Magnetic localization and manipulation of locking synchronous motors

Introduction

Collaboration between localization and manipulation systems is important for safe and efficient deployment of magnetic continuum robots^1,2 during diagnostic and therapeutic interventions³. Recent clinical demonstrations have shown the potential of these robots to navigate tortuous environments under magnetic manipulation^{4, 5, 6–7}. Meanwhile, traditionally large stationary manipulation systems^8,9 are being downsized for greater mobility and reduced floorspace, moving toward commercialization^{10, 11, 12–13}. These systems generate targeted magnetic fields toward manipulation of robots in vivo, which is facilitated by localization systems that reconstruct relative three-dimensional (3D) position and orientation information essential for control^14,15. In this regard, localization connects manipulation systems to microsurgical devices.

Conventional medical localization methods use technologies like stereo vision^14,16, biplane fluoroscopy^17,18, angulated C-arm fluoroscopy^19,20, ultrasound^{21, 22, 23–24}, or magnetic resonance imaging systems^{25, 26–27}. These methods are compatible with various types of microrobots and offer various spatial and temporal resolutions, penetration depths, and sizes of infrastructure²⁸. However, closed-loop magnetic manipulation is challenging due to often unknown coordinate transformations between physically disconnected reference frames of imaging and magnetic manipulation systems²⁹.

Alternatively, low-field localization methods (here defined in the nano- to milli-Tesla range), enable the development of magnetic tracking and manipulation systems that are independent of conventional medical imaging technologies³⁰. These methods rely on detecting magnetic fields and reconstructing the relative pose of the field source³¹. They typically involve external magnetic field sources combined with internal sensorized devices^{32, 33–34} or magneto-mechanical resonators with external magnetometer arrays^35,36.

Sensorized magnetic devices, often equipped with a single tri-axial magnetometer^{37, 38, 39–40}, can be localized relative to, and manipulated by, external field generating hardware^30,33. However, device miniaturization is limited by the space required for the sensor and the need for a rigid magnet-sensor connection to prevent saturation and maintain a consistent local field³⁰. Alternatively, resonators offer better miniaturization potential by using a single magnet for both localization and manipulation, but they require targeted excitation fields and external magnetometer arrays to measure oscillating fields³⁶. Increasing numbers of stationary magnetometers are required to expand the localization workspace when physically decoupled from magnetic manipulation...