Second Experiment: Calibration Testing

Task Description

At least two steps on each side are recorded using the {{XSENS}} for motion data and a digital camera for a visual analysis of single steps. The goal was to test the calibration of the {{XSENS}}.

Materials and Methods

The setup was quite similar to the first experiment, but only one bar was used.

Results

The data from the following tables could be found in the file experiment2-walking.ods.

Declarations

Step Number
starting point, both feed side by side.
Side
left or right foot earlier
Time
time of reading
Time [s]
relative time of reading
Position Straw (Front)
Position of straw (front of straw) on the measuring leash
Position relative
The measuring leash was fixed on the floor with ascending numbers in the walking direction.
Step Length (right/left)
See step length definition considering both left and right foot
Step Length (side)
See side specific step length definition
Accuracy on Photo
Quality of image regarding the accuracy of the measurement point.

The step lengths of all walks have been read from image files taken by a second person.

Walk12

Video of Walk12 showing a person taking walking several steps along a bar.

Visualised Movement Data

{{gallery::images/diagrams/walk12/info-plot.txt?w220}}

Measured Step Lengths

{{table::tables/experiment2/experiment2-walking-walk12.csv}}
Experimental data for Walk12.

Computed Step Lengths

{{table::images/diagrams/walk12/steplengths.csv}}
Computed data for Walk12.
{{gallery::images/diagrams/walk12/info-calc.txt?w220}}

Comparison of Measured and Computed Step Lengths

{{table::images/diagrams/walk12/steplengths-compared.csv}}
Compared steplengths from Walk12.
{{gallery::images/diagrams/walk12/info-comp.txt?w220}}

Walk13

Video of Walk13 showing a person taking walking several steps along a bar.

Visualised Movement Data

{{gallery::images/diagrams/walk13/info-plot.txt?w220}}

Measured Step Lengths

{{table::tables/experiment2/experiment2-walking-walk13.csv}}
Experimental data for Walk13.

Computed Step Lengths

{{table::images/diagrams/walk13/steplengths.csv}}
Computed data for Walk13.
{{gallery::images/diagrams/walk13/info-calc.txt?w220}}

Comparison of Measured and Computed Step Lengths

{{table::images/diagrams/walk13/steplengths-compared.csv}}
Compared steplengths from Walk13.
{{gallery::images/diagrams/walk13/info-comp.txt?w220}}

Free Walk

Video of Walk14 showing a person walking without further disturbance.

Visualised Movement Data

{{gallery::images/diagrams/walk14/info-plot.txt?w220}}

Computed Step Lengths

{{table::images/diagrams/walk14/steplengths.csv}}
Computed data for first steps of Walk14.
{{gallery::images/diagrams/walk14/info-calc.txt?w220}}

Discussion

As shown in Walk13 the calibration was quite accurate, but had some difficulties with the shoes of the person wearing the {{XSENS}}, which likely caused the problems in Walk12. As the feet of the person wearing the {{XSENS}} are quite smaller than the shoes, the contact detection on the ground was not working properly. Reprocessing the data of Walk12 with manual adjustments was found to be time consuming and insufficient.

Conclusion

To record data with high accuracy not only the calibration process, but also the clothes and shoes need to be considered. Accordingly to improve measurement using the {{XSENS}} it is recommended to wear tight fitting shoes. Also the KiC Engine Mode of the {{XSENS}} as described in the MVN User Manual in section 8.2 (page 32) and 18.4 (pages 85-86, MV0391P, Revision B, from May 26th 2010) might improve the quality of measurements on the lower limbs.