Published March 27, 2026 | Version v3
Other Open

A Low-Cost Platform for Measuring Backlash in Popular UART Servos

Authors/Creators

Description

This repository contains the source code and data analysis scripts for the research paper **"A Low-Cost Platform for Measuring Backlash in Popular UART Servos"**.

The project presents an open-source test stand for characterizing backlash in low-cost UART servo actuators (Feetech, Waveshare, etc.) using controlled force application and telemetry logging.
---

📂 Project Structure

 

```text
├── cad/                         # Hardware design files (.step and .stl)
├── logs/                        # Output directory for telemetry data (CSV)
├── software/
│   ├── backlash_test/
│   │   ├── .env                     # Environment variables
│   │   ├── .gitignore               # Git ignore rules
│   │   ├── app.js                   # Main Node.js controller application
│   │   ├── config.js                # Serial port configuration
│   │   ├── package.json             # Node.js dependencies and scripts
│   │   ├── sweepConfig.js           # Configuration for motion sequences
│   │   └── TelemetryLogger.js       # Module for CSV data logging
│   ├── logs_analysis/
│   │   ├── config/                  # Example config files
│   │   ├── log_calc.py              # Calculates backlash statistics based on provided CSV log file
│   |   ├── log_viz.py               # Generates visualisation from provided CSV log file
│   |   ├── config_utils.py          # Some common utilities used by analysis and visualisation scripts
```

 

🛠 Hardware Requirements

To reproduce the experiments, you will need:

  • Servos: 2x Feetech STS3215 (puller motors) + 1-2 servos for device under test.
  • Controller: USB-TTL Adapter (e.g., Feetech or Waveshare USB-TTL) connected to a PC.
  • Power Supply: 7.4V or 12V DC power supply (2A minimum).
  • Mechanical Assembly: 3D-printed servo holders and 100mm test levers (see paper for details).

🚀 Getting Started

1. Controller Setup (Node.js)

The Node.js application manages the servos, executes motion profiles, and logs telemetry.

Prerequisites: Node.js (v18+), NPM.

```bash
cd software/backlash_test

# Install dependencies
npm install

# Configure environment variables
# Create a .env file or set these manually
export SERIAL_PORT=COM3           # Or /dev/ttyUSB0 on Linux/Mac
export SERIAL_BAUD_RATE=1000000
```

Running the Experiment:

To start the control loop and logging:

```bash
node app.js
```
  • Configuration for motion patterns and servo IDs is located in `sweepConfig.js`.
  • Logs are automatically saved to the `logs/` directory.

2. Motor analysis utilities

Prerequisites: Python 3.8+, numpy, pandas, plotly.

`log_calc.py` handles motor-analysis scenario by reading a JSON configuration that describes which motors define the analysis phase window, which motors should be reported, and the stretched/relaxed targets for the actuated motors.

Run the script by passing the config and the log CSV:

```bash
python logs_analysis/log_calc.py logs_analysis/config/config_m1_m2.json /path/to/log.csv
```

`log_viz.py` uses the exact same config files to decide which motors to plot (from `report_motor_ids`) and which actuators provide the relaxed/stretched overlays. Invoke it the same way:

```bash
python logs_analysis/log_viz.py logs_analysis/config/config_m1_m2.json  /path/to/log.csv
```


📄 Research Paper

The full text of the research paper is located in the `paper/` directory.
You can compile it using any standard LaTeX distribution (TeX Live, MiKTeX) or online editor (Overleaf).


👥 Author Information

Boris Kotov
  • Senior Software Engineer, Robotics Control Systems.
  • Email: [boris.k@robonine.com](mailto:boris.k@robonine.com)
Company: Robonine
  • Developing accessible robotic solutions for education and research.
  • Website: [robonine.com](https://robonine.com)

 

📜 License

  • Hardware: Creative Commons Attribution 4.0 International (CC BY 4.0)
  • Software: GNU GPL v3.0
  • Documentation: Creative Commons Attribution 4.0 International (CC BY 4.0)

 

You are free to share and adapt the material as long as appropriate credit is given.

Abstract

Open-source test stand for measuring backlash in low-cost UART servo actuators (Feetech, Waveshare). Includes 3D-printable fixtures, Node.js controller, and Python analysis tools. ~$80-100 total cost.

Files

Measuring-Backlash-in-Popular-UART-Servos-main.zip

Files (603.2 kB)

Additional details

Software

Repository URL
https://github.com/roboninecom/Measuring-Backlash-in-Popular-UART-Servos
Programming language
Python , JavaScript
Development Status
Active