KINEMATIC SEQUENCE – CALCULATION METHODS (P4)
Example Kinematic Sequence Graph
Finally, the TPI 3D kinematic sequence method produces four segmental rotation speeds; pelvis and thorax around their internal anatomical up-down axes; lead upper arm and club around a normal to the instant swing plane of each. The strength of this method is that the local coordinate system of each segment moves with its segment so there are no projection or out of plane errors.
- This method graphs the angular velocity component of each of the pelvis, upper body, and composite arm around a spine axis fixed between the pelvis and upper body segments, then it adds the wrist release angular velocity as the fourth curve; three segments plus one joint. Apples and oranges?
- It forces the pelvis, upper body and “composite arm” to remain in a fixed plane relative to the spine axis line because it projects their lines into that plane; but in a swing they don’t remain in that plane; they tilt out of this plane significantly; this will cause high or low values that don’t really exist (called projection errors).
- The use of the composite arm in this method is a problem since it is a non-rigid segment that is forced to act as if it is a rigid segment; it is not; it is altered by the motions of two shoulders and two elbows. Note that in certain cases it may still be useful if you keep these limitations in mind; AMM also uses this segment in the 4 sensor system because no arms are available; but it is better if you have arms.
- This method graphs the angular velocity components of the pelvis, thorax, lead upper arm and club shaft around the appropriate local segmental axis; all four are segments; it doesn’t mix segments and joints. Each component is calculated around an internal anatomical local axis that moves with the segment. This method does NOT leave the results in the world or global coordinate system.
- The spine is not considered rigid so no out of plane errors occur.
- The lead upper arm is used instead of the composite arm, so the action of the thorax on the arm is seen directly. Note that we can also add the lead forearm as a fifth component of the sequence if we choose; this is especially of interest when there is a bend of the leading arm.