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Comparing Physical Test Data with Virtual Test Data

 
Importing Physical Test Data
Importing Virtual Test Data
Plotting Data
In this section, you will compare physical test data from a physical model with the virtual test data you generated in this tutorial.

Importing Physical Test Data

This section describes how to import physical test data from tests performed on a physical model in a test lab. The test data represents 10 seconds of motion data sampled at a rate of 51.2 points per second. This data is in RPC III format. There are the following five channels of data in the RPC III file:
■Upper control arm actuator drives data that controls jounce and rebound in the suspension.
■Rack and pinion actuator drives data that controls steer.
■Translational response of the spindle center measured in the global x-direction.
■Translational response of the spindle center measured in the global y-direction.
■Translational response of the spindle center measured in the global z-direction.

To import physical test data:

1. Open Adams PostProcessor.
2. From the File menu, point to Import, and then select RPC File.
The File Import dialog box appears.
3. Right-click the File to Read text box, and then select Browse.
The Select File dialog box appears.
4. Select physical_test.rsp, and then select OK.
5. Select OK.
6. In the RPC III File list, select physical_test.
7. Select the Surf check box.
8. From the Channel list, select Measure_Spindle_1, Measure_Spindle_2, and Measure_Spindle_3, and look at the plots.

Importing Virtual Test Data

Here you import virtual test data from the simulation you performed in the previous section.
Note:  
Virtual test data is stored in DAC or RPC III files and not in the modeling database. However, the DAC and the RPCIII file objects are stored in the database and they reference the virtual test data stored in the DAC and RPC III files.

To import virtual test data:

1. In the Adams PostProcessor File menu, point to Import, and then select DAC Files.
The File Import dialog box appears.
2. Right-click the Files to Read text box, and then select Browse.
The Select File dialog box appears.
3. Navigate to the working directory that you specified at the start of the tutorial (see Step 4 ).
Note:  
This becomes the default directory for any further file selections.
4. Select suspension_instrument_x.dac, and then press the Shift key and select suspension_instrument_z.dac to select all three files.
5. Select Open.
Adams PostProcessor enters the file names in the Files to Read text box.
6. In the DAC Object Name text box, enter instrument.
7. Select OK.
8. Set Source to DAC.
9. From the DAC list, select Instrument.
10. Select Surf.
11. From the File Data list, select REQUEST_1_X, REQUEST_1_Y, and REQUEST_1_Z, and look at the plots.

Plotting Data

Finally, you will compare the virtual test data from your suspension model with physical test data from the physical model of a suspension.

To plot data:

1. Set Source to RPC III.
2. Clear selection of Surf.
3. Select Clear Plot.
4. From the RPC III File list, select physical_test.
5. From the Channel list, select Measure_Spindle_1.
6. Select Add Curves.
7. Set Source to DAC.
8. From the DAC list, select instrument.
9. From the File Data list, select REQUEST_1_X.
10. Select Add Curves.
By default, Adams PostProcessor gives a slightly different scale for the two vertical axes. You need to manually adjust one of them.
11. Select the right vertical axis.
12. Clear the selection of Auto Scale.
13. Change the limits to match the other (left) vertical axis (that is, -75 to 0).
14. Compare the two plots.
15. Similarly, compare:
■Measure_Spindle_2 (RPCIII source) with REQUEST_1_Y (DAC source)
■Measure_Spindle_3 (RPCIII source) with REQUEST_1_Z (DAC source)
The virtual test results and the physical test results should be almost exactly the same, indicating that there is no phase shift, and that the displacement peaks are captured. There is a minor amplitude shift, however, due to possible joint relaxation in the physical test.
Note:  
Since a vibration of about 10-20 Hz was not damped out in the physical test, you will notice noise in the physical test data plots. The noise is most prevalent on the Measure_Spindle_1 and Measure_Spindle_2 plots.