An instrument drive unit (200) for use with a surgical instrument having jaw members (22, 24), the instrument drive unit comprising: a plurality of drive assemblies (300), each drive assembly comprising a drive screw (340) defining a longitudinal axis, the drive screw including a threaded portion； a drive nut (350) threadedly engaged with the threaded portion of the drive screw such that rotation of the drive screw results in longitudinal movement of the drive nut； a biasing element (370) disposed in mechanical cooperation with the drive nut； and a flexible drive element (380) disposed in mechanical cooperation with the biasing element, wherein longitudinal translation of the flexible drive element is configured to drive a function of the jaw members of the surgical instrument.
