Synchronous Impedance Control of Cable-Driven Parallel Robots With External Interaction

With the continuous emphasis on safety in human–robot interactions, where both compliance and accuracy must be considered, cable-driven parallel robots (CDPRs) serve as suitable systems because of their natural compliance resulting from the inherent flexibility and low weight of cables. Hence, a novel synchronous impedance control (SIC) scheme is proposed in this article to achieve high-precision control with excellent compliance when external interactions are involved. Superior to the traditional tracking-error-based impedance control of CDPRs that only involve kinematics, the synchronous motion characteristics among multiple cables are investigated by considering their parallel topology, and the global cable synchronization error is integrated into the dynamic model and impedance model to guarantee high-precision impedance control. The control stability is proved using the Lyapunov method. The trajectory tracking results indicate that the SIC scheme can achieve satisfactory accuracy with all cables moving in coordination and is robust against different types of disturbances. Moreover, the compliance ability is verified by indirectly calculating external forces using cable tension changes or measuring them directly using external force and torque sensors. Interaction experiments show that the SIC scheme can be used effectively in CDPRs in various scenarios with external force contact.