Phased Array Focusing for Acoustic Wireless Power Transfer

Abstract

Wireless power transfer (WPT) through acoustic waves can achieve higher efficiencies than inductive coupling when the distance is above several times the transducer size. This paper demonstrates the use of ultrasonic phased arrays to focus power to receivers at arbitrary locations to increase the power transfer efficiency. Using a phased array consisting of 37 elements at a distance nearly 5 times the receiver transducer diameter, a factor of 2.6 increase in efficiency was achieved when compared to a case equivalent to a single large transducer with the same peak efficiency distance. The array has a total diameter of 7 cm, and transmits through air at 40 kHz to a 1.1-cm diameter receiver, achieving a peak overall efficiency of 4% at a distance of 5 cm. By adjusting the focal distance, the efficiency can also be maintained relatively constant at distances up to 9 cm. Numerical models were developed and shown to closely match the experimental energy transfer behavior; modeling results indicate that the efficiency can be further doubled by increasing the number of elements. For comparison, an inductive WPT system was also built with the diameters of the transmitting and receiving coils equivalent to the dimensions of the transmitting ultrasonic phased array and receiver transducer, and the acoustic WPT system achieved higher efficiencies than the inductive WPT system when the transmit-to-receive distance is above 5 cm. In addition, beam angle steering was demonstrated by using a simplified seven-element 1-D array, achieving power transfer less dependent on receiver placement.

LCC-S Based Discrete Fast Terminal Sliding Mode Controller for Efficient Charging through Wireless Power Transfer

“…When the output power of the system is P op , the system will operate at maximum efficiency. Using Equation (17), P op can be obtained as,…”

“…The waves propagate through a medium and then are collected by the receiving side transducer, which converts it back into electrical signals. The benefit of AWPT is that it can achieve higher power beam directivity than electromagnetic transmitter of the same size and the power is transferred omnidirectional which reduces the losses such as coil misalignment but the power transfer capability and efficiency of the AWPT is very less compared to other WPT systems [12,17,18]. In RIPT, the power transfer takes place between a transmitter coil and a receiver coil using electromagnetic induction.…”

Limitations of wireless power transfer technologies for mobile robots

“…These are targeted toward sealed environments such as containers with hazardous objects [42]. The maximum efficiency achieved for transmission in the air was 4% at 0.045 m transmission distance [26]. Although the efficiency was lower compared to IPT at 0.045 m, the efficiency trails off slower compared to IPT (2% for APT compared to 0% for IPT at 0.12 m).…”

“…Max. efficiency 4% [26] 90% [27] 98% [28] 14% [29] 85% [30] 62% [31] Max. distance, m 0.05 [26] 0.3 [27] 7 [ 32] 1000 [33] 3 [ 34] 1600 [35] R tr 4.6 [26] 0.5 [27] 3.5 [32] 916 [33] 6 [ 36] 222 [35] Power transferred mW [26] k W [ 27] k W [ 37] k W [ 33] k W [ 38] k W [ 35] Potentially hazardous Yes Yes Yes Yes Yes Yes Fig.…”

A Review on the Fundamentals and Practical Implementation Details of Strongly Coupled Magnetic Resonant Technology for Wireless Power Transfer

“…Multiple receivers can be powered with just one transmitter. By implementing an array of antennas in the transmitter, it is possible to control the beam directionality so the power transfer can be transmitted to the receiver in a more efficient way [38]. On the other hand, the receiver is equipped with multiple antennas to capture more waves and, in turn, extract from them more energy.…”