Multi-degree of freedom torque-free linkage unit

A multi-degree of freedom torque-free linkage device comprising:

• a root link;
• a base link rotatably connected to the root link to form a base joint;
• a first link connected at one end thereof to the base link to form a first joint that intersects the base joint, the center of gravity of the first link being positioned so as to be spaced apart from the first joint along the longitudinal direction thereof;
• a counterbalancer comprising a first counterbalancer disposed at the first link in such a manner as to be disposed at one end thereof at a side of the first joint and disposed at the other end thereof along the longitudinal direction of the first link so that when the first link moves relative to the root link, the first counterbalancer can perform gravity compensation on the first link;
• and
• a curved parallelogram unit comprising a base reference part securely fixed to the root link, a first reference part rotatably disposed at the first joint formed by the base link and the first link and connected to the first counterbalancer, and a parallelogram transmission part configured to connect the base reference part and the first reference part to each other and form a reference position for achieving a gravity compensation for another link connected to the base link by rotating the first reference part around the first joint when the base link moves relative to the root link.