Universal

Joint allowing two rotational degrees of freedom about two orthogonal axes

 Description 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,${x}_{2}{y}_{2}$${z}_{2}$, with respect to the start frame, ${x}_{1}{y}_{1}$${z}_{1}$. In this example, the first rotation, α, is about the ${x}_{1}$axis, while the second rotation, β, is about the ${y}_{2}$ 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.

Connections

 Name Description ${\mathrm{frame}}_{a}$ Joint inboard frame ${\mathrm{frame}}_{b}$ Joint outboard frame

Parameters

 Symbol Default Units Description Modelica ID ${\stackrel{^}{e}}_{1}$ $⟨1,0,0⟩$ - Axis along which the joint allows rotational motion, expressed in the inboard frame RotAxis1 ${\stackrel{^}{e}}_{2}$ $⟨0,1,0⟩$ - Axis along which the joint allows rotational motion, expressed in the outboard frame RotAxis2 ${\mathrm{IC}}_{\mathrm{θ},\mathrm{ω}}$ Ignore - Indicates whether MapleSim ignores, tries to enforce, or strictly enforces the rotational initial conditions MechRotTree ${\stackrel{&conjugate0;}{\theta }}_{0}$ $\left[0,0\right]$ $\mathrm{rad}$ Initial rotation of the joint at the start of the simulation,  expressed about the ${\stackrel{^}{e}}_{1}$and ${\stackrel{^}{e}}_{2}$ axes respectively InitAng ${\stackrel{&conjugate0;}{\omega }}_{0}$ $\left[0,0\right]$ $\frac{\mathrm{rad}}{s}$ Initial velocity of the joint at the start of the simulation, expressed about the ${\stackrel{^}{e}}_{1}$and ${\stackrel{^}{e}}_{2}$ axes respectively InitAngVel