TMR Sensor-Based Detection of EVs in Semi-Dynamic Traffic for Optimal Charging

One of the challenges faced in the design of inductive power transfer (IPT) highway is the detection of electric vehicle (EV), to enable charging, as it travels along the highway. When a primary coil buried under the highway has sufficient coupling with the secondary coil mounted on the vehicle, it is energized to initiate IPT. In this paper, a tunneling magnetoresistance (TMR) sensor based EV detection method on an IPT highway is proposed. In the proposed scheme, a detection coil is wound around the outer boundary of the secondary coil and it is excited at 400 kHz. The TMR sensors are arranged close to the primary coil such that it senses the magnetic field generated by the detection coil. The TMR sensors are placed over the leading and trailing edges (in the direction of EV travel) of the primary coil. From the leading edge TMR sensor outputs, the energization point of that primary coil to begin IPT is decided. Similarly, from the trailing edge TMR sensor outputs, the de-energization point to stop IPT from that primary coil is decided. Also, the effective area of overlap between the coils due to lateral misalignment is estimated. This enables the driver in correcting the lateral misalignment so that efficient charging is possible from the subsequent primary pads. A laboratory scale prototype was built and was tested. The results obtained prove the usefulness of the scheme.