🚗 Realistic Vehicle & Powertrain Simulation (Unity)

High-fidelity vehicle dynamics & powertrain simulation built for realism, modularity, and AAA-grade extensibility.
Data-driven pipeline (ScriptableObjects), deterministic update order, rich telemetry, and plug-and-play subsystems: engine, clutch, gearbox, differentials, tires, suspension, aero, ABS/TCS/ESC.

Target: 90–120 FPS @ fixed Δt = 0.005–0.01 s (Unity 2022.3 LTS)

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📋 Contents

• 🎯 Goals & Principles
• 🧱 System Architecture
• 🌟 Key Features
• 🗂️ Data-Driven Pipeline
• ⚙️ Update Order & Integration
• 🧪 Tuning & Validation Workflow
• 📊 Telemetry Channels
• 🧩 Extensibility Points
• 🎮 Input & FFB
• 🧰 Demo Content
• 🚀 Quick Start
• 📦 Requirements
• 🔒 Quality & Testing
• 📁 Folder Structure
• 🗺️ Roadmap
• ✅ What This Demonstrates
• 📄 License

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🎯 Goals & Principles

• Realism first: physically-meaningful units (N·m, kg, m/s, °C).
• Modular composition: subsystems behind clear interfaces.
• Data-driven: all tuning via ScriptableObjects (no code edits).
• Deterministic: stable fixed-timestep order, repeatable replays.
• Tooling mindset: HUD telemetry, CSV logger, replay/ghost, validators.

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🧱 System Architecture

[VehicleController]
├─ Powertrain
│ ├─ EngineModel (torque curve, throttle, inertia, limiter, stall)
│ ├─ ClutchModel (manual/auto, slip, wear, heat)
│ ├─ Gearbox (H-pattern / sequential, ratios, synchro, shift cut)
│ ├─ Differentials (open / clutch LSD / torsen)
│ └─ Driveline (FWD / RWD / AWD torque split)
├─ Chassis
│ ├─ Suspension (springs, bump/rebound, ARB, motion ratio)
│ ├─ Tires (combined slip, load/camber sensitivity)
│ ├─ Steering (Ackermann, ratio, compliance)
│ └─ Brakes (bias, fade model, ABS)
├─ Control Aids
│ ├─ ABS / TCS / ESC (PID-based, per-wheel)
│ └─ Rev-Match / Auto-Blip / Launch Control / Hill-Hold
├─ Aero & Environment
│ ├─ Drag (CdA) / Downforce (per-axle maps, speed²)
│ └─ Surface μ scaling (dry/wet/ice), aquaplaning threshold
├─ Thermal & Damage
│ ├─ Engine coolant/oil temps, heat soak
│ └─ Clutch/brake fade, tire core/surface temp loops
└─ Telemetry & Tools
├─ HUD overlays, CSV logger, replay/ghost
└─ Asset validators & tuning presets

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🌟 Key Features

Powertrain

• EngineModel: RPM-based torque curve (lookup + spline), engine inertia, throttle dynamics, idle controller, soft/hard limiter, stall.
• ClutchModel: clamp force, friction μ, slip heat & wear, manual & auto-clutch strategies, bite-point calibration.
• Gearbox: H-pattern & sequential; ratios/final drive; synchro timing, shift latency, ignition/throttle cut under load.
• Differentials: open, clutch-type LSD (preload, accel/decel ramps), torsen (bias ratio).
• Driveline: FWD / RWD / AWD; static or dynamic torque split; viscous coupling.

Vehicle Dynamics

• Suspension: per-corner springs, bump/rebound damping, motion ratios, anti-roll bars, travel limits, bump stops.
• Tires: combined slip (long+lat), load & camber sensitivity, temperature-dependent μ; supports empirical or Pacejka-style curves.
• Steering: Ackermann geometry, rack ratio, compliance, return torque.
• Brakes: torque curves, thermal fade and recovery, front/rear bias, ABS (per-wheel slip targets).

Control Aids

• ABS/TCS/ESC (PID) with profiles (Wet/Dry/Sport/Off).
• Rev-Match / Auto-Blip, Launch Control, Hill-Hold (optional).

Aerodynamics & Environment

• Drag (CdA) & downforce (per-axle; speed²; ride-height maps).
• Weather: friction scaling by surface; standing water threshold for aquaplaning modeling.

Thermal & Damage

• Engine coolant & oil loops; heat soak after shutdown.
• Clutch thermal overload → glazing → reduced μ/holding torque.
• Brake temperature → fade curves; tire core/surface temp → μ change.

Tooling

• Telemetry HUD: RPM/gear, wheel slips, tire loads & temps, brake temps, aero forces, aids activity.
• CSV Logger: frame-accurate channels for external analysis.
• Replay & Ghost: deterministic input/state capture & playback.
• Validators: ratios, redline/limiter, axle loads, mass budget.

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🗂️ Data-Driven Pipeline (ScriptableObjects)

Asset	Purpose
EngineData	Torque curve, inertia, throttle, limiter
GearboxData	Ratios, final drive, synchro & shift timings
ClutchData	Clamp force, friction μ, bite-point, auto-clutch
DiffData	Type, preload, ramp/bias
SuspensionData	Spring, damper, ARB, motion ratio
TireCompoundData	μ vs slip/load/temp/camber curves
BrakeData	Brake torque, cooling, fade model
AeroData	CdA, downforce maps, ride-height dependency
AssistProfiles	ABS/TCS/ESC PID gains & slip targets
VehicleConfig	Mass, CoG, wheelbase, weight distribution

Designers tune without code; editor hot-reload supported.

