MiniSatellite Testbed
System Architecture
Unity C#
Magnetic Field Physical Simulation
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🧲 Simulation Physics engine core
◇ BiotSavartSolver.cs B-field from coil currents
◇ DipoleFieldGenerator.cs Ideal dipole approximations
◇ FieldVector3Grid.cs Discretized 3D field grid
◇ OrbitalMagneticModel.cs IGRF/WMM orbital B-field ref
◇ TimeStepController.cs Fixed Δt physics loop
🎨 Visualization 3D rendering & overlays
◇ FieldLineRenderer.cs GPU instanced B-vector lines
◇ HeatmapOverlay.cs |B| magnitude color map
◇ SatelliteAttitudeGizmo.cs Quaternion orientation gizmo
🌐 Networking WebSocket comms
◇ WebSocketClient.cs Connect to Python orchestrator
◇ SimStateSerializer.cs JSON / MessagePack packing
◇ CommandReceiver.cs Receive coil current setpoints
🖥️ UI In-editor controls
◇ SimControlPanel.cs Play/pause, field sliders
◇ TelemetryOverlay.cs FPS, |B| readout
→ IN: Coil current commands ← OUT: B-field vectors, torque
WebSocket
Python
Orchestrator — FastAPI + asyncio
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⚙️ Core State machine & config
◇ orchestrator.py IDLE → CONFIG → RUN → LOG
◇ scheduler.py Periodic task dispatch
◇ config.py YAML/TOML config loader
📡 Communication All network bridges
◇ ws_unity_bridge.py WS server ↔ Unity
◇ ws_arduino_bridge.py WS server ↔ ESP32s
🔌 REST API FastAPI endpoints
◇ GET /api/telemetry Latest sensor readings
◇ GET /api/status System health & state
◇ POST /api/command Manual override commands
◇ WS /ws/stream Real-time push to React
◇ messages.py Pydantic: SensorFrame, CoilCmd
◇ codec.py JSON / MessagePack codec
🎯 Control Attitude & field algorithms
◇ attitude_controller.py B-dot / PD detumbling
◇ field_mapper.py Desired B → coil currents
◇ orbit_propagator.py SGP4 / Keplerian orbit model
◇ safety_monitor.py Current limits, thermal WD
💾 Data Logging & sessions
◇ logger.py InfluxDB / CSV writer
◇ session.py Test session mgmt
◇ models.py Pydantic ORM models
→ IN: B-field from Unity → IN: Sensors from ESP32 ← OUT: Coil cmds to Arduino ← OUT: Telemetry to React
REST / Socket
React TS
Telemetry Display — Vite + React 18
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🔗 API Layer REST + WebSocket clients
◇ restClient.ts Axios, retry, interceptors
◇ wsClient.ts Auto-reconnect WS hook
◇ types.ts TS interfaces ↔ Pydantic
📦 Stores Zustand state management
◇ telemetryStore.ts Ring-buffer SensorFrames
◇ commandStore.ts Pending & sent commands
◇ systemStore.ts Connection, session info
📊 Telemetry Components Real-time visualizations
◇ AttitudeIndicator.tsx 3D quaternion globe (R3F)
◇ MagFieldChart.tsx Bx/By/Bz line chart
◇ AccelChart.tsx Accelerometer Ax/Ay/Az
◇ CoilCurrentGauge.tsx 3 radial gauges
◇ SensorTable.tsx Raw numeric table
🎛️ Controls Manual & session controls
◇ ManualOverridePanel.tsx Coil current sliders
◇ OrbitSelector.tsx Orbital scenario picker
◇ SessionControls.tsx Start/stop/export session
🪝 Hooks & Utils Shared logic
◇ useTelemetryStream.ts WS subscription hook
◇ useChartData.ts Downsample / window data
◇ quaternionMath.ts Quat → Euler, SLERP
