Hugbot: A Robot that Hugs in Exchange for Trash
How This Project Was (Finally) Born
Since the very first day of Fab Academy, I have been having approximately one new final project idea per hour. This resulted in a continuous internal brainstorming process, mild confusion, and a notebook full of crossed-out sketches.
At some point, I decided that my final project should have a real impact on children and help attract them to the Fab Lab. With that in mind, my first serious idea was to build the Death Star from Star Wars.
Unfortunately, after some research, I realised that I did not have access to any suitable planets to test its destructive capabilities, so this idea had to be abandoned.
The next idea was to build a killer robot. It was eye-catching, dramatic, and definitely memorable. However, I quickly discovered that finding volunteers to test a killer robot is harder than expected, especially when safety officers are nearby.
Finally, I decided it was time to change strategy and focus on saving the world instead of destroying it. This led to the current and final idea: a friendly robot that collects trash and rewards good actions with hugs.
The result is a robot designed to promote sustainability, kindness, and curiosity, while creating a positive and memorable experience for children at the Fab Lab. Fewer explosions, more hugs.
My final project is an interactive robot designed to attract children to the Fab Lab Ponferrada and promote environmental awareness. The robot will give a hug as a reward when a child brings and deposits trash in a dedicated container, linking play, technology, and sustainability.
The goal is to create an engaging character that children can interact with, while at the same time introducing them to the Fab Lab, digital fabrication tools, and basic concepts about recycling and caring for their environment.
Research
In this section I will document references to social robots, educational robots, and interactive installations used to engage children in public or educational spaces. I will also review examples of projects that promote recycling and environmental habits through playful interaction.
The research will cover:
- Existing robots designed for children (shape, size, safety, materials).
- Interaction modes: buttons, sensors, voice, lights, movement, and haptics.
- Mechanisms for detecting when trash has been deposited.
- Best practices for safe physical interaction (hugs, proximity, soft parts).
“The main design challenge is to make the robot friendly, safe, and robust enough for repeated interaction with children, while keeping the system simple and reliable for daily use in the Fab Lab.”
Concept and Interaction
The robot will have a clear and simple interaction loop:
- The child approaches the robot and is invited to collect and bring trash.
- The child deposits trash into a container or bin connected to the system.
- A sensor detects the trash (for example, weight sensor, IR sensor or switch).
- The robot reacts with lights, sound, and opens its arms for a hug.
- After the hug, the robot can give a short message about recycling or caring for the city.
The body will be made using digital fabrication techniques (laser cutting, CNC milling, and 3D printing), and covered with soft, safe materials in the hugging area.
2D and 3D Modeling
In this section I will document the design of the robot’s body, arms, base and trash container. The work will include:
- 2D drawings for laser-cut panels (structure, front panel, decorations).
- 3D models for mechanical parts, joints, and housings for electronics.
- Design of the “face” and visual identity of the robot to make it friendly for children.
The models will be created using tools such as FreeCAD and/or Fusion 360, and exported for fabrication in the Fab Lab Ponferrada.
Electronics, Control and Programming
The robot will be controlled by a microcontroller board (for example an ESP32 or a Fab Academy–designed board), connected to:
- Sensors to detect trash deposit (weight sensor, limit switch, or IR sensor).
- Actuators for the arms (servomotors or geared motors).
- LEDs or RGB strips for visual feedback.
- Speaker or buzzer for simple sounds or voice messages.
- Optional proximity or touch sensors for safer hug detection.
The firmware will manage the state machine of the robot: idle, invitation, detection of trash, hug sequence, and closing message. The code and schematic will be documented and shared in the repository.
Fabrication, Assembly and Testing
This section will describe the complete process of making the robot:
- Fabrication of structural parts using laser cutting and/or CNC.
- 3D printing of custom parts such as joints, brackets, and decorative elements.
- Assembly of the body, arms, and trash container.
- Wiring of electronics, sensors, and actuators inside the structure.
- Testing of the interaction flow with children in the Fab Lab environment.
I will document what works, what fails, and the iterations needed to improve robustness, safety, and user experience.
Materials
This table summarises the main components and materials planned for the project. Quantities and prices will be updated as the design is finalised.
| Qty | Description | Approx. Price | Link / Source |
|---|---|---|---|
| 1 | Main microcontroller board (ESP32 / custom Fab board) | 25.00 € | ESP32 |
| 2–4 | Servomotors or geared motors for arms | 40.00 € | Motors |
| 1 | Trash detection sensor (load cell / IR / switch) | 15.00 € | Sensor |
| 1 | LED strip or RGB module | 10.00 € | Led |
| 1 | Speaker or buzzer | 5.00 € | Speaker |
| – | Wood / MDF / plywood for structure | 30.00 € | Local supplier / Fab Lab stock |
| – | 3D printing filament and soft materials for padding | 25.00 € | Local supplier / Fab Lab stock |
Project Update as of 20/03/2026
As of March 20, 2026, the project has undergone a significant evolution both in its conceptual approach and its external design. Following a logo idea contest for FabLab Ponferrada, I decided that the robot should adopt the shape of the official mascot in order to strengthen its visual identity, make it more recognizable, and link it directly to the FabLab’s image.
Reference image used as the basis for the new robot design.
This decision affects not only the aesthetics of the project, but also its technical approach, since it has been necessary to adapt the electronic and functional architecture of the system to a new physical layout inspired by the mascot.
Update of the electronic and functional architecture
As a result of this change, the overall system diagram has been updated from the previous version. In the original architecture, a Raspberry Pi acted as the main controller of the robot, responsible for supervision, processing, and overall coordination of the different subsystems.
The Raspberry Pi remains the core of the system and continues to manage the main perception elements, especially the proximity sensor and the cameras. These devices allow the use of OpenCV to detect nearby people and trigger the robot’s behaviour. In this way, the robot can identify when a person approaches and activate the interaction sequence.
Arm movement is still distributed between two ESP32 modules, one for each arm. This design makes the system more modular, simplifies wiring, and makes it easier to maintain or expand in future iterations. Each ESP32 is responsible for controlling the motors or servos of its corresponding arm in order to perform the hugging action.
Communication between the Raspberry Pi and the ESP32 modules is carried out through MQTT, providing a flexible and scalable architecture. This allows the robot not only to coordinate both arms, but also to manage additional ESP32-based devices that may be incorporated later in the project.
Therefore, the updated diagram represents an adaptation of the previous architecture to a new mascot-inspired physical form. This means redistributing electronic components inside the body, redefining the position of cameras, sensors, and arms, and ensuring that the new structure preserves both the original functionality and a stronger visual identity.
Updated electronic and functional system diagram of the robot.
This change represents an important step forward in the final project, since it combines visual identity, industrial design, and electronic architecture into a single coherent proposal while maintaining the original technological basis of the system.