SimHub2A6 is a Windows bridge between the SimHub Motion Addon and a custom seven-axis motion rig built with StepperOnline A6 750 W servo motors and drives. SimHub sends calculated actuator positions over UDP; this application validates them and controls the A6 drives over Modbus RTU/RS-485.
The project includes homing, synchronized position updates, four-corner load leveling, load calibration, maintenance controls, greasing reminders, live diagnostics, and CSV motion recording.
The leveling workflow automatically compensates for uneven loads across the rig and keeps the platform balanced during operation. It measures the current load distribution, selects the most suitable fixed reference axis, and applies small corrective offsets to the active actuators until the platform sits within the configured tolerance. This reduces tilt, improves motion fidelity, and helps keep the rig mechanically stable over time.
The grease routine supports periodic maintenance for the rig's moving parts. It tracks operating time, reminds the user when lubrication intervals are due, and lets the operator run a controlled maintenance cycle for the selected axes. The system can record the last greasing event and accumulate runtime so the service schedule remains consistent and easy to monitor.
The analysis tools make it easier to inspect recorded SimHub motion data and verify how the rig behaves in real use. The project can load CSV recordings, plot target values and actual positions, compare motion traces, and highlight signals such as ground deviation or calculated actual position. This is useful for diagnosing setup issues, tuning geometry, and validating motion quality.
The mode selection controls the behaviour of the rig during operation. The available radio-button options let the user switch between normal SimHub-driven motion, actual-position reading, and a centered inactive mode. This makes it possible to test individual axes, inspect actual feedback, or safely move the rig to a neutral centered position without leaving SimHub control active.
A few videos of the rig are available on YouTube: G3org1970
Warning
This software moves high-power machinery. Start with the rig unloaded, use conservative speed limits, and keep a tested hardware emergency stop within reach. Read SECURITY.md before enabling servo power.
This project is designed for a custom seven-axis motion rig driven by StepperOnline A6 750 W servo drives and controlled through Modbus RTU over RS-485. The software acts as a bridge between SimHub motion data and the physical rig, validating incoming positions, applying safety checks, and sending synchronized actuator commands to the servo hardware.
The reference installation uses seven StepperOnline A6 750 W servo axes:
| Axis | Function | Default Modbus group |
|---|---|---|
| 1 | Front traction-loss slide | COM9 |
| 2 | Longitudinal/surge slide | COM9 |
| 3 | Rear traction-loss slide | COM9 |
| 4 | Front-left lift actuator | COM7 |
| 5 | Front-right lift actuator | COM6 |
| 6 | Rear-right lift actuator | COM7 |
| 7 | Rear-left lift actuator | COM6 |
Each A6 drive must have a unique Modbus slave ID matching its axis number. The
default connection is 115200 baud over three RS-485 adapters. Change the COM
ports and axis groups in INI/SimHub2SimRig.ini to match your wiring.
The supplied reference geometry is:
- 990 mm between the left and right lift actuators
- 1660 mm between the front and rear lift actuators
- 200 mm actuator stroke
- 900 mm center-of-gravity height
- 10 mm spindle pitch for axes 1–3 and 5 mm for axes 4–7
These values are installation-specific. Measure your rig and update the INI before moving any axis.
The rig is organized as a four-corner lift platform with a dedicated surge axis and two traction-loss axes. The actuators work together to generate pitch, roll, heave, and longitudinal motion while the controller keeps the load balanced and the safety limits enforced at software and hardware level.
- Windows 10 or Windows 11
- Python 3.10 or newer with Tkinter
- SimHub with the Motion Addon enabled
- Seven StepperOnline A6 750 W servo motor/drive sets
- RS-485 adapters and correctly terminated, grounded Modbus wiring
- Mechanical end stops, drive limits, brakes where required, and a hardware emergency-stop circuit
SimHub supports generic serial/UDP controllers for custom motion systems. Its official Motion Addon getting-started guide explains how to enable the addon and create a platform.
Open PowerShell in the directory that will contain the repository:
git clone https://github.com/Goersch/SimHub2A6.git
cd SimHub2A6
python -m venv .venv
.\.venv\Scripts\Activate.ps1
python -m pip install --upgrade pip
python -m pip install -r requirements.txtEdit INI/SimHub2SimRig.ini before the first run. At minimum, verify every
port, axes, geometry, spindle pitch, stroke, zero offset, speed, and
acceleration/deceleration value.
Run the application from the repository's parent directory because it is a Python package:
cd ..
