Concept of variable transmission for tendon driven mechanism

The transmission determines the speed and force of the driven part with respect to the actuator. Because the transmission ratio is generally fixed, the velocity and force of the driven part are in trade off relationship. In this paper, to vary the transmission ratio of the tendon driven links, variable moment arm mechanism is proposed. The moment arm of the wire to the joint is changed according to the increase of the tension of the wire. By the static analysis, the motion and force characteristics of the mechanism is verified. Simulation results show that the rotational joint with the mechanism can rotates faster and generates larger force compared with conventional rotational joints while same actuator is used.