3 Degree-of-Freedom Mechanism based on Tensegrity to Mimic Human Shoulder Motion

Abstract

This thesis proposes a 3-DOF joint mechanism inspired by tensegrity; this mechanism can simulate the motion of the human shoulder joint. Since it is a tensegrity structure, it is composed of strings and rigid bodies. The string used in tensegrity can only bear tension, while a rigid body can bear both tension and pressure. In tensegrity-based joints, rigid bodies do not contact each other, and the joints have certain flexibility. This structure is composed of three mutually perpendicular rotating axes, which combine the advantages of hard robot's rigidity and soft robot's flexibility. Considering the complexity of the robot working environment and the need for frequent contact with humans. The robot with a certain flexible joint cannot only protect its mechanism from damage to a certain extent but can also avoid human injury due to contact with the robot. Therefore, this type of 3-DOF mechanism has built-in flexibility and lightweight due to the properties of tensegrity. Every joint the proposed structure is inspired by the tensegrity, which is composed of strings and rigid bodies under tension or compression. It belongs to the class 1 tensegrity structure, in which the rigid bodies do not contact each other. So it has the characteristics of flexibility. It is composed of a rotary structure and a structure similar to a universal joint. 3 rigid bodies and 16 steel wires. Steel wires connected to the respective motors drive the rotating shafts of this joint mechanism. The range of each rotation axis is close to the range of human arm motion and verified by experimental verification.