Precise Localization and Trajectory Control of Magnetically Actuated Micro-Robots

Research on micro-robot systems capable of operating within the human body (such as digestive or circulatory systems) is scattered across various directions with diverse technologies. This study explores a magnetic control system comprising a 4×4 grid of electromagnetic coils and a 7×7 Hall sensor array to manipulate and track a microrobot on a planar surface. Position detection relies on magnetic field deviations induced by the presence of the robot, and is captured through multiple neighboring sensors. A novel pattern-recognition-based localization method is introduced, focusing on the relative relationships among sensor ensembles instead of absolute readings, while selectively activating one, two, or three adjacent coils to produce directed forces. The experimental evaluation showed a consistently high localization accuracy across all coil activation configurations. The performance is particularly strong with single-coil activation, slightly lower with dual coils, and remains robust even with three coils despite the increased motion complexity. The accuracy tends to be higher when the robot moves toward the coil centers compared to when it moves away. The relative pattern-recognition approach demonstrated excellent robustness against noise and residual magnetism. For trajectory and speed control, dynamic current adjustment using a PI controller with position and velocity feedback significantly outperforms constant-current methods, yielding superior positioning precision, speed stability, and success in reaching the target destinations. The proposed relative pattern recognition localization and dynamic speed control substantially improve the reliability and accuracy of magnetic microrobot manipulations. These improvements support precise navigation and controlled force application in challenging environments, thereby advancing prospects for clinical medical applications.