OpenMotion

6-DOF Motion Simulator (Stewart Platform)

OpenMotion is a real-time 6 Degrees of Freedom (6-DOF) motion simulator that drives a Stewart platform across X, Y, Z, roll (φ), pitch (θ), and yaw (ψ). The desktop app (Qt + ImGui/ImPlot3D) computes inverse kinematics and streams servo commands to an Arduino-based motion base; it can be driven manually via sliders or live from X-Plane Flight Simulator over UDP.

If you scroll down, you will find some information on the journey I went through to put together the physical platform. But thanks to SolidWorks and some 3D printing, I can show you the first full system test with a Flight Simulator (X-Plane). If possible, try not to look at how I wired the power lines :P. Here's the clip:

OpenMotion_first_full_test.mp4

Here is the test for the new and updated GUI that includes a platform simulation independent of any physical platform:

OpenSim_alpha_demo_comp.mp4

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What’s new

• Physical platform assembled and online (servo-driven).
• Inverse kinematics hooked directly to Arduino; end-to-end motion path working.
• X-Plane integration: live telemetry wired in; platform can be driven “From Sim”.
• 3D visualization: ImGuiGLWidget + ImPlot3D render base/top/legs at ~60 Hz.
• Serial I/O: auto-detects Arduino, retries if unplugged, streams CSV angles.
• Telemetry Dock: live roll/pitch/yaw, body rates, and accelerations.
• Safety/robustness: stale-sim watchdog decays pose toward zero; home/zero capture.

Geometry changed slightly after build; the Qt/ImPlot3D model is being updated to match the final hardware layout.

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Past Demos and Test for fun

Servo.test.rig.mp4

Platform.Quick.Test.mp4

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Features

Current

• Manual mode (sliders) and From Sim mode (X-Plane UDP).
• Inverse kinematics → per-servo angles with pairing/inversion and clamps.
• Real-time rendering (~60 Hz) with fixed/auto world bounds.
• Serial protocol: a,b,c,d,e,f\n (0–180°), HOME, PING, echo replies.
• Home/zero from current sim pose; watchdog decays pose when telemetry stalls.

Planned

• Motion cueing filters (washout, gains, limits).
• Geometry/rig editor and calibration tools.
• Smoother servo drives (rate/accel limiting, deadband, microseconds mode).
• Logging, plots, and replay.

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OpenMotion — Quick Start (Linux)

This project is built and run via Qt Creator using the provided OpenMotion.pro. No manual make steps needed.

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Dependencies

Required

• Qt 6.x (or 5.15+) — Widgets + OpenGL
• C++17 toolchain (g++, clang, etc.)
• Eigen (header-only linear algebra)
• Dear ImGui (core + OpenGL3 backend)
• ImPlot3D (already vendored in this repo: implot3d.*)

Recommended (Debian/Ubuntu/Kubuntu)

sudo apt update
sudo apt install qt6-base-dev build-essential cmake git libeigen3-dev

## Notes
- **ImPlot3D** is included; no extra install required.
- **Eigen** is header-only. If `libeigen3-dev` isn’t available, vendor headers into `Libraries/eigen/` and add that to your include path.
- **Dear ImGui** must be available in your include paths along with the OpenGL3 backend (`backends/imgui_impl_opengl3.*`). If you don’t already have it vendored:
```bash
git submodule add https://github.com/ocornut/imgui Libraries/imgui

• Then ensure your .pro includes the ImGui sources and backend.

Build & Run (Qt Creator)

1. Launch Qt Creator.
2. Open Project → select OpenMotion.pro.
3. Select a Kit (Qt 6 preferred).
4. Build → Run.

If Creator complains about missing headers

• Ensure Eigen is installed system-wide (/usr/include/eigen3) or vendored at Libraries/eigen/.
• Ensure Libraries/imgui/ exists (if you added it) and that the .pro file includes ImGui sources and backends/imgui_impl_opengl3.cpp.
• implot3d.* is part of this repo and is compiled with the app.

Configure X-Plane Input

1. In X-Plane, enable UDP Data Output and set the port to match XP_UDP_REC_PORT (see config.h).
2. Enable channels for roll/pitch/yaw (deg), p/q/r (rad/s), and accelerations (m/s²).
3. In OpenMotion, toggle Drive From Sim to feed the platform from X-Plane.

Arduino

• Sketch: stewart_platform_arduino_code.ino
  Pins: 3, 5, 6, 9, 10, 11 • Baud: 115200
• Protocol:
  • CSV: 90,90,90,90,90,90\n
  • Text: HOME, PING
• Odd channels can be inverted; per-channel trims/clamps are available in the sketch.
• Power: Use an external 5–6 V PSU for servos and common GND with the Arduino.

Safety: Verify mechanical limits offline; keep a power cut-off within reach.

Configuration Highlights

• config.h — network ports, update rates, UI defaults
• xplaneudpreceiver.h — minimal UDP receiver for X-Plane telemetry
• ImGuiGLWidget.* — OpenGL + Dear ImGui + ImPlot3D renderer
• mainwindow.* — UI, IK, serial, telemetry dock, drive modes

Current Status

• Hardware assembled and servo-driven platform online
• IK engine driving servos directly (unfiltered signals)
• Platform motion synchronized with X-Plane via OpenMotion
• Geometry adjustments identified for Qt/ImPlot3D model refinement

Next steps

• Update Qt visualization to match revised geometry
• Tune outputs for smoother, stable motion and alignment
• Implement motion cueing filters (washout, gains, limits)

License

GPL-3.0