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Arbitrary Waveform Import and Playout on EMA Systems with Shock6 Software

(Credit: S. Neitz, MTS SIE)  

Rev1 :: 2021-09-16

Contents :

Introduction

How to create the CSV file

CSV File Rules

How to create a custom test using the CSV file

How To Inspect The Imported Waveform

How to run the custom test

How to view the output

Shock6 settings that impact importing and running the custom test

Appendix

Complete Example Data Table

 


Introduction:

Shock6 software offers the ability to create a test using a time history of displacement formatted in a CSV file and play it out on the EMA actuator. This is useful for playing segments of recorded track data or arbitrary waveforms that can’t normally be created using the standard test creation options. This document outlines how to create the CSV file, import it into Shock6 and play out the waveform as well as Shock6 settings that will impact the importing and playout of the waveform.

Note: this document is written for Shock6 software version 6.6.8 and above. Older versions of the software may function similarly but are not guaranteed to operate in the same manner.

How to create the CSV file:

The easiest way to create a properly formatted CSV file will be to start with a blank Excel workbook and format it to look like Table 1. The full example data can be seen in Table 2 in the appendix.

Table 1: An example section of data displaying how to format a CSV file in Excel to import as a custom waveform in Shock6.

Time (s)

Displacement (mm)

Analog Out 0 (v)

Analog Out 1 (v)

0

0

1

2

0.1

1

1

2

0.2

2

1

2

0.3

3

1

2

0.4

4

1

2

0.5

5

1

2

0.6

6

1

2

0.7

7

1

2

0.8

8

1

2

0.9

9

1

2

1

10

1

2

1.1

11

1

2

1.2

12

1

2

1.3

13

1

2

1.4

14

1

2

1.5

15

1

2

CSV File Rules:

  • The first row contains column headers
    1. Use descriptive headers including units to make importing the files easier. For example, use the headers such as: Time (s), Displacement (mm), Analog Out 0 (V), Analog Out 1 (V). Use the appropriate units for the data you are importing.
  • The first column must be the time column
    1. The time data must start at a value of 0 and must always be increasing
  • At a minimum, two columns of data are required: time and displacement
  • If analog outputs are configured on the system and should play out a specific waveform during the custom test, include one or two columns of data for those channels (in units of volts)
  • The timestep between data points should be fairly small (0.1s or less, ideally 0.001s)
    1. Data with a time step greater than 1ms will be fit to a spline when played out. If time steps are large (such as 1+ seconds between data points), the resulting spline fit will not accurately represent the desired motion.
  • File length limitation: The ability to sustain playout for “long” periods of time will depend on the PC (and software’s) capability to hold enough information in memory. The rule of thumb is to keep files <120 seconds long.
    1. The CSV file is translated into a cam table file that the A3200 software loads and plays out. The CSV file size is not equivalent to the cam table file size. As the CSV file size increases, the cam table file size does increase.
      • Anything that adds more rows to the CSV file will increase cam table file size
        • Longer duration of test data
        • Higher sampling rate (smaller time step between data points)
    2. The controller’s memory is limited by the nonpaged memory of the PC (which may vary with the PC, OS, etc). This memory limit can’t be exceeded.
    3. The Nservo controller’s limiting factor is the PC’s available nonpaged memory which may vary depending on the PC.
  • System mechanical limitation: EMA systems are not durability systems. The system’s electric motors have a limit to how much heat they can dissipate to the surroundings. Operating the system under moderate to high loads for extended periods of time may exceed the system’s thermal limits, causing motor overheating and system thermal shutdown. The amount of time required for this to occur will depend on testing duty cycle, specimen characteristics, loading, and the waveform profile.

After formatting the Excel sheet as noted above, save the workbook in CSV format by selecting File > Save As and selecting the filetype as CSV

Figure 1: The Excel save as menu noting the CSV file type selection.


 

 

How to create a custom test using the CSV file:

  • Open Shock6.
  • Click the Create Test icon or select Test > Create (Figure 2).

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Figure 2: The two buttons that can be used to create a test.

  • Select Custom (Figure 3).

Figure 3: The custom selection in the Shock6 test type selection window.

  • Select the desired warmup type and enter any additional warmup parameters required based on the chosen selection (Figure 4).

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Figure 4: The warmup selection screen.

  • Select the gas and seal drag test type and enter any additional parameters required based on the chosen selection (Figure 5).

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Figure 5: The gas and seal drag test selection screen.

  • Select “Import drive profile from a file” (Figure 6).

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Figure 6: The custom waveform type selection screen.

  • Select the previously created, properly formatted CSV file containing time, drive and possibly analog output columns of data and headers (Figure 7).

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Figure 7: Select the CSV file to import.

  1. NOTE: Ensure that the file is not open in Excel when trying to import the file in Shock6. If the file is open in Excel when trying to also import it into Shock6, an error will result (see Figure 8), and the file will not be imported.

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Figure 8: The error screen that results while attempting to import the CSV file into Shock6 while it is still open in Excel.

  • Next, assign the data from the CSV file with the appropriate units and role in Shock6.

Figure 9: The profile signal window with improper units before units are assigned.

  • Start assigning units by changing the units of the displacement signal to match the units of the file. Select the “units” row and type or scroll to the appropriate unit (Figure 10).

Figure 10: An example of items in the dropdown menu for the units column

  • Do the same for the analog output channel (if you have included data in the CSV file for them)(Figure 11).

