Abstract
Magnetic nanorobots are recently used in a drug delivery system in order to perform minimally invasive medical procedures. One main difficulty for controlling nanorobots is the complicated behavior of hydrodynamic drag force and uncertain factors in their dynamics. The drag force depends on the blood velocity but unfortunately, it is apparently unknown. In previous feedback control system designs, the blood velocity was assumed to be known or set constant. This assumption did not reflect the reality and reduce the feasibility of the control systems. Considering this fact, this paper suggests an optimal observer for estimating blood velocity. The only information required for the proposed observer and overall control system is the position of nanorobots. The characteristic, stability, as well as gain tuning rules of the proposed optimal observer is discussed in detail. Simulation results are carried out in MATLAB/Simulink to demonstrate the effectiveness of the proposed optimal observer as well as the overall feedback control systems for nanorobot navigation in blood vessels.