Patent ID: 8677853

Claim:
A robot arm comprising: a closed link mechanism that forms a polygon arranged between a base and a first hand, and including a plurality of links, wherein the plurality of links include a first predetermined link that, during an operation, reaches a first average temperature T 1 , and a second predetermined link that, during the operation, reaches a second average temperature T 2 , a material of the first predetermined link is different from a material of the second predetermined link member, and an elongation ratio of the first predetermined link, in which a length of the first predetermined link at the first average temperature T 1 is divided by a length of the first predetermined link at a pre-operation temperature T 0 , is approximately equal to an elongation ratio of the second predetermined link, in which a length of the second predetermined link at the second average temperature T 2 is divided by a length of the second predetermined link at the pre-operation temperature T 0 .