A multibody dynamic model of the cross-country ski-skating technique
Bruzzo, John (2012)
Diplomityö
Bruzzo, John
2012
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe201209208129
https://urn.fi/URN:NBN:fi-fe201209208129
Tiivistelmä
The objective of this thesis is the development of a multibody dynamic model matching
the observed movements of the lower limb of a skier performing the skating technique in
cross-country style. During the construction of this model, the formulation of the equation
of motion was made using the Euler - Lagrange approach with multipliers applied to a
multibody system in three dimensions.
The description of the lower limb of the skate skier and the ski was completed by employing
three bodies, one representing the ski, and two representing the natural movements of
the leg of the skier. The resultant system has 13 joint constraints due to the interconnection
of the bodies, and four prescribed kinematic constraints to account for the movements
of the leg, leaving the amount of degrees of freedom equal to one.
The push-off force exerted by the skate skier was taken directly from measurements made
on-site in the ski tunnel at the Vuokatti facilities (Finland) and was input into the model
as a continuous function. Then, the resultant velocities and movement of the ski, center
of mass of the skier, and variation of the skating angle were studied to understand the
response of the model to the variation of important parameters of the skate technique.
This allowed a comparison of the model results with the real movement of the skier.
Further developments can be made to this model to better approximate the results to the
real movement of the leg. One can achieve this by changing the constraints to include the
behavior of the real leg joints and muscle actuation. As mentioned in the introduction of
this thesis, a multibody dynamic model can be used to provide relevant information to ski
designers and to obtain optimized results of the given variables, which athletes can use to
improve their performance.
the observed movements of the lower limb of a skier performing the skating technique in
cross-country style. During the construction of this model, the formulation of the equation
of motion was made using the Euler - Lagrange approach with multipliers applied to a
multibody system in three dimensions.
The description of the lower limb of the skate skier and the ski was completed by employing
three bodies, one representing the ski, and two representing the natural movements of
the leg of the skier. The resultant system has 13 joint constraints due to the interconnection
of the bodies, and four prescribed kinematic constraints to account for the movements
of the leg, leaving the amount of degrees of freedom equal to one.
The push-off force exerted by the skate skier was taken directly from measurements made
on-site in the ski tunnel at the Vuokatti facilities (Finland) and was input into the model
as a continuous function. Then, the resultant velocities and movement of the ski, center
of mass of the skier, and variation of the skating angle were studied to understand the
response of the model to the variation of important parameters of the skate technique.
This allowed a comparison of the model results with the real movement of the skier.
Further developments can be made to this model to better approximate the results to the
real movement of the leg. One can achieve this by changing the constraints to include the
behavior of the real leg joints and muscle actuation. As mentioned in the introduction of
this thesis, a multibody dynamic model can be used to provide relevant information to ski
designers and to obtain optimized results of the given variables, which athletes can use to
improve their performance.