Development of a Robot for False Casting in Fly Fishing*

This study aims to apply the technique of false casting, a fly fishing method, to robotic systems for throwing lightweight objects. Conventional throwing manipulators utilize the inertia of the end-effector, which makes them unsuitable for throwing lightweight, flexible objects such as strings. In contrast, false casting maintains the fishing line in the air through repeated motion and enables it to be thrown over a long distance. The purpose of this paper is to design a robot that can reproduce this motion as a first step toward developing a robotic system capable of applying this technique. First, based on human motion, we designed a planar 3–DOF robotic arm capable of manipulating a fishing rod. To reduce the influence of actuator inertia and weight, the actuators were mounted on the fixed links, and torque was transmitted to the joints through a belt–pulley mechanism. Furthermore, we evaluated the output characteristics of the system by integrating a discretized elastic rod model with the dynamic model of the robotic arm in a simulation. We conducted physical experiments to reproduce the false casting motion and confirmed the joint torques and output characteristics. Additionally, we observed the fishing line being maintained in the air, and examined the relationship between the elastic energy of the rod and the potential energy of the line. These results demonstrate the feasibility of reproducing the false casting motion using the designed robotic system.