Applications and Implications, Project Development
What does it do?
My final project is a wearable robotic hand exoskeleton designed to assist individuals in rehabilitating hand movement. The exoskeleton uses MG995 servo motors to replicate the flexion and extension of the fingers via a tendon-based mechanism. The design is lightweight and partially flexible thanks to the use of TPU and PLA materials. The device can be controlled through a physical button, aiming to offer autonomy and promote muscular reactivation during therapy sessions.
Who's done what beforehand?
This project is inspired by several previous hand exoskeleton systems developed for rehabilitation and assistive purposes. One example is the Exo-Glove Poly developed by Seoul National University, which uses tendon-driven actuation for finger movement. Other open-source designs, such as the Hand of Hope and the OpenExo platform, contributed ideas for motor control and ergonomic design. These references helped inform both the mechanical and electronic design decisions for my custom exoskeleton.
What did you design?
- A CAD model of the hand exoskeleton with a modular and parametric finger system.
- Mechanical mechanism driven by tendons for finger actuation.
- An integrated control system using MG995 servos and microcontroller integration.
- A PCB that controls the system, designed and manufactured with the XiaoESP32C3.
- A portable support structure adapted to the user’s hand size (15 cm x 9 cm).
4. What materials and components will be used?, Where will they come from?, How much will they cost?
This is the current Bill Of Materials (BOM):
Materials and Components
🔩 Electronics and Mechanical Components
| Component | Supplier / Link | Approx. Cost (MXN) | Notes |
|---|---|---|---|
| TPU Filament 1.75 mm (1 kg) | MercadoLibre | $320.00 | Flexible material for 3D printing the exoskeleton |
| Nylon Thread 0.60 mm (100 m) | MercadoLibre | $62.00 | Used as tendon for finger movement |
| OLED Displays 128x32 I2C (2 pcs) | MercadoLibre | $115.00 | Used to display system data |
| AMS1117-5V Voltage Regulators (10 pcs) | MercadoLibre | $49.00 | Only a few units used |
| AMS1117-3.3V Voltage Regulators (10 pcs) | MercadoLibre | $49.00 | Only a few units used |
| MG995 Servo Motor | MercadoLibre | $89.00 | High torque, ideal for finger movement |
| Female Header 40 pins (10 pcs) | MercadoLibre | $39.00 | For interconnecting modules |
| Male Header 36 pins | Steren | $15.00 | For soldering to circuit board |
| Phenolic Board 10x15 cm | Steren | $24.00 | Used for manual circuit assembly |
| 60/40 Tin-Lead Solder (17 g) | Steren | $25.00 | For soldering components |
🧰 Components Provided by the FabLab Ibero Puebla (Free of Charge)
| Component | Quantity / Use | Cost | Notes |
|---|---|---|---|
| Xiao ESP32-C3 | 1 unit | $0.00 | Main microcontroller |
| 4.7µF SMD Capacitors | Several | $0.00 | Used for voltage filtering |
| SMD PushButtons | Several | $0.00 | Used for user interaction |
💰 Total Estimated Cost
Purchased Components Total: $787.00 MXN
FabLab Provided Components: $0.00 MXN
What parts and systems were made?
So far, I have designed, milled, and soldered the PCB. I am currently testing the motors to ensure they work properly. I also designed and printed the fingers and the hand structure where the tensioning mechanism will be attached to the motors. The design is about 70% complete and undergoing some final modifications.
What processes were used?
- 2D and 3D design
- Additive and subtractive fabrication processes
- Electronics design and production
- Embedded microcontroller interfacing and programming
- System integration and packaging
What questions need to be answered?
My main question is about the placement of the motors on the wrist. Even though I have a clear idea, I need to find a way that is comfortable for the user.
What worked? What didn't?
From everything I’ve done so far, the hand and finger design and printing worked well. There are a few tweaks needed, but they’re minor. The PCB is also functioning and undergoing testing. I still need to design the housing for the motor mechanism, which I believe I will laser cut. However, I need to make a decision on that soon.
How will it be evaluated?
The project will be evaluated based on its ability to assist hand movement effectively and safely. Key criteria include the functionality of the tendon mechanism, responsiveness to control input, comfort and wearability, and the integration of electronics. Evaluation will also consider the quality of documentation, the use of digital fabrication processes, and overall project coherence.
What tasks have been completed?
- Design and printing of the mechanical components (fingers and hand base).
- Design, milling, and soldering of the PCB.
- Testing individual components like the MG995 motors and XiaoESP32C3.
- Initial tendon mechanism setup and alignment with servos.
What tasks remain?
- Final testing of the integrated system.
- Assembly of the motor housing structure.
- Fine-tuning of the tendon tension and calibration.
- Programming of the button-based control logic.
- Ergonomic adjustments for better user comfort.
What has worked? What hasn't?
- Worked: The finger design and printing, PCB fabrication, servo testing, and tendon-based actuation setup.
- Hasn't worked (yet): Final placement of the motors on the wrist remains a challenge. Some mechanical parts need ergonomic refinement.
What questions need to be resolved?
The main question is the optimal placement of the servo motors on the wrist to maintain comfort while ensuring precise tendon movement. I have a preliminary concept, but it requires testing and ergonomic validation.
What will happen when?
- This week: Complete motor mount design and test full finger actuation with tendons.
- Next week: Final system integration, refine housing, finalize code and user interface.
- Final week: Full functionality test, documentation, and presentation preparation.
What have you learned?
I have learned about integrating mechanical design with electronics, managing 3D printing constraints for wearable applications, and designing PCB layouts tailored for specific microcontrollers and sensors. I've also gained experience with embedded programming and prototyping wearable assistive devices.