Design and analysis of a novel cable-driven parallel robot with variable stiffness and rigid–flexible coupling

This study presents a novel cable-driven parallel robot integrated with rigid–flexible coupling and a variable stiffness system, specifically designed to replicate the motion characteristics of the human cervical spine. Kinematic control of the robot is achieved by establishing a functional relationship between its configuration space and actuation space, where cable length variations are constrained within ±40 mm. Furthermore, this work explores static and dynamic modeling methodologies, highlighting their critical role in evaluating the robot's performance under operational poses. A detailed analysis is conducted to investigate the synergistic effects between the rigid–flexible coupling structure and the variable stiffness system. By incorporating adjustable stiffness parameters, a dynamic model is developed to reveal the robot's behavioral characteristics under different poses. Simulation results demonstrate that the robot achieves a maximum bending angle of 30° under cable tensions from 0 to 80 N, while its operational stiffness can be dynamically modulated from 3900 to 4700 N m −1 (with a tuning bandwidth of up to 100 %). These quantitative findings confirm the validity of the proposed model and illustrate the capabilities of the robot in flexible bending motion and stiffness regulation, providing a valuable reference for the design and analysis of other cable-driven flexible mechanisms.