Introduction
Advancements in prosthetics have always pushed the boundaries of what's possible, combining cutting-edge technology with the drive to improve human lives. However, for many across the globe, these marvels of engineering remain out of reach due to high costs. My project at North Central College, under the mentorship of Dr. Scott Milkovich, sought to change this narrative by creating an affordable, 3D-printed bionic claw, controlled by EMG muscle sensors, to offer a functional prosthetic solution.
Background
Disabilities affecting limbs can significantly impact quality of life. The World Health Organization estimates that over a billion people face some form of disability. Prosthetic arms can offer a semblance of normalcy but often come at a prohibitive cost, especially in developing regions. This project aimed to develop a low-cost alternative that doesn't sacrifice functionality for affordability.
Concept and Design
The Bionic Claw is powered by muscle movements, detected through EMG sensors connected to my arm through electrodes, driving a series of 3D-printed components to mimic the actions of a human hand. The initial design sketches (Figure 1) laid the groundwork for the 3D modeling phase, where each component was meticulously designed for optimal fit and function.
Engineering Process
The project lifecycle was managed through Gantt charts and detailed planning, ensuring each phase from sketching, prototyping, to testing was executed with precision. The use of an Arduino Uno R3 microcontroller and MG996R Servos for finger movement provided the necessary control over the prosthetic's movements, while keeping the design compact.
The Evolution of the Bionic Claw:
My commitment to innovation and functionality is showcased through the extensive prototyping phase. Here, I present the evolutionary journey of the Bionic Claw, highlighting the design challenges and improvements at each stage:
Prototype 1: My initial model faced a significant challenge; the supports were too thin and lacked the necessary durability, leading to breakage. Unfortunately, this prototype is not pictured due to its compromised state.
Prototype 2: To enhance the manipulation capabilities, I introduced static supports, which proved to be a step in the right direction. However, the rigidity of these supports made the opening and closing motion of the fingers strenuous.
Prototype 3: Addressing the limitations of the previous model, I integrated hinges for increased flexibility. This improvement allowed for the fingers to move more freely. However, a new issue arose – the fingers would overlap during closing, leading to a less smooth operation due to the square-shaped supports and the thin fingertips.
Prototype 4: With the insights gained, I refined the design by rounding the supports, which enhanced the fluidity of finger movement and prevented overlapping. I also reshaped the fingertips for a more efficient grip.
Prototype 5: I further refined the design by adding springs to facilitate the automatic closing of the fingers, along with a threaded screw for precision control.
Muscle Sensor and Electrodes: Bridging Biology and Mechanics
An integral part of the Bionic Claw's responsiveness is the muscle sensor system. Attached to my arm, the electrodes detect nuanced muscle movements, translating them into signals that control the claw's motion. A live demonstration below exhibits how muscle contractions with varying intensities are captured and plotter waves on the Arduino IDE serial plotter, with larger amplitudes indicating stronger muscle compressions. This real-time data is crucial for the precision and adaptability of the Bionic Claw, bridging the gap between biological input and mechanical output.
Final Design : The culmination of my efforts resulted in a design that not only addressed all previous concerns but also included a base for the servo motor and a circuit housing, bringing the Bionic Claw to full functionality.
Manufacturing and Testing
Utilizing the facilities at North Central College's 3D Lab, various iterations were printed, assembled, and tested. Finite Element Analysis (Figure 2) ensured the design could withstand actual use. The project culminated in a fully operational prototype (video above), showcasing the successful integration of the mechanical and electronic components.
Results & Impact
The Bionic Claw project incorporates sophisticated features that significantly enhance its functionality and user interaction, making it a more effective and intuitive prosthetic device. Through the integration of a Force Sensitive Resistor (FSR) and a limit switch, the device demonstrates advanced capabilities in object manipulation and user safety, respectively.
Enhanced Control:
The inclusion of the FSR allows the Bionic Claw to detect when it comes into contact with an object, enabling it to adjust the gripping force dynamically. This feature is critical for handling a wide variety of objects with different material properties and fragility levels. By measuring the force applied to the object, the Bionic Claw can modulate its grip to apply just enough pressure to hold the object securely without risking damage. This adaptability is achieved through real-time processing of the force sensor readings, which, when exceeding a predefined threshold, trigger the servo to stop, thus preventing excessive force application.
Improved User Safety and Device Durability:
The integration of a limit switch serves as a safeguard against over-extension of the fingers, which could potentially damage the base or the fingers themselves. When the limit switch is activated, indicating that the fingers have reached their maximum safe extension, the servo is automatically detached, halting any further movement. This not only protects the user from potential harm but also extends the lifespan of the device by preventing mechanical overstrain.
Technical Implementation:
The device's operation is controlled through a series of checks within the loop function. The muscle sensor's readings are continuously monitored for significant changes, which are used to control the opening and closing of the claw in response to the user's muscle movements. The force sensor reading is crucial for adjusting the grip based on the detected pressure, ensuring objects are handled with care. Additionally, the state of the limit switch is constantly checked to prevent over-extension of the fingers.
Impact:
The implementation of these features into the Bionic Claw has resulted in a more sophisticated and affordable prosthetic solution. The ability to dynamically adjust grip strength based on real-time feedback from the force sensor significantly enhances the device's versatility and safety, making it suitable for a wide range of tasks. Moreover, the inclusion of a limit switch ensures the longevity of the device and the safety of its operation, instilling confidence in users during use.
In summary, the Bionic Claw project's integration of a force sensitive resistor and a limit switch, guided by the thoughtful coding and hardware setup, demonstrate step forward in prosthetic technology. It offers a glimpse into the future of prosthetics where functionality, safety, and user experience are in harmonious balance, showcasing the potential for significant improvements in the quality of life for individuals requiring prosthetic assistance.
Conclusion
This project not only represents an academic achievement but also serves as a compelling showcase of how additive manufacturing can revolutionize the field of prosthetics, making life-changing technologies more accessible and paving the way for a future where advanced medical aids are within reach for everyone, regardless of economic barriers.
