A robotic arm, modeled with one BEAM188 element, is initially aligned along the global Z-axis with one end at the origin. On the node at the origin displacements are fixed, and non-zero rotations are applied in all three directions. Two ways of applying rotations are shown: sequential and simultaneous. Animations are provided to show the differences in results.
The rotations are applied in the following manner:
| Sequential rotations - The beam is first rotated by 60° clockwise about the X-axis, followed by a 90° counterclockwise rotation about the local z-axis, and finally another 90° counterclockwise rotation about the local x-axis. The rotations about each axis are imposed in separate load steps. |
| Simultaneous rotations - The total values for the compound rotations are the same as the sequential case, but the rotations are imposed in a single load step. The beam is rotated by 60° clockwise about the X-axis, by (90°)(sin(60°)+cos(60°)) counterclockwise about the Y-axis and by (90°)(sin(60°)-cos(60°)) clockwise about the Z-axis. |
For the case of sequentially applied rotations, two sample inputs are given: one with imposed rotations and the other with imposed rotational velocities. This demonstrates that the use of imposed rotations and imposed rotational velocities both achieve the same results in a static analysis.