Large-range Rotation-to-translation Compliant Transmission Mechanism

Abstract

A large-range-of-motion compliant transmission mechanism is introduced that uses the screw degree-of-freedom (DOF) of a multi-DOF compliant module, sandwiched between two other single-DOF compliant modules, to convert a rotational input to a collinear translational output and vice versa. The geometric advantages (i.e., transmission ratios) of the mechanism when driven with a rotation to a translation or with a translation to a rotation can be tuned as desired. The freedom and constraint topologies (FACT) approach is used to design the mechanism, and stiffness matrices are used to explain why the transmission ratio of the mechanism is different depending on whether the mechanism is driven with its rotational or translational inputs. A version of the mechanism is fabricated and its transmission ratio is measured to be ~1.36 mm/° when the mechanism is driven with a rotation, and is measured to be the inverse of ~1.89 mm/° when the mechanism is driven with a translation. The transmission ratios both remain impressively constant over the mechanism's full range of motion and only vary slightly when they are actuated in different directions (i.e., counterclockwise or clockwise if the mechanism is driven with a rotation, or pushing or pulling if the mechanism is driven with a translation).