Design and Development of a Voice-Controlled Humanoid Robotic Mouth for Facial Expression Simulation

Abstract

Human facial expression plays an important role in communication between humans and robots. This paper presents the design and development of a voice-controlled humanoid robotic mouth capable of generating lip and mouth expressions to enhance human-robot interaction. The proposed system integrates mechanical design, electronic control and embedded programming using an Arduino Uno microcontroller, HC-05 Bluetooth module, and five SG90 servo motors. Voice commands are captured through an Android smartphone application with speech recognition capability and transmitted wirelessly to the robot via Bluetooth. The compact robotic mouth, measuring 130 x 131 x 83 mm, was fabricated using 3D-printed Polylactic Acid (PLA) material and designed with five degrees of freedom to imitate natural lip movements. Four basic facial expressions, namely relax, smile, sad and surprise, were successfully implemented by assigning specific servo angle combinations. Experimental results demonstrated that the robotic mouth was capable of producing distinguishable and visually recognizable facial expressions with stable mechanical operation. Bluetooth communication remained stable up to approximately 8 meters under test conditions. The developed prototype demonstrates the feasibility of combining low-cost components and voice recognition technology to create an expressive robotic interface for future humanoid robot applications.