|
Coordinate System: The coordinate system is
right hand rule. X cross Y gives Z and Roll is right
hand rule about X, Pitch is right hand rule about Y, and
Yaw is right hand rule about Z.
Vector Storage:
All linear three vectors (LinPos, LinVel) store their
values as [X, Y, Z]. All angular three vectors (AngVel)
store their values as [Roll, Pitch, Yaw]. The
transformation matrix TM is stored:
Pre-multiplying a local vector by the TM will generate
the vector in global coordinates.
Multibody Dynamics, Link Numbers and 60 and 20 Length
Vectors:
Please refer to
Multibody Dynamics and 60 Length Vectors for
information on 60
length vectors.
Methodology:
The component models a distance constraint which is
equivalent to a set of spherical joints connected by a
cut massless link. The component forces the linear
accelerations LinAccel1 and LinAccel3 to be equal in the
axis defined by the points LinPos1 and LinPos3. This is
done by adding an algebraic acceleration constraint to
the set of differential equations that represent the
open loop model.
Due to error growth during integration of the joint
angles and positions, a position or velocity
difference can accumulate. The error terms ErrorA and
ErrorB are used to calculate an acceleration difference
between LinAccel1 and LinAccel3 that keeps the distance
constraint at its default length. This acceleration
difference is similar to a proportional derivative
controller which returns the position and velocity
difference to zero. This is a far more robust error
control method than Newton Raphson iterations thereby
reducing the requirement for exact positioning of the
bodies at initialization. |
