Open MicroManipulator: A Sub-Micrometer 3D Motion Control Platform

The Open Micro-Manipulator is an open-source, budget-friendly, and accessible motorized XYZ platform designed to achieve sub-micron precision. This system is ideal for high-precision tasks such as:

• Microscopy
• Probing electronic components
• Optical alignment

🛠 Technical Architecture

The device utilizes a parallel kinematic structure combined with miniature ball joints, which ensures a high degree of mechanical rigidity while maintaining a generous range of motion.

Control & Precision

The system is powered by standard, off-the-shelf stepper motors. These are managed by a closed-loop controller operating at $30\text{ kHz}$ using a highly precise PWM signal.

To push the limits of low-cost hardware, the project employs a "magnetic gearing" technique. This method amplifies the resolution of standard magnetic rotary encoders by a factor of 30, enabling incremental steps as small as $50\text{ nm}$.

[!IMPORTANT] Note: It is critical to distinguish between resolution (the smallest detectable change) and accuracy (how close the position is to the true value).

Software Stack

The platform is controlled via G-Code commands transmitted through a USB serial interface, making it highly compatible with existing automation workflows. The internal firmware features a sophisticated motion planning stack with look-ahead capabilities to ensure paths are followed smoothly and accurately.

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🚀 Getting Started

If you are looking to replicate this build, follow the workflow outlined below:

Build Checklist

• Review the primary documentation and tutorial videos.
• Purchase all components listed in the Bill of Materials.
• Construct the physical frame and electronic circuits.
• Adjust the hw_config.h file to match your specific build.
• Upload the firmware using the PlatformIO plugin in VSCode.
• Perform the axis calibration.

Struggling with the build? Join the community on the project's Discord Server.

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✨ Hardware Evolution: Version 4.0

The latest hardware iteration (v4.0) addresses several shortcomings of the previous design:

Additionally, the FreeCAD model has been overhauled to include all fasteners and pins, serving as a comprehensive mechanical reference.

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💻 Software & Integration

Graphical User Interface (GUI)

A dedicated Python-based GUI is available to simplify operation. It features:

1. Manual Controls: Easy movement of the manipulator.
2. Visual Feedback: Integrated live camera stream.
3. Automation: A built-in G-code runner.
4. Intuitive Input: Real-time control via mouse.

🐍 Python API

For developers, a lightweight API (open_micro_stage_api.py) handles all serial communication. After installing the requirements.txt dependencies, you can integrate the stage into your own code.

Implementation Example:

from open_micro_stage_api import OpenMicroStageInterface

# Initialize interface and establish connection
oms = OpenMicroStageInterface(show_communication=True, show_log_messages=True)
oms.connect('/dev/ttyACM0')

# Calibrate the three joints
for i in range(3):
    oms.calibrate_joint(i, save_result=True)

# Home the device and move to coordinates (x=0.1mm, y=0, z=0) at feedrate 10
oms.home()
oms.move_to(0.0001, 0.0, 0.0, f=10)

# Block execution until movement is complete
oms.wait_for_stop()

Key API Reference

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⚙️ Firmware v1.0.4 Updates

The latest firmware release introduces significant bug fixes and a powerful new feature: Tool Support.

Using the two GPIO pins on the J5 connector of the PCB, users can now integrate tools (e.g., a laser for engraving). These tools are fully integrated into the motion planner for precise timing. The system utilizes the PIO (Programmable I/O) feature to provide hardware-level PWM without taxing the CPU.

Example G-Code for Tool Control:

M3 T0 S0.7  ; Set Tool 0 PWM output to 70%
G4 S0.001   ; Dwell for 0.001 seconds