A synthetic fiber rope is potentially capable of replacing a stainless steel wire rope because it is light weight, and has high tensile strength and flexibility. In order to exploit the maximum tensile strength of the rope, a terminal fixation method with a sufficient fixing force is essential. However, this is extremely difficult in the case of synthetic fiber ropes due to their small friction coefficients. This paper proposes a new terminal fixation method combined with a grooved pulley and pin. The grooved pulley is utilized in order to increase the friction between the synthetic fiber rope and the pulley, and the rope is wound around the grooved pulley. The extremity of the rope is fixed at a pin by hanging a loop with a figure-eight knot. The appropriate groove shape is found experimentally and it is confirmed that our method achieves maximum fixation force of 91.3% against the rope breaking force. We provide implementations examples for a long-reach tendon-driven manipulator.

This paper proposes a new wire-driven mechanism in order to relay many ropes very simply and compactly. Ropes pass through in a joint while bundled. Synthetic fiber rope can slide and twist, exploiting its low friction coefficient. In order to use this mechanism, it is necessary to investigate the influence of sliding on tension transmission efficiency and rope strength. The results of this study reveal that it is feasible for a robot arm using this mechanism to have more than 15 joints. Sliding has little influence on rope strength. The feasibility of this system was studied through hardware experiments and its mechanical performance was evaluated by constructing a horizontally extendable manipulator with three degrees of freedom.

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A synthetic fiber rope, which is lightweight and has a high tensile strength and flexibility, is receiving much attention as a replacement for a stainless steel wire rope. To exploit the maximum tensile strength of the rope, it is essential to develop a terminal fixation method with the sufficient fixing force. However, practical difficulty exists in the case of the synthetic fiber ropes because the synthetic fiber ropes have very small frictional coefficients compared with a stainless wire rope. This paper proposes a new terminal fixation method using a grooved pulley, a loop with figure-eight knot, and a pin. The grooved pulley is introduced to increase the friction between the synthetic fiber rope and the pulley by wedge effect, and the rope is wound around the grooved pulley. The end of the rope is hanged at a pin by a loop with a figure-eight knot. We experimentally derived the appropriate groove shape, and demonstrated that our method permits the maximum fixation force over 90 % of the rope breaking force. An example of implementation for a prototype model of a coupled-tendon multi-joints manipulator is also described.