.\SimHub2A6\.venv\Scripts\python.exe -m SimHub2A6.SimHub2SimRigTo request a clean shutdown from another terminal:
.\SimHub2A6\.venv\Scripts\python.exe -m SimHub2A6.ShutDown- In SimHub, open Add / Remove Features and enable Motion.
- Open Motion → Configure your platform.
- Configure the reference rig as a four-corner 3DOF linear platform plus a dedicated surge axis and dual front/rear traction-loss axes.
- Enter the measured geometry. For the reference rig, use 990 mm width, 1660 mm length, 200 mm lift stroke, and 900 mm center-of-gravity height.
- Add a Generic UDP output controller with seven axes.
SimHub's official controller documentation notes that generic UDP output is intended for DIY or unsupported controllers whose protocol is known. Review the supported controllers and supported motion setups pages before configuring a different geometry.
Use these controller settings:
| Setting | Value |
|---|---|
| Target IP address | 127.0.0.1 |
| Target UDP port | 9999 |
| Controlled axes | 7 |
| Axis resolution | 17 bit (0–131071) |
| Axis format | Decimal string |
| Startup command | START |
| Startup delay | 0 ms |
| Update command | POSITIONS <Axis1> <Axis2> <Axis3> <Axis4> <Axis5> <Axis6> <Axis7> |
| Update command delay | 10 ms |
| Shutdown command | END |
| Shutdown delay | 0 ms |
The command text is case-insensitive in SimHub2A6, but the SimHub placeholders
such as <Axis1> are case-sensitive.
Assign and test one output at a time:
- Axis 1 → front traction loss
- Axis 2 → dedicated surge/longitudinal slide
- Axis 3 → rear traction loss
- Axis 4 → front-left lift
- Axis 5 → front-right lift
- Axis 6 → rear-right lift
- Axis 7 → rear-left lift
Reverse an axis in SimHub only when its physical direction is opposite to the table. Confirm direction at low gain with nobody in the rig.
The included helper checks or updates three values in SimHub's active motion profile:
- Front/Rear Traction Loss smoothing:
15 - Generic UDP update delay:
10 ms - Four-lift geometry actuator spike filter:
135 mm/s
Close SimHub first. Run a preview from the repository directory:
python tools\update_simhub_motion_config.pyIf the detected device, profile, game, and changes are correct, open PowerShell as Administrator and apply them:
python tools\update_simhub_motion_config.py --applyThe helper creates a timestamped backup next to SimHub's
MotionPlugin.GeneralSettingsV2.json and restores it if the write fails.
Profile gains and effects remain rig- and game-specific; begin at low gain and
tune one effect at a time.
- Disconnect mechanical loads where possible and clear the motion envelope.
- Verify the hardware emergency stop disables every drive.
- Configure each A6 slave ID and the INI COM-port mapping.
- Start SimHub2A6 while SimHub motion output is disabled.
- Use Maintenance to home and test one axis group at a time.
- Confirm the displayed actual position and direction.
- Test SimHub's manual axis assignment at minimum gain.
- Only after every axis is correct, enable the complete geometry.
If homing, direction, limits, brakes, or communications are uncertain, stop and remove servo power before troubleshooting.
INI/SimHub2SimRig.inicontains serial, geometry, motion, leveling, greasing, UI, and optional room-light settings.INI/Language.inicontains every user-visible dialog string.INI/grease_data.json,INI/leveling_offsets.json, andINI/simrig_load_values.jsonare generated locally and intentionally ignored by Git. Neutral examples are available inINI/examples/.LOG/andSimHubData/contain local logs and recordings and are ignored.
The room-light URL in the checked-in INI is only a localhost example. Replace it with your own endpoint or do not use the light buttons.
SimHub2A6 listens on the configured UDP address and accepts semicolon-separated ASCII commands:
START
POSITIONS 65535 65535 65535 65535 65535 65535 65535
END
POSITIONS requires exactly seven integers in the configured inclusive range.
START begins motion recording, and END stops it. SHUTDOWN is reserved for
the included shutdown client and returns shutdown status datagrams.
python -m pip install -r requirements-dev.txt
python -m pytest
ruff check .
pyrightGitHub Actions runs the test suite on every push and pull request. Additional developer information is in DEVELOPMENT.md.
The source code is available under the MIT License.
SimHub is a product of its respective owner. StepperOnline and A6 are marks of their respective owner. This independent project is not affiliated with or endorsed by SimHub or StepperOnline. Obtain the current A6 manual directly from the manufacturer; the third-party PDF is intentionally not redistributed here.