indicator
4.5 Optional: Create a Time Signal in Time Signal Calculator
5. System Identification and System Verification
6. SAWR Control
7. Post Test: Batch Printing
1. Shaker, Amplifier, and Controller Setup
A closed loop Single Axis Waveform Replication (SAWR) test consists of several components as shown in Figure 1.
Figure 1: Diagram of closed loop shaker control items.
Components include:
- Controller Computer: PC with Simcenter Testlab installed. Vibration signals are shown on the screen in real-time during the test.
- Simcenter SCADAS Hardware: Hardware that digitizes incoming analog accelerometer signals and outputs analog signal to amplifier/shaker.
- Amplifier/Shaker: The SCADAS analog output is input into the amplifier and shaker to vibrate the test object.
- Test Object: Product or device under test (also called DUT).
- Control accelerometers: The control accelerometer is actively monitored during the test to maintain a specified vibration profile.
- Measurement accelerometers: Accelerometers on test object that monitor vibration at other locations aside from the control.
The Simcenter SCADAS must be equipped with a control card ending with “-V”. The “-V” option (short for vibration control) indicates that the sources are equipped with an extra safety that will always shutdown gradually as not to damage the shaker or test object.
There is a “STOP” connector that must be in place for the Simcenter SCADAS to be able to output an analog signal from the source. The stop is shown in Figure 2 below:
The stop can be hooked up to a DAC shutdown as shown in Figure 3.
Figure 3: DAC Shutdown.
The DAC shutdown has a large yellow or red button that can be used to quickly stop a test in progress.
2. Starting Simcenter Testlab Single Axis Waveform Replication Control
To start the Simcenter Testlab Single Axis Waveform Replication control workbook, look in the “Testlab Environmental” folder. With the Simcenter SCADAS connected and turned on, double click on the “Single Axis Waveform Replication” icon as shown in Figure 4:
The Single Axis Waveform Replication software requires 43 tokens to run if using token licensing. More about token licensing in the knowledge article: Simcenter Testlab Tokens: What are they, and how do they work?.
2.1 Setting the Shaker Definition
After the control software is started, choose “Tools -> Options -> Shaker” to make sure the correct shaker is selected for the test as shown in Figure 5.
The shaker configuration menu lets important physical limits of the shaker be entered (maximum displacement, maximum acceleration, frequency range, etc). The Single Axis Waveform Replication software will check any vibration profiles to ensure that no shaker limits will be exceeded during a vibration test.
If the appropriate shaker is not listed, it will need to be setup. Press the “Configure” button and enter the appropriate information for the shaker being utilized.
2.2 Saving the SAWR Workbook Project File
After starting the software, choose “File -> Save As” to create a project file as shown in Figure 6.
Figure 6: Choose "File -> Save As..." to store project and its settings. Use the worksheets at the bottom of the screen from left to right to setup and execute a test.
The project (*.lms) can be stored in any directory.
While using the Simcenter Testlab software, the test setup parameters (frequency range, settings, vibration profile, etc) and any data collected will be stored in the project file.
2.3 Worksheet Ribbon
The bottom ribbon of the SAWR Workbook interface has several worksheet tabs, as noted in Figure 6. The worksheets can be utilized from left to right to setup, perform, and then document a test.
3. Channel Setup Worksheet
In the “Channel Setup” worksheet, all accelerometer sensor information can be entered as shown in Figure 7.
Each row in the table corresponds to one sensor input:
- Control/Measure: At least one channel must be set as the control channel. Multiple channels can be set as control for use as average or extremal control. Channels marked as control will be used as the reference measurement location for the target vibration profile.
- Measurement Information: The location of the channel and engineering unit.
- Transducer Information: Transducer model, serial number, sensitivity.
Some additional channel setup resources:
4. SAWR Setup Worksheet
To define a SAWR setup, Click on the "SAWR Setup" tab in the workflow bar (at the bottom of the project window) as shown in Figure 8.
Note: At this point in the workflow, the status message in the bottom of the SAWR Setup worksheet should read “Add an existing profile to the profile table or create a new profile” as shown in Figure 9. If not, the Channel table has not been fully defined with a control channel.
Figure 9: Status message.
The minimum requirements to define a SAWR setup are:
- Set the desired control parameters in the “Control” pane.
- Define a valid target trace in the “SAWR Profiles” pane.
- Set the SAWR profile in the “Schedule” pane.
- After all the required parameters in both the SAWR Setup and Channel Setup worksheets are defined correctly, the Setup Status turns green and displays "verification OK".
4.1 The Control Pane
The Control pane (Figure 10) defines the parameters that will be used for control. The minimum required settings are the Control Strategy, Min. frequency, Max. frequency and Frequency Resolution. All other parameters can be left at their default settings.
The control strategy drop down determines what strategy will be used for control during a test. The four available options are:
- Open Loop: During open loop control replay, no corrections are made to the drive and the Inverse Transfer Function (ITF) is not updated. The open loop control strategy generates a drive based on the available Inverse Transfer Function and the target trace and plays the drive from the previous replay.
- Iterative: During iterative control, the drive signal is generated from the previous replay's drive and a time domain correction for the error between the target trace and the measured control response is applied.
- Offline Adaptive: During offline control, the drive is generated based on the available ITF and the target trace. At the end of every replay, the ITF is updated. The updated ITF is used for the next replay.
- Online Adaptive: During online adaptive control, the ITF is updated during replay. The generation of the drive is based on the target trace and the most recent available ITF. The updates of the ITF are determined by the statistical degrees of freedom parameter.
