Bending Cycles and Cable Properties of Polymer Fiber Cables for Fully Constrained Cable-Driven Parallel Robots

In most practical applications for cable-driven parallel robots, cable lifetime is an important issue. While there is extensive knowledge of steel cables in traditional applications such as elevators or cranes, it cannot be easily applied to cable robots. Especially new polymer based materials behave substantially different, but also the conditions for the cable change dramatically. Cable robots have more bending points and a higher variability in cable force and speed than traditional applications. This paper presents a form of bending cycle analysis which can be applied to assess cable wear. This algorithm counts the number of bends per trajectory in each cable segment. The sum gives an indication how much wear a cable receives. Experiments are conducted on a cable robot using different kinds of polymer fibers. The results show that this method is successful in predicting the point at which a cable finally breaks.