HTEC foot: A novel foot structure for humanoid robots combining static stability and dynamic adaptability

Passive bionic feet, known for their human-like compliance, have garnered attention for their potential to achieve notable environmental adaptability. In this paper, a method was proposed to unifying passive bionic feet static supporting stability and dynamic terrain adaptability through the utilization of the Rigid-Elastic Hybrid (REH) dynamics model. First, a bionic foot model, named the Hinge Tension Elastic Complex (HTEC) model, was developed by extracting key features from human feet. Furthermore, the kinematics and REH dynamics of the HTEC model were established. Based on the foot dynamics, a nonlinear optimization method for stiffness matching (NOSM) was designed. Finally, the HTEC-based foot was constructed and applied onto BHR-B2 humanoid robot. The foot static stability is achieved. The enhanced adaptability is observed as the robot traverses square steel, lawn, and cobblestone terrains. Through proposed design method and structure, the mobility of the humanoid robot is improved.