Trajectory Tracking of Cable-Driven Parallel Robot via a Hybrid Structure of Type-2 Fuzzy Controllers and Sliding Mode Control Under Disturbances and Pulley Friction With Vibration Analysis

Cable-driven parallel robots have demonstrated significant advantages worldwide, especially in handling increasingly complex tasks that demand more degrees of freedom and a greater number of cables. In this study, Interval Type-2 Fuzzy Controllers (IT2FCs) and Sliding Mode Control (SMC) are integrated through a Bounded Linear Least Squares (BLLS) approach for trajectory tracking of a 6-DOF eight-cable-driven robot (CDR). The IT2FCs fully exploit their capability to incorporate system characteristics and the designer’s experience, while the SMC provides robustness in generating the required moment to stabilize angular deviations. Considering cable tension limits, the BLLS algorithm redistributes the total force generated by the IT2FCs to ensure that the required moment specified by the SMC is fulfilled, thereby guaranteeing full rigid-body control of the CDR. The simulation conditions are designed to increasingly approach real-world challenges, with external disturbances and Coulomb friction taken into account. In addition, the relationship between the trajectory and the elastic cable stiffness, as well as the influence of increasing cable tension on the perturbation of the end-effector around equilibrium point, is also discussed. Simulation results confirm the effectiveness of the proposed combination of IT2FCs, SMC, and BLLS in achieving high-precision positioning with minimal position error and angular deviation, even under increasingly harsh simulation conditions.