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Dexterous magnetic manipulation of conductive non-magnetic objects

Abstract

Dexterous magnetic manipulation of ferromagnetic objects is well established, with three to six degrees of freedom possible depending on object geometry1. There are objects for which non-contact dexterous manipulation is desirable that do not contain an appreciable amount of ferromagnetic material but do contain electrically conductive material. Time-varying magnetic fields generate eddy currents in conductive materials2,3,4, with resulting forces and torques due to the interaction of the eddy currents with the magnetic field. This phenomenon has previously been used to induce drag to reduce the motion of objects as they pass through a static field5,6,7,8, or to apply force on an object in a single direction using a dynamic field9,10,11, but has not been used to perform the type of dexterous manipulation of conductive objects that has been demonstrated with ferromagnetic objects. Here we show that manipulation, with six degrees of freedom, of conductive objects is possible by using multiple rotating magnetic dipole fields. Using dimensional analysis12, combined with multiphysics numerical simulations and experimental verification, we characterize the forces and torques generated on a conductive sphere in a rotating magnetic dipole field. With the resulting model, we perform dexterous manipulation in simulations and physical experiments.

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Fig. 1: Induced forces and torques on a conductive sphere in three canonical positions relative to a rotating magnetic dipole.
Fig. 2: Typical numerical and experimental results for force-torque characterization.
Fig. 3: Dexterous manipulation of a copper sphere in simulated microgravity.

Data availability

All data generated and scripts for analyses during this study are included in the published article and can be found using the following link: https://osf.io/uk3rx/.

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Acknowledgements

This work was supported by the National Science Foundation under grants 1841845 and 1846341.

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Authors

Contributions

J.J.A. and T.H. proposed the research. All authors participated in the planning of the article. L.N.P. and J.J.A. performed the dimensional analysis and designed the experiments to characterize force-torque. L.N.P. and J.L.B.A. performed the numerical simulations to characterize force-torque. G.F.T. and T.H. designed the numerical microgravity manipulation simulator and control scheme, and integrated the controller into the experimental manipulation system. L.N.P., G.F.T. and A.P. designed and performed the manipulation experiments. L.N.P., G.F.T. and J.J.A drafted the manuscript. All other authors performed a critical revision.

Corresponding author

Correspondence to Jake J. Abbott.

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Competing interests

J.J.A. has patents and patents pending on electromagnet and permanent-magnet devices designed to generate rotating magnetic dipole fields. The other authors declare no competing interests.

Additional information

Peer review information Nature thanks Eric Diller and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

This document comprises the complete supplementary information associated with the article, organized in eight sections, ordered as the respective topics are introduced in the article: 1. Dimensional analysis. 2. Characterization of force and torque. 3. Model derivation. 4. Experimental verification of force and torque. 5. Comparison of numerical and experimental results. 6. Manipulation numerical simulations. 7 Manipulation experiments. 8. Discussion.

Supplementary Video 1

Numerical simulation of dexterous manipulation of a copper sphere in microgravity, with 3-DOF position control along the edges of a cube and uncontrolled orientation, using six dipole-field sources surrounding the sphere. The black line is the path taken, and an orthonormal frame depicts the sphere’s orientation. Highlighting indicates which single dipole-field source is activated at any given instant.

Supplementary Video 2

Numerical simulation of dexterous manipulation of a copper sphere in microgravity, with 3-DOF position control along the edges of a cube and 3-DOF constant-orientation control, using six dipole-field sources surrounding the sphere. The black line is the path taken, and an orthonormal frame depicts the sphere’s orientation. Highlighting indicates which single dipole-field source is activated at any given instant.

Supplementary Video 3

Dexterous manipulation of a copper sphere floating in a raft on the surface of water, with 2-DOF position control along the edges of a square in the horizontal plane and uncontrolled orientation about the vertical axis, using four electromagnetic dipole-field sources located below the sphere. The yellow line is the path taken, and a red arrow depicts the sphere’s orientation, which is logged over time. Highlighting indicates which single dipole-field source is activated at any given instant, with a blue arrow depicting the axis of rotation of the rotating magnetic dipole.

Supplementary Video 4

Dexterous manipulation of a copper sphere floating in a raft on the surface of water, with 2-DOF position control along the edges of a square in the horizontal plane and 1-DOF orientation control about the vertical axis, using four electromagnetic dipole-field sources located below the sphere. The yellow line is the path taken, and a red arrow depicts the sphere’s orientation, which is logged over time. Highlighting indicates which single dipole-field source is activated at any given instant, with a blue arrow depicting the axis of rotation of the rotating magnetic dipole.

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Pham, L.N., Tabor, G.F., Pourkand, A. et al. Dexterous magnetic manipulation of conductive non-magnetic objects. Nature 598, 439–443 (2021). https://doi.org/10.1038/s41586-021-03966-6

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