Design of 3D Positioning Algorithm Based on RFID Receiver Array for In Vivo Micro-Robot

The clinical applications of capsule endoscopes have been increasing consistently since the invention of a passive capsule endoscope was made. Though the capsule endoscopes are effective in detecting large lesions along human digestive tract, they cannot meet doctors´ requirements of active control of the capsules to carefully examine small lesions. The poor precision of positioning system is one of the major hurdles blocking robots from approaching the accurate position of suspected areas. In this paper, we propose a novel algorithm to exploit the radiation pattern of a radio frequency (RF) tag inside the capsule, which forms shadows or traces on a set of receiver arrays. According to the shape of the traces and the radiation pattern, the position of the radiation source, i.e. the tag inside the capsule can be calculated with our algorithm. The details of our algorithm are presented with the simulation results in the paper. With the settings under medical constraints, the degree of positioning precision in simulation is improved to less than 1 cm horizontally and 2 cm vertically.