MRI-powered closed-loop control for multiple magnetic capsules

Control of multiple magnetic particles inside the human body may have many potential applications, such as drug delivery in places where conventional procedures cannot reach. A natural candidate for powering as well as tracking these magnetic particles is the MRI scanner. Although it offers the means to control the particles, it also poses difficulties: the magnetic field is applied uniformly to the group, thus making the independent control of each particle a challenging issue, while the actuation and the tracking are interleaved which can result to delays in actuation and measurement. The closed-loop control of a group of millimeter-scale particles, immersed in fluid, driven by the MRI scanner is studied in this paper. More specifically, this problem is presented in a unified manner, handling such issues as delays, constraints, as well as disturbances, and results in a robustly stable controller. We also propose a condition that effectively answers when the system should be in tracking mode versus actuation mode. In addition to theoretical results, the capability of the proposed controller is illustrated through simulation results.