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    Computerized Exercise System

    Ariel Dynamics is proud to introduce the new generation of the revolutionary ACES (Ariel Computerized Exercise System), the most unique system and advanced exercise technology on the market today.
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    The Ariel Performance Analysis System (APAS) is a video-based 3D motion analysis system. APAS can capture video from multiple cameras simultaneously and perform a biomechanical analysis automatically.
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Stationary Test

Page
Published on Sunday, March 2, 1997 by Gideon Ariel

 

Stationary Test 0-cm

   The stationary test measured the ability of the system to maintain static measurements when a moving marker passed in the vicinity of a stationary marker.  With most marker-based systems, this is a major problem which necessitates human intervention to manually correct the problem.  The point is, a stationary marker should not move.

PIC00020.jpg (44205 bytes)
Slide 19. Measures from Static Marker. (Slide was photographed in the original presentation)

   This important test measures the influence of a moving marker on a static marker, which remains immobile, or on another marker.  Theoretically, movement analysis should minimize noise created by movements which do not actually exist.  Slide 19, illustrates the moving markers relative to the stationary marker.

TestStationary

    Rank Max Rank Markers Rank Total Rank Sub-Total
  0 cm Score Error Score Crossed Score Error Score Score
Ariel 0.140 5 0.245 5 No 5 0.385 5 20
Motion 0.147 4 0.604 4 No 5 0.751 4 17
Peak *** 0.282 2 1.183 2 Yes 0 1.465 3 7
Qualisys 0.299 1 3.206 1 No 5 3.505 1 8
Vicon *** 0.183 3 1.725 3 Yes 0 1.908 2 8

2-cm-separation

   Slide 20 illustrates the error for the 0-cm separation.  Motion Analysis performed the best and the APAS was second.  Peak and Vicon were unable to keep the markers on track so there was switching of the markers.   However, the investigator of this research chose not to include these errors in the statistical analysis.  If these measurements had been included in the statistics, the error would be much larger !!!

Slide 20. RMS Error at 0-cm separation. (Slide was photographed in the original presentation)

PIC00024.jpg (36819 bytes)

   Table 4 illustrates the data for the 0-cm separation.  As can be seen, the APAS system performed the best with an average error amounting to 1.4 mm in a 3000 mm volume.  This result was the lowest of all other companies.  The maximum error amounted to 2.4 mm, again the lowest of all companies.  For both Peak and Vicon, only a subset of the data points were used since the markers crossed and switched.

Table 4. 0-cm test results

***Markers crossed, only subset of data which was properly indentified was use for analysis.

    Rank Max Rank Markers Rank Total Rank Sub-Total
  2 cm Score Error Score Crossed Score Error Score Score
Ariel 0.210 2 0.588 2 No 5 0.798 2 11
Motion 0.153 3 0.571 3 No 5 0.724 3 14
Peak *** 0.256 1 1.623 1 Yes 0 1.879 1 3
Qualisys 0.054 4 0.210 5 No 5 0.264 5 19
Vicon *** 0.083 5 0.458 4 Yes 0 0.541 4 13
 

 

 

[Go to Home Page] [Top] [Back]  [Next Page - Results] .

 

   Slide 22 shows the incredible error the Peak and Vicon produced in tracing markers. This means that when markers approach approximately 1 cm distance from each other, neither the Peak nor the Vicon system can detect the difference between the markers.  The APAS was able to do a perfect job. Markers were never switched regardless of the distance between them.  Even at a  0-cm separation, which means no separation, the APAS system was able to detect the markers.

PIC00023.jpg (37914 bytes)
Slide 22. Marker Switching at 1-cm Separation.
                   (Slide was photographed in the original presentation)

 

   As can be seen in Slide 21, the APAS system out performed all of the other systems.  As was seen previously with other conditions, both Peak and Vicon demonstrated problems with a switching of the targets although the largest error was observed in the Qualisys system.

PIC00026.jpg (36748 bytes)
Slide 21. Maximum Error at 0-cm Separation



    

   In the 2 cm separation test, Qualisys had the smallest total error.  Vicon and Peak again had a problem with switching of the points between the stationary and the moving targets.  However, in spite of this crossing problem, they were given a score.  One should keep in mind that the error is only 2 mm in 3M volume.  This is approximately a .06 percent error. INCREDIBLE !!!

 

Table 5.  2-cm separation test results

Reference: /topics2/apas/comparison/stationary_test.htm
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Stationary Test

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