Study of a Wireless Energy Transmission System for an Endoscopy Capsule with Dynamic Tuning

Wireless Power Transfer (WPT) is a technique employed to transmit energy from a source to one or multiple loads, usually located over short distances by near-field inductive coupling. An inductive link is connected to each load through a matching capacitive network for tuning the system and optimizing the whole power transfer process. However, when the frequency of the source is constant and the capacitive compensation network is fixed, the optimized operating points can only be guaranteed for fixed loads and for fixed positions between the transmitting and receiving coils. When the coils are nonstationary or the load is variable, the tuning of the inductive link must be dynamically adjusted to maintain a constant output power. This work presents the development of an optimized WPT control method for the application of an endoscopy procedure, guaranteeing sufficient energy to power a camera and a communication system allocated inside a small capsule of $\approx 26.1\times 9$ mm. A 3D receiver coil is located inside the capsule moving freely inside a transmitter coil with 400 mm diameter through translations and revolutions. The proposed system compensates disturbances such as the mechanical misalignments between the transmitter and three receiver coils in quadrature and load variation, by the dynamic adjustment of both the frequency and the matching compensation network. Preliminary results have shown reasonable power levels on the load even with low magnetic coupling coefficients ( $k\ \approx\ 0.002$ ), featured by the experimental endoscopic arrangement, providing energy to power the electronics to collect and transmit data to an external receiver.