Argus Gate: ROS 2 Airsoft Sentry Turret

Argus Gate is a custom robotic project for an autonomous Airsoft Sentry Turret (Pitch & Yaw). The system uses ROS 2 Humble (running on Ubuntu 22.04) for high-level logic and vision, while a Siemens S7-1214C PLC handles the physical motion with Point-to-Point (PTP) interpolation for precise axis control.

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🧩 System Overview

The Argus Gate system is structured as a modular ROS 2 graph with five functional levels, ensuring safety, modularity, and efficient communication. Each level handles specific responsibilities, from hardware interaction to high-level decision-making.

Architecture Diagram

[GUI Level] (Planned)
    ↓ Subscribes: PlcStatus, Camera Stream
    ↑ Publishes: Mode Requests, Overrides

[Logic Level]
    ↓ Subscribes: TeleopCommand, Perception Data
    ↑ Publishes: PlcCommand
    • Mode Arbitration (IDLE, MANUAL_JOG, MANUAL_TRACK, AUTO_TRACK)
    • Safety Watchdog (Heartbeat Monitoring)

[Teleop Level]
    ↓ Subscribes: sensor_msgs/Joy
    ↑ Publishes: TeleopCommand
    • Maps joystick inputs to turret commands

[Perception Level] (Planned)
    ↓ Subscribes: DepthAI 3D Detections
    ↑ Publishes: Target Setpoints
    • TF2 Coordinate Transformation

[Drivers Level]
    ↓ Hardware I/O
    ↑ Publishes: PlcStatus, sensor_msgs/Joy, DepthAI Data
    • PLC UDP Bridge (100Hz)
    • Joystick Driver (SFML)
    • DepthAI Camera Driver

Levels Description

1. GUI Level (Planned): Web-based dashboard for monitoring and control.
2. Logic Level: Central brain managing modes and safety.
3. Teleop Level: User input processing from joysticks.
4. Perception Level (Planned): Vision processing for autonomous targeting.
5. Drivers Level: Low-level hardware interfaces.

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📦 ROS 2 Packages

The project is organized into the following ROS 2 packages:

• argus_bringup: Launch files and configuration for starting the entire system.
• argus_description: URDF models and STL meshes for robot description and simulation.
• argus_drivers: Hardware drivers and interfaces (includes plc_bridge_node, joystick_driver_node).
• argus_interfaces: Custom message definitions and interfaces (includes TeleopCommand, PlcCommand, PlcStatus).
• argus_logic: Core logic and state management (manager_node).
• argus_teleop: Teleoperation utilities (teleop_joy_node).

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🔄 How the System Works

The Argus Gate turret integrates ROS 2 for high-level decision-making and Siemens PLC for motor control.

Overall Functionality

• ROS 2 Side: Handles user inputs, mode arbitration and communication with the PLC with UDP bridge. It also calculates target positions to reach using TF2 transforms for coordinate transformations.
• PLC Side: It parses incoming commands, controls stepper motors in open-loop via pulse outputs, and sends back status (positions, errors).

Motion Control and PTP Interpolation

Motor control is managed through PLCopen Motion Control (MC) function blocks:

• PTP (Point-to-Point) Interpolation: For positioning moves, the PLC uses PTP interpolation. This moves the axes directly to target positions without intermediate path planning, ensuring fast and accurate point-to-point motion. Coordinated multi-axis moves (pitch + yaw) are handled by the LAxesGrpCtrl function block, which applies kinematics for smooth interpolation and synchronization between axes.

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⚙️ Hardware Details

• ROS2 PC: Raspberry Pi 4 running Ubuntu 22.04.
• PLC: Siemens S7-1214C PLC.
• Motors: 2x Nema 23 Stepper Motors (Pitch & Yaw).
• Drivers: 2x DM542 digital stepper drivers.
• Control Method: The PLC manages the motors in Open Loop using high-speed pulse outputs (PTO).
• Vision: Luxonis OAK-D S2 Depth Camera.

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📐 Mechanical Design & CAD

• Preview CAD Model: Available as turret.stl in the /hardware/cad folder.
• ROS Meshes: STL files for simulation (base_link, pitch_link, yaw_link) in argus_description/meshes.
• Range of Motion: +-120° Yaw rotation / +-45° Pitch.

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🚀 System Capabilities

• ROS 2 Workspace: Standardized modular package structure.
• PLC Bridge: Reliable 100Hz UDP communication with PLC.
• Manual Teleoperation: Full control with Joystick interface.
• Rviz Digital Twin: Real-time 3D simulation and visualization.
• TF2 Integration: Dynamic coordinate transformation for targeting.
• Flet Dashboard: Web GUI for telemetry and remote control.
• Autonomous Tracking: Full-Auto mode using AI vision.

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🛠️ Getting Started

Prerequisites

• Ubuntu 22.04
• ROS 2 Humble (installation instructions: ROS 2 Humble Installation)
• Colcon build tools
• Python 3 and pip

Installation

1. Clone the repository:

   git clone https://github.com/Luca-G49/argus_gate.git
   cd argus_gate_ws

2. Install dependencies:

   rosdep install --from-paths src --ignore-src -r -y

Building the Workspace

colcon build --symlink-install

Running the System

1. Source the workspace:

   source install/setup.bash

2. Launch the system (example launch file):

   ros2 launch argus_bringup gate_launch.py

For specific launch files, refer to the argus_bringup package.

🔗 Third-party Libraries and Dependencies

This project relies on the following open-source libraries and frameworks. We acknowledge and comply with their respective licenses:

• ROS 2 Humble: Apache 2.0 License - ROS 2 Documentation
• SFML (Simple and Fast Multimedia Library): zlib License - SFML Website
• DepthAI (Luxonis): Apache 2.0 License - DepthAI GitHub
• Flet: Apache 2.0 License (for planned GUI) - Flet GitHub

For full license texts, refer to the respective repositories or the LICENSE files in their distributions.

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.