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|Title: ||Measurement of grip force and evaluation of its role in a golf shot|
|Authors: ||Schmidt, Erin R.|
|Issue Date: ||2007|
|Publisher: ||© Erin R. Schmidt|
|Abstract: ||This study was conducted with the aim of establishing a method to measure time-varying
forces at multiple locations at the hand-grip interface, using this method to record how golfers
of varying abilities grip the club during a standard tee shot and investigating a potential link
between the variations in vibration seen at the grip and the grip force applied near impact. It is
hoped that additional knowledge about grip force during a golf shot will lead to improved
training techniques and grip design in the future.
An assortment of technologies were available for the measurement of grip force, but thinflexible
sensors were chosen as they could be applied to the grip or gloves without altering the
characteristics of the club. Reliability and performance for these sensors were not well
established and, therefore, a novel set of tests were developed to evaluate their capabilities.
Thin-film force sensor performance was examined under controlled laboratory conditions to
give an indication of each sensor's quasi-static accuracy, hysteresis, repeatability and drift errors,
dynamic accuracy and drift errors, and the effects of shear loads and surface curvature. With
this newly developed set of tests, five varieties of thin-film force sensor utilizing four different
technologies were assessed.
The sensors had varying levels of success under the controlled conditions of the evaluation
tests. Three of the sensors performed well under static and quasi-static loading conditions, with
accuracy errors of 10% or less, hysteresis errors near 6%, repeatability near 6% or below, and
drift at 60 s after load application under 15%. Two of these sensors were further tested and
demonstrated little change in sensor output to loads applied over curved surfaces, although
shear sensitivity and dynamic accuracy errors were more substantial. It was also found that
some of the sensors lost sensitivity with repeated loading. Even with these drawbacks, the
potential of these sensors to provide useful grip force information was clear.
With an understanding of sensor performance in controlled laboratory settings, one sensor
type was used to determine regions of peak pressure at the hand-grip interface and three others
were used in player tests to obtain time-varying measurements of grip force during a swing.
During the player tests, grip force was measured for 10-12 tee shots and impact time was
determined Total force was computed for each shot taken by summing the force output of all
the sensing elements positioned on either the grip or gloves. When these total force traces were
aligned by impact and plotted for each of the golfers tested, an interesting and previously unreported phenomenon became apparent. Each player appeared to have their own grip force
'signature', i.e. total grip force for a particular golfer was very repeatable, but varied considerably
between golfers. A grip force signature existed for all players tested regardless of ability, and the
level of consistency for an individual golfer and the similarities between golfers was analysed
using a cross correlation. It was found that nearly all of the golfers tested had swings that were
dominated by the left hand, and that the most notable contributions of the right hand occurred
after impact. Variations in grip force were also related to key phases of the swing using high
speed video footage.
Previously it has been noted that for the same ball, club, and impact location that the
vibration on the shaft is remarkably consistent for many different golfers but there is a much
greater variation in the vibration at the grip. It was hypothesized that the way a golfer grips the
club affects the way vibration is transmitted into their hands and arms. A final set of player tests
was therefore conducted with the aim of identifying how grip force affects vibration
transmission from the shaft to the hands and the players' perceptions of this vibration.
Vibration was measured on the shaft just below the grip and on the golfer'S left thumbnail, force
was monitored at 18 locations on the hands, and impact location and clubhead speed were
recorded. Each golfer's perceptions of the vibration caused by impact were also noted for two
standard drivers. It was found that changes in the amount of vibration travelling from the shaft
into the hands is affected by the grip force applied by the golfer. This is the first study to
analyse the effects of grip force on vibration transmission into the hands and arms due to a golf
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University|
|Appears in Collections:||PhD Theses (Mechanical, Electrical and Manufacturing Engineering)|
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