Tracking and Dynamic Tuning of a Wireless Powered Endoscopic Capsule

Abstract

This work presents an inductive wireless power transfer system for powering an endoscopy capsule supplying energy to power electronic devices allocated inside a capsule of ≈26.1 mm × 9 mm. A receiver with three coils in quadrature with dimensions of ≈9 mm × 9 mm × 10 mm is located inside the capsule, moving freely inside a transmitter coil with 380 mm diameter through translations and revolutions. The proposed system tracks the variations of the equivalent magnetic coupling coefficient compensating misalignments between the transmitter and receiver coils. The power on the load is estimated and optimized from the transmitter, and the tracking control is performed by actuating on a capacitance in the matching network and on the voltage source frequency. The proposed system can prevent load overheating by limiting the power via adjusting of the magnitude of voltage source VS. Experimental results with uncertainties analysis reveal that, even at low magnetic coupling coefficients k ranging from (1.7 × 10−3, 3.5 × 10−3), the power on the load can be held within the range of 100–130 mW. These results are achieved with any position of the capsule in the space, limited by the diameter of the transmitter coil and height of 200 mm when adjusting the series capacitance of the transmitter in the range (17.4, 19.4) pF and the frequency of the power source in the range (802.1, 809.5) kHz.

Optimal Frequency and Wireless Power Budget for Miniature Receivers in Obese People

“…For systems at the lower end of the frequency spectrum, [45,47,62], efficiency values are higher than the proposed design. While this can accommodate applications such as WCE, the dimensions of Tx and Rx are much larger.…”

“…Ultra-deep, miniature receivers: For the first time, mm sized receivers are investigated at depths up to 20 cm in the body, for the inclusion of all body types. Existing studies either focus on smaller depths, <10 cm, for deep implants [36,[40][41][42][43][44], target larger receivers [45][46][47], or include tissue only for a small part of the Tx-Rx distance [48].…”

“…User comfort: The limitations on Tx dimensions ensure that the hardware has a convenient form factor: A 10 cm coil can easily be worn on the body without hindering. A coil worn around the body as in [45,46] would be more cumbersome, needs an electrical connection to close the loop, and would require individual sizing. No need for contact gel as for US WPT also improves the user experience.…”

A New Transmitting Coil for Powering Endoscopic Capsules Using Wireless Power Transfer

“…In this work, we use four rectangular coils that can be independently excited to produce a magnetic field inside the human body with all non-zero rectangular components, as explained in the following sections. There are mainly two advantages of the proposed excitation system: a monoaxial receiving coil permits researchers to miniaturize the components that need to be installed on the capsule, as a receiving coil based on triaxial coil should require a lot of space and a more complex electronic unit to handle all the three windings [17][18][19][20][21][22][23][24][25][26][27][28][29]. The second important advantage is the possibility to easily adapt the system to different human body conformations, while maintaining very good uniformity of the field inside the body for all the three field components.…”

Analysis of the Magnetic Field Magnetoinductive Wave Characteristics of a Wireless Power Transfer System

“…Wireless power transfer (WPT) systems are prospective power transfer technologies in electrical areas [1][2][3][4]. The analysis and calculation of the electromagnetic field of WPT systems has received considerable attention from researchers.…”