Electromagnetic Steering of a Magnetic Cylindrical Microrobot Using Optical Feedback Closed-Loop Control

Abstract

Control of small magnetic machines in viscous fluids may enable new medical applications of microrobots. Small-scale viscous environments lead to low Reynolds numbers, and although the flow is linear and steady, the magnetic actuation introduces a dynamic response that is nonlinear. We account for these nonlinearities, and the uncertainties in the dynamic and magnetic properties of the microrobot, by using time-delay estimation. The microrobot consists of a cylindrical magnet, 1 mm long and 500 lm in diameter, and is tracked using a visual feedback system. The microrobot was placed in silicone oil with a dynamic viscosity of 1 Pa.s, and followed step inputs with rise times of 0.45 s, 0.51 s, and 1.77 s, and overshoots of 37.5%, 33.3%, and 34.4% in the x, y, and z directions, respectively. In silicone oil with a viscosity of 3 Pa.s, the rise times were 1.04 s, 0.72 s, and 2.19 s, and the overshoots were 47.8%, 48.5%, and 86.8%. This demonstrates that closed-loop control of the magnetic microrobot was better in the less viscous fluid.

Magnetic microrobot control using an adaptive fuzzy sliding-mode method

“…In this problem, it is assumed that the coils are ideal. Moreover, by considering a linear response of the magnetic cores, the magnetic field is described by the linear superposition of the individual fields of the electromagnetic coils [29]. The magnetic field of each coil is proportional to its corresponding current.…”

RectMag3D: A Magnetic Actuation System for Steering Milli/Microrobots Based on Rectangular Electromagnetic Coils

“…In the actuation process, in addition to actuation by an external force F m applied by the magnetic field, the milli/microrobot is also subjected to liquid viscous forces F d that opposes its direction of motion, as well as F g and buoyancy forces F b in the liquid environment. The electrostatic force and Van der Waals force have a weak influence on the milli/microrobot motion compared with the above-mentioned main forces [28][29][30][31][32] by considering the milli/microrobot's millimeter-scale shape. As a result, they both have been ignored in order to simplify the dynamic model, which is shown as follows:…”

Bioinspired reorientation strategies for application in micro/nanorobotic control

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