Equalization of force resolutions for forceps force sensors with double diaphragm spring structure

Abstract

In minimally invasive surgery robots, force sensing is required to improve its manipulability. To perform delicate surgery, three-axis force sensing is desired. However, in general, the force resolution in the axial direction is worse than that in the radial direction owning to a slender shape of a forceps. This paper proposes a double diaphragm structure for forceps flexural elements. The distance between the two diaphragms can adjust the rigidity in the radial direction without changing the rigidity in the axial direction when the thickness of the diaphragm is constant. Thus, the thickness of the diaphragm adjusts the rigidity in the axial direction, while the distance between the two diaphragms adjusts the rigidity in the radial direction. A planar spiral cutting in the cross section of the diaphragm can reduce the maximum stress applied on it. Moreover, by adjusting the two spiral phases and direction, the crosstalk of the radial and axial forces can be reduced. In 5 mm forceps simulation, the rigidity of the axial direction is almost equal to that of the radial direction when the distance between the two diaphragms is 6.0 mm. We performed experiments of 10 mm forceps model and confirmed that the resolution of the radial direction is almost equal to that of the axial direction when the distance between the two diaphragms is 12.0 mm.

Keywords

• diaphragm
• forceps
• force sensor
• surgical robot
• resolution