Hybrid Force-Position Control for Cable-Driven Parallel Robots Based on Tension Optimization Distribution

Cable-driven parallel robots (CDPRs) exhibit distinct advantages over conventional rigid mechanisms in terms of lower mass and extended workspace, demonstrating critical applications in aerospace engineering, including but not limited to astronomical observation, astronaut rehabilitation training, and motion simulation. To address the stringent requirement for high-dynamic trajectory tracking capability of end-effectors, this study conducts an investigation into a force-position hybrid control strategy for an eight-cable-driven six-degree-of-freedom parallel robot. Considering flexibility of the cables, a time-varying flexible multibody dynamic model is developed to more accurately capture the nonlinearities and rigid-flexible coupling effects inherent in the system. To satisfy unidirectional force transmission characteristics of cables, a closed-form force distribution (CFFD) algorithm is introduced to achieve coordinated regulation of cable tensions under actuation redundancy, thereby ensuring effective utilization of redundancy and compliance with dynamic tension constraints. Building upon the tension distribution framework, a hybrid control architecture is further proposed, comprising two independent PID-based control loops for position and force regulation. This architecture integrates feedback from both cable tensions and end-effector position to simultaneously control the end-effector trajectory and real-time cable tension. Simulation results demonstrate that the proposed control strategy not only ensures accurate trajectory tracking but also effectively suppresses abrupt tension fluctuations, resulting in a well-balanced performance across both tracking precision and tension coordination control.