Omnidirectional Wireless Power Transfer Based on Constant Coupling Polarity Concept

Abstract

With the rapid development of industrial and service robots, the cross-joint dynamic wireless power transfer (WPT) technology has attracted more and more attention. Unfortunately, the current range of motion angles that can achieve WPT coverage is limited, with the maximum coverage spanning from an axial angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bm{\theta }}$</tex-math></inline-formula> ranging from 0° to 75° and a circumferential angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bm{\varphi }}$</tex-math></inline-formula> of 360°. Currently, the realization of an omnidirectional WPT (omni-WPT) system remains elusive. This article pioneers in highlighting that maintaining constant coupling polarity (CCP) between the transmitting ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tx</i> ) and receiving ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rx</i> ) coils throughout the entire relative motion range is a fundamental requirement for achieving omni-WPT. Leveraging this insight, the cross-joint WPT with an omnidirectional operating angle is achieved for the first time. Subsequently, guidelines for designing a coupler based on CCP are provided, balancing the need for high transfer efficiency and low coupling fluctuation. To validate the effectiveness, a 13.56 MHz cross-joint omni-WPT system with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bm{\theta }}$</tex-math></inline-formula> ε [0°, 180°], <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bm{\varphi }}$</tex-math></inline-formula> ε [0°, 360°] is designed, constructed and tested. The experimental results show that high efficiencies of more than 90% are achieved with low efficiency fluctuation of 1.73%. Meanwhile the output power fluctuation on the load is only 4.89%.