Modelling on mutual inductance of wireless power transfer for capsule endoscopy

Wireless capsule endoscopy (WCE) is noninvasive, painless, and riskless on detection for gastrointestinal disease. It attracts increasing attention. Wireless power transfer (WPT) technology is utilized to supply power for WCE. Receiving coil (RC) of WPT is capsulated into WCE. Its position and direction change all through gastrointestinal tract. Transmitting coil (TC) is worn by the patient. So the mutual inductance varies all the time. It should be studied to ensure sufficient receiving power. However, existing analytical methods do not reach satisfactory accuracy. They can only solve simple cases with positional misalignment. Numerical simulation models are time-consuming. Furthermore, an entirely new simulation must be repeated when any change in alignment occurs. Thus, based on geometry and misalignment of RC and TC, a model for mutual inductance is proposed. Compared with analytical methods, it is applicable to not only circular and rectangular RC, but also the elliptic, with directional misalignment. It costs below 0.1% of computational time of the simulation for the same accuracy. Moreover, any change in misalignment is easily handled by a simple change of parameter in the model. It reaches a tradeoff between computational accuracy and time. Receiving power is evaluated rapidly and accurately with proposed model.