OPC UA Controlled Cobot and Conveyor System

This project features a 3D-printable 6-axis collaborative robot (Cobot) and a conveyor belt system, both designed to be controlled remotely via OPC UA servers running on Raspberry Pi. The system is a complete mechatronics project, including 3D CAD models, electronic circuit diagrams, and Python control scripts.

Note: This project is designed to be tested with the OPC UA Fusion application available at roshbeng/opcua_fusion. This client provides a user interface to connect to the servers and execute the defined methods.

Features

• Remote Control: Utilizes the OPC UA protocol for robust and standardized industrial communication.
• Raspberry Pi Based: The control logic runs on Raspberry Pi, leveraging its GPIO capabilities to drive servo motors.
• Complete Design Files: Includes comprehensive CAD models in various formats (.f3d, .step, .ipt, .pdf) for both the cobot and the conveyor.
• Asynchronous Operation: Built with Python's asyncio and the asyncua library for efficient, non-blocking server operation.
• Hardware Control: Directly interfaces with servo motors for physical movement and includes a physical shutdown button for safety.
• Modular: The cobot and conveyor operate as separate, independent systems, each with its own OPC UA server.

Project Structure

.
├── requirements.txt
├── CAD models
│   ├── cobot_model
│   │   ├── cobot individual components in step format
│   │   └── cobot_model_v1_inventor
│   └── conveyor_model
│       ├── conveyor individual components in step format
│       └── conveyor_model_v1
├── opcuaprojectcobot
│   ├── cobot_model_3d_cad_design.png
│   ├── the_electronic_circuit_of_the_cobot_model.PNG
│   ├── opcua_cobot_server.py
│   ├── initialze.py
│   ├── robo_arm_without_opc.py
│   └── shutdownbutton.py
└── opcuaprojectconveyor
    ├── conveyor_model_3d_cad_design.png
    ├── the_electronic_circuit_of_the_conveyor_model.PNG
    ├── opcua_conveyor_server.py
    └── shutdownbutton.py

1. Collaborative Robot (Cobot)

The cobot is a 6-axis robotic arm designed for pick-and-place operations. It is controlled by five servo motors for its joints and one for the gripper.

Cobot Electronics

The cobot is controlled by a Raspberry Pi connected to six servo motors and a physical shutdown button.

Cobot OPC UA Server (opcua_cobot_server.py)

This script creates an OPC UA server on a Raspberry Pi to expose control methods for the cobot.

• Endpoint: opc.tcp://192.168.1.3:4840/cobot_arm
• GPIO Pins Used:
  • Servos: 16, 25, 23, 24, 26
  • Shutdown Button: 6
• OPC UA Methods:
  • move_arm(command_bool): Executes a pre-programmed sequence of movements. Returns True on completion.
  • reference_cobot(): Moves the cobot to a home/reference position. Returns True.
  • stop_cobot(): Stops all servos and initiates a system shutdown of the Raspberry Pi.
• OPC UA Variables & Properties:
  • claw_position: A variable to hold the gripper's position (not fully implemented in the provided script).
  • server_timestamp: A variable that updates every second with the current server time.
  • Manufacturer: "HomeBuiltCobot"
  • Version: "1.0"

2. Conveyor System

A simple conveyor system designed to transport parts. It is driven by a single continuous rotation servo motor.

Conveyor Electronics

The conveyor is controlled by a separate Raspberry Pi, connected to one servo and a shutdown button.

Conveyor OPC UA Server (opcua_conveyor_server.py)

This script creates an OPC UA server to control the conveyor motor.

• Endpoint: opc.tcp://192.168.1.2:4840/conveyor
• GPIO Pins Used:
  • Servo: 18
  • Shutdown Button: 6
• OPC UA Methods:
  • initialize(): Moves the conveyor to an initial/home position. Returns True.
  • move_and_supply(): Runs the conveyor motor to transport items. Returns True.
• OPC UA Variables & Properties:
  • server_timestamp: A variable that updates every second with the current server time.
  • Manufacturer: "HomeBuiltConveyor"
  • Version: "1.0"

3. CAD Models

The CAD models directory contains all the source files for 3D printing and assembly.