- Min. frequency: The lowest frequency of the control test. Lower frequencies are removed from the target trace, ITF, measurement results, and the generated drive.
- Max. frequency: The highest frequency of the control test. All higher frequency signal content is removed from the target trace, ITF, measurement results, and the generated drive.
- Frequency resolution: The frequency resolution parameter determines the sample rate at which data is acquired. The frequency resolution for the control algorithm and the measured data are both affected by this setting.
4.2 The SAWR Profiles Pane
The SAWR Profiles pane is located at the bottom left of the screen. It is used to define the time history to be used for the control (Figure 11):
To create a profile, click the “Create Profile” button in the SAWR Profiles pane. This will open the Profile Editor as seen in Figure 12.
Figure 12: The Profile Editor dialogue.
To create a Target Profile:
- Click “Select Source Trace” and navigate to an .ldsf file with the desired recorded data (Figure 12, Area 1).
- To display the source data properties, select the “Use source trace” radio button, and click the “Update” button (Figure 12, Area 2).
- Enter the desired preprocessing parameters and select “Update Profile” (Figure 12, Area 3).
- The Profile name is entered in the Target Profile Properties pane. Best practice is to use a distinctive name, especially when defining more than one Target Profile (Figure 12, Area 4).
4.3 The Schedule Pane
The schedule pane (Figure 13) is located on the right hand side in the middle of the screen.
Figure 13: Schedule pane of SAWR Setup worksheet.
The schedule pane is where the target profile is selected from the list of available target traces in the drop-down list, as indicated in Figure 13.
4.4 Status Indicator
If all parameters have been entered correctly, the Status Indicator (Figure 8, Area 7) will display “Verification OK” as seen in Figure 14. If not, the Status Indicator will display what parameter need to be adjusted.
Figure 14: Status indicator displaying the “Verification OK” message.
4.5 Optional: Create a Time Signal in Time Signal Calculator
A target trace can be created using the Time Signal Calculator. To use the Time Signal Calculator, first the corresponding add-in must be enabled in the Tools>Add-ins menu as shown in Figure 15.
Figure 15: Loading the Time Signal Calculator Add-in.
After the Add-in is loaded, the time signal calculator should appear in the Time Data Selection Worksheet as seen in Figure 16.
Figure 16: Time Data Selection Worksheet (bottom) with the Time Signal Calculator (left bottom) displayed.
To generate a Random signal, use the “GENERATE_RANDOM” and “FILTER_BP” formulae to create a pre-processed time trace that can be used as a target trace in SAWR.
Suggested parameters are indicated in Figure 17.
Figure 17: Time Signal Calculator interface with suggested parameters.
Once the desired time signal parameters are entered, click “Calculate” to create the time signal. The created time signal is shown in the Data Set pane with the view check box highlighted in orange.
Figure 18: The “Save As…” dialogue in the Time Data Selection Worksheet.
The last step is to click “Save As…” to save the created time signal. This will open the “Save As…” dialogue as seen in Figure 18. This saves the time signal to the project file, which can be navigated to when creating a target time trace.
More information on the Time Signal Calculator can be found here:
5. System Identification and System Verification
After finishing setup successfully, the next step is System Identification and Verification. Select the Worksheet at the bottom of SAWR as shown in Figure 19:
Figure 19: The System Identification Worksheet with Min. and Max. source voltages and the “Start” button displayed.
The System Identification Worksheet is particularly important as the data acquired during System Identification is used to calculate the shaker system Inverse Transfer Function (ITF) that is used for control. Generally, the default voltage values are too conservative. A Min. RMS and Max. RMS of 0.02 V and 0.06 V respectively is suggested as a next step should the default values prove too conservative, however each shaker system is different and good judgement should be applied when selecting these parameters.
To start the System Identification, click the “Start” button as indicated above.
After the process is complete, move to the System Verification worksheet as shown in Figure 20.
Figure 20: System Verification worksheet.
Review the system identification results (FRFs, coherence, etc).
More information: Vibration Control: System Identification and Verification
6. SAWR Control
The next step is to run the test. Navigate to the SAWR Control Worksheet as shown in Figure 21.
Figure 21: The SAWR Control Worksheet with the “Arm” and “Start” buttons indicated.
To start a test, click the “Arm” button, and then the “Start” button. The status message to change to “Running” for the duration of the test. The diagonal line in the upper right display indicates the error between the actual drive and the target. The closer it is to a true diagonal, the more faithful the replication.
7. Post Test: Batch Printing
After the test is finished, a report can be made quickly using the Batch Reporting worksheet (Figure 22):
Figure 22: Batch Reporting worksheet.
After highlighting the test, click on the Print button to make the report. Use “File -> Print Options” to select the desired printer or a Powerpoint/Word file for the report.
There are two ways to change the Siemens logo to a different logo in Batch Printing:
- Edit the files directly in C:\Program Files (x86)\Simcenter\Testlab {revision}\central\Application Resources. This will change the logo for anyone using the computer.
- Copy them to your local Application Resources directory (C:\Simcenter \UserConfiguration\{user}\Testlab {revision}\Application Resources) and edit the logo file. This will change the logo for the user login only.
Logo.bmp is the Siemens logo in the top right corner.
LmsHeading1.bmp is the Header you see in the top left corner in some versions of Simcenter Testlab.
Questions? Email william.flynn@siemens.com or post a reply to this article.
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