Two-dimensional point suspension characteristics of a magnetic robot driven by dual electromagnets within a fluid pipe

Abstract. Manipulating microrobots within narrow conduits has significant potential in medical and industrial applications, including disease diagnosis and treatment within body lumens and inspection of fluid transport pipelines. To address the challenges of operating in fluid environments, this paper proposes a method for suspending a magnetic robot within the two-dimensional plane of a fluid conduit. Two vertically arranged electromagnets generate a non-uniform magnetic field that drives the magnetic ball. Hall sensors and visual measurement jointly provide positional feedback to the controller. The effects of drive current and fluid velocity on the levitation characteristics of the magnetic ball are investigated experimentally. Results indicate that, when the magnetic ball is suspended within the fluid pipe, higher fluid velocity or greater distance from the electromagnet axis results in larger horizontal displacement of the ball. Compared with a single-electromagnet drive, the dual-electromagnet drive effectively constrains the horizontal displacement of the magnetic ball and reduces fluctuations during fixed-point suspension. The horizontal deviation is reduced by up to 58 %. Maximum horizontal fluctuations decrease from 0.35 to 0.21 mm, while maximum vertical fluctuations decrease from 0.20 to 0.11 mm. Furthermore, by adjusting the current of each electromagnet, the magnetic ball achieves precise point suspension and stepwise motion within a confined fluid domain, with position control errors below 0.1 mm. The dual-electromagnet drive demonstrates superior performance in positioning control of the magnetic ball, providing a robust basis for future applications.