Figure 11: An example of unit selection for the analog outputs

  • Select the appropriate role for each signal. The displacement signal is assigned to the Drive Profile role. The analog outputs are assigned to their corresponding analog output role (if they are included in the CSV file for use on the system).

Figure 12: Selection of the Drive Profile role for the displacement signal

Figure 13: All roles selected for the displacement signal and analog output signals.

  • Click Ok
  • In the parameters window (Figure 14), enter the zero position where the actuator should travel to before starting the custom waveform playout. Enter the amount of damper preload that is typically used (how much the damper is compressed using the crosshead upon specimen installation). Enter the maximum damper travel that is typically used with this test.

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Figure 14: The test offset and displacement check screen.

  1. NOTE: if the zero position, preload and test waveform amplitude add up to a number larger than the damper travel, the test will not be allowed to be saved as the stroke is too big for the damper you intend to use. Revisit these parameters in relation to the stroke of the damper and stroke of the actuator to reformat the test so the actuator travel or damper travel is not exceeded.
  2. NOTE: Do not use more than 1 cycle as it will not repeat the waveform as this is a software bug. Instead, make the CSV file contain any necessary repetitions.
  • Enter a test name and save the test by clicking Finish (Figure 15).

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Figure 15: The name and save the test screen.


 

 

How To Inspect The Imported Waveform

  • At the test control panel, the custom test is now in the list of tests that can be run (Figure 16).

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Figure 16: Note the custom test in the list of tests able to be run.

  • Select “View Wave” while selected on the custom test to see a representation of the waveform to be played out.
    • Note the zero position that the waveform starts at as was set during the end of the test creation (Figure 14). Note the amplitude of the test is as desired and the length of the test in seconds is as desired. Also note the blue and green lines denote the analog outputs, although the values are auto scaled but are represented correctly based on the imported data.

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Figure 17: A preview of the custom waveform.

  • Use the up and down arrow keys to cycle the crosshairs from one signal to another on the chart (see Figure 18 and Figure 19). Use the left and right arrow keys to drive the crosshairs down and up on the time axis of the chart. This allows for inspection of the “Y” value of each profile.

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Figure 18: The up/down arrow keys were used to move the crosshair over to trace the Analog Out 0 signal to verify it contains the appropriate signal.

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Figure 19: The up/down arrow keys were used to move the crosshair over to trace the Analog Out 1 signal to verify it contains the appropriate signal.

  • Click Ok to close the waveform preview.


 

 

How to run the custom test:

  • In the test control panel, click “start test”
  • Enter in any shock parameter info

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Figure 20: The file properties window where test and shock settings and notes can be entered and stored with the test data

  • Enter in the damper travel

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Figure 21: The Dyno starting window which checks test actuator travel against damper travel to ensure no harm occurs

  • Click Ok to run the test and wait until the test completes.


 

 

How to view the output:

  • After the test has completed, view the data
  • Open the Graph > signals vs time menu

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Figure 22: The Graph dropdown with the Signals vs. Time selection highlighted

  • Select the signals to view (hold ctrl and click on the signals you wish to view to highlight them, then select Ok once the desired signals are all highlighted blue).

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Figure 23: The signal selection window for the signals vs time graph

  • Inspect the data plots.
    1. Note: No automated analysis is performed on custom test data.


 

 

Shock6 settings that impact importing and running the custom test:

  • First, open the Shock6 Preferences window (hit the F12 key). With the Preferences window open, hold ctrl+shift and type the letters r e i. A window like Figure 24 will be displayed.
    1. Min cycle time should be 0.
    2. Cycles to sample is not related to custom waveform and may be 3 or 5 depending on other system settings.
    3. Wave editor rate should stay at 1,000.
    4. Match algorithm should be “command and Drive Profile”.

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Figure 24: The REI system parameters window

  • In the top bar select Hardware > Motor.

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Figure 25: The Hardware > Motor dropdown

  • In the popup window select Yes.

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Figure 26: The warning screen that displays when navigating into the Motor settings of Shock6

  • Leave the motor configuration as the selection that pops up normally. Select Configure.

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Figure 27: The motor configuration window

  • In the window that displays, select “Custom Properties” in the lower left hand corner. Then select “Properties” in the list on the upper left below “Gains”. The parameters that impact the custom waveform will all be displayed in the window on the right.
    1. It is not suggested to change any of these properties from the default values
    2. Method: Camtable
    3. Download Period: As Recorded
    4. Run Period: 1.000 ms
    5. Multicycle Transition Speed: 127 mm/s
    6. Profile Tuning Factor: 1.0

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Figure 28: The custom properties selection of the motor settings menu

Appendix:

Complete Example Data Table

Table 2: An example of a complete set of data for a custom waveform

Time (s)

Displacement (mm)

Analog Out 0 (v)

Analog Out 1 (v)

0

0

1

2

0.1

1

1

2

0.2

2

1

2

0.3

3

1

2

0.4

4

1

2

0.5

5

1

2

0.6

6

1

2

0.7

7

1

2

0.8

8

1

2

0.9

9

1

2

1

10

1

2

1.1

11

1

2

1.2

12

1

2

1.3

13

1

2

1.4

14

1

2

1.5

15

1

2

1.6

16

1

2

1.7

15

1

2

1.8

14

1

2

1.9

13

1

2

2

12

1

2

2.1

11

1

2

2.2

10

1

2

2.3

9

1

2

2.4

8

1

2

2.5

7

1

2

2.6

6

1

2

2.7

5

1

2

2.8

4

1

2

2.9

3

1

2

3

2

1

2

3.1

1

1

2

3.2

0

1

2

 

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