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Abstract
In this paper a new topology for contactless energy transfer is proposed and tested that can transfer energy to a moving actuator using inductive coupling. The proposed topology provides long-stroke contactless energy transfer capability in a plane and a short-stroke movement of a few millimeters perpendicular to the plane. In addition, it is to lerant to small rotations. The experimental setup consists of a platform with one secondary coil, which is attached to a linear actuator and a 3-phase brushless electromotor. Underneath the platform is an array of primary coils that are each connected to a half-bridge square wave power supply. The energy transfer to the electromotor is measured while the platform is moved over the array of primary coils by the linear actuator. The secondary coil moves with a stroke of 18cm at speeds over 1m/s, while up to 33W power is transferred with 90% efficiency.
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.
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.
A lot of systems use 2D spiral coils for the primary and secondary coil, since the spiral coil geometry allows relatively high coupling (upto60%) and some tolerance form is alignment of the coils. However, to allow the secondary coil to move from one primary coil to the next, the tolerance for misalignments should be increased. In the proposed system this is done by using a 3D geometry for the primary coil. This results in a fairly constant B-field around the primary coil, which accommodates good coupling in a large area. Further more, since the system is supposed to transfer power to a load moving in a plane, it is convenient to use a shape that is symmetrical in 2D for both the primary coil and the secondary coil:
a square for instance. The geometry of the primary and the secondary coils are optimized with FEM using Maxwell 3D10 Optimetrics.
CONTACTLESS ENERGY TRANSFER
Abstract
In this paper a new topology for contactless energy transfer is proposed and tested that can transfer energy to a moving actuator using inductive coupling. The proposed topology provides long-stroke contactless energy transfer capability in a plane and a short-stroke movement of a few millimeters perpendicular to the plane. In addition, it is to lerant to small rotations. The experimental setup consists of a platform with one secondary coil, which is attached to a linear actuator and a 3-phase brushless electromotor. Underneath the platform is an array of primary coils that are each connected to a half-bridge square wave power supply. The energy transfer to the electromotor is measured while the platform is moved over the array of primary coils by the linear actuator. The secondary coil moves with a stroke of 18cm at speeds over 1m/s, while up to 33W power is transferred with 90% efficiency.
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.
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.
A lot of systems use 2D spiral coils for the primary and secondary coil, since the spiral coil geometry allows relatively high coupling (upto60%) and some tolerance form is alignment of the coils. However, to allow the secondary coil to move from one primary coil to the next, the tolerance for misalignments should be increased. In the proposed system this is done by using a 3D geometry for the primary coil. This results in a fairly constant B-field around the primary coil, which accommodates good coupling in a large area. Further more, since the system is supposed to transfer power to a load moving in a plane, it is convenient to use a shape that is symmetrical in 2D for both the primary coil and the secondary coil:
a square for instance. The geometry of the primary and the secondary coils are optimized with FEM using Maxwell 3D10 Optimetrics.
