An electro-mechanical direct drive valve servo system for an aircraft including a drive mechanism that couples the rotary output motion of a rotary force motor to linear motion at a sliding-type valve. The drive mechanism includes a pair of axially spaced rotary members connected to the force motor and a wobble member journaled between and canted by the rotary members with axial thrust bearings interposed between axially aligned opposed planar faces of the rotary and wobble members. A radial output arm on the wobble member is connected to the valve and is constrained for arcuate nutating movement whereby controlled rotation of the rotary member effects nutating movement of the wobble member and output arm which movement effects controlled linear movement of the valve. Additional control inputs such as braking and recentering function inputs are accommodated by the drive mechanism at its input end to take advantage of the mechanism's inherent gearing force ratio.