Progress and minimization of sensory technologies used in wearable systems has enabled
a rich development development of new applications. Information acquired with wearable
sensors can be used in different areas such as medicine, biomechanics, sport, sociology, psychology,
and engineering. A combination of gyroscope, accelerometer, and magnetometer
as an inertial measurement unit is considered to be the most useful for the assessment of
orientation of the body segments and study of the biomechanics of an athlete’s movement.
The raw signals measured by each sensor are processed using sensory fusion to assess the
orientation of the sensor, or simply improve the basic measurement of the sensor’s physical
quantity. In addition to a small size, which makes them wearable, sensors are also energy
efficient and therefore suitable for monitoring athletes over longer periods of time.
Chapter 2 is describing the aerodynamics of a typical ski jump. The technical division of
the jump into stages is described along with aerodynamic forces interacting with the jumper,
and more importantly, their influence on the ski jump length. A brief description of infrastructure
and equipment used for ski jumping is given. Tools and instruments used to study
the biomechanics of the ski jumps and assist the trainers are presented at the end of the chapter.
A special emphasis is given to devices used for measuring the kinematic and dynamic
parameters of the jump. The proposed measuring system can be used in different weather
conditions and seasons.
Chapter 3 describes the wearable measurement system used to analyse the ski jump. The
measurement system consists of 10 inertial measurement units. After attaching the measurement
units to different spots on athlete’s body, the calibration procedure is carried out. The
implemented sensory fusion differs from other applications, since the ski jumper has ground
contact during in–run and does not have the ground contact during different phases of flight.
To estimate the dynamic parameters, a biomechanical link–segment model was developed.
The model uses the Newton–Euler inverse dynamic analysis. The model is composed as a multi–segment rigid body with constant mass. The recursive procedure sequentially calculates
the variables form the first to the last segment in the chain. An automatic procedure for
detection timing of the ski jump is presented.
Chapter 4 presents the results of the experiment, where the ability to measure the kinematic
parameters was verified. The wearable measuring system was used in laboratory environment.
The results obtained from inertial measurement units coincide with the results
of the reference system. The dynamic model was verified using a built–in pressure plate in
the laboratory. This way, different recursive procedures for calculating the joint forces and
moments were tested.
The evaluation of the measurement system and algorithms were carried out on a ski hill,
and the results are presented in Chapter 5. Obtained kinematic parameters match those from
the literature. All calculated forces and torques comply with previous simulation studies.
The proposed system is capable of indirectly providing the values of joint forces and torques
during the ski jump. In addition, the ground reaction forces during in–run and take–off
phases of the jump are provided with comparable precision to the force platform built in the
take off table. This way it is possible to calculate the kinematic and dynamic parameters at
any ski hill, regardless of weather conditions and season.
Chapter 6 presents the possibility of automatic judging of the ski jump performance.
Analysis of the judges guidelines for deduction of points for each jump stage was a starting
point for a mathematicalmodel that can judge the ski jumpers performance. Each stage of the
jump is described and assessed using different parameters, which together give a deduction
sum and thus a final judge rating. At the end of the chapter the results of automatically
determined sum of deduction points for three groups are presented.
The last goal of the dissertation is presenting an analysis of a full set of biomechanical
parameters of the entire jump acquired with wearable measurement system during several
jumps. The results are described in Chapter 7. The analysis is performed for each separate
parameter with correlation to the length of the jump, judge rating and the total score.
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