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Universal

Joint allowing two rotational degrees of freedom about two orthogonal axes

 

 

Description

Connections

Parameters

See Also

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,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.

Connections

Name

Description

framea

Joint inboard frame

frameb

Joint outboard frame

Parameters

Symbol

Default

Units

Description

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

0,0

rads

Initial velocity of the joint at the start of the simulation, expressed about the e^1and e^2 axes respectively

InitAngVel

See Also

Joints and Motions

Multibody Overview