• The proposed RFHJ achieves motion decoupling and independent variable stiffness in two orthogonal planes, addressing a key limitation of existing continuum robots.
• The hybrid rigid-flexible design combines safe human-robot interaction with accurate control and reliable stiffness variation, offering a promising solution for practical applications.
• Experimental validation shows a wide variable stiffness range of [1.2, 49.9] N·m/rad, demonstrating the joint's tunability and effectiveness.
• The RFHA prototype with three RFHJs in series exhibits decoupled driving, bidirectional stiffness tunability, and self-stability, paving the way for advanced continuum robotic systems.