Magnetic Positioning Technique Integrated with Near-Field Communication for Wireless EV Charging

Abstract

For wireless electric vehicle charging, the relative position of the primary and secondary coils has significant impacts on the transferred power, efficiency and leakage magnetic flux. In this paper, a magnetic positioning method using simultaneous power and data transmission (SWPDT) is proposed for power coil alignment. Four signal coils are installed on the primary coil to detect the secondary coil position. By measuring the positioning signal amplitudes from the four signal coils, the power coil relative position can be obtained. Moreover, all the communication needed in the positioning process can be satisfied well by SWPDT technology, and no extra radio frequency (RF) communication hardware is needed. The proposed positioning method can work properly both in power transfer online condition and in power transfer offline condition. Thus, a highly integrated wireless charging system is achieved, which features simultaneous power transfer, data transmission and position detection. A positioning experimental setup is built to verify the proposed method. The experimental results demonstrate that the positioning resolution can be maintained no lower than 1 cm in a 1060 mm × 900 mm elliptical region for a pair of 510 mm × 410 mm rectangular power coils. The three-dimensional positioning accuracy achieves up to 1 cm. Accordingly, the extra hardware cost and control cost for the misalignment tolerance improvement can be reduced. Therefore, for a commercialized wireless EV charger, the cost of improving position detection accuracy and the cost of improving misalignment tolerance should be traded off.Some position detection methods available on the market have been considered for WEVC, such as radio frequency (RF) positioning [14][15][16][17][18][19][20], optical positioning [21,22] and acoustical positioning [23]. However, RF positioning and acoustical positioning both suffer signal multipath impairment and non-line-of-sight impairment when they work in a complex environment. The optical positioning methods, including visual image analysis and infrared positioning, are susceptible to obstacles, dust and harsh weather. Meanwhile, all the methods above are limited by their high cost and difficulty in integrating with the power pads. Magnetoresistive (MR) sensors are investigated to be used for coil misalignment detection [24][25][26][27], but this method has not achieved precise three-dimensional (3D) coordinate output, and plenty of sensors involved in the sensor matrix greatly increase the system cost and complexity. Moreover, some magnetic positioning methods are proposed in [28][29][30][31][32][33], which utilize auxiliary coils to measure the magnetic field generated by the primary power coil. The magnetic positioning methods are of high accuracy, low cost, not susceptible to the environment and are easy to integrate with power pads. In [28][29][30][31][32][33], the primary power coil needs to generate a very weak magnetic field for positioning. Thus, the primary resonant tank is excited by a very low-voltage source...

A Review of Technologies and Techniques for Indoor Navigation Systems for the Visually Impaired

“…The advantage of the method is its computational simplicity, regardless of the physical or organizational aspect of the scenario. Examples of RFID-based proximity methods can be found in the works of Singh et al, Qian et al, and Wu et al, where the authors review the RFID-based location methods available in the literature [66][67][68]. Proximity methods provide accurate position estimations of rooms using low-complexity algorithms [65].…”