Integrated and nonlinear dynamic model of a polymer cable for low-speed cable-driven parallel robots

Cable-driven parallel robots (CDPRs) have been widely used in various industrial applications requiring high sensitivity. These CDPRs mainly use high strength polymer ropes with light weight and low inertia. However, the polymer cable used in CDPR has the complicated dynamic characteristics such as nonlinear elongation, hysteresis, creep and short and long-term recovery. As CDPR cables are loaded and unloaded under various forces and velocities, dynamic creep and recovery due to loading and unloading strain rate occurs in real time. We proposed the integrated nonlinear dynamic model of polymer cable for the low tensile rate. All of dynamic behaviors were described with only integrated nonlinear dynamic model based on the visco-elastic model. Since the total time when the tension is applied to the system is an important factor in the dynamic creep characteristics, we calculated the loading and unloading time using the concept of equivalent force and the Newton–Raphson method. The constructed model was verified by comparing with experimental results for the hardening effect, dynamic creep, hysteresis and short- and long-term recovery. The proposed model had a good agreement with experimental result.