Patent ID: 8132481

Claim:
A parallel mechanism comprising: a base; actuators attached to the base; a plurality of arms coupled together in parallel; wherein each of the arms includes: a first link, one end of which is coupled to the actuator; a second link through which another end of the first link and a bracket are coupled together; a first ball joint through which one end of the second link and the another end of the first link are swingably coupled together; and a second ball joint through which another end of the second link and the bracket are swingably coupled together; each of the first and second ball joints includes a ball stud including a ball-shaped head, a socket swingably holding the ball-shaped head of the ball stud, and a conductive member interposed between and in contact with the ball-shaped head and the socket such that the ball stud and the socket are electrically continuous with each other via the conductive member; a sensing device arranged to sense when at least one of the first and second ball joints is loose, based on whether or not the ball stud and the socket are electrically continuous with each other, such that the sensing device senses that the at least one of the first and second ball joints is loose when the ball stud and the socket are electrically discontinuous with each other.