In order to determine the three-dimensional(3D)position of a detecting microcapsule in the gastrointestinal tract

a novel positioning method is presented based on alternating magnetic field and particle swarm optimization(PSO)algorithm. In telemetering two cylindrical energizing coils are located on the abdomen. Both coils are excited by time-sharing sinusoidal signal

and three induction coils whose axes are orthogonally mounted are sealed in the microcapsule. According to Biot-Savart law and Lenz law

a positioning model describing the relation between the induced electromotive force and the 3D position is derived. Then the position and orientation of the microcapsule are calculated via a nonlinear equation system by the improved PSO algorithm. The experiment shows that the positioning method is correct and the model has high precision. The PSO algorithm succeeds in solving high dimension problems

and its precision and performance are superior to conventional algorithms. The positioning method needs not special and expensive apparatus

and the miniaturization and integration can be easily realized.