MODEL ANGULAR MOMENTUM

For more information on Angular Momentum see [here]

Angular Momentum of a Particle

Given a particle with momentum p = m v.

The angular momentum (L) of this particle about a distal point is:

L= r x p

Model Center of Mass (COM)

The center of mass of an object is a theoretical point where all of the object’s mass can be considered to be concentrated

Compute the Center of Mass of the model from the location of the center of mass of each segment.

Total Mass of the Model

Location of the center of mass of the model.

Segment COM relative to Model COM

Vector from the COM of the Model to the COM of a segment. (e.g. Red vector in the figure above)

Velocity of the COM

Velocity of a Segment COM relative to the laboratory

Velocity of the Model COM relative to the laboratory

Velocity of a vector from the Segment COM to the Model COM in Laboratory coordinates.

Segment Angular Moment in Local Coordinates

Compute in Local Coordinates

= Segment angular velocity in Lab Coordinates

= Segment orientation matrix, which transforms a vector from Lab coordinates to Local coordinates

Compute the segment angular velocity in Segment Local Coordinates

= Segment Angular Momentum in Local Coordinates

Segment Angular Moment in Lab Coordinates

Segment Angular Momentum in Lab Coordinates

Angular Momentum of one Segment Relative to the COM

The angular momentum for one segment about the total body center of mass in Laboratory Coordinates is:

Angular Momentum of Model Relative to the COM

Now that all the angular moment values in a common coordinate system, we can simply add them.

The angular momentum for the total body about the total body center of mass is:

Where N = total number of segments

Note: The tricky calculation is so the algorithm works around this issue by not actually calculating the value.

Courtesy of Fred Yeadon

Much of the contents of this page are courtesy of Fred Yeadon.

Yeadon, M.R. 1993. The biomechanics of twisting somersaults. Part I: Rigid body motions. Journal of Sports Sciences 11, 187-198.

Yeadon, M.R. 1993. The biomechanics of twisting somersaults. Part II: Contact twist. Journal of Sports Sciences 11, 199-208.

Yeadon, M.R. 1993. The biomechanics of twisting somersaults. Part III: Aerial twist. Journal of Sports Sciences 11, 209-218.

Yeadon, M.R. 1993. The biomechanics of twisting somersaults. Part IV: Partitioning performance using the tilt angle. Journal of Sports Sciences 11, 219-225.

Yeadon, M.R. 1993. Twisting techniques used by competitive divers. Journal of Sports Sciences 11, 4, 337-342.