The present disclosure can include a system including a surgical arm, a retractor connected to the surgical arm, a force sensor mounted on the surgical arm, the force sensor configured to receive sensor data indicating force on the retractor from the force sensor, and a magnetorheological fluid actuator for actuating the surgical arm, the actuator configured to actuate according to the received sensor data, and adjust the surgical arm according to the received sensor data so as to maintain a constant retraction force. The present disclosure can additionally include a method for retracting tissue including applying force to the tissue with a magnetorheological fluid actuator to induce a retraction force, sensing a change in force applied to the tissue using a force sensor, and maintaining the retraction force by adjusting the force applied to the tissue.
