Apparatus for controlling motion of an invasive probe relative to a sheath enclosing the probe. The apparatus includes an outer casing, configured for connection to the sheath. The apparatus further includes a drive mechanism, fixedly connected to the outer casing. The drive mechanism has a first set of components, configured to translate the probe along a direction parallel to an axis of the probe, in order to advance and retract the probe with respect to the sheath in a translational stepwise manner. The drive mechanism also includes a second set of components, configured to rotate the probe around the axis of the probe, in order to rotate the probe clockwise and counter-clockwise, with respect to the sheath, in a rotational stepwise manner.
