An Eight-Leg Walking Robot Using SMA Wires as Actuators

This paper presents mechanical and temperature analyses and walking experimental results of a developed 8-leg walking robot using thin shape memory alloy (SMA) wires as actuators. Two SMA wires are strung between a leg and the robot body. As an SMA wire pulls the leg in the horizontal direction and another wire pulls the leg in the vertical direction, the leg moves in an elliptical orbit by sending the wires sine- and cosine-curve electric currents. The maximum step of the leg is about 8 mm and the walking velocity is 6 mm/s. Temperature-time variation of the SMA wire was analyzed, applying the law of the conservation of energy. Then, the walking step and velocity of the robot were calculated from the experimental result of the hysteresis loop between the strain and temperature. The calculated results were in good agreement with the experimental results.