Run a Half-Car Study
- Open Study and select Half Car · 4 DOF. Quarter Car remains available for Transient, Frequency, Explore, Compare and Motion.
- Start with the generic passenger-car parameters. Adjust body and suspension groups; tire, unsprung and initial-state controls are under Advanced inputs.
- Use Front then rear for a smooth bump that excites pitch, Same at both axles for symmetry, or Independent to prescribe both axle roads.
- Run Half-Car Study. Inspect body, pitch, suspension and tire responses, then export the completed evidence.
Road timing is scenario generation
The rear delay is wheelbase divided by speed: (a + b) / (speed in km/h / 3.6). The default 2.7 m wheelbase and 32.4 km/h speed yield 0.300 s. Speed must be 1–250 km/h, and both events must finish within the study duration. The solver consumes two explicit road definitions; speed is not part of the equations.
Equations and sign convention
Upward-positive displacements are offsets from static equilibrium. Pitch θ is positive nose-up. Front and rear suspension deflections are δf = zs + aθ − zuf and δr = zs − bθ − zur. Each suspension force is F = kδ + cδ̇.
State order: body heave, heave velocity, pitch angle, pitch rate, front unsprung displacement and velocity, rear unsprung displacement and velocity. Authoritative states use metres, seconds and radians. Model: vehiclelab.half-car.linear-passive v0.1.0; fixed-step RK4 v0.1.0.
Generic parameters
| Parameter | Value | Unit |
|---|---|---|
| Sprung mass | 1200 | kg |
| Pitch inertia | 2000 | kg·m² |
| CG to front axle | 1.2 | m |
| CG to rear axle | 1.5 | m |
| Front suspension stiffness | 30000 | N/m |
| Front suspension damping | 2500 | N·s/m |
| Rear suspension stiffness | 32000 | N/m |
| Rear suspension damping | 2700 | N·s/m |
| Front unsprung mass | 60 | kg |
| Rear unsprung mass | 65 | kg |
| Front tire stiffness | 220000 | N/m |
| Rear tire stiffness | 230000 | N/m |
Evidence, units and freshness
Five separate plots keep heave displacement, heave acceleration, pitch angle, suspension travel and tire deflection on unambiguous axes. Front is solid and rear dashed. Display converts displacement to mm and pitch to degrees. CSV exports all 19 original channels in SI with stable unit-labelled columns, without smoothing or resampling.
The persistent Engineering Report action exports the last completed record and marks it stale after physics-affecting edits. Restoring the exact definition makes it current again. Switching models clears incompatible results. PNGs use the shared 1600 × 1000 Canvas2D renderer; PDFs use the same plots and never rerun physics.
Reproducible projects
The additive vehiclelab.project.v1 model union preserves existing quarter-car files. Half-car files contain definitions and project metadata only. Import restores explicit front/rear roads in Independent mode and preserves all initial states; run again to create authoritative results. Invalid files leave the workspace unchanged.
Model boundary
This is a small-angle, linear passive longitudinal half-car with generic parameters and prescribed road contact. It has no roll, lateral dynamics, nonlinear suspension, tire contact loss, active control or measured vehicle correlation. Independent numerical verification is not physical validation.
Half Car supports Transient Study only. Frequency, Explore, Compare and Motion remain quarter-car capabilities; no half-car pitch animation or video export is provided.