Compact manipulator with flexible parallel mechanisms and variable stiffness for keyhole procedures

Keyhole procedures frequently necessitate passing instruments through narrow, elongated surgical channels, presenting a significant challenge in designing manipulators with compact structures and superior remote dexterity. In this work, we propose a novel 7 degrees-of-freedom variable stiffness dexterous surgical manipulator based on a flexible parallel mechanism. The manipulator has an outer diameter of 4.5 mm and is characterized by a hollow structure that incorporates a central channel measuring 1.8 mm. This design facilitates the integration of tool drives and sensors within the manipulator, enhancing its overall functionality. The kinematics and stiffness model of the flexible parallel mechanism are derived. Additionally, a prototype of the proposed manipulator is presented and evaluated through sufficient experiments. We performed a teleoperation test to characterize the model accuracy of the prototype, and the average error is approximately 0.49 mm. Furthermore, we conduct a series of experiments to verify the prototype's performance, including workspace, stiffness, and dexterous operation. The results confirm that the surgical manipulator demonstrates excellent performance in the challenging environment of keyhole procedures.