Add mean motion constraint and use rotation vector as default convention#46
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Refactor MeanMotion constraint internals, improve robustness and performance, and add regression tests. Key changes: - Vectorize finite-rotation prediction and Jacobian assembly to avoid per-node loops and speed up Newton iterations. - Replace manual surface-node mapping with scipy.spatial.cKDTree query and validate exact mapping. - Replace custom element-measure logic with surface_mesh.get_element_volumes() and accumulate weights with np.add.at. - Introduce _phys_dof_index for fast indexing of physical DOFs and simplify/get_total_physical_values and updates to problem._dU. - Remove unused mode_matrix and related code paths; fix projection row mapping using _mode_indices when building MPCs. - Ensure linear-path MPCs pick unique slave DOFs by threading a used_slave_cols set through _make_mpc calls. - Force relinearization for finite_rotation by setting _update_during_inc = True and mark constraint out-of-balance in the NR loop via _bc_residual_norm so convergence gating accounts for BC residuals. - Adjust NR rollback/restart semantics: roll back state on too-small dt (to_start) and keep restart True so failed increments are not finalized. - Misc: small reshapes/array allocation fixes and clearer comments. Also add tests/tests_mean_motion.py containing regression tests that lock in correct projection-row selection, unique slave selection, and finite-rotation behavior.
…nto feature/mean_motion
When finite_rotation is enabled, force _update_during_inc=True so MPCs are relinearized every Newton iteration (finite rotation is nonlinear even on geometry-linear problems where a user set finite_rotation=True). Also simplified the comment in _finite_tangent_and_prediction to note broadcasted ops for node-independent rotation terms. Removed the tests/test_mean_motion.py file (tests for MeanMotion were deleted or relocated).
…nto feature/mean_motion
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Summary
This PR adds a new
MeanMotionconstraint to control selected mean displacement and rotation components using global DOFs.MeanMotioncan be used for displacement-only control throughMeanDisp, rotation control throughMeanRot, or mixed mean motion control. When a surface mesh is passed, nodal weights are computed from surface area/length, making it suitable for face-average constraints. For nonlinear geometry with rotational components, finite rotation is enabled automatically and uses a rotation-vector convention.Main changes
fd.constraint.MeanMotion.nlgeomis active.RigidTieto use the rotation-vector convention (using linearization function from simcoon).RigidTieandMeanMotiontorsion constraints.Validation
tests/test_mean_motion.pytests/test_rigid_tie_rotvec.pyexamples/02-constraints/mean_rigid_motion_torsion.py