Design and Fabrication of a Low-Cost Mechanical Humanoid Robot Head for Social Interaction (M.H.R.S.I.)

Abstract

This paper presents the design, numerical analysis, fabrication, and system integration of a mechanical humanoid robot head intended for basic social interaction via facial expressions, eye motion, and speech-based question answering. The proposed prototype, named M.H.R.S.I. (Mechanical Humanoid Robot for Social Interaction), integrates a multi-servo facial actuation scheme, a linkage-based eye movement mechanism, and an embedded computing stack based on Raspberry Pi. The head is modeled in SolidWorks and its structural feasibility is evaluated through static simulation using gravity loading, a hinge torque case, and an external force case. A physical prototype is fabricated using fused deposition modeling (FDM) with PLA filament, followed by assembly and integration of seven SG90 micro servo motors, an ultrasonic sensor for proximity awareness, and audio I/O using a microphone and Bluetooth speaker. For interaction, a speech-to-text → question answering → text-to-speech pipeline is implemented, using a lightweight pretrained QA model (deepset/tinyroberta-squad2) adapted with a custom context database related to the robot and its environment. Results demonstrate the feasibility of a low-cost, interdisciplinary workflow for developing an expressive humanoid head prototype and provide a reusable methodology for future social robotics development.