Hybrid Humanoid Robotic Head Mechanism: Design, Modeling, and Experiments with Object Tracking

The head mechanism is a critical part of a humanoid healthcare robot for potential healthcare or elderly care. The head structure of a humanoid robot should provide both motion and perception capabilities to mimic head function (e.g. object tracking) for Human-robot interaction (HRI) at the head level. In this paper, an innovative hybrid head mechanism consisting of one rotational servo motor and two linear servos has been proposed. Structural design, kinematic analysis, and automation have been studied to advance locomotive capability as well as functionality. Additionally, a visual servoing object tracking system was implemented as a perception unit to achieve real-time object tracking function. For the structural design, a parallel configuration of two linear actuators was selected to simplify the kinematic analysis, which enables precise control of joint angles. For the perception part, a vision-based real-time Aruco maker tracking system with proportional-integral-derivative (PID) control was set as a test scenario to mimic human head function with joint control of 3 DOFs (yaw, pitch, and roll). The functionality of this head mechanism has been validated by tests on potential use case (visual servoing object tracking). This head mechanism can servo as a valuable platform for broader HRI applications with humanoid healthcare robots.