Linear voice coil actuator with compensating coils
View Patent ↗An actuator is provided in which one or more separate compensating coils are employed to alter the distribution of the magnetic flux density in the air gap to produce a substantially constant force throughout the stroke; and in which current in the separate compensating coils can be adjusted with the stroke using separate power supplies and position feedback.
1. A voice coil actuator comprising
a core having an axis;
a permanent magnet having a longitudinal axis, and positioned so that the longitudinal axis of the permanent magnet is substantially parallel to the axis of the core;
a moving coil positioned to interact with the permanent magnet along the axis of the core; and
a compensating coil positioned apart from and to interact with the moving coil, wherein a magnitude of a magneto-motive force in the compensating coil is adjusted as a function of a position of the moving coil.
2. An actuator comprising
a core;
a permanent magnet having a longitudinal axis, and positioned so that the longitudinal axis of the permanent magnet is substantially parallel to an axis of the core;
a moving coil positioned to interact with the permanent magnet along the axis of the core; and
a compensating coil positioned apart from and to interact with the moving coil and having a magneto-motive force having a magnitude which is adjusted as a function of a position of the moving coil.
3. The actuator of claim 1 or 2 , wherein the compensating coil is positioned about the core.
4. The actuator of claim 3 , wherein the compensating coil extends along substantially the entire length of the core.
5. The actuator of claim 1 or 2 , further including
a position sensor responsive to the position of the moving coil; and
a power supply responsive to the position sensor and coupled to power the compensating coil.
6. The actuator of claim 4 , wherein the actuator is closed-ended.
7. The actuator of claim 4 , wherein the actuator is open-ended.
8. The actuator of claim 1 or 2 , wherein the actuator has a rectangular cross section.
9. The actuator of claim 1 or 2 , wherein the actuator has a cylindrical shape.
10. An actuator comprising
a core;
a permanent magnet having a longitudinal axis, and positioned so that the longitudinal axis of the permanent magnet is substantially parallel to an axis of the core;
a moving coil positioned to interact with the permanent magnet along the axis of the core; and
a compensating coil positioned to interact with the moving coil and having a magneto-motive force having a magnitude which is adjusted as a function of a position of the moving coil;
wherein the permanent magnet is positioned with respect to the core to define a cavity between the core and an end of the permanent magnet; and further wherein the compensating coil is positioned in the cavity.
11. The actuator of claim 10 , wherein the compensating coil fills the cavity.
12. The actuator of claim 10 , wherein a second cavity is defined at another end of the permanent magnet between the permanent magnet and the core, and further wherein a further compensating coil is positioned in the second cavity.
13. A voice coil actuator comprising:
a field blank which forms a housing;
a core;
a permanent magnet having a longitudinal axis, and positioned so that the longitudinal axis of the permanent magnet is substantially parallel to an axis of the core;
a coil positioned about the core to be moveable along and to interact with the permanent magnet along the axis of the core, wherein magnetic flux is produced in an air gap between the moveable coil and the permanent magnet;
a compensating coil positioned apart from and to interact with the moveable coil; and
a power supply coupled to the compensating coil so that magneto-motive force is produced in the compensating coil of a magnitude which is adjusted as a function of positions of the moveable coil along the core to alter the magnetic flux in the air gap.
14. The voice coil actuator of claim 13 , wherein the compensating coil is positioned about the core.
15. A voice coil actuator comprising:
a field blank which forms a housing;
a core;
a permanent magnet having a longitudinal axis, and position so that the longitudinal axis of the permanent magnet is substantially parallel to an axis of the core;
a coil positioned about the core to be moveable along and to interact with the permanent magnet along the axis of the core, wherein magnetic flux is produced in an air gap between the moveable coil and the permanent magnet;
a compensating coil positioned to interact with the moveable coil; and
a power supply coupled to the compensating coil so that magneto-motive force is produced in the compensating coil of a magnitude which is adjusted as a function of positions of the moveable coil along the core to alter the magnetic flux in the air gap, in which the core, the permanent magnet, the moving coil and the compensating coil are positioned in the housing formed by the field blank, and wherein the compensating coil is further positioned at an end of the permanent magnet along the longitudinal axis of the permanent magnet and in a cavity between the permanent magnet and the field blank.
16. The voice coil actuator of claim 15 , wherein the voice coil actuator has a rectangular cross section.
17. An actuator comprising
a core;
a permanent magnet having a longitudinal axis, and positioned so that the longitudinal axis of the permanent magnet is substantially parallel to an axis of the core;
a moving coil positioned to interact with the permanent magnet along the axis of the core; and
a compensating coil positioned to interact with the moving coil and having a magneto-motive force having a magnitude which is adjusted as a function of a position of the moving coil;
wherein the permanent magnet is positioned with respect to the core to define a cavity between the core and an end of the permanent magnet; and further wherein the compensating coil is positioned in the cavity.
18. The actuator of claim 17 , wherein the compensating coil fills the cavity.
19. The actuator of claim 17 , wherein a second cavity is defined at another end of the permanent magnet between the permanent magnet and the core, and further wherein a further compensating coil is positioned in the second cavity.