feat(mechanical): single canonical mechanical spin ODE + bearing friction#9
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…tion - Add dynbem_rs::mechanical (omega_derivative + step_omega) as the one canonical place the rigid-body rotor spin ODE is evaluated/stepped, with Coulomb bearing friction as a first-class parameter. - step_omega is semi-implicit in the aerodynamic torque term (freezes a local damping time constant tau = I*omega/Q_aero), so pure aero drag can never overshoot omega past zero; motor torque and friction are treated explicitly with a zero-crossing clamp so friction alone can't reverse rotation direction. - Fix a real bug: at omega ~= 0, step_omega previously dropped Q_aero entirely, so a windmill/driving torque on a stopped rotor would never spin it up. Both the omega~=0 branch and the invalid-tau fallback now share one full_explicit_step helper. - Add windmill-mode and realistic corner-case unit tests (spin-up from rest, autorotation-entry branch crossing, equilibrium under friction, no chattering near Q_aero sign flips, settle-and-stay-at-rest). - Consistency pass: replace every remaining hand-rolled/duplicate explicit-Euler omega step with the canonical integrator -- quasi_static_bem.rs test, vpm_viz/src/main.rs, envelope/point_mass.py (2 call sites), tests/test_oye.py -- and refresh stale doc comments in aero_io.rs pointing at the old ad hoc formula. - Bump dynbem to 0.7.0 (Cargo workspace + dynbem/pyproject.toml).
…le map - README.md / docs/API.md: replace old omega_derivative + plain-Euler examples (and stale "semi_implicit_step_omega" name) with the canonical step_omega(omega, spin_angle, ...) call. - dynbem_rs/README.md: add mechanical.rs to the module map, fix omega_rad_s / Q_spin field docs to point at crate::mechanical::step_omega instead of the old raw formula, bump the Cargo.toml usage snippet to dynbem_rs = "0.7".
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Summary
Consolidates the rotor's mechanical (rigid-body spin) ODE into one canonical implementation,
dynbem_rs::mechanical, exposed to Python asdynbem.mechanical.omega_derivative/dynbem.mechanical.step_omega, and audits the whole codebase for remaining hand-rolled duplicates.bearing_friction_Nm, default 0.0).step_omegais semi-implicit in the aerodynamic torque term: it freezes a local damping time constanttau = I*omega/Q_aeroover the step, so pure aero drag can never overshoot omega past zero. Motor torque and friction are treated explicitly with a zero-crossing clamp so friction alone can't reverse rotation direction.omega ~= 0,step_omegapreviously droppedQ_aeroentirely, so a windmill/driving torque acting on a stopped rotor would never spin it up. Both theomega~=0branch and the invalid-taufallback now share onefull_explicit_stephelper.Q_aerosign flips, settle-and-stay-at-rest.dynbem_rs/src/quasi_static_bem.rs(spindown time-integration test)vpm_viz/src/main.rs(standalone VPM visualization binary)envelope/point_mass.py(2 call sites)tests/test_oye.py(1 call site)dynbem_rs/src/aero_io.rsthat pointed at the old ad hoc formula.dynbemto0.7.0(Cargo workspaceversion.workspace,dynbem/pyproject.toml).Scope note
This branch was created directly off
origin/main(post-merge of #8) so it contains only the mechanical-ODE work above — no windmill/helicopter BEM branch changes are included since those are already merged.Testing
cargo fmtcargo test --release --workspace— 76 passed, 0 failedcargo check --workspace(post version bump) — clean,Cargo.lockunchanged