Using Test Data
Applying Test Data
Once you reference test data using a spline, you use the INTERP function to apply the spline as a
force (torque) or
motion.
Using an INTERP Function in a Force or Torque
To apply a spline to a force in a dynamic model, you modify the force and specify a function expression that includes an
INTERP function that references the spline. For example, to modify a single-component force (
SFORCE) to use test data that is scaled by -1000, follow the steps below.
To modify an SFORCE:
1. In your model, right-click the Force icon, point to Force:force_name or Torque:torque_name, and then select Modify.
The Modify a Force dialog box appears.
2. In the F(time,...)= text box, enter the following function: where:
■-1000 is the scale you need to apply to the spline data.
■time is the independent variable that specifies what you are interpolating.
■3 is the method of interpolation, which indicates cubic interpolation between data points. 1, which indicates linear interpolation, is also a valid entry.
■spline_name is the name of the referenced spline.
3. Select OK.
Note: | If you enter the function incorrectly, you receive an error when you select OK. Check your function syntax carefully. |
Step 1: | You can specify any expression of time in the first argument of the INTERP function. For example, you can have a spline that references test track data with a 110-second duration, but only simulate the last 30 seconds of this data. The INTERP function in this case would be: INTERP(time+80, 3, spline_name) In addition, you would set the simulation time from 0 to 30 seconds. |
Using an INTERP Function in a Motion
To apply a spline in any motion, you modify the motion and specify an
INTERP function that references the spline. For rotational motion, test data in DAC and RPC III files may be acquired in degrees, so you would add a conversion from degrees to radians (DTOR) in your function expression because Adams Solver expects rotational motion in radians.
To modify a joint motion:
1. In your model, right-click the Joint motion icon, point to Motion:motion_name, and then select Modify.
The impose
Joint Motion dialog box appears.
2. In the F(time,...)= text box, enter one of the following functions:
■For rotational motion: INTERP(time, 3, spline_name)*DTOR
■For translational motion: INTERP(time, 3, spline_name), where:
■time is the independent variable that specifies what you are interpolating.
■3 is the method of interpolation, which indicates cubic interpolation between data points. 1, which indicates linear interpolation, is also a valid entry.
■spline_name is the name of the referenced spline.
■DTOR is the degrees to radians conversion function.
3. Select OK.
If you enter the function incorrectly, you receive an error when you select OK. Check your function syntax carefully.
Browsing RPC III or DAC Data
To assist you in defining a spline using RPC III or DAC file input, you can use the Database Navigator to view file header or detailed data.
To view RPC III or DAC file headers:
2. In Adams View, from the Tools menu, select Database Navigator.
3. In the Filter area of the Database Navigator dialog box, use the pull-down menu to select All.
4. If necessary, widen the Database Navigator dialog box so that you can see the column that specifies the type of object.
5. Select the object RPC_FILE or DAC_FILE.
6. Select OK to open an Information window.
7. If you haven’t selected it previously, select the Verbose check box, and then select Apply.
Tip: You must select the Clear button to erase the data in the Information dialog box. Closing the dialog box leaves the data in the dialog box the next time you open it.
8. When you’re done, select the Close button.
To view RPC III or DAC file data:
1. If necessary, follow Steps 1 through 4 in the procedure above.
2. To expand the object to show the data in the file, double-click the object RPC_FILE or DAC_FILE.
3. Select the desired data channel (note that DAC files only have a single data channel), and select OK to open an Information window. This displays a summary of the data from the header. If you want to see the actual data values continue with Step 4.
Warning: The entire channel of data appears in the dialog box. If the data has millions of data points this could take a significant amount of time to load and display.
4. If you haven’t selected it previously, select the Verbose check box, and then select Apply.
Creating a Spline
You use a spline to reference time history test data in
RPC III Format or
DAC Format. Each spline that you define uses one independent variable (time) and one dependent variable (or channel) from the DAC or RPC III file. By definition, DAC files only contain one channel of data, while RPC III files can contain multiple channels identified by an integer channel number.
This procedure provides a brief overview on how to create splines for use with Adams Durability. Learn more about data element
Splines.
To create a spline:
1. From the Build menu, point to Data Elements, point to Spline, and then select General.
2. In the Spline Name text box, enter the name you want to use for your spline.
3. Right-click the File Name text box, and select Browse.
The Select File dialog box appears.
4. Select the DAC or RPC III file.
Because these files can have any file extension, Adams View opens the file and reads the file header to determine the file type during the verification stage of the simulation. If the file type is RPC III, you must enter a valid channel number in the Channel text box. If no channel or an invalid number is specified for RPC III spline data, Adams View reports an error and stops the simulation.
5. In the Channel text box, enter the channel number you want this spline to use.
Note: | The range of valid numbers is from 1 to the number of channels in the file. |
6. Select OK.
Adams View creates a spline that references the physical test data from the channel in the file.
Notes: | ■Adams View ignores the Linear Extrapolate text box for splines that reference DAC or RPC III files because Adams Durability only allows constant extrapolation of test data. In constant extrapolation, Adams Durability uses the last recorded value in the test file if the simulation extends beyond the duration of the test in the file. ■Adams View ignores the Block Name text box for splines that reference DAC or RPC III files. |
Filtering Test Data
There are two ways to filter your test data stored in RPC III or DAC files:
■Use the Curve Edit Toolbar in Adams PostProcessor to modify the data once the file has been imported and plotted in Adams PostProcessor. For more information, see the
Adams PostProcessor online help.
Referencing Test Data
Here, you'll find information on the types of test data that you can input to Adams Durability, and the method for applying that data to an Adams model. When you input physical data to Adams Durability, you create a Spline data element and define the output channel used to record the data of interest.
Using Adams Durability you can access test data in two formats: