Self-Tuning Omnidirectional Wireless Power Transfer Using Double-Toroidal Helix Coils

Abstract

We suggest and study a novel omnidirectional wireless power transfer (WPT) system based on unusual double toroidal helix coils. The suggested antenna is a double-helix coil wounded around a torus. It creates two mutually orthogonal magnetic fields. One is toroidal and confined inside the torus, another one is poloidal and is distributed outside it. The intensities of these two fields can be independently tuned via the geometry of the turns. The coupling coefficients are tailored to ensure high efficiency regardless of the receiver position and orientation, without active circuitry for tuning or control. This topology provides self-tuning functionality which is achieved when the coupling between the transmitter and receiver is minimized while the coupling in the pairs transmitterrepeater and repeater-receiver is strong. The system consists of three transmitter-repeater pairs orthogonal to each other, ensuring omnidirectional functionality. Experimental results confirm self-tunability and high efficiency for any position and orientation of receivers. The proposed doublehelix antenna is applicable to different WPT applications where the coupling/decoupling between coils can be freely controlled.

C2DD—An omnidirectional receiver based on single‐coil transmitter

“…SS compensation is also used for the C2DD Rx, but the inductance is low due to the quadrature DD coils generates opposite magnetic field. KVL is applied on Figure 3 21 : where is supply voltage, is the impedance of Tx, ( ) is the impedance of Rx. …”

“…To reduce the system complexity, scholars studied WPT systems without control circuitry. The double toroidal helix coil Tx can remain transmission efficiency above 90%, 21 but the Rx also need to be made into the double toroidal helix coil which required a certain space, so the application is limited. The coupler was designed as dipole-cross or dipole-cubic, [22][23][24] but the ferrites will increases the volume of Rx.…”

Broadband and precise reconfiguration of megahertz electromagnetic metamaterials for wireless power transfer

“…Nowadays, it undergoes a growing need for developing EMMs that can be dynamically controlled in real-time to precisely manipulate magnetic fields within WPT systems [21][22][23][24] (see figure 1(b)). Taking inspiration from the recent advancements in metamaterials encompassing novel materials [25][26][27], intricate structures [28][29][30][31], and equivalent theories [32,33], there has been a burgeoning research focus on bestowing EMMs with exceptional reconfigurability. At present, one prevalent way to adjust the electromagnetic properties of an EMM unit cell is to introduce external capacitance [34][35][36] (see figure 1(c)).…”

Design and Performance Analysis of a Repeater-Assisted Multireceiver Wireless Power Transfer System Operating at MHz Frequencies

“…Further considerations regarding efficiency or load-independence requirements are investigated for the ball-shaped WPT systems. Paper [17] focused on a maximum-efficiency tracking and power allocation method for multiple Rxs, while a self-tuning omnidirectional WPT was realized in [18] by introducing additional repeater coils. However, blind spots may easily form in the ball-shaped multi-coil WPT systems, where the freeposition characteristics are usually reached by dynamically controlling the amplitude or phase of the coil supplies.…”

“…Combining the coils in series or parallel to use one common converter and tuning circuit [20] reduces the charging flexibility, more specifically, it creates blind zones where the Rx could not get power. However, having individual Tx-coil control can only solve the blind zone issue for single-Rx charging applications [18] by actively shifting them to another position in the charging space. Neither ON/OFF nor active phase control will help when the second Rx happens to be located at the new blind-zone position shifted due to the control for first Rx.…”