Universal
Joint allowing two rotational degrees of freedom about two orthogonal axes
Description
Connections
Parameters
See Also
A universal joint, sometimes called a Hooke or Cardan joint, is shown in the diagram below with the two bodies that it connects. A universal joint allows two relative rotations of the two connected frames, about orthogonal axes; this joint type prevents all of the other relative motions of the two frames. In the diagram below, the joint angles, α and β, represent the relative rotation of the end frame,x2y2z2, with respect to the start frame, x1y1z1. In this example, the first rotation, α, is about the x1axis, while the second rotation, β, is about the y2 axis.
The universal joint can be considered as a composite joint comprised of two revolute joints, and an intermediate massless body can be considered the cross. The first rotation occurs about one of the axes of the cross and the second rotation occurs about the second axis.
Name
framea
Joint inboard frame
frameb
Joint outboard frame
Symbol
Default
Units
Modelica ID
e^1
1,0,0
Axis along which the joint allows rotational motion, expressed in the inboard frame
RotAxis1
e^2
0,1,0
Axis along which the joint allows rotational motion, expressed in the outboard frame
RotAxis2
ICθ,ω
Ignore
Indicates whether MapleSim ignores, tries to enforce, or strictly enforces the rotational initial conditions
MechRotTree
θ&conjugate0;0
0,0
rad
Initial rotation of the joint at the start of the simulation, expressed about the e^1and e^2 axes respectively
InitAng
ω&conjugate0;0
rads
Initial angular velocity of the joint at the start of the simulation, expressed about the e^1and e^2 axes respectively
InitAngVel
Joints and Motions
Multibody Overview
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