Basic Study for Drive Mechanism with Synthetic Fiber Rope : Feasibility Study of a Tension Measurable High-Strength Synthetic Fiber Rope

Lightweight and high-strength synthetic fiber ropes are widely used as components in tendon-driven manipulators. However, measuring their tension involves structural and electrical complexity, which makes it difficult to take measurements in the middle of the rope. Through a comparison of three commercially available conductive ropes, we confirmed that the organic conductive fiber Thunderon exhibits high linearity between rope tension and electrical resistance. However, Thunderon alone has a low breaking strength, making it insufficient for application in a tendon-driven manipulator that requires high tension. To improve the breaking strength, we prototyped a composite rope using the high-strength fiber Zylon as the jacket. Tensile tests showed that the breaking strength was improved by more than 25 times and that a stable electrical response was obtained even under high tension. By implementing this rope in a coupled tendon-driven manipulator, we demonstrated that tension changes along the rope could be detected through resistance changes. This method is expected to be a new approach that enables tension measurement in coupled tendon-driven manipulators.