SQE Robotic Welding Backend

Backend components of the robotic welding project:

Component	Used Technology
Web Framework	FastAPI
Object Relational Mapping (ORM)	SQLAlchemy
Database	PostgreSQL
Database Migrations	Alembic
Testing	pytest

Project Structure

• scripts: Utility scripts for developing
• src: Source code of the backend
  • alembic: Database migrations and configuration of alembic
  • app: Backend application
    • api: Endpoints
    • codegen: Code generation implementation and utility based on Jinja2 templates
    • core: Core functionality, currently only application configuration
    • crud: CRUD base class and CRUD implementation for each entity
    • db: Everything related to the database connection. E.g. session objects or initialization of the databse itself
    • models: Code-First ORM entity classes
    • parser: Custom file parser for reading project files
    • schemas: DTO schemas
    • templates: Pre-defined templates for the codegen
    • tests: Tests for the application

Prerequisites

• Python 3.10+ (only when running locally)
• Docker 20.10+

Building and running

For running as docker, execute from the repository root:

docker compose up -d --build

Or, for running locally, execute from the repository root:

• Install dependencies first: pip3 install -r src/requirements.txt
• Start the database docker compose up -d --no-deps sqe_database
• Run the backend application with uvicorn: cd src && uvicorn app.main:app
• If you want to start the backend in development mode (hot reloading etc.) use uvicorn app.main:app --reload instead

Available variables and functions in templates

The templates are Jinja2 templates. An example template can be found here.

Variables

The following list is an example input for templates:

welding_points": [{
        "id": 1,
        "project_id": 1,
        "robot_id": 1,
        "welding_order": 0,
        "name": "P1",
        "description": "Initial welding point",
        "x_original": 1.57,
        "y_original": 0,
        "z_original": 0.1,
        "x": 1.60,
        "y": 0.01,
        "z": 0.057,
        "x_rel": 1.046,
        "y_rel": -5.54,
        "z_rel": -15.454,
        "roll": 0.2,
        "pitch": 0.1,
        "yaw": 0.05,
        "tolerance": 0.1
    }],
"robot": {
        "id": 1,
        "robot_type_id": 1,
        "project_id": 1,
        "name": "Scratchy",
        "description": "Robot with the scratch on arm",
        "position_x": 0.554,
        "position_y": 5.554,
        "position_z": 15.554,
        "position_norm_vector_x": 0,
        "position_norm_vector_y": 0,
        "position_norm_vector_z": 1,
    }

Data can be accesed in templates with expressions: the robot name can be used as {{robot.name}}, and the first welding point description with {{welding_points[0].description}}. As the welding points are given as list, a loop can be used to iterate over it.

A note about the values x_rel, y_rel, z_rel: These values are the relative x, y and z positions as seen from the robot for this welding point. They are calculated with e.g., x_rel = welding_point.x - robot.x.

Utility functions

There is currently only one utility function available: generate_blockly_block_id(), which returns a 20 characters long random string. It can be used as ID for blockly blocks.