Robust Electromagnetic Control of Microrobots Under Force and Localization Uncertainties

Microrobots are promising tools for micromanipulation and minimally invasive interventions. Robust electromagnetic control of microrobots can be achieved through precisely modeled magnetic steering systems and accurate localization. Error-free modeling and position information, however, are not realistic assumptions, and microrobots need to be controlled under force and localization uncertainties. In this paper, methods to account for these types of uncertainties are presented. Initially, the uncertainties in electromagnetic force generation of a new class of manipulation systems are quantified. Subsequently, a drag-force uncertainty model for linear dynamics is proposed. This model can be employed for microrobots whose fluid dynamics are not well understood. A set of performance measures is introduced in the design of controllers, and a PID and a robust H_∞ controller are synthesized and evaluated through simulations. To demonstrate the capabilities of the synthesized controllers under localization and force uncertainties, low update rates are considered. The H_∞ controller can provably respect the performance measures under higher uncertainties than the PID controller, and its performance is further quantified through experiments in a prototype electromagnetic control system.