What is a Humanoid Robot?
In general, a humanoid robot refers to a bipedal robot designed to mimic the form and movements of a human, aiming for versatility. These robots possess a wide range of capabilities—from basic actions such as grasping and carrying objects to learning and performing various tasks. With the rapid advancement of AI technologies in recent years, some humanoid robots have also acquired sophisticated intelligence and natural conversational abilities. A key characteristic of humanoid robots is their humanlike structure, typically consisting of a head, torso, two arms, and two legs. This resemblance contributes to their social acceptability and facilitates easier integration into environments originally designed for humans. For this reason, humanoid robots are expected to find applications across a wide range of fields, including industry, healthcare and caregiving, disaster response, and entertainment. On the other hand, challenges related to safety and ethics have been pointed out as essential issues to address before humanoid robots can become widespread. Despite these challenges, the market potential for humanoid robots is projected to be extremely high, driving active investment and development efforts, particularly in the United States and China. As AI and sensor technologies continue to advance, humanoid robots are expected to play an increasingly significant role in human society in the years to come.
Gears Used in Humanoid Robots
The complex, humanlike movements of humanoid robots rely heavily on the precision of their internal mechanical components and the accuracy of their control systems. Among these components, gears play a crucial role—particularly in the joints, including the fingers—where they are used for acceleration, deceleration, and torque amplification. Commonly used types include spur gears, which offer general versatility; worm gears, which are compact and provide high reduction ratios along with self-locking capability; bevel gears, which change the direction of motion typically at a 90-degree angle; hypoid gears, which offer higher reduction ratios; and internal gears, which are used as part of planetary gear mechanisms where the input and output shafts are coaxial and capable of generating high torque. In addition, strain wave gearing—which combines multiple gears to achieve both high reduction ratios and excellent positioning accuracy—is widely adopted in humanoid robots. To ensure precise robotic motion, gears are sometimes ground to improve accuracy, and surface hardening processes such as heat treatment are applied in areas where high torque is required. Moreover, minimizing backlash, which significantly affects motion precision, remains a critical challenge in gear design for humanoid robots.