Automatic Control of Magnetic Helical Microrobots for On-Plane Docking

Docking is a common step in magnetic helical microrobot operations. However, the boundary effect causes helical microrobots to drift laterally near the container bottom. The mismatch between orientation and movement direction further complicates manual steering. In this paper, an automatic control method for on-plane docking of magnetic helical microrobots is proposed, which divides the docking process into preparation, alignment, and insertion stages. First, the docking path is planned according to the position and orientation of the helix and the target. Second, a steering-based path-following controller guides the helix swim to the ready position for alignment. Third, another path-following controller realizes the position alignment through rotational-frequency-controlled movement direction while locking the helix orientation aligned with the target. Finally, the docking is completed in the insertion stage. Experiments verified the automatic docking of helical microrobots with static targets, including inserting into a slender gap/tube, assembling with a micro-shaft axially, and leaning against a rod radially. This method can eliminate the negative impact of operator’s fatigue and inexperience on docking operations and has the potential to be applied in biomedical and microoperations.
Note to Practitioners
—This paper is motivated by the problem of docking magnetically driven helical-shaped swimming microrobots with target objects on Petri dishes, which is a common step in capture, loading, assembly, and delivery operations. Here, two closed-loop path-following controllers based on steering and rotational frequency control guide the microrobot to approach and align with the target respectively along a calculated path. In alignment, the non-ideal lateral drift of helical microrobots is controlled by rotational frequency for position alignment. Experiments verified the automatic docking of micro-helixes with static targets, including inserting into a slender gap/tube, connecting with a micro-shaft, and leaning against a rod.