Update math

[gr812b]

Description
Complete update to the math in the backend, major refactor. Variables names and such but also whole new equations.

This PR performs a major refactor of the CVT simulation “math”/state representation in the Python model and propagates the new schema through the backend API types and frontend consumers (unit conversion, graphs, 3D viewer, and input/session UX).

Changes:

• Refactors backend simulation state to a 4-DOF core (SystemState) and moves kinematic signals into a derived-state layer; restructures outputs into a drivetrain breakdown and adds a termination context.
• Updates traction/slip + pulley dynamics math (torque bounds, axial-force modeling), adds rolling resistance, and introduces new helper utilities for state conversions/integration.
• Updates frontend types, conversion utilities, graph accessors, and UI elements to match the new API shape; improves session/edit/new flows and some layout/visualization controls.

[Copilot]

Pull request overview

This PR performs a major refactor of the CVT simulation “math”/state representation in the Python model and propagates the new schema through the backend API types and frontend consumers (unit conversion, graphs, 3D viewer, and input/session UX).

Changes:

• Refactors backend simulation state to a 4-DOF core (SystemState) and moves kinematic signals into a derived-state layer; restructures outputs into a drivetrain breakdown and adds a termination context.
• Updates traction/slip + pulley dynamics math (torque bounds, axial-force modeling), adds rolling resistance, and introduces new helper utilities for state conversions/integration.
• Updates frontend types, conversion utilities, graph accessors, and UI elements to match the new API shape; improves session/edit/new flows and some layout/visualization controls.