• Fusion 360 (.f3d): The primary source files for the assemblies.
• STEP (.step): A neutral format for use in any CAD software. Individual components are also provided in this format.
• Inventor (.ipt, .iam): Native files for Autodesk Inventor.
• PDF (.pdf): 2D technical drawings of the components.

Getting Started

Prerequisites

• Hardware:
  • 2 x Raspberry Pi (3B+ or newer recommended)
  • ~6 x Servo Motors (e.g., MG996R or similar)
  • 2 x Push Buttons
  • Breadboards, jumper wires, and an appropriate power supply for the servos.
  • Ethernet cables and a network switch for direct connection (optional but recommended).
• Software:
  • Python 3.7+
  • Git

Installation & Setup

1. Clone the repository:

   git clone https://github.com/roshbeng/opcua_fusion_test_servers_and_hardware.git
   cd opcua_fusion_test_servers_and_hardware

2. Install Python dependencies:

   pip install -r requirements.txt

   Note: RPi.GPIO can only be installed and used on a Raspberry Pi.

3. Hardware Wiring:

   • For the Cobot Pi: Connect the servo signal wires to GPIO pins 16, 25, 23, 24, 26. Connect the shutdown button to GPIO 6.
   • For the Conveyor Pi: Connect the servo signal wire to GPIO pin 18. Connect the shutdown button to GPIO 6.
   • Ensure all servos and the Raspberry Pis have a common ground (GND). Power the servos with a separate, adequate power supply.

4. Network Configuration: The scripts use hardcoded IP addresses: 192.168.1.3 for the cobot and 192.168.1.2 for the conveyor. You must either:

   • Option A (Recommended): Set up a direct Ethernet connection to your laptop by creating a network bridge. See the section below.
   • Option B: Assign these static IPs to your Raspberry Pis on your existing network.
   • Option C: Modify the endpoint URL in each server script (opcua_cobot_server.py and opcua_conveyor_server.py) to match the actual IP addresses of your devices.

🔌 Connecting Hardware Directly via Ethernet (Network Bridge)

To connect the Raspberry Pi-based hardware directly to the laptop running the client application without an external router, you can create a network bridge.

Network Topology

(Internet) --- Wi-Fi ---> [ Laptop (Running Client) ] --- Ethernet ---> [ Switch ] --- Ethernet ---> [ Pi 1: Conveyor (192.168.1.2) ]
                                                                             |
                                                                              --- Ethernet ---> [ Pi 2: Cobot (192.168.1.3) ]

Laptop Setup Guide

Your laptop must have a static IP address on the same network as the hardware. We will use the 192.168.1.x subnet.

On Windows:

1. Open Network Connections: Press Win + R, type ncpa.cpl, and press Enter.
2. Set Static IP on Ethernet Port: Right-click your Ethernet adapter > Properties > Internet Protocol Version 4 (TCP/IPv4) > Properties. Select "Use the following IP address" and enter:
   • IP address: 192.168.1.1
   • Subnet mask: 255.255.255.0
3. Share Wi-Fi Connection: Right-click your Wi-Fi adapter > Properties > Sharing tab. Check the box "Allow other network users to connect..." and select your Ethernet adapter from the dropdown.

On macOS:

1. Open System Settings > Network.
2. Set Static IP on Ethernet Port: Select your Ethernet adapter > Details... > TCP/IP. Set "Configure IPv4" to Manually and enter:
   • IP Address: 192.168.1.1
   • Subnet Mask: 255.255.255.0
3. Share Wi-Fi Connection: Go to System Settings > General > Sharing. Turn on Internet Sharing. Configure it to share from Wi-Fi to computers using your Ethernet adapter.

Running the Servers

1. On the Cobot Raspberry Pi, run:

   python opcuaprojectcobot/opcua_cobot_server.py

2. On the Conveyor Raspberry Pi, run:

   python opcuaprojectconveyor/opcua_conveyor_server.py

You should see a message indicating that the OPC UA server has started on each device.

Interacting with the System

Use an OPC UA client to connect to the servers and control the hardware. The opcua_fusion project is recommended.

1. Start the client application on your laptop.
2. Connect to the Cobot server endpoint: opc.tcp://192.168.1.3:4840/cobot_arm
3. Connect to the Conveyor server endpoint: opc.tcp://192.168.1.2:4840/conveyor
4. Once connected, you can browse the OPC UA objects and call the methods (e.g., move_arm, initialize) to operate the system.