A surgical system includes an instrument driver having a distal end positionable in a body cavity and a user input device. The instrument driver and user input device are positioned to removably receive distal and proximal portions, respectively, of a surgical instrument. The user input device is configured to generate movement signals in response to manual manipulation of the proximal portion of the surgical instrument. At least one motor operable to actuate the instrument driver in response to the movement signals and to thereby change position of the distal portion of the surgical instrument within the body cavity.