Reviewed changes

Copilot reviewed 66 out of 69 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
frontend/src/utils/conversion/timeStepDataConversion.ts	Converts new derived_state + drivetrain time step shape and adds termination time conversions.
frontend/src/utils/conversion/constantsConversion.ts	Converts newly added inertia + rolling resistance constants.
frontend/src/types/ramp.ts	Updates default ramp segment sign/quadrant conventions.
frontend/src/types/parameter.ts	Updates default parameter ramp configurations to new conventions.
frontend/src/types/graph.ts	Migrates graph accessors/series to derived_state/drivetrain fields and adds external load torque graphs.
frontend/src/types/api.ts	Regenerates/updates OpenAPI-derived schema types to reflect new backend models and fields.
frontend/src/pages/input/Input.tsx	Adds top bar showing selected parameter set + “changes” badge; passes ramp changed-state into ramp builder.
frontend/src/pages/input/Input.module.scss	Styles new top bar/session info and adjusts home button layout.
frontend/src/pages/dashboard/Dashboard.module.scss	Adjusts dashboard layout behavior (overflow/flex shrink).
frontend/src/hooks/useSimulations.ts	Fixes edit flow ordering: clears session params, sets loaded simulation id, sets parameters, navigates.
frontend/src/hooks/useSessionPersistence.ts	Reworks hydration/restore priority (session > loadedId), adds recent-run restore, revises change detection logic.
frontend/src/hooks/useFormState.ts	Keeps form state synced with external context updates (session restore / edit / new).
frontend/src/contexts/ParameterContext.tsx	Simplifies initialization by loading from storage in reducer init; removes load-on-mount action.
frontend/src/constants/defaultSimulations.ts	Updates default simulation ramps and adds a new “Best shift curve” preset.
frontend/src/components/simulationsTable/SimulationsTable.module.scss	Improves table scrolling/flex sizing.
frontend/src/components/scene3DViewer/Scene3DViewer.tsx	Migrates to new drivetrain fields, adjusts angle handling, defaults grids off, adds cross-section clipping toggle.
frontend/src/components/scene3DViewer/Scene3DViewer.module.scss	Styles new cross-section toggle button.
frontend/src/components/rampBuilder/RampPreview.tsx	Improves axis bounds handling for ramps with positive/negative heights; memoizes CSS-derived colors.
frontend/src/components/rampBuilder/RampBuilder.tsx	Adds “changed” badge/header and supports hasChanged prop; wraps internal class styling.
frontend/src/components/rampBuilder/RampBuilder.module.scss	Adds styles for ramp header/changed badge.
cvtModel/test/utils/test_theoretical_models.py	Updates tests for renamed theoretical model methods and ratio naming.
cvtModel/test/utils/test_system_state.py	Updates tests for 4-DOF SystemState and clamping behavior.
cvtModel/test/utils/test_simulation_result.py	Updates tests for 4-DOF solver output parsing/CSV fields and plot default field.
cvtModel/test/utils/test_ramp_config.py	Adds tests for payload coercion/validation (quadrant parsing).
cvtModel/test/simulations/test_belt_simulator.py	Removes belt simulator tests (file deleted).
cvtModel/src/cvt_simulator/utils/theoretical_models.py	Adds sign/rolling resistance helpers, renames geometry accessors, switches to effective radius/ratio methods.
cvtModel/src/cvt_simulator/utils/system_state.py	Redefines solver state as 4 DOF, clamps shift distance in from_array.
cvtModel/src/cvt_simulator/utils/state_computations.py	Adds centralized kinematic conversions + trapezoidal integration helper.
cvtModel/src/cvt_simulator/utils/simulation_result.py	Adds derived outputs (positions/velocities) to CSV writing and updates parsing/plotting for new state.
cvtModel/src/cvt_simulator/utils/simulation_constraints.py	Updates velocity constraint to use computed car velocity; adds mid-shift steady/wake events.
cvtModel/src/cvt_simulator/utils/simulation_args.py	Removes deprecated geometry fields; fixes default secondary ramp factory usage.
cvtModel/src/cvt_simulator/utils/print_progress.py	Removes unused progress-printing utility (file deleted).
cvtModel/src/cvt_simulator/utils/generate_graphs.py	Refactors graph generation to read CSV and output fixed image files via a CLI.
cvtModel/src/cvt_simulator/utils/frontend_output.py	Emits new derived_state, drivetrain, and a structured termination context for the frontend.
cvtModel/src/cvt_simulator/utils/diagnostics/solver_slowdown_diagnostic.py	Adds a diagnostic script for investigating solver slowdowns and transition/event behavior.
cvtModel/src/cvt_simulator/utils/cvt_ratio_utils.py	Renames/expands CVT geometry APIs; adds effective ratio + derivative calculations.
cvtModel/src/cvt_simulator/solvers/shift_initiation/shift_initiation_solver.py	Updates solver logic and documentation for axial-force based shift initiation and new slip API.
cvtModel/src/cvt_simulator/solvers/prim_engagement/primary_cvt_engagement_solver.py	Updates engagement solver to use primary torque bounds with engine torque/inertia inputs.
cvtModel/src/cvt_simulator/models/system_model.py	Replaces prior engine/car breakdown with primary/secondary pulley dynamics breakdown under DrivetrainBreakdown.
cvtModel/src/cvt_simulator/models/slip_model.py	Replaces t_max-based logic with per-pulley torque bounds and traction-limited coupling torque.
cvtModel/src/cvt_simulator/models/secondary_pulley_model.py	Adds a secondary-side angular acceleration model and inertia aggregation.
cvtModel/src/cvt_simulator/models/ramps/theta_ramp_visualization.py	Adds visualization tooling for the new theta-ramp helix representation.
cvtModel/src/cvt_simulator/models/ramps/theta_ramp.py	Introduces ThetaRamp converting helix-angle ramps into circumferential displacement / rotation.
cvtModel/src/cvt_simulator/models/ramps/ramp_preview.py	Updates example ramp preview config to new positive angle/quadrant convention.
cvtModel/src/cvt_simulator/models/ramps/ramp_config.py	Adds robust numeric coercion and quadrant validation for payload parsing.
cvtModel/src/cvt_simulator/models/ramps/circular_segment.py	Updates quadrant semantics/validation and simplifies position-angle mapping.
cvtModel/src/cvt_simulator/models/ramps/init.py	Exports ThetaRamp.
cvtModel/src/cvt_simulator/models/pulley/secondary_pulley_torque_reactive.py	Refactors secondary pulley model to theta ramp helix and returns detailed torque bounds breakdown.
cvtModel/src/cvt_simulator/models/pulley/secondary_pulley_interface.py	Updates geometry/velocity accessors for new effective radius and 4-DOF state.
cvtModel/src/cvt_simulator/models/pulley/pulley_interface.py	Changes pulley force modeling to axial-only + belt centrifugal axial term; introduces torque bounds API.
cvtModel/src/cvt_simulator/models/pulley/primary_pulley_interface.py	Updates geometry/velocity accessors for new effective radius and 4-DOF state.
cvtModel/src/cvt_simulator/models/pulley/primary_pulley_flyweight.py	Updates primary flyweight ramp convention and refactors torque bounds computation + ramp admissibility checks.
cvtModel/src/cvt_simulator/models/primary_pulley_model.py	Adds a primary-side angular acceleration model using engine torque and coupling torque.
cvtModel/src/cvt_simulator/models/model_initializer.py	Rewires model initialization for new primary/secondary dynamics models and theta ramp for helix.
cvtModel/src/cvt_simulator/models/external_load_model.py	Adds rolling resistance and returns force + torque breakdown at secondary; takes full SystemState.
cvtModel/src/cvt_simulator/models/engine_accel_model.py	Removes legacy engine acceleration model (file deleted).
cvtModel/src/cvt_simulator/models/dataTypes.py	Renames/expands breakdown dataclasses for drivetrain, forces, torque bounds, and external load terms.
cvtModel/src/cvt_simulator/models/cvt_shift_model.py	Converts shift dynamics to use axial forces and effective CVT ratio.
cvtModel/src/cvt_simulator/models/car_model.py	Removes legacy car model (file deleted).
cvtModel/src/cvt_simulator/constants/constants.py	Updates friction constant value.
cvtModel/src/cvt_simulator/constants/car_specs.py	Adds inertias + rolling resistance coefficient; updates defaults and exports new constants.
cvtModel/src/cvt_simulator/init.py	Updates public exports to new breakdown type names.
cvtModel/README.md	Documents local simulation + validation graph generation workflow.
backend/app/api/endpoints.py	Adds 400 responses for invalid inputs (ValueError) for /run and /solvers.
.gitignore	Ignores generated plot artifacts directories.

Comments suppressed due to low confidence (1)

frontend/src/hooks/useSessionPersistence.ts:131

• baselineParameters is memoized with [parameters] but reads from storage (getLoadedSimulationId(), getSessionParameters(), etc.). This causes the "baseline" to be recomputed as parameters change and, in the session_baseline case, can effectively move the baseline forward as session storage is auto-saved, making hasChanges() compare against the last save rather than the initially loaded baseline. Consider capturing the baseline once during hydration (e.g., store it in a ref/state in the init effect) and make the memo depend on a stable loadedId value instead of parameters (and update the comment which currently claims it only recomputes when loadedId changes).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.