Project Overview

With the design finalized, the last step was to manufacture and assemble the full system. All components were 3D printed using lightweight infill to reduce print time and material usage while maintaining enough strength for operation. After printing, parts were lightly sanded and cleaned to remove imperfections and ensure smooth assembly.

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The hand and forearm were assembled using standard fasteners, with each servo mounted into the forearm housing and aligned with its corresponding tendon path. Fishing line was then routed from each fingertip down to its respective servo pulley and tied off with consistent tension. This step required careful adjustment—too much slack would reduce responsiveness, while too much tension would restrict motion or overload the servos.

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Once assembled, the system was fully wired and powered, and initial testing began. While the hardware functioned correctly, a major issue emerged: only one finger would move at a time, even though multiple signals were being sent simultaneously.

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After investigating, I found that the issue was not with the wiring, but with how the Arduino was executing commands. The control logic was written in a way that processed each instruction sequentially. When a command was received (e.g., move a finger to a certain position), the program would fully execute that motion before checking for the next command. Because servo movement was implemented using step-by-step position updates with delays, the microcontroller was effectively “blocked” while moving a single finger, preventing it from responding to other inputs.

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To resolve this, I redesigned the control approach to be non-blocking. Instead of commanding a servo to complete its entire motion immediately, each servo was assigned a target position, and the Arduino loop was structured to incrementally move all servos toward their targets over time. By using time-based updates instead of delays, the system could continuously check for new inputs while updating all servos in parallel. This allowed simultaneous and independent movement of all five fingers, as well as the ability to interrupt and reverse motion mid-actuation.

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Another issue encountered during testing was that the servos were moving too quickly, causing the fishing line to slip or fail to properly engage with the pulley walls. To improve accuracy and reliability, I introduced controlled speed reduction by adjusting the rate at which servo positions were updated. Slowing the motion ensured the tendons remained properly tensioned and allowed for more consistent and repeatable finger movement.

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With these refinements, the system was able to reliably replicate real-time finger motion. Each finger could be actuated independently or simultaneously, controlled entirely through webcam-based hand tracking. This final stage brought together all aspects of the project—mechanical design, electrical integration, and software control—into a fully functional robotic hand.