A Magnetic Force Calculation of Permanent Magnet for Magnetic Surgical Instruments

Abstract

When magnetic surgical instruments are used to perform surgical operations, two situations must be strictly avoided to ensure the safety: 1) the magnetic surgical instrument fall down in the abdominal cavity; 2) the pushing forces between the inner wall of the abdominal cavity and the magnetic surgical instruments are too high to harm human body. However, when calculating the magnetic force applied to the magnetic surgical instruments, the variation of the magnetic field within the space which is occupied by the internal permanent magnets (IPMs), placed inside the surgical instrument, is normally omitted. In this paper, to calculate the magnetic field generated by the external permanent magnets (EPMs), a multi-dipole model is proposed considering the variation of the magnetic field in the region where IPMs locate, and a numerical integration method to calculate the magnetic force is introduced. The experimental results showed that the multi-dipole model could predict the magnetic flux density within the distance of 20 - 50 mm away from the permanent magnet. And the magnetic force calculation model can predict the magnetic force variation trend well.