Eddy Current Damping of Magnetically Actuated Neurosurgical Instruments

Abstract

Flexion based magnetically actuated minimally invasive neurosurgical tools tend to oscillate for an extended period of time due to the lack of avenues for energy dissipation. This study proposes eddy current damping as the mechanism for reducing the vibrations present for such magnetic tools. After determining the necessary damping coefficient (4.31 × 10−9 Ns m−1 for a settling time less than 0.5 s and 2.01 × 10−6 Ns m−1 for critical damping), a feasibility study was conducted by approximating the potential damping that could be generated. An experimental study was performed to validate these values and relationships determined by the approximations by measuring the oscillation of a 2 mm by 2 mm by 4 mm N52 Neodymium magnet attached to a nitinol beam. Six measurements were taken at gap sizes between the magnet and conductor of 0 µm, 100 µm, 200 µm, 300 µm, 400 µm, 500 µm, 750 µm, 1000 µm, 1500 µm, and 2000 µm with copper conductors of thicknesses 0.127 mm to 0.635 mm in 0.127 mm increments. It was shown that sufficient damping could be generated experimentally (the maximum damping documented is 1.24 × 10−6 Ns m−1).