STISIM Drive
(SDL) - PI - Performance Index
This event performs the
performance index (PI) task that is built into the simulation. When this option
is chosen, the program will begin to collect various simulation data values
that will be used at the end of the simulation run to compute a performance
index on the driver. The performance index is used to determine if the driver
passed or failed a predetermined set of criteria. The PI event can also be used
to collect sets of data based on time instead of distance. The problem here is
that the final data is averaged over the entire segment and does not include
the individual data points. Furthermore, the data has to be collected in
continuous segments that are each the same length.
When the PI event is used,
STISIM Drive collects data and stores it in individual segments
for use after the simulation run has been completed. You specify the number of
data segments that will be collected and the length of each individual segment.
At the end of the final segment, the simulation run will automatically end, and
all of the data that was collected is used to compute segment mean and RMS
values for each variable. The segment mean and RMS data is then manipulated
using the PI coefficients (found in the STAT.DAT file located on the STISIM
Drive diskette) to determine a score in each of 6 separate categories.
Each of these individual scores is then compared to a predetermined (found in
the STAT.DAT file) pass/fail criteria and the driver is graded on their
simulation run. For additional information on how the PI criteria were
determined, and what the PI event has been used for in the past, see references
9, 10, 11 and 12.
The first segment of every
PI run is automatically discarded, and since the performance index computations
include standard deviation (this means you need at least 2 data segments that
actually have data) the minimum number of segments should be 3. The STISIM Drive Data File section
gives a more detailed description of the PI data that is collected and saved to
the STISIM Drive Data File
that is created at the end of each run, and the computation of the pass/fail
criteria.
A couple of final notes
about using the PI event. When using the PI event, you cannot use the RMSB/RMSE events. If
you do try to use the RMSB/RMSE events, portions of your PI data will most
likely be written over by the RMS data and the final results of the PI will be
useless, and will in all likelihood make no sense. The STAT.DAT file that is
contained on the STISIM Drive diskette must be located in the
directory that STISIM Drive is run from, if it is not, an error
will occur.
EVENT PARAMETERS:
|
PARAMETER 1: |
Not used (set to zero). This remains in the format to keep event files that were created for previous versions of the program compatible with this version. |
|
PARAMETER 2: |
The amount of time, in seconds, of each individual performance index segment. |
|
PARAMETER 3: |
The number of individual performance index segments that will be acquired. The minimum number of segments should be 3. At the end of the final segment, the simulation run will automatically end no matter what longitudinal run distance was specified. |
|
PARAMETER 4: |
Flag that tells the program whether or not to try and use the STAT.DAT performance index criteria file. If this parameter is 0 then the program will use the STAT.DAT file and determine passing or failing, otherwise, the performance index passing criteria will be ignored. |
|
PARAMETER 5: |
This is a crash option flag. The original PI event returns the driver to their initial lane position, but keeps the current speed and does not play any crash recording. The crash flag has the following 2 options: 0 - Use the standard PI
crash |
EXAMPLE:
0,PI,0,120,4,0
In general the PI event is
only used when you are trying to create a task that has requires a pass/fail
criteria. Before you can actually compute a pass/fail, you will need to collect
sample data and analyze it and compute coefficients for use in the STAT.DAT
file. Needless to say this is not an easy task and in general no one uses this
event. However it is included in order to keep it compatible with earlier
versions of the program that actually used the PI event.
In the example shown, the
PI event begins at the beginning of the simulation because its ON DISTANCE
is set to 0. The simulation will run for 480 seconds (4*120) and 4 120 second
segments of data will be collected during the run. Since the final parameter is
0, the STAT.DAT file will be used to compute a pass/fail result.