Three-rotational-degree-of-freedom connection mechanism, robot, robot arm, and robot hand

A three-rotational-degree-of-freedom connection mechanism comprising:

• a joint for enabling a second member to rotate with respect to a first member around a torsion axis having a direction being fixed with respect to either the first member or the second member, and to connect the second member rotatably to the first member with three rotational degrees of freedom;
• three actuators, each of the three actuators including a variable length link having a variable length and a power source for generating force changing the length of the variable length link;
• three first-member-side link attaching units, each of the three first-member-side link attaching units being attached rotatably with one end of each of the three variable length links with at least two rotational degrees of freedom, and being provided in the first member having a fixed relative positional relationship with the joint;
• and
• three second-member-side link attaching units, each of the three second-member-side link attaching units being attached rotatably with the other end of each of the three variable length links with at least two rotational degrees of freedom, and being provided in the second member having a fixed relative positional relationship with the joint, wherein
• the first-member-side link attaching units and the second-member-side link attaching units are disposed such that the variable length link has a twisted relationship with the torsion axis in each state within a movable range of the joint,
• the three first-member-side link attaching units form three first-member-side center angles,
• the three first-member-side center angles are determined by line segments connecting a first-member-side torsion center and the three first-member-side link attaching units,
• the first-member-side torsion center is an intersection of the torsion axis and a first-member-side link attaching plane determined by the three first-member-side link attaching units
• the three second-member-side link attaching units form three second-member-side center angles,
• the three second-member-side center angles are determined by line segments connecting a second-member-side torsion center and the three second-member-side link attaching units,
• the second-member-side torsion center is an intersection of the torsion axis and a second-member-side link attaching plane determined by the three second-member-side link attaching units, and
• the first-member-side link attaching units and the second-member-side link attaching units are disposed such that the three first-member-side center angles differ from the three second-member-side center angles.