New control strategy can dynamically change wireless charging through multiple transmitter coils in robots and electric cars
Wireless power transfer has proven to be quite useful in electronic devices such as medical implants and smartphones. Often, this is achieved by aligning or ‘coupling’ two separate coils of wire (transmitter Tx and receiver Rx). The electrical current circulating in the Tx coil then creates a magnetic field that transfers energy to the Rx coil.
Although single-Tx systems can provide maximum efficiency for wireless transfer of power, achieving the same with multiple Tx coils is challenging because the Rx could be located anywhere over the surface covered by the Txs, leading to stronger coupling with some and negligible coupling with others. To date, there had been no control schemes that can optimize the currents delivered to each Tx in real time—until now.
Scientists at the Incheon National University, South Korea have devised an effective control strategy that can maximise efficiency in multi-Tx wireless charging. To accomplish this, relationships between many variables in the problem were established, such as the connection between the degree of coupling of each Tx to the Rx, its ‘perceived’ or ‘reflected’ impedance from the Rx and the optimal current that should be fed.
With this knowledge, the researchers implemented a novel, maximally efficient and relatively simpler method for multi-Tx wireless charging. “Our strategy breaks away from the more traditional approach of locating the Rx with a position sensor and only turning on the Tx closest to it,” explains Professor Dukju Ahn. “We found that the coupling degree of each Tx can be measured indirectly in real-time through its impedance, allowing us to dynamically adjust the output of each Tx coil to achieve maximum efficiency.”
Prof Ahn also stated that the performance of other published techniques was assessed as well by having the Rx stand still in different locations. “Wireless charging technology is aimed for applications involving moving receivers. In this sense, our work is the first to verify the efficiency of a multi-Tx control scheme compatible with a receiver that’s actually moving in real-time,” he remarks.
Wireless charging technology will help remove the hurdles of wired power supplies in many applications. With efficient multi-Tx wireless power transfer, we might be able to do away with the large and heavy batteries that current electric vehicles and industrial robots use, making them cheaper and easier to move.
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