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⚙️ Update Order & Integration

• Fixed timestep simulation (Time.fixedDeltaTime = 0.005–0.01 s).
• Order: Input → Powertrain → Tires/Chassis → Aids → Aero → Thermal → Telemetry.
• Physics in FixedUpdate; visuals in Update (interpolation).
• Optional sub-stepping for high-slip events (launch, ABS).

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🧪 Tuning & Validation Workflow

1. Baseline: mass, CoG, wheelbase → verify static axle loads.
2. Powertrain: import dyno curve; set redline/limiter, engine inertia, idle target.
3. Gearing: choose ratios for target 0-100/Vmax; validate RPM drop per shift.
4. Suspension: front/rear ride frequencies; ARB balance for under/oversteer.
5. Tires: compound selection; calibrate μ vs temp & load to reference behavior.
6. Brakes: bias & torque; ABS slip targets; long-run fade test.
7. Aero: CdA for top speed; downforce & balance for stability.
8. Aids: tune profiles (Wet/Dry/Sport); compare lap deltas.
9. Validation: run asset validators; export CSV telemetry for review.

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📊 Telemetry Channels (Sample)

• Kinematics: speed, accel, yaw rate, slip angles, ride heights, suspension travel.
• Tires: Fx/Fy/Fz per wheel, slip ratio/angle, μ used, surface/core temps.
• Powertrain: engine/input/output RPM, gear index, clutch slip, torque flows.
• Brakes: pressure, temp, fade factor; ABS state per wheel.
• Aero: drag/downforce per axle; aero balance % front.
• Aids: ABS/TCS/ESC enable flags, controller outputs.
• Environment: surface μ, water depth (if enabled), air density.

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🧩 Extensibility Points (Interfaces)

• ITireModel: swap empirical/Pacejka implementations.
• IDiffModel: add active center diff or e-diff/torque vectoring.
• IAeroMap: speed & ride-height-dependent downforce models.
• IController: custom aids (rally ABS, drift mode, yaw control).
• IRecorder: pluggable logging/replay backends.

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🎮 Input & FFB

• Unity Input System: wheel/pedals/shifter bindings.
• Clutch axis with bite-point curve; analog handbrake.
• FFB hooks (aligning torque, load-based cues) exposed for wheel SDKs.

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🧰 Demo Content

• RWD Sports: manual H-pattern + clutch LSD.
• AWD Street: sequential + active torque split.
• FWD Hot-Hatch: open diff tuned with ABS/TCS for torque steer.

Each demo includes tuned ScriptableObjects, telemetry HUD, and lap replay.

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🚀 Quick Start

1. Install: Import the package into Unity 2022.3 LTS project.
2. Create assets: EngineData, GearboxData, ClutchData, DiffData, SuspensionData (4×), TireCompoundData, BrakeData, AeroData, AssistProfiles, VehicleConfig.
3. Setup scene:
   • Add VehicleController to a car prefab with 4 wheel objects.
   • Assign data assets on VehicleController inspector.
   • Ensure Time.fixedDeltaTime is 0.005–0.01; Physics set to Discrete.
4. Telemetry: Enable HUD & CSV Logger in VehicleController → Tools.
5. Drive: Play the scene; use profiles (Wet/Dry/Sport/Off) to verify aids.

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📦 Requirements

• Unity 2022.3 LTS
• Physics: Discrete solver, fixed Δt 0.005–0.01 s
• Scripting: .NET Standard 2.1

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🔒 Quality & Testing

• Unit tests: torque flow, ratio math, limiter & stall behavior.
• Scenario tests: μ-split ABS braking, launch control, long-run brake fade.
• Performance budgets per subsystem; CPU/GPU profiling guides included.
• Deterministic replay verification across platforms/builds.

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📁 Folder Structure

/Runtime
/Core
/Powertrain (Engine, Clutch, Gearbox, Diff, Driveline)
/Chassis (Suspension, Tires, Steering, Brakes)
/Aero
/Aids (ABS, TCS, ESC, Controllers)
/Thermal
/Telemetry (HUD, Logger, Replay, Validators)
/Data (ScriptableObjects)
/Demo (Prefabs, Scenes, Presets)
/Editor
(Inspectors, Validators, Debug Windows)
/Tests
(Unit + Scenario)

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🗺️ Roadmap

• Active center diff & e-diff torque vectoring
• Wet surface film depth → aquaplaning lateral model
• Nonlinear bushing compliance & chassis flex approximation
• Advanced FFB profiles per vehicle archetype

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✅ What This Demonstrates (For Recruiters)

• End-to-end realistic, physically-grounded vehicle systems.
• Modular, interface-driven architecture ready for feature swaps.
• Data-driven workflow enabling fast designer iteration.
• Production-minded tooling: telemetry, replay, validators, tests.
• Performance awareness (fixed Δt, sub-stepping, profiling, budgets).

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📄 License

Copyright © 2025. All rights reserved.