Robust ℋ∞ control for electromagnetic steering of microrobots

Electromagnetic systems for in vivo microrobot steering have the potential to enable new types of localized and minimally invasive interventions. Accurate control of microrobots in natural fluids requires precise, high-bandwidth localization and accurate knowledge of the steering system´s parameters. However, current in vivo imaging methodologies, such as fluoroscopy, must be used at low update rates to minimize radiation exposure. Low frame rates introduce localization uncertainties. Additionally, the parameters of the electromagnetic steering system are estimated with inaccuracies. These uncertainties can be addressed with robust H_∞ control, which is investigated in this paper. The controller is based on a linear uncertain dynamical model of the steering system and microrobot. Simulations show that the proposed control scheme accounts for modeling uncertainties, and that the controller can be used for servoing in low viscosity fluids using low frame rates. Experiments in a prototype electromagnetic steering system support the simulations.