A Fast Local Imaging Method for Magnetic Microrobot Planar Spin Velocity Measurement

Magnetic microrobots (MMs) enable precise, minimally invasive manipulation via external magnetic field (MF), allowing remote operation in complex or inaccessible environments. Common actuation methods for MMs include gradient-based and rotational MF strategies, with the latter requiring significantly weaker MF to achieve efficient propulsion compared to gradient-driven approaches. To optimize the functionality of rotationally actuated MMs, their fundamental spin dynamics must be systematically characterized. This necessitates advanced MF generation systems capable of rapid motion-tracking and wide-range measurement to ensure precise analysis. This study introduces a real-time planar spin velocity measurement scheme, combining a tracking-based local imaging framework with a practical estimation algorithm to simultaneously achieve high-speed and large-scale measurement. The proposed method tracks one target MM to focus on the small local region, enabling the imaging system to dramatically enhance its capturing speed. Based on the fast imaging strategy, a singular value decomposition (SVD)-based orientation detection algorithm is then applied to calculate spin velocity of the target MM in real-time. Experimental study was carried out to demonstrate the capability of the proposed measuring scheme.