→ IN: WS telemetry stream → IN: REST snapshots ← OUT: Commands via REST POST
WebSocket (WiFi)
C++ Arduino
ESP32 Firmware — PlatformIO
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🔧 Shared Modules Common to both firmwares
◇ Protocol.h Packed message structs
◇ CRC8.h Packet checksum
◇ PinConfig.h GPIO pin mapping
◇ WiFiManager.cpp STA connect, mDNS
◇ WebSocketHandler.cpp WS client ↔ Python
🧲 Emulator Firmware Helmholtz cage ESP32
◇ CoilDriver.cpp PWM → 3 coil channels
◇ RelayController.cpp H-bridge polarity switching
◇ CurrentSensor.cpp INA219 / ACS712 feedback
◇ StatusLED.cpp WS2812 status indicator
🛰️ Satellite Firmware MiniSat ESP32
📡 SensorHub Aggregate all sensors
◇ Magnetometer.cpp QMC5883L I²C → µT
◇ Accelerometer.cpp MPU6050 I²C → m/s²
◇ IMUFusion.cpp Madgwick → quaternion
◇ Magnetorquer.cpp PWM coil driver + B-dot
◇ Camera.cpp JPEG capture + MJPEG srv
◇ Telemetry.cpp SensorFrame packing
→ Emulator IN: CoilCommand ← Emulator OUT: CurrentFeedback → Satellite IN: TorquerCmd ← Satellite OUT: SensorFrame
⚙ Physical Layer
Magnetic Field Emulator
Helmholtz Cage — 3-Axis
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📟 ESP32 DevKit V1 Main controller
◇ WiFi 802.11 b/g/n Lab router / AP
◇ GPIO 25, 26, 27 PWM → MOSFET drivers
◇ GPIO 32, 33, 34 (ADC) Current sense feedback
◇ I²C (GPIO 21/22) INA219 monitors ×3
◇ GPIO 4 WS2812 status LED
⚡ Power Supply 30V / 10A bench PSU
◇ +V_COIL rail Feeds 3 H-bridges
◇ +5V / +3.3V LDO Logic & ESP32 power
🧲 Coils ×3 (X/Y/Z) Helmholtz pairs
◇ ~100 turns, 15cm radius Per pair
◇ Max field: ~2 mT/axis At center
◇ R ≈ 2Ω, L ≈ 5 mH Per coil
🔌 H-Bridge ×3 BTS7960 / L298N
◇ PWM input Duty → current magnitude
◇ Direction pins Field polarity control
◇ Current sense output Feedback → ESP32 ADC
🛡️ Safety Systems Protection & E-stop
◇ Thermal fuses On each coil
◇ Software watchdog No heartbeat → shutdown
◇ Hardware E-stop Cuts V_COIL relay
MiniSatellite
1U Test Article — Free Rotation
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📟 Main ESP32 WROOM-32 controller
◇ WiFi 802.11 b/g/n Telemetry uplink
◇ I²C Bus Mag + Accel sensors
◇ PWM ×3 Magnetorquer drivers
◇ UART → ESP32-CAM Camera trigger / xfer
◇ ADC Battery voltage monitor
📷 ESP32-CAM OV2640 — 2MP JPEG
◇ MJPEG HTTP server LAN streamable
◇ PSRAM 4MB Frame buffer
◇ microSD slot On-board image storage
🧭 Magnetometer QMC5883L — I²C 0x0D
◇ 3-axis B-field sensing ±800 µT range
◇ Resolution: 0.2 µT 12-bit ADC
◇ Calibration Hard-iron + soft-iron matrix
📐 IMU — MPU6050 6-DOF — I²C 0x68
◇ Accelerometer ±16g Configurable range
◇ Gyroscope ±2000°/s Angular rate sensing
◇ Madgwick / Mahony Attitude fusion → quat
🔄 Magnetorquer ×3 Air-core / PCB coils
◇ N-ch MOSFET + PWM Per-axis drive
◇ Max dipole: ~0.1 Am² Scaled for testbed
◇ B-dot detumble On-board fallback ctrl
🔋 Power System LiPo + LDO
◇ Li-Po 3.7V 1000mAh Main battery
◇ 3.3V LDO regulator Logic rail
◇ Voltage divider → ADC Battery monitoring
📦 Structure ~10cm cube frame
◇ 3D-printed frame PLA / PETG
◇ Air bearing mount Free 3-axis rotation
◇ CoM aligned To rotation point