Contactless Energy Transfer

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1.INTRODUCTION
Most high-precision machines are positioning stages with Multiple degrees of freedom(DOF), which often consist of cascaded long-and short-stroke linear actuators that are supported by mechanical or air bearings. Usually, the long stroke actuator has micrometer accuracy, while the Submicron accuracy is achieved by the short-stroke actuator. To build a high-precision machine, as much disturbances as possible should be eliminated. Common sources of disturbances are vibrations, Coulomb and viscous friction in bearings, crosstalk of multiple cascaded actuators and cable slabs. A possibility to increase throughput, while maintaining accuracy is to use parallel processing, i.e. movement and positioning in parallel within section, calibration, assembling, scanning, etc. To meet the design requirements of high accuracy while improving performance, a new design approach is necessary, especially if vacuum operation is considered, which will be required for

the next generation no lithography machines. A lot of disturbance sources can be eliminated by integrating the cascaded long-and short-stroke actuator into one actuator system. Since most long-stroke movements are in a plane, this can be done by a contactless planar actuator.

The topology proposed and tested in this paper provides long-stroke contact less energy transfer (CET) in a plane with only small changes in power transfer capability.

2.DESCRIPTION
ACTUATOR

Actuator is a mechanical device used for moving or controlling a mechanism or system. It converts electrical signals into motion.
Here we are using a linear actuator; it converts electrical signals into linear motion i.e. the movement is linear in manner along a plane.

CET TOPOLOGY

The design of the primary and secondary coil is optimized to get a coupling that is as constant as possible for a sufficiently large area. This area should be large enough to allow the secondary coil to move from one primary coil to the next one without a large reduction in coupling. If this can be achieved, the power can be transferred by one primary coil that is closest to the secondary coil. When the secondary coil moves out of range the first primary coil is turned off and the next one will be energized. To ensure a smooth energy transfer to the moving load, the position dependence of the coupling should be minimized, while keeping the coupling high enough to get a high-efficiency energy transfer.

Fig 1

Fig 2

The drawing in Fig.3 shows one secondary coil above nine primary coils. The black square shows the area in which the center of the secondary coil can move while maintaining good coupling with the middle primary coil. The secondary coil is situated in the bottom-left corner of the area of interaction with the middle primary coil. The coupling between the primary coil and the secondary coil within that area is calculated with Maxwell 3D 10Optimetrics and measured

STEADY-STATE ELECTRIC CIRCUIT ANALYSIS

Since the system will be used in a maglev application based on repulsive forces between coils and permanent magnets, the use of iron or ferrites is prohibited. In addition, the use of cores will limit the stroke of the system. Therefore, a coreless or air core inductive coupling is used to transfer the energy. To keep the efficiency of an air core inductive coupling high a resonant capacitor is used for both the primary and the secondary coil. Moreover, due to the position dependent coupling, a series resonant capacitor is used for both coils to ensure that the resonant frequency of the circuit does not depend on the coupling. The electric circuit of the CET system is shown in Fig.5, where V 1 is the RMS voltage of the power supply, I 1 is the RMS current supplied by the power supply, I 2 the RMS current induced in the secondary circuit. C 1and C 2 are the series resonant capacitors in the primary and secondary circuit, R 1 is the...
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