J.J. kirjoitti: (9.7.2013 15:58:31)
Joskus olin itsekin kiinnostunut matemaattisista malleista – myös golfsvingin suhteen – mutta en enää jaksa niihin kauheasti paneutua.

Matskua löytyy netistä ihan älyttömästi. Tässä vähän valmiiksi jäsenneltyä taustaa niille, jotka haluavat alkaa miettiä asiaa. Ehkäpä joku on tuhannen viestin aikana tämän ja vastaavia jo aiemminkin postannut. Viitteitä löytyy lopusta paljon.

Golf swing modeling

Kiitokset J.J. Siinä mukavaa iltalukemista. Pisti silmään yksi kohta tuplaheilurin isiltä:

Therefore, some researchers have introduced another hinge in the model representing a simplified shoulder joint. Cochran and Stobbs state that they considered this option when suggesting their model and mention that they found that adding another joint to their model helped to achieve increased club head velocity at impact. However, they concluded that utilizing another joint would make it more difficult to coordinate the segments in a way that would result in an efficient swing.

ja myöhemmin muiden osalta

Unsurprisingly, they were able to demonstrate that if the model configuration was set to ignore physiological muscle limits, higher club head velocities could be achieved. However, the unrealistic, steep changes in joint torque showed that the resulting motion patterns could never be reproduced by real golfers. This shows that the physiological properties of muscle have to be kept in mind when modeling the swing.

Using inverse dynamics, they calculated the joint torques applied by the golfers. Results for the wrist joint were almost the same for both models. For the shoulder joint, however, some characteristics of the individual swings were no longer distinguishable when using the two-link model of the swing.
Iwatsubo et al. [28] concluded that the more complex, four-link model of the swing is better suited to analyze the skill level of golf players.

ja voi kuinka vanhan mieli hyrrääkään lukiessaan tällaista..

Golfers perform their swing in 3-D space, and it is unclear how much the simplified view of regarding the swing as a planar motion influences the results of the studies presented in the previous section. Therefore, potentially more realistic, yet also more complex models have been developed that consider the movement of up to 15 body segments in 3-D space

Using this model, they showed that by keeping the shoulder torque constant, the ki- netic energy of the club head at impact could be maximized if the wrist release coincided with the time point at which the deflection of the oscillating shaft became zero for the second time. Once the optimum release point had been identified, they theorized that additional energy could be transmitted to the club if the players applied a ramp-like shoulder torque profile. They proved that these torque profiles could in fact increase club head velocity and suggested that highly-skilled players could use their full-body motion in order to be able to create these torque profiles

Ja vastaavatpa vielä datan kysmykseenkin DB-mallin puutteista

Typical characteristics of some of the 2-D swing models are:
1. Club head, hands, and a fixed pivot point (‘shoulder’ or ‘neck’) all stay in one static plane for the entire down- swing.
2. There is no translational movement of the pivot point of the upper segment.
3. The distance between the central fixed pivot and the wrist pivot point remains constant throughout the downswing.
4. Only rotations at a small number (two to four) of
simplified joints are assumed to have a meaningful effect on the outcome of the swing; the movement of the rest of the body is neglected.
5. The effect of gravity on the swing dynamics is neglected.
6. The shaft is considered to be rigid.
7. The centre of gravity of the club head is projected to the
tip end of the shaft; there is no offset from the swing plane.
8. The torque profiles that drive the model are simplified.
9. The right arm is not included.
10. Analysis starts from the point at which the downswing commences; the backswing is not included.

Minust on hienoa, että maailmalla jaksetaan asioita tutkia. Samoin on hienoa päästä päivittäin tutkimaan vastaavin tiedoin omien oppilaiden tuotoksia.