Large Torsion Thin Artificial Muscles Tensegrity Structure for Twist Manipulation

Tensegrity structures have been actively studied in recent years because they are lightweight, compliant, and flexible, which are properties not typically found in conventional robots. This structure can be modularized to create soft robots that operate in unknown environments such as cave or space with more complex and effective behavior. The basic deformation elements in modularization are stretching, bending, and torsion. Among them, torsional motion is important for proper manipulation and rotational operation. However, active, and large torsion in soft tensegrity structures has not been developed. Therefore, this study describes torsional deformation and a novel arrangement method for thin artificial muscles. The proposed method leads to the optimal placement of artificial muscles for torsion, by which we generated a large torsion of $\pm$ 50 deg. This is more than 2.5 times larger than that of a previous tensegrity without compromising the favorable properties of the structure. Furthermore, by modularizing the tensegrity structure, a tensegrity arm capable of removing a plastic bottle cap was developed. The applicability of torsional deformation and the usefulness of modularization of the structure are demonstrated.