Ski deflection measurement during skiing and estimation of ski direction and edge angle |
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| Authors: | Takeshi Yoneyama Nathan Scott Hiroyuki Kagawa Kazutaka Osada |
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| Institution: | (1) Department of Human and Mechanical Systems Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan;(2) School of Mechanical Engineering, University of Western Australia, 35 Stirling Hwy, Crawley, 6009, Australia;(3) Ogasaka Ski Company, 653 Kurita St, Nagano 380-0921, Japan |
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| Abstract: | A new sensor for detecting ski bending and torsional deflection during an actual ski turn on the snow has been developed.
It consisted of bending and torsion sensors connected by light rigid beams. This structure was fixed to the upper surface
of a ski and passed through a tunnel in the central binding plate. The bending and torsion sensors were strain cells, designed
to reject strain orthogonal to the desired measurement direction. The calibration factor for each sensor was determined in
a jig, then the calibration of the overall sensor assembly was checked by static bending experiments and a free vibration
test. A data logger recorded the strain signals synchronously with other data such as the components of the earth’s magnetic
field measured by a sensor on the ski. The data set allowed reconstruction in software of the instantaneous shape, direction
and edge angle of the ski. The purpose of this paper is mainly to introduce the equipment used and methods developed. Tests
of the sensor performance are described. Results from a ski run on snow are presented to show how the various types of data
can be combined. A skilled ski athlete performed long turns with the ski at about 60 km/h on a groomed snow surface at Shiga
Kogen in Japan. The experiment on snow showed that the deformation of the ski was predominantly bending; torsional deflection,
although measurable, had only a small effect on the shape of the running edge. The ski edge adopted a symmetrical circular
bent shape with an unexpectedly small radius when on the outside, but was unconstrained, lightly loaded and nearly straight
when on the inside. |
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| Keywords: | Angle Carving Deflection Measurement Ski Turn |
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