An instrument driver comprises opposing rotatable gripping pads. Each of the gripping pads includes an outer circular rim and a center hub. The pads are configured for applying a gripping force to an elongated member. The instrument driver further comprises shafts affixed to the center hubs, and a driver assembly configured for rotating at least one of the shafts, thereby causing the pads to rotate in opposite directions to linearly translate the gripped member. Each of the pads further includes a framework for partially collapsing in response to the gripping force, such that portions of the rims flatten to contact each other. Each rim has a concave gripping surface in order to facilitate vertical centering of the member between the pads. Each of the pads further includes a pair of upper and lower sprockets for interlacing with each other to prevent the elongated member from slipping out between the pads.
